An intermediate black hole was recently observed, contrary to Don's claim. Unexpectedly, it was located outside a small galaxy, not at the center of a small galaxy. Astronomers always looked for intermediate black holes at the centers of small galaxies, since the centers of galaxies is where supermassive black holes have always been found and the well-established pattern is that the mass of a supermassive black hole is proportional (roughly speaking) to the mass of the galaxy around it. It should also be noted that a fourth type of black hole has been theorized: primordial black holes created at the big bang, small enough that most would have already evaporated if Hawking's theory about black hole evaporation is correct.
Another great show, thank you. Now for a suggestion / request. I'd love to see "A day in the life" style show. A show where you show us what one of these experiments actually looks like at FERMILAB. The warts and all theory behind the experiment, the actual experiment and the hours of what the data looks like before those incredible brains make sense of it.
Amazing episode as always.. thank you Doc for putting in all the effort for us mortals.. Physics as we know of it right now leads us to believe that the time exists because of gravity.. however in ancient indian physics books we've been given to understand that gravity is a curve, a bend in time and exists only cuz time exists.. Would be great if you could pls reflect upon the idea and some ramifications of the same. Thanks for the lovely stuff!! :)
Thank you for this amazing series professor!! Question 1: How the supermassive blackholes were formed in the beginning of the universe ? Question 2: Supermassive blackholes present at the centre of radio galaxies become active when they burp after eating matter from accretion disk, but this is not a continuous process, Why??
1. They seem to have grown from smaller black holes. This is evident from a fact that quazars (active galaxies with smaller central black holes) can only be seen in early universe. As for where the original "seed" black holes came from, that's the big question. They could've formed from mergers of early stars and their remnants, but if so, it's unclear how they could've grown so fast. 2. The "burp" in question was short on universal scale, but it was most definitely continuous and long process.
KohuGaly The leading theory these days is NOT smaller black holes, as we didn’t have enough time for so many mergers. Instead, it is likely that in the early eage of the universe, the densest parts of the universe has collapsed straight into black holes, skipping the star-phase. Less dense parts became stars. Dr Becky had an episode explaining all these hypotheses recently.
Question 1: This is currently an unsolved mystery which scientists have yet to resolve. Regardless we have evidence of quasars when the Universe was only half a billion years old so they had to grow very fast too fast for them to grow to their masses via accretion alone. They might have formed by direct collapse, over dense star clusters, extremely massive Pop III stars and or by frequent black hole merger events or other mechanisms we haven't even thought of yet. Question 2:The reason the process isn't continuous is due to multiple reasons first to accrete matter you need more material falling in on the black hole however the radiation and outflows of ejected material from the accretion disk has the potential to heat up the in falling material preventing it from infalling further or forming new stars via a process known as quenching. This is more of a thing in the later universe since the black holes have largely consumed all the gas and dust around them. In this case further accretion depends on something new falling in say a new supply of gas via a galaxy merger, a tidal disruption event etc. basically the answer is that after the quasar epoch ended black holes largely ran out of "food" when a new "meal" arrives they then begin to flare up again until they exhaust their new supply of material
Hi Don! Do you think that we as a species have enough data and know enough phenomena to derive a theory of everything if only someone looked at things the right way, or do you think we are missing critical pieces of the puzzle that will keep an answer out of reach until we observe them? Where in between those two extremes do you think we are, and what are some of the more promising lines of investigation going on today to find the missing pieces and/or reinterpret the existing data?
Hi, another week, another question. If a black hole makes us loose information how does it work with entangled particles? Say I have two photons entangled so knowing one's polarization I also know the other one's. But if that one falls into a black hole, shouldn't these properties get "lost"? To me it sounds like I could have additional information about the interiours of a black hole that way. Is that possible?
Entangled particles should remain entangled in the situation you describe. You have no information about the BH interior though, just like you would have no information about the environment of any entangled partner that is far away. Entanglement does not convey information between partners. It’s just a known correlation.
You just described how Hawking came up with his idea for Hawking radiation. 😊 And the last part of what you are saying is called the black hole information paradox. Fascinating material to read up on. Kip Thorne, Leonard Susskind and Hawking all had bets about the resolution to this over the last couple of decades.
@@cloudpoint0 What I mean is, consider I would create a black hole only consisting of these entangled particles. I then would have knowledge of these properties, too. (Except in case their polarisation, spin or what ever would get lost) But I understood black holes won't have these kind of properties, which leads me to the assumption that it can get lost. But how, aince they are entangled?
@@ebenolivier2762 Isn't Hawking radiation something different? Like the emission from the black hole? What I meant to ask was the conflict of a) knowing properties for sure since particles are entangled and b) the definition that a black hole doesn't have any of these properties (any more)
davidgreenwitch Hawking radiation is indeed an emission (radiation) from the black hole. You are delving into very deep and technical territory with your very good questions. 😊 For a very long time the information loss in a black hole could not be reconciled with quantum theory. The holographic principle by Susskind and t'Hooft seems to resolve this, but then there was the firewall problem...
I would like to see the math for why no energy is gained by fusion after iron. I do have a math degree but i lack the physics knowledge to even guess where to look.
courses.lumenlearning.com/physics/chapter/32-5-fusion/ Iron is the most stable nucleus. Below iron, moving to a heavier element releases energy (e.g. fusion). Above iron, moving to a lighter element releases energy (fission). Look at figure 2 in the link.
Basically, iron and nickel are about tied for the highest atomic bonding strength, so it takes more energy to break them apart than you get out of the reaction. It becomes a pure deficit for energy returns, in addition to being harder to make happen in the first place.
Think of degenerate solutions to a set a equitions, continuous or discrete, does not change the concept. In chemistry degenerate solutions are common both litterallyI in experiments for example in isothermal reactons even when isolated from the environment. But also theretically, many molecules have or materials have degerate states..meaning.. yes, something changed but no energy was used to expelled from or in the system volume. Same goes for quit a handfull of particles near irons most common isotope. They are indifferent/degenerate in requiring energy or expelling energy to/from the surroundings. The optimum is at iron Like DrDon pointed out. And thus there is sort of an optimal energy drainage going on toward that iron region. But nickel will be also present but much just less so. But just like in more mundane stuff like atoms reacting etc there is a spread at least spanning several kT worth of energy when transitios/reaction are possible. Constantly switching between electonvolt and joules/mole and wavenumber and wavelenght euiqvalents to make sense..I prefer electronvolts actually in thinking about stuff happening step based, and joules are awesome for bb guns haha and more macro scale. Really it does not matter. it is the whole range that makes it interesting. In nanomaterials, when making particles with a certain size it is possible to get them from the ge- go almost exactly at e.g. 10 nanometer... but yeah, that just means the peak is at 10 and drop extremely fast either smaller particles or larger, still when examining there you will find the oddball 5 nanometer weirdo. Representing also a extreme outlie-er in "effective melting temperture". For example..god will melt with ease at ~200 if small enough. weird. not really. Cool, yeah. I come from a more nanomaterials background, so im never able to put my finger how to feel a chemist, experimentalist, psycisist or more generalally, scientist. After all, science is everything, including phsysics and why not phylosophy while were at it.. PhD anyone ? ;p I must be bored. Great video Dr Don.
YCCCm7 Soooo... since the pressure and temperature is still quite high when iron starts forming, would it be more accurate so say that iron fusion happens but sucks up energy, so that the core basically cools down and looses pressure?
@@drdon5205 His question was WHY anything heavier than iron will fission with energy release, and lighter than iron will fuse with energy release. There's a QM rule somewhere explaining this, although I recently pondered this question myself but haven't looked it up yet although it know it has to do with the total binding energy (strong force interaction) within the hadron.
8:58 , sir don said that matter when have a temperature of 2.7 Kelvin would emit radiation in the form of radio waves , so sir if we have a object which has a temperature of about -270.45°C which is equal to 2.7 K , then it would also be emmiting radio waves ??
That is exactly what will happen. Every object emits thermal radiation (black-body radiation, described by Planck's law). Depending on the temperature, the frequency of the radiation changes - for cold objects the emitted frequency is low and increases as the object gets hotter (so called Wien's displacement law). To be more accurate, the emitted radiation is a spectrum of frequencies - for an object that has the temperature of 2.7 K, the peak wavelength of the emitted radiation is at 1.1 mm, but many other wavelengts are emitted as well - starting at approximately 0.25 mm and going to approximately 10 mm. The most of the emitted energy is what we call radio waves (1-10mm), some of it is infrared (0.25-1mm).
That was an unexpectedly thorough explanation about the temperature of space. So I guess when physicists refer to the temperature of space, they just mean the (current) temperature of the cmb. The temperature of the photons black holes always absorb and thus they can’t leak energy until the cmb cools off some more. Thanks!
At 9:22 you start to discuss theoretical vs. experimental physics considerations for Swapnil Kumar who currently appears to be studying engineering. I have another suggestion. It was about 40 years ago when I graduated, but I studied engineering physics. At the end of that course you could do further studies in various engineering disciplines, experimental or theoretical physics. I found it to be a great course for those who were not sure which way they wanted to go when starting university, and my classmates took a variety of paths. Considering that one that took the pure physics route won a noble price for her work, this certainly was not a path that result in limited opportunities for those that chose physics over engineering after undergrad work was complete.
My question was not replied in this video. Can we observe radiation from a stationary charge when we are accelerated. If we can observe, then we should feel a retarding force due to loss of energy as radiation. Whether it is tested in lab.
This statement and queston contradicts it self let me explain why. You say stationary, but can it give off radiation. This means the object or particles are not stationary and are in fact moving at the speed of light because radiation is light. Having no movement would be zero kelvin. Something believe to be unreachable.
would a black hole made of anti matter be any different than one made of regular matter? would any of them behave different if they suck the opposite kind of matter that made them?
If you want to get is a submarine and shrink down to donsurgery knside slmeone, is it easier to shrink the atoms or should you just use very tiny atoms?
Hi Don! if a single photon is bombarded at a microscopic black hole before it evaporates, will we get a stable (or rotating) black hole with increased mass & an accretion disk, which will devour the particle accelerator (& the planet ) OR the photon trapped will be emitted as Hawking Radiation instantly OR what ?
Whatever a black hole consumes is competing with Hawking radiation losses, and what matters is which one predominates over the long haul, so a single photon would just delay the completion of evaporation by a short time.
Hi Don, what's your opinion about what's happening to the things beyond Schwarzschild radius? How do you imagine the interior of a black hole? Like matter being squeezed up to Planck density as written here arxiv.org/pdf/1401.6562.pdf or if you have some cool scientific hunch. Or if you simply think "we'll see". Or something inbetween? Thank you.
Hi Don! Is there any difference from the point of view of the rest of the universe between a virtual electron/positron pair appearing & annihilating near an event horizon (neither going in) vs a pair appearing and both falling in before they annihilate? Sorry for double questions if that's not polite!
Hi Don, one Question? As a high end physicist, are you able to solve mathematical problems such as a simple fourier transformation or laplace to a really reaaaaally hard integer without using symbolab or something like that
Bob Jones I would rephrase this question. If I bounce a ball, obviously it is also governed by quantum physics in the end. But I can calculate it’s future path without it, because quantum physics doesn’t cause any meaningful difference. An interaction with a photon is greatly dependent on quantum physics, as we can see in the double-slit experiment. We NEED quantum physics to calculate where it will hit the wall. Organic matter is obviously between those 2 extremes. Does quantum physics (like Heisenberg uncertainity , quantum tunneling, etc) really affect organic life? Does DNA copying in the cells affected by the randomness brought by quantum physics? Are the neurons in the brain affected?
@@BobJones-dq9mx Afaik, mutation happens when there is a change in the DNA, so at least a nucleobase (consisting of several atoms) changes. That's not subatomic.
Great episode! My question: When something (e.g. a person) falls into a black hole, crossing the event horizon, would they even survive that? The part of your body inside the black hole couldn't effect the part of the body still outside, so wouldn't it slice you up? Or rather, if you were held in place by a rocket, the lower part would just dissappear into the black hole, if you then fell in completely the two parts of your body would have separated! Sorry for making you read this...
That's the case only for the solar-mass black holes. If you were falling into a supermassive black hole, you wouldn't really notice crossing the event horizon - you wouldn't get spaghettified or sliced up. Event horizon is not a physical thing, nothing special happens there, it is "only" a point beyong which we cannot see from the outside. The closer you would get to the black hole, the smaller radius it would appear to have. Only an observer outside would be able to tell you when you crossed it.
@@Tomas.Malina > The closer you would get to the black hole, the smaller radius it would appear to have. So the event horizon would seem to shrink as you fall in? Black holes get crazier every time you learn more about them xD
@@lordkekz4 yes. That is because if you look from the outside, the event horizon is a place beyond which nothing (matter or light) can escape to reach you. If you were falling into the black hole, light from beyond the horizon would be able to reach you - the more you'd fall in, the more into the BH you'd be able to see. The event horizon is a radius from which light can escape to infinity, to a place with zero gravitational potential, if we use the correct terminology. The closer you are to a BH, the lower potential you have. At a certain point, even if you would send a particle out with the speed of light, it wouldn't have enough energy to overcome the potential difference. However, if you were halfway into the BH, the particle (or light) would not need to reach the zero potential, but would only need to reach you. Therefore, more particles farther into the BH are able to reach you and you are able to see them.
As far as spaghettification occurring inside of the event horizon of a supermassive black hole, wouldn't that only happen if the mass inside the event horizon was rather close to being a point mass? I remember from previous videos that you (and most physicists) don't think that a true singularity exists beyond the event horizon. That being the case, wouldn't it be more likely that you'd go (for lack of a better term) *splat* upon impacting whatever form of matter exists inside rather than being stretched?
Solar mass black holes will spaghettify matter near the event horizon because the force of gravity is greater then the chemical bonds holding the atoms together. This isn't true for supermassive black holes because the event horizon is sufficiently far from the singularity. However, as matter approaches the singularity the force from gravity will increase and eventually be stronger than the chemical bonds - ripping apart every single atom from its neighbors (spaghettification). And to be fair each atom goes splat when it impacts the singularity.
There is no need for a singularity in order for the spaghettification to appear. If the "thing" inside the BH is sufficiently small enough, it will create a sufficient gravitational gradient in order for the spahettification to occur (at a certain distance form the "thing"). You would be flattened (go *splat*) only if the radius of the "thing" were large enough so that the gradient is not that prominent. However, it can be assumed that since the density of solar-mass black holes is so large that spaghettification occurs at the event horizon, there is no reason for the supermassive BHs to have a lower density - so the spaghettification will almost certainly occur, only beyond the event horizon and you won't be able to see it from the outside.
hi don, i have a question about a earlier video. you talked about object very close to a black hole at the event horizon, where gravitation is very strong. the light of this object needs a lot of energy in order to leave the vicinity of the event horizon. therefore only blue light (shorter wavelength) would leave it. this makes sense. but what i dont understand is, why a observer would see this object as red and not blue?? the only thing i imagine is, as the blue light leaves the vicinity of the black hole, the wavelength gets stretched, and redshifts. but im not sure about it. thanks
Hi Don, can't figure out even where to send you a question. Hoping against hope I am asking you my question here - my apology if it is too pedestrian: Is cosmological constant and dark energy terms same/identical? It seems that "cosmological constant" term has fallen out of fashion and replaced by "dark energy". If your answer is yes or no -- could why kindly explain why? Many thanks in advance, Boris
Energy is an observer-dependent measurement. If you were to travel at the same velocity and in the same direction that a red-shifted galaxy sending you light is apparently moving, voila, the light would no longer be red-shifted, you’d see it at its original frequency. The lost energy would still be there. We only see energy as being lost because we are measuring from a different reference frame than the emitting galaxy. As long as you acknowledge that you answering from your own reference frame (your only option really), you can just say the energy is lost.
Technically we have finally gotten convincing evidence for an intermediate mass black hole and there are other unverified sources which increasingly seem to hint that intermediate mass black holes do exist. Many of these candidates are surprisingly in the outskirts of their host galaxies which according to models should actually be expected in the case of direct collapse black holes thanks to galactic mergers easily displacing them and the low cross sectional area of interaction for an intermediate mass black hole not yet sufficient for run away accretion if not in the right place at the right time since they are unlikely to come close enough to any stars to actually become active and any that did become active would have already grown into supermassive black holes in the early universe. The one strong candidate that seems highly likely to be one of these black holes is as these models predict in the outskirts of its host galaxy as are the majority of other known candidates the major exception being the still contentious claim for a few thousand solar mass object in orbit around Sagittarius A* though a few alternative explanations exist for that object. Interestingly if direct collapse models hold up there might even be up to a dozen or so of these black holes lurking in the halo or disk of the Milky Way. And there is even potentially a hyper velocity star which traces a trajectory back into the disk of the Milky Way suggesting a black hole in excess of a thousand solar masses. Of course as with everything in science this is just a model which may or may not be true. Only further evidence will allow us to better resolve this question but I think it is still too soon to say they don't exist.
Remind which intermediate black hole you're referring to? There have been so many hints that have been disputed up until now. Do you have a link to the paper?
Suppose we had a superconducting, super strong wire. Could we use it to lower a camera past the event horizon of a supermassive black hole for imagery?
Since the gravity is so strong not even light can escape, I assume it is impossible to create a wire strong enough to resist being ripped apart. Edit: I'm curious though what would happen if it and the camera were infused with unbreakable stats
Information over a wire is carried by electromagnetic wave (photons). It will take infinite time (for the outside observer) for the photons to cross the event horizon.
"Nothing can escape" just means you have to have speed greater than "c" to escape on your own. I dont see reason why you could not. On the other hand you would see just few fotons on the way down and lot of nothing. Vsauce th-cam.com/video/3pAnRKD4raY/w-d-xo.html
Help! We know space time is expanding and also speeding up. But does this also infer that the higgs feild, which permeates all of spacetime, is also expanding?
Do you have a pet theory for what you think happens to matter at "the singularity"? Mine is that it's not a singularity at all, but all of the energy and matter crushed down into a gluon-quark plasma sphere the size of the planck length (LQC scaling actually), where quantum effects are the driving force of activity, but I love how everyone who thinks about black holes for long develops one :D
I’m opening restaurants at CERN and Fermilab and calling them “The Accretion Disk”. Super hot Buffet style food on a rotating central platform. Free spaghetti with entree!
Not one that is absolute. Any reference time is perfectly valid, so you pick the most convenient one and stick with it. In cosmology this is usually a clock that moves with the hubble flow. en.wikipedia.org/wiki/Cosmic_time en.wikipedia.org/wiki/Comoving_and_proper_distances
Question on Hawking radiation: Hawking radiation is the result of a particle - antiparticle pair popping into existence on opposite sides of the event horizon. The antiparticle is within the event horizon and annihilates with the mass-energy of the black hole (effectively reducing its mass). The normal matter particle flies out into the universe and can be seen as radiation. So - why do antiparticles come into existence (in statistically greater numbers) within the event horizon? Intuitively I'd think it'd be 50-50 for which kind of particle came into existence on either side of the event horizon, but then the black whole wouldn't lose mass.. right? Please help me understand what I'm missing - thanks!
Don’t take this answer as authoritative, because I don’t know what I’m talking about, but my impression was that half the Hawking radiation *is* antimatter, and that which is produced doesn’t matter for the purpose of whether the black hole mass is decreased. My understanding is that a black hole made of antimatter would behave in exactly the same way as one made of matter, and would be entirely indistinguishable from the outside.
Hey Logan , the particle antiparticle pair come into existence due to the Heisenberg uncertainty principle, in which there is an uncertainty in energy and time so the particle come into existence due to the certainty in the energy as the uncertainty in the time remains , so they come into existence for infinite time and we could measure its energy but not the time .
Logan , the point at which these particles come into being is the same , it is not different , like if you are in new York and a real particle came there but the antiparticle would also be formed there only not in Texas .............. This is the reason why the black hole loses mass , the pair comes into being and annihilate very quickly but when the antiparticle goes into the event horizon , the real particle is emmited as the hawking radiation , hope it helps
It's best not to think of particles and antiparticles at all in this context; it's a metaphor of sorts (and considering the Hawking radiation is almost exclusively electromagnetic and photons are their own antiparticles, not a very good one). A different metaphor (also imperfect) is identical waves out of phase. YMMV
@@davidklang8174 Wait, Hawking radiation is mostly photons?! That doesn't make sense for the conservation of quantum numbers. Please elaborate (or point me to a book or lecture).
Isn't it that case that with a supernova the outer layers of the star 'bounce off' the inner layers due to a density difference when the gravitational collapse takes place, instead of them 'boiling off' due to the heat or am I wrong with that statement?
Spaghettification is easy to understand for photographers, it is similar as when you take a photo with strobe or other artificial light, if you are near light source falloff is great - e.g. nose exposure is serveral stops higher than ears, if you are far away from the light source exposure falloff is small. It was explained less understandably - massive black hole has Schwarzschild radius far away thus smaller falloff. I was confused why even Schwarzschild radius was used for Spaghettification explanation.
Two questions: 1) when two black holes get close to merging , shouldn’t there be a point between them where the gravitational pull balances? A point that otherwise would have been inside the event horizon? And 2) going back to quarks - how do we know quarks exist if they can never exist independently from each other?
@@drdon5205 Thanks! What is the reason? Are the orbiting frequencies too low for those? Or are they extremely unlikely events over the distances we can detect?
Another good video. Thanks for keeping this series going! Question - Is relativity relative or absolute? What are the relativistic effects at the Lagrange points? Have the atomic clock experiments been tried with a weight suspended above them?
Well, relativity is "absolute" as in we assume that it applies in the same way everywhere, because if physics itself changed depending on your location, then we could not know what it is like outside of the area, unless there is a universal way to describe how it changes, which would then be the deeper physical truth and therefore wouldn't change.
@@matteodelgallo1983 You obviously failed to understand my question. I blame myself for not wording it more clearly. Do relativistic effects depend on the absolute energy levels, or the gradient?
Question : Can you talk about pilot wave theory and and make a video about it and what are the new discoveries in this theory today in 2020 ? Please answer me
Pilot wave (developed in the 20's), has been largely abandoned, but there is a more modern version, the de Broglie-Bohm theory, which i think I recall PBS Spacetime did a great video on :)
Sir, most space-time diagrams for black holes are formed using geodesics, but according to second law of thermodynamics, doesn't these break causality ?
I have a question since light is a collection of fotons and when it reflect on object how it takes information about it in which forn taking into consideration that foton has no mass how a massless object carry something and it stay without a mass?!
Vsauce did a video with Adam Savage about the brachistochrone which mostly answers your question. It relies on snells law and the way light refracts in order to travel the quickest
Adarshvir Singh Light travels in every directions. Please see the double-slit experiment. Light is basically the energy which is released when the electron returns to a lower “orbit” (which is a lower energy state) around the atomic nucleus.
@@sahilsekhon8335 US has better universities. Better than Canada. Physicists work at telescopes, LIGO, CERN, they research and publish their papers solve mysteries and equations, make new theories etc And I'm sure you know what professors do.
Maybe the total energy of the universe is 0. No need for a source, just positive energy locked up in matter and light and negative energy locked up as potential energy in gravity. No need for a source if the total is 0.
For outsider observers, we that pass event horizon of BH may be dead, but from our frame of reference, we still alive and safely entered the event horizon. I have read a theory that explain it like that.
Question on event horizon for supermassive black holes:. If the difference in gravity is not so great near the event horizon of a supermassive black hole, what would happen if someone put a camera at the end of a stick from outside the event horizon and push it beyond? Would they be able to retrieve the camera using the stick and what it has recorded?
>>Would they be able to retrieve the camera using the stick and what it has recorded? No. Once you pass the event horizon you can't get out. Also, you would not be able to maintain a position just outside the event horizon without a lot of effort. It would not be a stable orbit.
Don used a formula from Newtonian gravity, it's not right near the horizon. You need to use en.wikipedia.org/wiki/Proper_acceleration which becomes infinite at the horizon, so a difference between some finite value outside and the value at the horizon is also infinite. Which just shows it's impossible for a massive body to stay at the horizon.
Question In black holes the accretion disk increase the temperature and causes materials to electromagnetic radiation. Why does this phenomenon ocures and why do these oscillation exist
Do you mean why do hot things radiate? Because the charged particles in them move back and forth in various ways, depending on the temperature. Roughly speaking; The higher the temperature the more energy the particles have and the more they move apart, but they are held together by atomic bonds and such so they move back together again, so they oscillate. And oscillating charges create electromagnetic radiation. Or do you mean why does the accretion disk heat up? Because the matter speeds up as it is pulled towards the black hole and orbit it. Fast particles bounce against each other. This basically creates friction and thus heat.
Sir , in the merging of the black holes , the total mass of the new black hole is not the integral sum of the masses of the other two black holes , why does this happens , does the mass is released in the form of energy which is blown off in the form of gravitational waves ?!
Isn't the temperature of space also to do with the temperature which an object, when left in space will tend towards? I believe it's the same temperature but it's a slightly more intuitive perspectove on it.
Yes, in a universe without stars or hotter things to radiate more energy on to the object the temperature should be that of the CMB. Without the CMB and all else I'd expect the temperature to as near as possible to 0 K.
Next week, can you talk about the generations of matter? How sure are physicists that there isn't a generation below the up/down/electron generation, or one above the top/bottom generation? How do we know?
Hi Don, great content, as always. Me and my cats are a huge fan of your vids. I have a question related to black holes and the information paradox. I understand the problem is that Hawking radiation is random and thus cannot carry information. But what about the remnant of the black hole after the evaporation? When the evaporation reaches a point where the black hole collapses then it surely happens in a unique way, right? And that unique explosion could actually convey information about what was in the black hole and thus no paradox exists. Whats your view on this? Thanks, Bence
And physics is awesome.. and also want my son to take a look in experimental physics.. he likes to watch an educative cartoon 'fiksiki' (made by Russians and translated.. awesome! Highly recommended) and reproduce their ideas.. sounds like a profile? 😁
The bursts of energy you're talking about are caused by energy falling towards the black hole that then create magnetic fields which then guides some of that matter towards the poles and outwards. The result is two jets of matter that shoots outwards, made by matter that never got in the black hole.
Dr. Don, some time ago I read that in the early days, the event horizon of a black hole was considered to be the singularity, this was derived from the equation. This later turned out to be a mathematical error. Event Horizon being the singularity actually sounds very compelling to me, and this raises my question: Do you know of this error, and can you explain it? Thank you so much, in advance.
A coordinate singularity (not a physical one) does in fact happen at the event horizon. It is avoided by changing the coordinates being used. A coordinate singularity is something like trying to continue moving north when at the North Pole. Move where you say the poles are and you can continue. Maybe this is where you got the event horizon singularity idea.
@@cloudpoint0 No, it was inspired by something else. It had to do with how time dilation will cause the infalling, indestructible observer to never reach the event horizon, IN NEITHER cases, not local, nor remote frame of reference. Why do I think this? because of hawking radiation, the black hole has a life span in our spacetime. The infalling observer will see the universe around him evolve into infinity as he reaches the point where spacetime inflow reaches c. That also means the event horizon will shrink before his very eyes, his time dilation will enable him to outlive the black hole. The black hole will have blinked out before he reaches the point of no return. Or is my thinking flawed?
@@paulmichaelfreedman8334 I’m not quite certain what you mean by “spacetime inflow reaches c”. Spacetime is understood to be static. It’s probably poetry that means the gravitational field is extremely curved such that an object within it falls reaching and even passing c relative to flat outside space. But one can also slowly drift across the event horizon and travel to the center of a black hole at a relatively leisurely pace, perhaps drifting much of the way if the gravitational field is very gently curved, at considerably less than c anyway. It can take from milliseconds to a few days to travel to the center of a black hole in internal time, depending on the temporal extent (mass) of the black hole. But let’s forget about this. Read web.stanford.edu/~oas/SI/SRGR/notes/SRGRLect6_2007.pdf if you want to dig deeper ...“So even though you observe objects moving at different speeds through space, they are all moving at the speed of light through spacetime.” … “Every second your clock ticks, you have moved 3 x 10^8 m from where you were before.” If there is a flaw in what you said, it is that time dilation is a phenomenon perceived mainly by a distant observer watching the in-falling, indestructible observer, and not much by the latter. The in-falling, indestructible observer is seen to fade to red and then to black in probably a few seconds. Sharp distant infrared, microwave or radio eyes might see a shadow impression of him for some time afterwards but not for very long. Time dilation happens because the different reference frames due to extreme gravity make the speed of light seem quite different at the two vantage points. For the in-falling observer the dilation effect between his current position and the event horizon disappears as the black hole is approached, as both occupy the same reference frame. He perceives nothing special about crossing the event horizon (if spaghettiification is not a factor). Perhaps if the in-falling observer somehow stopped falling and hovered for a long time just outside the event horizon, then things might be somewhat as you describe for him. I’m less knowledgeable about this scenario.
@@cloudpoint0 But does the observer falling in, not see the universe blueshifted and aging with a speed increasing logarhythmically to infinity? let's say we have an outside observer who is immortal and keeps watching and watching...let's say he watches the black hole for a googol years. By that time the infalling object still hasn't reached the event horizon (let's say we a magical device that can tell us what the position is of the object as it approaches the event horizon), as time dilation is infinite at the event horizon. But by that time the black hole has also evaporated. In other words, he will see the black hole evaporate over that period of a googol years, see the event horizon shrinking as the object slowly catches up with it, but slower and slower , asymptotically. These events must also be experienced by the infalling object, with the only difference being the time elapsed in the event. for the infalling, maybe a minute or so, for the outside a googol years.
@@paulmichaelfreedman8334 I suppose an observer falling in theoretically sees the universe blueshifted and rapidly aging, at least until he crosses the event horizon. The observer is entering a zone of very slow moving time near the black hole while the rest of the universe runs at it normal quick pace. In practice what he sees looking back when still outside is the universe collapsing into a small blue dot surrounded by blackness. My understanding is once you cross the event horizon, nothing that is still outside is visible to you anymore. I believe this is because all directions are down once inside. You can’t look up or out. You might see light that fell in after you passing by. What you said about the forever watching outside observer agrees with what I said earlier for the distant observer. Except fewer and fewer photons would be received over time by the watcher, each one farther separated in time, which is perceived as red shifting and fading to black by the watcher, effectively a slow motion video clip. Since the watcher has near infinite patience I think he would see one second-to-last photon a billion years before the black hole evaporates, and then see the very last photon just prior to it evaporating a billion years later. In practice the watched object would become invisible after a short time. Time dilation is not quite infinite at the event horizon, it’s a bit less. Infinite time dilation means time stopped completely and that can’t happen. If by experienced you mean the elapsed time to fall in was exceptionally long in outside terms although brief to the object, that’s true. They both experienced it differently though. The outside observer never sees the object actually fall inside while the object does actually fall inside, and in short order according to the clock it carries. It’s not crossing the event horizon just before the black hole fully evaporates, although the observer might have this impression. More info at link below: “Believe it or not - despite the fact that we’re talking about an event horizon that might be around a light-hour in diameter in our reference frame - it would only take around 20 seconds to reach the singularity once you crossed the event horizon. Severely curved space sure is a pain!” www.forbes.com/sites/startswithabang/2018/01/19/what-would-you-see-as-you-fell-into-a-black-hole Animation: th-cam.com/video/JcHneuh6DKo/w-d-xo.html
@@bozo5632 indeed. But thats not the question. Im sorry if i didnt make clear: what does it take to make it explode? It's a question ive had trouble with for a long time. And a question i never see asked/answered. Any insight is appreciated.
@@patrickaycock3655 It can't explode. Anything that happens inside always falls further inside. The escape velocity at the horizon exceeds the speed of light, so nothing can escape. Very energetic things can happen on the outside as stuff falls in, so you can get light and x-rays and high energy particles spewing out of the accretion disc - more energetic than a zillion nuclear bombs - but that's on the outside, made of stuff falling in. The black hole just gets bigger. Theoretically Hawking radiation will very, very slowly fizzle away a black hole. When they get very small, like the mass of just a mountain, but smaller than a grain of sand, they fizzle away faster and faster, and then much faster, until they're gone, which is pretty much the same as exploding. To make that happen you only have to wait trillions of trillions of years for the universe to cool down to almost zero so it can start fizzling, then wait trillions of trillions more years while it shrinks, then - presto! It blows up. Easy as that.
@@bozo5632 firstly, i agree with most of what you said. I am aware of how they work. The only thing i disagree with is the cant explode part. We have never tried to make one explode. I guess another way of looking at the question, is what will it take to spontaneously rip a black hole apart? And as far as i know, they warp spacetime, which is fancy for stretching and compressing. Since no one has been in or near one yet, it is my understanding that space inside a bh is kinda like a pocket dimension, with infinite room to grow but has a limited size. In other words, the space below the horizon stretches out for infinity (no data on expansion rate), making it extremely difficult if not highly improbable, that classical explosions would not work. Taking a classical approach, we would assume a "bomb" be placed inside the bh and detonated. But as you pointed out that idea wont work, as far as we know. This is still theoretical. And id like to say thank you for responding.
Thank a lot Dr.Don, my ambition was to become a Theorist, but I changed the decision and taking Expirimental Physics but I was confused. Btw can you recommend a good book on *particle* *physics* .
I recently found an article on mirror matter (as a candidate for dark matter), and although I didn't came close to understanding it, it reminded me of supersymmetry's proposed cousin particles. Are they the same, or we could have a bunch more layers to the standard model?
When you're fusing light elements, the mass of the two lighter elements is larger than the mass of the final product - eg. when you fuse two deuterium (2H) nuclei (mass 2.014 au) into a 4He (4.003 au), you have "lost" the mass of 0.025 au. This mass that you lose is converted into energy (by Einstein's equation for mass-energy equivalence, E=mc2). This is why nuclear fusion is able to generate energy (ie. why the sun is hot and emitting light). Once you get to heavier elements like iron, combining two 56Fe (mass 55.93 au) into an element with 112 nucleons (would be likely 112Cd, mass 111.90 au), the mass of the product is larger than the combined mass of two iron atoms (by 0.04 au), therefore you'd have to add energy in order to compensate for the increase in mass. Therefore, since this reaction isn't exothermic, it stops (it would need a constant supply of energy in order to run). This is also the reason why for heavy elements, energy can be gained from them by fission instead of fusion - in a nuclear power plant, uranium (235U) is split into lighter elements while energy is released, because the combined mass of the products is smaller than the mass of a 235U isotope.
An intuitive way to see why fusion can't go forever is to remember that inside a nucleus you've got two opposing forces: electromagnetic force tries to push protons apart but residual strong force tries to bind them (and neutrons) together. However while EM force is long-range, the residual strong force is short range. So a proton can push away other protons via EM force even when they are far, but it can only attract other protons and neutrons via the strong force when they are near. When the nucleus is small the strong force takes over and will gladly accept more protons/neutrons into the nucleus, they just need to pass the barrier created by the repulsive EM force. When the nucleus becomes big, each proton/neutron can only attract a limited number of neighbors but the repulsive EM force is felt from all the protons in the nucleus. So in a large enough nucleus EM force takes over and will gladly throw away protons, they just need to overcome the limited energy barrier created by the strong force. This imbalance between attractive strong force and repulsive EM force makes small and big nuclei behave differently in terms of fusion & fission.
I would prefer to be the Experimental physicist. I've always like building things and the challenges to make them work and to improve on the original design. The ITER project is right down my alley.
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I heared that a massless quark could explain the strong CP symmetry, could you make a video about that? In my mind, it would be basically indetectible, right? Every process that could generate a massles quark/antiquark pair would make them annihilare instantly because they are massless.
Question about black holes, as you cross the event horizon, is all matter disintegrated? Molecules are held together by bonds, but as one atom crosses over, the bond would lose connection with the atom on the other side of the horizon. Maybe the same happens even with quarks and the strong force, so that every particle that crosses over becomes unbound. But with a super massive blackhole, the gravity changes so slowly, so Im not sure what to think.
Only if you try to hover there (which implies near infinite g-force, which becomes infinite at the horizon). If you're free falling, the horizon passes you by with light speed, so inability of signals from your lower parts to reach the higher parts through the horizon are just the ordinary inability of signals to outrun speed of light. Bonds should not break. In other words, your higher parts will follow the lower parts quickly enough so that signals from the lower parts won't have to cross the horizon to reach them.
The event horizon doesn't exist unless all the mass is compressed into the Schwarzschild radius. It doesn't lurk beneath the surface and if you dig down to it you're inside a black hole. A black hole is a completely distinct state. But the line where the horizon would be exists for every object. The earth's "phantom horizon" is a sphere of around a one centimeter radius at its center.
Thank you Sir for giving us knowledge, I am always fascinated by astrophysics and particle physics though I am an engineering student I would love y to work in this fields
I have a couple questions concerning observational physics and black holes. With all the talk about the possibility (though slim) of "Planet 9" actually being a small black hole, what type of experiments could be performed by a New Horizons sized craft if we sent it to explore a black hole in our own star system? Are there any unanswered questions that such a voyage could answer for us?
An intermediate black hole was recently observed, contrary to Don's claim. Unexpectedly, it was located outside a small galaxy, not at the center of a small galaxy. Astronomers always looked for intermediate black holes at the centers of small galaxies, since the centers of galaxies is where supermassive black holes have always been found and the well-established pattern is that the mass of a supermassive black hole is proportional (roughly speaking) to the mass of the galaxy around it. It should also be noted that a fourth type of black hole has been theorized: primordial black holes created at the big bang, small enough that most would have already evaporated if Hawking's theory about black hole evaporation is correct.
Dr. Lincoln, as always you present the best science channel of all. Thank you.
You are a wonderful Science communicator Don. This channel on TH-cam will definitely inspire the next Generation of curious minds.
Oh yeah, it's fermilab time
Spoken in a Randy the Macho Man Savage voice.
@@johngrey5806 Damn.. would love to see that :D
Oh yeah, snap into a Fermilab!
I'm reading an excellent book on anti-gravity. I can't put it down.
Would you like to share the title?
@@paulellis2518 Certainly. It's called "Falling For It."
@@richtalk34 thanks a lot!
😂🤣😂 Good one.
I am watching a fascinating documentary about a down syndrome squirrel. I made it... it's on my channel...
Another great show, thank you. Now for a suggestion / request. I'd love to see "A day in the life" style show.
A show where you show us what one of these experiments actually looks like at FERMILAB. The warts and all theory behind the experiment, the actual experiment and the hours of what the data looks like before those incredible brains make sense of it.
Thanks for the weekly videos Don. They are very much appreciated.
Dr.Don, thanks for fully explaining what is meant by the concept "temperature of space".
Amazing episode as always.. thank you Doc for putting in all the effort for us mortals..
Physics as we know of it right now leads us to believe that the time exists because of gravity.. however in ancient indian physics books we've been given to understand that gravity is a curve, a bend in time and exists only cuz time exists..
Would be great if you could pls reflect upon the idea and some ramifications of the same.
Thanks for the lovely stuff!! :)
Can you please tell which ancient Indian physics book it is ? Just curious
Was this book about Achilles and the turtle and the chicken and the egg, where they race, and the question was which one came first?
@@preethiyogesh9821 try vaisheshika sutras by rishi kanad or listen to sadhguru jaggi vasudev on TH-cam abt yogic opinion on creation
@Goofy Gangster thanks for sharing information ,please do mention other physics related ancient Indian books ,interested in finding out 🙏
Thank you for this amazing series professor!!
Question 1: How the supermassive blackholes were formed in the beginning of the universe ?
Question 2: Supermassive blackholes present at the centre of radio galaxies become active when they burp after eating matter from accretion disk, but this is not a continuous process, Why??
1. They seem to have grown from smaller black holes. This is evident from a fact that quazars (active galaxies with smaller central black holes) can only be seen in early universe. As for where the original "seed" black holes came from, that's the big question. They could've formed from mergers of early stars and their remnants, but if so, it's unclear how they could've grown so fast.
2. The "burp" in question was short on universal scale, but it was most definitely continuous and long process.
KohuGaly The leading theory these days is NOT smaller black holes, as we didn’t have enough time for so many mergers. Instead, it is likely that in the early eage of the universe, the densest parts of the universe has collapsed straight into black holes, skipping the star-phase. Less dense parts became stars.
Dr Becky had an episode explaining all these hypotheses recently.
@@juzoli Yeah, probably.
Question 1: This is currently an unsolved mystery which scientists have yet to resolve. Regardless we have evidence of quasars when the Universe was only half a billion years old so they had to grow very fast too fast for them to grow to their masses via accretion alone. They might have formed by direct collapse, over dense star clusters, extremely massive Pop III stars and or by frequent black hole merger events or other mechanisms we haven't even thought of yet.
Question 2:The reason the process isn't continuous is due to multiple reasons first to accrete matter you need more material falling in on the black hole however the radiation and outflows of ejected material from the accretion disk has the potential to heat up the in falling material preventing it from infalling further or forming new stars via a process known as quenching. This is more of a thing in the later universe since the black holes have largely consumed all the gas and dust around them. In this case further accretion depends on something new falling in say a new supply of gas via a galaxy merger, a tidal disruption event etc. basically the answer is that after the quasar epoch ended black holes largely ran out of "food" when a new "meal" arrives they then begin to flare up again until they exhaust their new supply of material
Hi Don! Do you think that we as a species have enough data and know enough phenomena to derive a theory of everything if only someone looked at things the right way, or do you think we are missing critical pieces of the puzzle that will keep an answer out of reach until we observe them? Where in between those two extremes do you think we are, and what are some of the more promising lines of investigation going on today to find the missing pieces and/or reinterpret the existing data?
Hi, another week, another question.
If a black hole makes us loose information how does it work with entangled particles?
Say I have two photons entangled so knowing one's polarization I also know the other one's.
But if that one falls into a black hole, shouldn't these properties get "lost"?
To me it sounds like I could have additional information about the interiours of a black hole that way.
Is that possible?
Entangled particles should remain entangled in the situation you describe. You have no information about the BH interior though, just like you would have no information about the environment of any entangled partner that is far away. Entanglement does not convey information between partners. It’s just a known correlation.
You just described how Hawking came up with his idea for Hawking radiation. 😊 And the last part of what you are saying is called the black hole information paradox. Fascinating material to read up on. Kip Thorne, Leonard Susskind and Hawking all had bets about the resolution to this over the last couple of decades.
@@cloudpoint0 What I mean is, consider I would create a black hole only consisting of these entangled particles. I then would have knowledge of these properties, too. (Except in case their polarisation, spin or what ever would get lost)
But I understood black holes won't have these kind of properties, which leads me to the assumption that it can get lost. But how, aince they are entangled?
@@ebenolivier2762 Isn't Hawking radiation something different? Like the emission from the black hole?
What I meant to ask was the conflict of a) knowing properties for sure since particles are entangled and b) the definition that a black hole doesn't have any of these properties (any more)
davidgreenwitch Hawking radiation is indeed an emission (radiation) from the black hole. You are delving into very deep and technical territory with your very good questions. 😊 For a very long time the information loss in a black hole could not be reconciled with quantum theory. The holographic principle by Susskind and t'Hooft seems to resolve this, but then there was the firewall problem...
Thanks for the back story Don that was awesome! The predictive power and precision of science persuaded me
I would like to see the math for why no energy is gained by fusion after iron.
I do have a math degree but i lack the physics knowledge to even guess where to look.
courses.lumenlearning.com/physics/chapter/32-5-fusion/
Iron is the most stable nucleus. Below iron, moving to a heavier element releases energy (e.g. fusion). Above iron, moving to a lighter element releases energy (fission).
Look at figure 2 in the link.
Basically, iron and nickel are about tied for the highest atomic bonding strength, so it takes more energy to break them apart than you get out of the reaction. It becomes a pure deficit for energy returns, in addition to being harder to make happen in the first place.
Think of degenerate solutions to a set a equitions, continuous or discrete, does not change the concept. In chemistry degenerate solutions are common both litterallyI in experiments for example in isothermal reactons even when isolated from the environment. But also theretically, many molecules have or materials have degerate states..meaning.. yes, something changed but no energy was used to expelled from or in the system volume.
Same goes for quit a handfull of particles near irons most common isotope. They are indifferent/degenerate in requiring energy or expelling energy to/from the surroundings. The optimum is at iron Like DrDon pointed out. And thus there is sort of an optimal energy drainage going on toward that iron region. But nickel will be also present but much just less so.
But just like in more mundane stuff like atoms reacting etc there is a spread at least spanning several kT worth of energy when transitios/reaction are possible. Constantly switching between electonvolt and joules/mole and wavenumber and wavelenght euiqvalents to make sense..I prefer electronvolts actually in thinking about stuff happening step based, and joules are awesome for bb guns haha and more macro scale. Really it does not matter. it is the whole range that makes it interesting.
In nanomaterials, when making particles with a certain size it is possible to get them from the ge- go almost exactly at e.g. 10 nanometer... but yeah, that just means the peak is at 10 and drop extremely fast either smaller particles or larger, still when examining there you will find the oddball 5 nanometer weirdo. Representing also a extreme outlie-er in "effective melting temperture". For example..god will melt with ease at ~200 if small enough. weird. not really. Cool, yeah.
I come from a more nanomaterials background, so im never able to put my finger how to feel a chemist, experimentalist, psycisist or more generalally, scientist.
After all, science is everything, including phsysics and why not phylosophy while were at it.. PhD anyone ? ;p
I must be bored.
Great video Dr Don.
YCCCm7 Soooo... since the pressure and temperature is still quite high when iron starts forming, would it be more accurate so say that iron fusion happens but sucks up energy, so that the core basically cools down and looses pressure?
@@drdon5205 His question was WHY anything heavier than iron will fission with energy release, and lighter than iron will fuse with energy release. There's a QM rule somewhere explaining this, although I recently pondered this question myself but haven't looked it up yet although it know it has to do with the total binding energy (strong force interaction) within the hadron.
4.40 In which orientation do we look on the black hole?
Why is the upper right of the picture dimmer?
Gravitational lensing, the what you see at the top is actually the accretion disk that is behind the black hole. With the light bent around the BH.
8:58 , sir don said that matter when have a temperature of 2.7 Kelvin would emit radiation in the form of radio waves , so sir if we have a object which has a temperature of about -270.45°C which is equal to 2.7 K , then it would also be emmiting radio waves ??
That is exactly what will happen. Every object emits thermal radiation (black-body radiation, described by Planck's law). Depending on the temperature, the frequency of the radiation changes - for cold objects the emitted frequency is low and increases as the object gets hotter (so called Wien's displacement law). To be more accurate, the emitted radiation is a spectrum of frequencies - for an object that has the temperature of 2.7 K, the peak wavelength of the emitted radiation is at 1.1 mm, but many other wavelengts are emitted as well - starting at approximately 0.25 mm and going to approximately 10 mm. The most of the emitted energy is what we call radio waves (1-10mm), some of it is infrared (0.25-1mm).
@@Tomas.Malina thanks , I wanted to be sure that if radio waves would also be emmited from an ice ??
That was an unexpectedly thorough explanation about the temperature of space. So I guess when physicists refer to the temperature of space, they just mean the (current) temperature of the cmb. The temperature of the photons black holes always absorb and thus they can’t leak energy until the cmb cools off some more. Thanks!
You put a smile on my face, Fermilab ;P
At 9:22 you start to discuss theoretical vs. experimental physics considerations for Swapnil Kumar who currently appears to be studying engineering. I have another suggestion. It was about 40 years ago when I graduated, but I studied engineering physics. At the end of that course you could do further studies in various engineering disciplines, experimental or theoretical physics. I found it to be a great course for those who were not sure which way they wanted to go when starting university, and my classmates took a variety of paths. Considering that one that took the pure physics route won a noble price for her work, this certainly was not a path that result in limited opportunities for those that chose physics over engineering after undergrad work was complete.
My question was not replied in this video. Can we observe radiation from a stationary charge when we are accelerated. If we can observe, then we should feel a retarding force due to loss of energy as radiation. Whether it is tested in lab.
This statement and queston contradicts it self let me explain why. You say stationary, but can it give off radiation. This means the object or particles are not stationary and are in fact moving at the speed of light because radiation is light. Having no movement would be zero kelvin. Something believe to be unreachable.
would a black hole made of anti matter be any different than one made of regular matter? would any of them behave different if they suck the opposite kind of matter that made them?
Thank Don for this nice and illuminating series! Thanks for the answers to the many questions too! Cheers, Eddy.
Plot twist -- "subatomic stories" videos about black holes lead to a theory of everything
I'm in! You go first. :)
If you want to get is a submarine and shrink down to donsurgery knside slmeone, is it easier to shrink the atoms or should you just use very tiny atoms?
I wish I could go back and do grad school, but I cant so it's so nice to have channels like these.
Can we use black holes as a kind of ultimate heat sinks, dumping excess heat into them?
Stanislav Vladimirsky Don’t give AOC any ideas...
@@john-or9cf Pushing "trash" into a "black community"? She'd hate it.
And make the trash can bigger till it's too big
Sure, you put the heat inside penne, throw it into black hole and the heat is gone as soon as pasta turns into spaghetti
14:55 "It's both unpleasant, and lonely." 😄
Yes that one nearly made me piss my pants.
Hi Don! if a single photon is bombarded at a microscopic black hole before it evaporates, will we get a stable (or rotating) black hole with increased mass & an accretion disk, which will devour the particle accelerator (& the planet ) OR the photon trapped will be emitted as Hawking Radiation instantly OR what ?
Whatever a black hole consumes is competing with Hawking radiation losses, and what matters is which one predominates over the long haul, so a single photon would just delay the completion of evaporation by a short time.
Hi Don,
what's your opinion about what's happening to the things beyond Schwarzschild radius? How do you imagine the interior of a black hole? Like matter being squeezed up to Planck density as written here arxiv.org/pdf/1401.6562.pdf or if you have some cool scientific hunch. Or if you simply think "we'll see". Or something inbetween?
Thank you.
Hi Don! Is there any difference from the point of view of the rest of the universe between a virtual electron/positron pair appearing & annihilating near an event horizon (neither going in) vs a pair appearing and both falling in before they annihilate? Sorry for double questions if that's not polite!
Hi Don, one Question? As a high end physicist, are you able to solve mathematical problems such as a simple fourier transformation or laplace to a really reaaaaally hard integer without using symbolab or something like that
Some. And smart physicists can do much better.
Question?? Is there a connection with particle physics and organic matter?
Same connection as between the alphabet and a novel.
Bob Jones I would rephrase this question.
If I bounce a ball, obviously it is also governed by quantum physics in the end. But I can calculate it’s future path without it, because quantum physics doesn’t cause any meaningful difference.
An interaction with a photon is greatly dependent on quantum physics, as we can see in the double-slit experiment. We NEED quantum physics to calculate where it will hit the wall.
Organic matter is obviously between those 2 extremes. Does quantum physics (like Heisenberg uncertainity , quantum tunneling, etc) really affect organic life? Does DNA copying in the cells affected by the randomness brought by quantum physics? Are the neurons in the brain affected?
@@juzoli WOW! Thanks for the question!
@@thedeemon Would you agree that when a sub-atomical particle shifts in organic material , then a mutation in the organic matter occurs?
@@BobJones-dq9mx Afaik, mutation happens when there is a change in the DNA, so at least a nucleobase (consisting of several atoms) changes. That's not subatomic.
Great episode! My question: When something (e.g. a person) falls into a black hole, crossing the event horizon, would they even survive that? The part of your body inside the black hole couldn't effect the part of the body still outside, so wouldn't it slice you up? Or rather, if you were held in place by a rocket, the lower part would just dissappear into the black hole, if you then fell in completely the two parts of your body would have separated!
Sorry for making you read this...
Correct.
That's the case only for the solar-mass black holes. If you were falling into a supermassive black hole, you wouldn't really notice crossing the event horizon - you wouldn't get spaghettified or sliced up. Event horizon is not a physical thing, nothing special happens there, it is "only" a point beyong which we cannot see from the outside. The closer you would get to the black hole, the smaller radius it would appear to have. Only an observer outside would be able to tell you when you crossed it.
@@Tomas.Malina
> The closer you would get to the black hole, the smaller radius it would appear to have.
So the event horizon would seem to shrink as you fall in? Black holes get crazier every time you learn more about them xD
@@lordkekz4 yes. That is because if you look from the outside, the event horizon is a place beyond which nothing (matter or light) can escape to reach you. If you were falling into the black hole, light from beyond the horizon would be able to reach you - the more you'd fall in, the more into the BH you'd be able to see.
The event horizon is a radius from which light can escape to infinity, to a place with zero gravitational potential, if we use the correct terminology. The closer you are to a BH, the lower potential you have. At a certain point, even if you would send a particle out with the speed of light, it wouldn't have enough energy to overcome the potential difference. However, if you were halfway into the BH, the particle (or light) would not need to reach the zero potential, but would only need to reach you. Therefore, more particles farther into the BH are able to reach you and you are able to see them.
Does spaghettification also happen near Neutron stars and White dwarf stars?
No. The gravitational field doesn't change rapidly enough.
THANK YOU PROFESSOR LINCOLN...!!!
Waiting for the new updated physics...!!!
As far as spaghettification occurring inside of the event horizon of a supermassive black hole, wouldn't that only happen if the mass inside the event horizon was rather close to being a point mass? I remember from previous videos that you (and most physicists) don't think that a true singularity exists beyond the event horizon. That being the case, wouldn't it be more likely that you'd go (for lack of a better term) *splat* upon impacting whatever form of matter exists inside rather than being stretched?
Solar mass black holes will spaghettify matter near the event horizon because the force of gravity is greater then the chemical bonds holding the atoms together. This isn't true for supermassive black holes because the event horizon is sufficiently far from the singularity. However, as matter approaches the singularity the force from gravity will increase and eventually be stronger than the chemical bonds - ripping apart every single atom from its neighbors (spaghettification). And to be fair each atom goes splat when it impacts the singularity.
There is no need for a singularity in order for the spaghettification to appear. If the "thing" inside the BH is sufficiently small enough, it will create a sufficient gravitational gradient in order for the spahettification to occur (at a certain distance form the "thing"). You would be flattened (go *splat*) only if the radius of the "thing" were large enough so that the gradient is not that prominent. However, it can be assumed that since the density of solar-mass black holes is so large that spaghettification occurs at the event horizon, there is no reason for the supermassive BHs to have a lower density - so the spaghettification will almost certainly occur, only beyond the event horizon and you won't be able to see it from the outside.
Another excellent tutorial!
You showed the first picture of a black hole. It got me thinking. In your opinion, what are the most significant or important photos in physics?
hi don, i have a question about a earlier video. you talked about object very close to a black hole at the event horizon, where gravitation is very strong. the light of this object needs a lot of energy in order to leave the vicinity of the event horizon. therefore only blue light (shorter wavelength) would leave it. this makes sense. but what i dont understand is, why a observer would see this object as red and not blue?? the only thing i imagine is, as the blue light leaves the vicinity of the black hole, the wavelength gets stretched, and redshifts. but im not sure about it. thanks
You nailed it in your final sentence.
Thank you for giving your time and energy.
Hi Don, can't figure out even where to send you a question. Hoping against hope I am asking you my question here - my apology if it is too pedestrian:
Is cosmological constant and dark energy terms same/identical? It seems that "cosmological constant" term has fallen out of fashion and replaced by "dark energy". If your answer is yes or no -- could why kindly explain why?
Many thanks in advance, Boris
Since the expansion of space is increasing the wavelength of radiation and reducing the temperature, where does that energy go?
Lost. www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/
@@thedeemon I wouldn't say lost but added into entrophy.
Energy is an observer-dependent measurement. If you were to travel at the same velocity and in the same direction that a red-shifted galaxy sending you light is apparently moving, voila, the light would no longer be red-shifted, you’d see it at its original frequency. The lost energy would still be there. We only see energy as being lost because we are measuring from a different reference frame than the emitting galaxy. As long as you acknowledge that you answering from your own reference frame (your only option really), you can just say the energy is lost.
@@cloudpoint0 What about the energy from places that are moving away faster than light due to expansion of space? Is it negative energy now?
@@duggydo you'll never see that light, so why would you describe it as lost?
Technically we have finally gotten convincing evidence for an intermediate mass black hole and there are other unverified sources which increasingly seem to hint that intermediate mass black holes do exist. Many of these candidates are surprisingly in the outskirts of their host galaxies which according to models should actually be expected in the case of direct collapse black holes thanks to galactic mergers easily displacing them and the low cross sectional area of interaction for an intermediate mass black hole not yet sufficient for run away accretion if not in the right place at the right time since they are unlikely to come close enough to any stars to actually become active and any that did become active would have already grown into supermassive black holes in the early universe.
The one strong candidate that seems highly likely to be one of these black holes is as these models predict in the outskirts of its host galaxy as are the majority of other known candidates the major exception being the still contentious claim for a few thousand solar mass object in orbit around Sagittarius A* though a few alternative explanations exist for that object. Interestingly if direct collapse models hold up there might even be up to a dozen or so of these black holes lurking in the halo or disk of the Milky Way. And there is even potentially a hyper velocity star which traces a trajectory back into the disk of the Milky Way suggesting a black hole in excess of a thousand solar masses.
Of course as with everything in science this is just a model which may or may not be true. Only further evidence will allow us to better resolve this question but I think it is still too soon to say they don't exist.
Remind which intermediate black hole you're referring to? There have been so many hints that have been disputed up until now. Do you have a link to the paper?
I LOVE THIS SERIES!!!!!!!!!!!!!!!
Thank you Doc for this amazing series!
Woww your videos are amazing man, I love them all❤️❤️🙏🙏✨✨
0:52 You can't make energy by fusing elements heavier than I am.
Suppose we had a superconducting, super strong wire. Could we use it to lower a camera past the event horizon of a supermassive black hole for imagery?
Since the gravity is so strong not even light can escape, I assume it is impossible to create a wire strong enough to resist being ripped apart.
Edit: I'm curious though what would happen if it and the camera were infused with unbreakable stats
Information over a wire is carried by electromagnetic wave (photons). It will take infinite time (for the outside observer) for the photons to cross the event horizon.
Yes, but we wouldn't be able to pull the camera back out and neither could the signal travel up the wire.
"Nothing can escape" just means you have to have speed greater than "c" to escape on your own. I dont see reason why you could not. On the other hand you would see just few fotons on the way down and lot of nothing. Vsauce th-cam.com/video/3pAnRKD4raY/w-d-xo.html
Does sphaleron process carryout in the black hole?
Help! We know space time is expanding and also speeding up. But does this also infer that the higgs feild, which permeates all of spacetime, is also expanding?
So, specification occurs at a particular distance from the singularity.
And in Supermassives that distance falls within the event horrizon?
Do you have a pet theory for what you think happens to matter at "the singularity"?
Mine is that it's not a singularity at all, but all of the energy and matter crushed down into a gluon-quark plasma sphere the size of the planck length (LQC scaling actually), where quantum effects are the driving force of activity, but I love how everyone who thinks about black holes for long develops one :D
Kip Thorne says its converted into the warping of spacetime, that there is no matter inside a black hole.
How do I know black holes exist? Because Rush described it on “A Farewell to Kings”. That’s all the proof I need.
I’m opening restaurants at CERN and Fermilab and calling them “The Accretion Disk”. Super hot Buffet style food on a rotating central platform. Free spaghetti with entree!
That would explain my steadily increasing mass.
Pastafarians would like that.
Is there any reference time in universe
Not one that is absolute. Any reference time is perfectly valid, so you pick the most convenient one and stick with it. In cosmology this is usually a clock that moves with the hubble flow. en.wikipedia.org/wiki/Cosmic_time
en.wikipedia.org/wiki/Comoving_and_proper_distances
Wasnt there just a video about a lab tour? Why did it get taken down..
Is it possible that while falling into a black hole, because time moves faster outside of it, you could see the black hole evaporating behind you?
Is a gravitational wave from BHs merge is catastrophic to nearby stars as it carries so much energy?
Question on Hawking radiation:
Hawking radiation is the result of a particle - antiparticle pair popping into existence on opposite sides of the event horizon. The antiparticle is within the event horizon and annihilates with the mass-energy of the black hole (effectively reducing its mass). The normal matter particle flies out into the universe and can be seen as radiation.
So - why do antiparticles come into existence (in statistically greater numbers) within the event horizon? Intuitively I'd think it'd be 50-50 for which kind of particle came into existence on either side of the event horizon, but then the black whole wouldn't lose mass.. right?
Please help me understand what I'm missing - thanks!
Don’t take this answer as authoritative, because I don’t know what I’m talking about, but my impression was that half the Hawking radiation *is* antimatter, and that which is produced doesn’t matter for the purpose of whether the black hole mass is decreased.
My understanding is that a black hole made of antimatter would behave in exactly the same way as one made of matter, and would be entirely indistinguishable from the outside.
Hey Logan , the particle antiparticle pair come into existence due to the Heisenberg uncertainty principle, in which there is an uncertainty in energy and time so the particle come into existence due to the certainty in the energy as the uncertainty in the time remains , so they come into existence for infinite time and we could measure its energy but not the time .
Logan , the point at which these particles come into being is the same , it is not different , like if you are in new York and a real particle came there but the antiparticle would also be formed there only not in Texas .............. This is the reason why the black hole loses mass , the pair comes into being and annihilate very quickly but when the antiparticle goes into the event horizon , the real particle is emmited as the hawking radiation , hope it helps
It's best not to think of particles and antiparticles at all in this context; it's a metaphor of sorts (and considering the Hawking radiation is almost exclusively electromagnetic and photons are their own antiparticles, not a very good one). A different metaphor (also imperfect) is identical waves out of phase. YMMV
@@davidklang8174 Wait, Hawking radiation is mostly photons?! That doesn't make sense for the conservation of quantum numbers. Please elaborate (or point me to a book or lecture).
So does that mean stars orbiting a black hole close enough would be caught in the time dilation effect? Like in interstellar?
Yes, gravitational time dilation
Random statement of the day: thermometer is the velicity tracker for molecules.
Hi Don, What is your viewpoint about Tachyons?
Isn't it that case that with a supernova the outer layers of the star 'bounce off' the inner layers due to a density difference when the gravitational collapse takes place, instead of them 'boiling off' due to the heat or am I wrong with that statement?
Hey Dr Lincoln, Why does gravity effect light, when light is massless; and what is gravity's effect on red-shift?
Spaghettification is easy to understand for photographers, it is similar as when you take a photo with strobe or other artificial light, if you are near light source falloff is great - e.g. nose exposure is serveral stops higher than ears, if you are far away from the light source exposure falloff is small. It was explained less understandably - massive black hole has Schwarzschild radius far away thus smaller falloff. I was confused why even Schwarzschild radius was used for Spaghettification explanation.
Yes, both intensity of light and curvature of space are proportional to 1/R^2, good analogy.
Two questions: 1) when two black holes get close to merging , shouldn’t there be a point between them where the gravitational pull balances? A point that otherwise would have been inside the event horizon? And 2) going back to quarks - how do we know quarks exist if they can never exist independently from each other?
@Dr Deuteron Shiiiiit, you *are* helpful af
@Dr Deuteron thank you.
Hi Don. Do you know what the probability is of LIGO detecting the merger of 2 supermassive black holes? Or maybe after a future upgrade?
Zero. It's outside the facility's capabilities.
@@drdon5205 Thanks! What is the reason? Are the orbiting frequencies too low for those? Or are they extremely unlikely events over the distances we can detect?
@@roanbrand7358 The frequencies are too low.
Wait, what!?!? Behind the doc's shoulder is a book I'm currently in the middle of on the French Revolution ("Citizens") .
is it good?
arcade Quite. Excellent reading for anyone interested in French history.
@@scottmuck Ok, I've been meaning to educate myself about the French Revolution for a while now. Gonna check it out
Another good video. Thanks for keeping this series going!
Question - Is relativity relative or absolute? What are the relativistic effects at the Lagrange points? Have the atomic clock experiments been tried with a weight suspended above them?
Well, relativity is "absolute" as in we assume that it applies in the same way everywhere, because if physics itself changed depending on your location, then we could not know what it is like outside of the area, unless there is a universal way to describe how it changes, which would then be the deeper physical truth and therefore wouldn't change.
@@matteodelgallo1983 You obviously failed to understand my question. I blame myself for not wording it more clearly.
Do relativistic effects depend on the absolute energy levels, or the gradient?
Question : Can you talk about pilot wave theory and and make a video about it and what are the new discoveries in this theory today
in 2020 ? Please answer me
There is a PBS Space time video on that: th-cam.com/video/RlXdsyctD50/w-d-xo.html
Pilot wave (developed in the 20's), has been largely abandoned, but there is a more modern version, the de Broglie-Bohm theory, which i think I recall PBS Spacetime did a great video on :)
Sir, most space-time diagrams for black holes are formed using geodesics, but according to second law of thermodynamics, doesn't these break causality ?
I have a question since light is a collection of fotons and when it reflect on object how it takes information about it in which forn taking into consideration that foton has no mass how a massless object carry something and it stay without a mass?!
can you explain why light travels and what decides its direction ?
Vsauce did a video with Adam Savage about the brachistochrone which mostly answers your question. It relies on snells law and the way light refracts in order to travel the quickest
@@georgel5812 Well you misunderstood the question. I meant why light travels not why it slows down in mediums.
Adarshvir Singh Light travels in every directions. Please see the double-slit experiment.
Light is basically the energy which is released when the electron returns to a lower “orbit” (which is a lower energy state) around the atomic nucleus.
@@juzoli I asked why light travels not what generates photons and how does a photon decide upon the direction to travel in once emitted?
@ *Adarshvir Singh*
Welcome to the internet where questions are always partially answered.
How can one become a theoretical physicist and whats about carreer in it like salary life??
Please anybody reply
@@sahilsekhon8335 US has better universities. Better than Canada. Physicists work at telescopes, LIGO, CERN, they research and publish their papers solve mysteries and equations, make new theories etc
And I'm sure you know what professors do.
@@sahilsekhon8335 yeah they can. With a degree you can actually work both jobs.
You can dm me on my ig: _thewayilovetay
@@sahilsekhon8335 will you please dm me on my ig
Edit: you use Instagram?
@@sahilsekhon8335 you need to go to a good university then, you got to have atleast masters if not PhD in physics
@@sahilsekhon8335 my id: _thewayilovetay
What is the source of Energy of Universe ?
Maybe the total energy of the universe is 0. No need for a source, just positive energy locked up in matter and light and negative energy locked up as potential energy in gravity. No need for a source if the total is 0.
Why is there no noticeable red shifting in the blackhole images? (Matter closer to the blackhole should appear redder)
Before you move on from black holes, could you do an episode about about the hypothetical quantum mass that possibly resides at core of black holes?
I think Sheldon Cooper would be quite upset if he saw this video 😀 Love your videos btw, my favorite series on TH-cam.
Well I get upset everytime big bang theory is on tv so sheldon can suck it
For outsider observers, we that pass event horizon of BH may be dead, but from our frame of reference, we still alive and safely entered the event horizon. I have read a theory that explain it like that.
Do you have a couple of un-returned library books on the shelf behind you Don?
Seriously, you are so excellent. Thanks much.
Nope. All mine.
Question on event horizon for supermassive black holes:.
If the difference in gravity is not so great near the event horizon of a supermassive black hole, what would happen if someone put a camera at the end of a stick from outside the event horizon and push it beyond? Would they be able to retrieve the camera using the stick and what it has recorded?
>>Would they be able to retrieve the camera using the stick and what it has recorded?
No.
Once you pass the event horizon you can't get out. Also, you would not be able to maintain a position just outside the event horizon without a lot of effort. It would not be a stable orbit.
Don used a formula from Newtonian gravity, it's not right near the horizon. You need to use en.wikipedia.org/wiki/Proper_acceleration which becomes infinite at the horizon, so a difference between some finite value outside and the value at the horizon is also infinite. Which just shows it's impossible for a massive body to stay at the horizon.
Question
In black holes the accretion disk increase the temperature and causes materials to electromagnetic radiation. Why does this phenomenon ocures and why do these oscillation exist
Do you mean why do hot things radiate? Because the charged particles in them move back and forth in various ways, depending on the temperature. Roughly speaking; The higher the temperature the more energy the particles have and the more they move apart, but they are held together by atomic bonds and such so they move back together again, so they oscillate. And oscillating charges create electromagnetic radiation.
Or do you mean why does the accretion disk heat up? Because the matter speeds up as it is pulled towards the black hole and orbit it. Fast particles bounce against each other. This basically creates friction and thus heat.
Sir , in the merging of the black holes , the total mass of the new black hole is not the integral sum of the masses of the other two black holes , why does this happens , does the mass is released in the form of energy which is blown off in the form of gravitational waves ?!
Hi sir, I have a doubt.If by gravity every object attracts the other object that means two protons should attract but they repel why sir?
They are both positively charged
They do attract gravitationally. But they repel electromagnetically. And the electromagnetic effect is much, much stronger so it wins out.
Narf Whals thx
Isn't the temperature of space also to do with the temperature which an object, when left in space will tend towards? I believe it's the same temperature but it's a slightly more intuitive perspectove on it.
Yes, in a universe without stars or hotter things to radiate more energy on to the object the temperature should be that of the CMB. Without the CMB and all else I'd expect the temperature to as near as possible to 0 K.
Next week, can you talk about the generations of matter? How sure are physicists that there isn't a generation below the up/down/electron generation, or one above the top/bottom generation? How do we know?
Not the next one, but 5 or 6 from now.
Hi Don, great content, as always. Me and my cats are a huge fan of your vids. I have a question related to black holes and the information paradox. I understand the problem is that Hawking radiation is random and thus cannot carry information. But what about the remnant of the black hole after the evaporation? When the evaporation reaches a point where the black hole collapses then it surely happens in a unique way, right? And that unique explosion could actually convey information about what was in the black hole and thus no paradox exists. Whats your view on this? Thanks, Bence
Hi Don.. if light cant scape blackholes, what are those ray bursts that seem to eject from the center of some blackholes?
And physics is awesome.. and also want my son to take a look in experimental physics.. he likes to watch an educative cartoon 'fiksiki' (made by Russians and translated.. awesome! Highly recommended) and reproduce their ideas.. sounds like a profile? 😁
The bursts of energy you're talking about are caused by energy falling towards the black hole that then create magnetic fields which then guides some of that matter towards the poles and outwards.
The result is two jets of matter that shoots outwards, made by matter that never got in the black hole.
Dr. Don, some time ago I read that in the early days, the event horizon of a black hole was considered to be the singularity, this was derived from the equation. This later turned out to be a mathematical error. Event Horizon being the singularity actually sounds very compelling to me, and this raises my question: Do you know of this error, and can you explain it? Thank you so much, in advance.
A coordinate singularity (not a physical one) does in fact happen at the event horizon. It is avoided by changing the coordinates being used. A coordinate singularity is something like trying to continue moving north when at the North Pole. Move where you say the poles are and you can continue. Maybe this is where you got the event horizon singularity idea.
@@cloudpoint0 No, it was inspired by something else. It had to do with how time dilation will cause the infalling, indestructible observer to never reach the event horizon, IN NEITHER cases, not local, nor remote frame of reference. Why do I think this? because of hawking radiation, the black hole has a life span in our spacetime. The infalling observer will see the universe around him evolve into infinity as he reaches the point where spacetime inflow reaches c. That also means the event horizon will shrink before his very eyes, his time dilation will enable him to outlive the black hole. The black hole will have blinked out before he reaches the point of no return. Or is my thinking flawed?
@@paulmichaelfreedman8334
I’m not quite certain what you mean by “spacetime inflow reaches c”. Spacetime is understood to be static. It’s probably poetry that means the gravitational field is extremely curved such that an object within it falls reaching and even passing c relative to flat outside space. But one can also slowly drift across the event horizon and travel to the center of a black hole at a relatively leisurely pace, perhaps drifting much of the way if the gravitational field is very gently curved, at considerably less than c anyway. It can take from milliseconds to a few days to travel to the center of a black hole in internal time, depending on the temporal extent (mass) of the black hole. But let’s forget about this.
Read web.stanford.edu/~oas/SI/SRGR/notes/SRGRLect6_2007.pdf if you want to dig deeper ...“So even though you observe objects moving at different speeds through space, they are all moving at the speed of light through spacetime.” … “Every second your clock ticks, you have moved 3 x 10^8 m from where you were before.”
If there is a flaw in what you said, it is that time dilation is a phenomenon perceived mainly by a distant observer watching the in-falling, indestructible observer, and not much by the latter.
The in-falling, indestructible observer is seen to fade to red and then to black in probably a few seconds. Sharp distant infrared, microwave or radio eyes might see a shadow impression of him for some time afterwards but not for very long. Time dilation happens because the different reference frames due to extreme gravity make the speed of light seem quite different at the two vantage points.
For the in-falling observer the dilation effect between his current position and the event horizon disappears as the black hole is approached, as both occupy the same reference frame. He perceives nothing special about crossing the event horizon (if spaghettiification is not a factor). Perhaps if the in-falling observer somehow stopped falling and hovered for a long time just outside the event horizon, then things might be somewhat as you describe for him. I’m less knowledgeable about this scenario.
@@cloudpoint0 But does the observer falling in, not see the universe blueshifted and aging with a speed increasing logarhythmically to infinity? let's say we have an outside observer who is immortal and keeps watching and watching...let's say he watches the black hole for a googol years. By that time the infalling object still hasn't reached the event horizon (let's say we a magical device that can tell us what the position is of the object as it approaches the event horizon), as time dilation is infinite at the event horizon. But by that time the black hole has also evaporated. In other words, he will see the black hole evaporate over that period of a googol years, see the event horizon shrinking as the object slowly catches up with it, but slower and slower , asymptotically. These events must also be experienced by the infalling object, with the only difference being the time elapsed in the event. for the infalling, maybe a minute or so, for the outside a googol years.
@@paulmichaelfreedman8334
I suppose an observer falling in theoretically sees the universe blueshifted and rapidly aging, at least until he crosses the event horizon. The observer is entering a zone of very slow moving time near the black hole while the rest of the universe runs at it normal quick pace. In practice what he sees looking back when still outside is the universe collapsing into a small blue dot surrounded by blackness. My understanding is once you cross the event horizon, nothing that is still outside is visible to you anymore. I believe this is because all directions are down once inside. You can’t look up or out. You might see light that fell in after you passing by.
What you said about the forever watching outside observer agrees with what I said earlier for the distant observer. Except fewer and fewer photons would be received over time by the watcher, each one farther separated in time, which is perceived as red shifting and fading to black by the watcher, effectively a slow motion video clip. Since the watcher has near infinite patience I think he would see one second-to-last photon a billion years before the black hole evaporates, and then see the very last photon just prior to it evaporating a billion years later. In practice the watched object would become invisible after a short time.
Time dilation is not quite infinite at the event horizon, it’s a bit less. Infinite time dilation means time stopped completely and that can’t happen. If by experienced you mean the elapsed time to fall in was exceptionally long in outside terms although brief to the object, that’s true. They both experienced it differently though. The outside observer never sees the object actually fall inside while the object does actually fall inside, and in short order according to the clock it carries. It’s not crossing the event horizon just before the black hole fully evaporates, although the observer might have this impression.
More info at link below:
“Believe it or not - despite the fact that we’re talking about an event horizon that might be around a light-hour in diameter in our reference frame - it would only take around 20 seconds to reach the singularity once you crossed the event horizon. Severely curved space sure is a pain!”
www.forbes.com/sites/startswithabang/2018/01/19/what-would-you-see-as-you-fell-into-a-black-hole
Animation: th-cam.com/video/JcHneuh6DKo/w-d-xo.html
Dr. Lincoln,
What does it take to make a black hole go BOOM? How much energy/force is needed to make it explode?
Thanks
Putting energy or stuff into a black hole makes it bigger.
@@bozo5632 indeed. But thats not the question. Im sorry if i didnt make clear: what does it take to make it explode?
It's a question ive had trouble with for a long time. And a question i never see asked/answered. Any insight is appreciated.
@@patrickaycock3655 It can't explode. Anything that happens inside always falls further inside. The escape velocity at the horizon exceeds the speed of light, so nothing can escape.
Very energetic things can happen on the outside as stuff falls in, so you can get light and x-rays and high energy particles spewing out of the accretion disc - more energetic than a zillion nuclear bombs - but that's on the outside, made of stuff falling in. The black hole just gets bigger.
Theoretically Hawking radiation will very, very slowly fizzle away a black hole. When they get very small, like the mass of just a mountain, but smaller than a grain of sand, they fizzle away faster and faster, and then much faster, until they're gone, which is pretty much the same as exploding. To make that happen you only have to wait trillions of trillions of years for the universe to cool down to almost zero so it can start fizzling, then wait trillions of trillions more years while it shrinks, then - presto! It blows up. Easy as that.
@@bozo5632 firstly, i agree with most of what you said. I am aware of how they work. The only thing i disagree with is the cant explode part. We have never tried to make one explode. I guess another way of looking at the question, is what will it take to spontaneously rip a black hole apart? And as far as i know, they warp spacetime, which is fancy for stretching and compressing. Since no one has been in or near one yet, it is my understanding that space inside a bh is kinda like a pocket dimension, with infinite room to grow but has a limited size. In other words, the space below the horizon stretches out for infinity (no data on expansion rate), making it extremely difficult if not highly improbable, that classical explosions would not work. Taking a classical approach, we would assume a "bomb" be placed inside the bh and detonated. But as you pointed out that idea wont work, as far as we know. This is still theoretical.
And id like to say thank you for responding.
All you need is patience. The smaller the BH the quicker it evaporates releasing more energy, so its last moments indeed look like an explosion.
Thank a lot Dr.Don, my ambition was to become a Theorist, but I changed the decision and taking Expirimental Physics but I was confused.
Btw can you recommend a good book on *particle* *physics* .
Understanding the Universe
I recently found an article on mirror matter (as a candidate for dark matter), and although I didn't came close to understanding it, it reminded me of supersymmetry's proposed cousin particles.
Are they the same, or we could have a bunch more layers to the standard model?
Why fusion reaction stop on iron, particularly?
When you're fusing light elements, the mass of the two lighter elements is larger than the mass of the final product - eg. when you fuse two deuterium (2H) nuclei (mass 2.014 au) into a 4He (4.003 au), you have "lost" the mass of 0.025 au. This mass that you lose is converted into energy (by Einstein's equation for mass-energy equivalence, E=mc2). This is why nuclear fusion is able to generate energy (ie. why the sun is hot and emitting light). Once you get to heavier elements like iron, combining two 56Fe (mass 55.93 au) into an element with 112 nucleons (would be likely 112Cd, mass 111.90 au), the mass of the product is larger than the combined mass of two iron atoms (by 0.04 au), therefore you'd have to add energy in order to compensate for the increase in mass. Therefore, since this reaction isn't exothermic, it stops (it would need a constant supply of energy in order to run). This is also the reason why for heavy elements, energy can be gained from them by fission instead of fusion - in a nuclear power plant, uranium (235U) is split into lighter elements while energy is released, because the combined mass of the products is smaller than the mass of a 235U isotope.
An intuitive way to see why fusion can't go forever is to remember that inside a nucleus you've got two opposing forces: electromagnetic force tries to push protons apart but residual strong force tries to bind them (and neutrons) together. However while EM force is long-range, the residual strong force is short range. So a proton can push away other protons via EM force even when they are far, but it can only attract other protons and neutrons via the strong force when they are near. When the nucleus is small the strong force takes over and will gladly accept more protons/neutrons into the nucleus, they just need to pass the barrier created by the repulsive EM force. When the nucleus becomes big, each proton/neutron can only attract a limited number of neighbors but the repulsive EM force is felt from all the protons in the nucleus. So in a large enough nucleus EM force takes over and will gladly throw away protons, they just need to overcome the limited energy barrier created by the strong force. This imbalance between attractive strong force and repulsive EM force makes small and big nuclei behave differently in terms of fusion & fission.
Thanks for answering
thedeemon best explanation 👍
I would prefer to be the Experimental physicist. I've always like building things and the challenges to make them work and to improve on the original design. The ITER project is right down my alley.
I heared that a massless quark could explain the strong CP symmetry, could you make a video about that? In my mind, it would be basically indetectible, right? Every process that could generate a massles quark/antiquark pair would make them annihilare instantly because they are massless.
Question about black holes, as you cross the event horizon, is all matter disintegrated? Molecules are held together by bonds, but as one atom crosses over, the bond would lose connection with the atom on the other side of the horizon. Maybe the same happens even with quarks and the strong force, so that every particle that crosses over becomes unbound. But with a super massive blackhole, the gravity changes so slowly, so Im not sure what to think.
Only if you try to hover there (which implies near infinite g-force, which becomes infinite at the horizon). If you're free falling, the horizon passes you by with light speed, so inability of signals from your lower parts to reach the higher parts through the horizon are just the ordinary inability of signals to outrun speed of light. Bonds should not break. In other words, your higher parts will follow the lower parts quickly enough so that signals from the lower parts won't have to cross the horizon to reach them.
Hello there. Can we call neutron star just the black hole with the event horizon below its surface?
The event horizon doesn't exist unless all the mass is compressed into the Schwarzschild radius. It doesn't lurk beneath the surface and if you dig down to it you're inside a black hole. A black hole is a completely distinct state.
But the line where the horizon would be exists for every object. The earth's "phantom horizon" is a sphere of around a one centimeter radius at its center.
Thank you Sir for giving us knowledge, I am always fascinated by astrophysics and particle physics though I am an engineering student I would love y to work in this fields
What actually Energy is ?
Read what Feynman had to say on that subject: www.feynmanlectures.caltech.edu/I_04.html
I have a couple questions concerning observational physics and black holes. With all the talk about the possibility (though slim) of "Planet 9" actually being a small black hole, what type of experiments could be performed by a New Horizons sized craft if we sent it to explore a black hole in our own star system? Are there any unanswered questions that such a voyage could answer for us?