"Black Hole Explosions?" Not only a unique paper by Steven Hawking, but 1974's version of click bait. Hawking ahead of his time in more ways than just physics.
One of the first things you learn about scientific papers is that there's a lot of them. So the challenge is to make other scientitists read _your_ paper. Having an exciting title is one way to do this. The challlenge is of course to actually come up with an exciting title that is still relevant to your work.
Yep except for the lack of a click, bait goes way back. Titles and short descriptions that get quoted in articles and catalogs sometimes worded to get you to go get the whole thing and read it.
I saw Stephen Hawking speak at Berkeley (around 1989?); he could use his hand to control the speech synthesizer at that time. After the talk there was a Q&A. Some guy stood up and said, "Do you think that general relativity might be wrong, and if so.." "No!" came out of the speech synthesizer. It was hilarious.
That's a great story, I wonder if a video of that exists somewhere. If parents brought their camcorders to their kids' class plays years before 1989, surely at a talk of Hawking, someone would have brought something there.
I remember watching this video as a high schooler when Stephen Hawking passed away. Understanding nothing, scratching my head. Three years down the line, I am happy I have the chance to revisit these videos and actually follow throw the description as a physics major. Don't worry y'all, you have got this!
I don't. Because I don't study any of this. But I appreciate that these videos make it quite clear that I'm not getting it. Unlike some other popular science channels that just completely obmit the crux of the topics.
yeah i recently gained a passion for space and im a junior in high school and after this video im thinking i needa learn some more building blocks first, i seriously wanna get into astrophysics tho, dedicating my time into studying this💪
Not to distract from the honouring of Stephen Hawking, but I just gotta say: Matt O'Dowd, you are by far one of the best science explicators of our day. Hawking himself would be proud! I never would have gotten the concept of Hawking Radiation so completely without this video. It is so incredibly information-dense, it's almost a singularity in itself! ;-) [I should give credit also to Graeme Gossel (co-writer) and Grayson Blackmon for his excellent illustrative graphics. But c'mon you two, Matt _is_ an awesome science explicator anyway, even if he got expert assistance from you guys, ain't he? ;-D ]
“Remember to always look up to the stars and not your feet” Stephen Hawking is one of the main reason as to why I began perusing Quantum and Theoretical Physics. Thank you for everything Dr. Hawking.
It's very important not to look up to your feet. Because if you are looking up to your feet, it means you're upside down and probably about to land on your head. Then again, in that situation, maybe looking up to your feet is a good idea after all, because then maybe the back of your head will strike the ground instead of the top of it straight on, and that may be less traumatic.
de Broglie nope its not predetermined.you choose if you want to take the time to check before crossing. Next time you cross the street...stop and think "should a double check first or just walk without looking" I hope u check first.
Sorry but these words shouldn't belong to someone who had such a great imagination and contributed so much to science. Perhaps, his hate towards "God" made him to desperately deny His existence due to his condition? We'll probably never know. I mean, what is so difficult to understand that if they don't check the road, it is destiny. If they do, that is also destiny. From his quote, one would think that people who believe in destiny should just sit where they are until they die. But that is not how teaching of destiny works in religious and non-religious belief. This is the best explanation of reasoning behind "belief in destiny" from a non-religious point of view: th-cam.com/video/o0GN4urbA_c/w-d-xo.html
Nicat Memmedov he actually talks a lot about "God" and not once did he say he hates God. And actually its the other way around. He believed that because of his condition he was able to spend more time thinking about the things "normal" people wouldn't. So I'd say he was not in hatred for god but also based on what he has said, his version god is far from what the religions want you to believe
I know this might sound a little crazy but I've been thinking about this for a long time if matter is mostly empty space then could the universe as a whole be a solid I hope you don't think I'm insane
@@charlesdrury1587 The universe contains matter but it is not matter itself. So it cannot be any state of matter. You could describe it like a web or any other analagous structure, but the universe is not actually made of anything, it just is. A stage has actors but does not recite lines.
Little Tivor In his honor we did an animated video explaining his famous hawking radiation theory, if you want for a fun animated yet very educative video you can check our Hawking radiation video in our channel !
@@jonnnnniej bc many of us pay for no ads, and now the channels spend ten plus minutes promoting their sponsors so we can't escape it. Some channels, like psych2go, do their promotion right smack in the middle of their videos.
How so? At the graduate program level all of us learn to do days'-worth of math in our heads. We only write it down so our peers can check our work in real time. Peer reviews are the reason there's still chalkboards in universities. Or if you're working on a problem during a walk, you'd use pencil and paper, snap a pic, and send it off for review. It's really the only time we ever write equations down.
@@HolyGuacamolean wait, really? I can barely remember things just a second after looking at them half the time, and you can remember that many equations at once?
@@noahwilliams8996 Ah. You've got to work your brain 🧠 like a muscle. If you do math with calculators only, you'll experience what a lot of people experience with GPS these days....they know how to drive and the rules of the road, but not how to get there on your own because you were never paying attention to the route and the surroundings. Just the GPS directions.
I mean this quite literally when I say Stephen Hawking introduced me to the love of my life. From the day that I snagged "The Universe in a Nutshell" off of my father bookshelf I fell deeply and madly in love with all things physics. The more I researched the more I loved it. The more I learned about Hawking the more I respected him and marveled at all his accomplishments. My life and the life of millions of others will never be the same. RIP Professor Hawking.
@@anom3778 ooooor because he was way smarter than the average person.. Dopamine pleasure is nice to know about, but isn't the reason behind everything..
@@dwiski I understand but if we could create a world where people could study all day and have no other distractions we would have a lot more smart geniuses like hawking einstein and Newton. I think most people have that potential they just don't know it.
@@pathayes1757 Read books!! Watch more videos!! It'll be frustrating in the beginning but you'll slowly start recognizing terms and understanding better. I'd also recommend watching kurzgezagt videos. They explain many topics in layman's terms. Read hawking's books as well and if you come across a term you don't understand, stop and find out more about it before continuing. (Ik it's time consuming but if you're really interested, it's worth it!). Hope this helps :)
Time has stopped for poor decrepit old Hawking, so no more delusions of science fiction to infect the minds of our youth with his self-contradicting drivel. Oh no, Mr Hawking will be instantly transported to the end of time where he will face the Eternal Creator and Judgement for his crimes against humanity. Good riddance stephen, because I cannot imagine eternal life with a repulsive little nutter denialist like you as my neighbor:) eg. of classic Hawking drivel - "“Because there is a law such as gravity, the universe can and will create itself from nothing,” “Spontaneous creation is the reason there is something rather than nothing, why the universe exists, why we exist. It is not necessary to invoke God to light the blue touch paper and set the universe going.” BWAHAHAHAHA - like I said, self contradicting drivel from a delusional old fool.
delawarecop Ah, must be this Christian love, to have fun imagining someone get punished, because he doesn't agree with ones fairy tales. Crawl back into your hole, troll.
delawarecop 1) The Bible contradicts both science and itself several times on the first page: *In the beginning God created the heavens and the earth.* [a] 2 The earth was formless and empty, and darkness covered the deep waters. And the Spirit of God was hovering over the surface of the waters. 3 Then God said, *“Let there be light,” and there was light. 4 And God saw that the light was good. Then he separated the light from the darkness. 5 God called the light “day” and the darkness “night.”* And evening passed and morning came, marking the first day. 6 Then God said, *“Let there be a space between the waters, to separate the waters of the heavens from the waters of the earth.” 7 And that is what happened. God made this space to separate the waters of the earth from the waters of the heavens. 8 God called the space “sky.”* And evening passed and morning came, marking the second day. 9 Then God said, “Let the waters beneath the sky flow together into one place, so dry ground may appear.” And that is what happened. 10 God called the dry ground “land” and the waters “seas.” And God saw that it was good. 11 Then God said, “Let the land sprout with vegetation-every sort of seed-bearing plant, and trees that grow seed-bearing fruit. These seeds will then produce the kinds of plants and trees from which they came.” And that is what happened. 12 The land produced vegetation-all sorts of seed-bearing plants, and trees with seed-bearing fruit. Their seeds produced plants and trees of the same kind. And God saw that it was good. 13 And evening passed and morning came, marking the third day. 14 Then God said, *“Let lights appear in the sky to separate the day from the night.* (Emphasis on "lights" and "seperate the day from night") Let them be signs to mark the seasons, days, and years. 15 Let these lights in the sky shine down on the earth.” And that is what happened. 16 God made two great lights-the larger one to govern the day, and the smaller one to govern the night. *He also made the stars.* (Emphasis on "also") 17 God set these lights in the sky to light the earth, 18 *to govern the day and night, and to separate the light from the darkness.* (See second bold) And God saw that it was good. 2) If you were born in Nordic times, you would look at lightning, not understand how it works, and then blame it on Thor. Just because we cannot currently explain something doesn't mean that an invisible unicorn-riding leprechaun did it. 3) None of Hawking's work contradicts itself.
delawarecop It looks like you are dancing on the grave of Hawking and your God will let him but for eternity.... ...Christians are so full of love! Bless you!
I think this was the best tribute to Stephen Hawking. He'll forever be remembered as being one of the great scientists like Einstein. Rip Stephen Hawking EDIT: I think some people took it the wrong way. Here, when I said "He'll forever be remembered as being one of the great scientists like Einstein" I am not comparing Hawking to Einstein or their ideas. My intension behind that was just that even though he's dead, his ideas will live on and he'll be remembered as one of the great scientists. I am NOT comparing Einstein to Hawking or their ideas.
I think some people took it the wrong way. Here, when I said "He'll forever be remembered as being one of the great scientists like Einstein" I am not comparing Hawking to Einstein or their ideas. My intension behind that was just that even though he's dead, his ideas will live on and he'll be remembered as one of the great scientists. I am NOT comparing Einstein to Hawking or their ideas.
I think he'll be remembered for a very long time. Like Einstein, as you clarified, no. But like Gauss, certainly. Someone whose name still inspires awe among the informed over a century and a half after he died, but not well known among lay people.
A truly marvelous tribute, remembering Hawking through his incredible work and explaining his ideas with fair detail and rigour. Will always have respect for Hawking and PBS Spacetime.
zero132132 In his honor we did an animated video explaining his famous hawking radiation theory, if you want for a fun animated yet very educative video you can check our Hawking radiation video in our channel !
FINALLY an explanation that talks about the actual calculation, i.e. transforming the vacuum state between two null surfaces. The interpretation of particle-antiparticle pairs near the horizon is very flawed and little more than an easy-to-understand oversimplification.
kindlin, that question demands a bit of a complicated answer. So the key thing to understand here is that this wave is not a "literal" wave. It's an "imagined" wave. If a wave were actually there, it'd behave like that, but we are just imagining. In quantum field theory those "imagined waves" are very important concepts. We call them "modes". In a theory of classical waves, these modes could have any amplitude, but in a quantum theory, they only come in discrete bits, which we call particles. We borrow the theory of something called the quantum harmonic oscillator to describe particles. For each mode you can talk about objects called "creation" and "annihilation" operators, which are mathematical objects that, as the name says, "create" and "annihilate" particles. There is a state from which you can't remove any more particles with the annihilation operator: that state is called "the vacuum". You can find all other possible states, with all possible numbers of particles, by applying creation operators for the various modes to the vacuum. The "chomping a bit of wave" by the black hole does something interesting: it changes what kinds of modes exist before and after the black hole forms. This means that if space was empty before, it is no longer empty _after._ Mathematically, this is represented by a relationship between the creation and annihilation operators before, and the creation and annihilation operators after. It's like the presence of the black hole changes what it _means_ for space to be empty.
Essentially the vacuum state is not the same for all observers. You can see that in for accelerating observers (who perceive Unruh radiation) and observers in a gravitational field who are not in free-fall (so essentially in an accelerating frame). Hawking showed that the same is true for black hole geometries for past null infinity and future null infinity. What is quite brilliant, and somewhat confusing, about this is that unlike the accelerating frame, which can be contrasted to an inertial frame, and the frame of a body hovering above some mass at a finite distance, which exists locally in curved spacetime, the frame of something very far away from the black hole is asymptotically flat. So we see that in Hawking's example, which is a dynamic spacetime in which a horizon had not formed in the past but does eventually form, the existence of a horizon changes the vacuum. But the best reason for why BHs must have a finite temperature comes from thermodynamics. So think of two cases where some gas with a finite temperature collapses to form a BH, but with the first case you have more gas than in the second case. If BHs have no temperature, then it would appear that black holes are destroying entropy (note that this is DIFFERENT from the BH information paradox!). So to rectify this BHs must have a temperature, which is proportional to the curvature of the horizon, and an entropy, which is proportional to the surface area of the horizon. Bodies with a finite temperature must emit thermal radiation, so there.
Vacuum Diagrams: Thanks for the insightful explanation. Two easy questions: What is a quantum field made of: I know it is a mathematical construct, but it must also exist in the real world in order for modes like particles to come into being. And what is the difference between a quantum field and a classical field like the EM field? We know the magnetic field is physical because it can move iron filings on a piece of paper. So EM fields must be composed of forces at every point in space or something like that. Can you explain, please?
I'll answer your second question first: what does it mean for something to be a quantum "anything"? Generally, it means that the observable properties of this thing "don't commute". This is mathematical lingo to say that measurement of one quantity _must_ affect a subsequent measurement of the other. For example, if you measure a quantum particle's position, you automatically change its momentum in a random way. So the results of the measurements depend on the order in which they're done, that is, they can't be "switched", or... "commuted". When you see someone use the word "noncommutative" with regards to quantum mechanics, that's what it means. In a quantum field, there are analogous properties to position and momentum which do not commute. These are, for example, the value of the field, and the "field momentum", which you can think of as proportional to the rate at which the value of the field changes over time, just like momentum is proportional to the rate at which position changes over time. The specific commutation relations depend on what kind of theory you want to study. Most often (though not always) we use quantum field theory to study relativistic systems, so the recipe we follow is the following: we pick a reference frame, and we select a time in that reference frame (simultaneity is relative, so this time will correspond to a bunch of other times in other reference frames). We then say that almost everything commutes, except for the field value and the field momentum at each given point, where they follow a similar rule as ordinary position and momentum. Then you have to actually think about the dynamics of the theory to see how these commutation relations evolve over time. This all sounds complicated, but it's actually very reasonable: all it means is that a measurement of the field here couldn't possibly affect a measurement in the andromeda galaxy. But a measurement here can surely affect other measurements here, and my measurement can potentially affect other measurements in my future light cone as well. So... what is it made of? Nobody knows! Nobody knows even whether that's a sensible question to be asking. It could well be, so I'm not disparaging, but it might not be. All we know is that these are very "delicate" objects, in a sense, which are always affected by measurement in a way we think we understand.
76 With ALS we all should be grateful he was alive for so long while being so sick. He made us think question doubt everything, he has inspired his successors and will always be known as one of the legends of science.
Stephen was the subject of my conversation today from Florida to Israel and I couldn't say enough about him. I wish I had this video ready to play. There's always tomorrow.
shatley123 In his honor we did an easy to understand animated video explaining his famous hawking radiation theory, if you want for a fun animated yet very educative video you can check our Hawking radiation video in our channel !
Basically hawking radiation is the release of some sort of energy since black holes lose more energy or mass then they gain so it slowly shrinks down until it collapses on itself.
Even though I am 2 yr late the particles called virtual particle is randomly created from nothing and is formed in pair which annihilate each other a when it is formed near black hole one of the pair like negative one go in it and positive goes away hence the Hawking radiation and black hole will be smaller and smaller or evaporates out until it is no more and for small black hole it takes1*10^60yr and bigger black hole 1*10^100yr
@@APXSTUDIO I've heard that explanation for years and never could understand how the black hole absorbed mostly antimatter instead of absorbing an equal or near equal amount of matter and antimatter.
With Stephen Hawking no longer in our life it feels like they’re a new found void in the world that no great mind will ever be able to fill in the way he did. Not only was he an amazing physicist, he was also an amazing person. He will be remembered for both his work and person for centuries to come. While his work will remain, his person will be greatly missed by all. ❤️
This series of episodes is, in my opinion, a marvel of education. You actually pulled through, and I for one feel enlightened on the subject after decades of hobbying around it. Thank you very much.
I came here from a video suggesting I watch this video first in a playlist, to understand that video...and yet this video also has a playlist to under what this video is talking about...it's playlists all the way down
It's so ironic. On Tuesday afternoon, the day that he passed away, i was telling some friends about the internet rumor that he had died several years earlier. Less than 12 hours later i hear the news.
Stephen Hawking who stood on the shoulders of giants who came before him, now joins them to broaden the surface on which humanity have to stand on. Thank you for your contributions. You will be missed and I hope that those who build on your work in the future sends you a thought of respect every now and then. You were given a bad hand but made more with it than most could ever dream of. I wish I had a fraction of your strength and determination. We can all learn from your example. Truly, you were one of a kind.
Julia-6 In his honor we did an animated video explaining his famous hawking radiation theory, if you want for a fun animated yet very educative video you can check our Hawking radiation video in our channel !
That's because Hawking started from the assumption of a vacuum evolving forward in time to the infinite future. If you do it in reverse, from the future to the past, you'd find only antiparticles "escaping". Still, the whole derivation is based on math hacks, and while some physicist might tell you otherwise, Hawking radiation is far from a real thing. We've never observed it, and it leads to multiple paradoxes. Usually, paradoxes where thought of as stemming from erroneous assumption (this is basically how Einstein derived special relativity), but for the last 50 years or so paradoxes and infinities have been brushed under the rug with the excuse that our theories are not complete, not that they are based on wrong assumptions. You can thank Bohr and the Copenhagen school for that.
@@ffffffffffffffff5840 Then we would have to abandon all hope to make sense of the universe. The whole premise of science is that we can make sense of it, and assuming otherwise is just not constructive.
@@FunkyDexter that's fair. I mean clearly we've made some sense of the universe, since we're both able to use technology to communicate with each other even though we've never met. A lot of the sense the universe has made has been counter intuitive, so maybe it will get even crazier from here. Time will tell, the scientists are working on it as we speak
He also disproved time travel by throwing a time traveler party but non turned up he released a press conference about it the day after he had the party...The man is a legend
Thank you for this video! I have always wondered that why the negative/anti-matter half of the virtual-particle-pair falls in the black hole and not the positive one. Now that you explained it I don't understand it at all, but that's ok, nature does not own me explanations :)
All real particles are have positive mass / energy and obey the usual energy-momentum-mass relations. Black holes have an entropy and non-zero energy, so they have finite temperature. Objects with finite temperature emit thermal radiation. For black holes that's Hawking radiation.
>Now that you explained it I don't understand it at all That's why I like this channel. It doesn't give me the false sense of having understood a complex topic that I only have a superficial grasp of.
I was 100% convinced that Hawking Radiation does not evaporate black holes... your explanation along with the visual graphics in this video has demonstrated that it could at least be a possibility, justifying further research into this topic. Well done, you have peaked my curiosity. 🤔👍
If Hawking radiation can be thought of as quantum entangled matter/antimatter pairs that are being ripped apart, is there any conceivable way to be able to study the particle of the pair that is trapped in the black hole by looking at the one that is outside, thereby sort of "seeing" inside the black hole?
that is pretty much one of the proposed solutions to the information paradox. That the hawking radiation ultimately contains information of all the stuff that fell in, because stuff falling in change its properties.
I wonder though about the effects of gravitational time dilation on the entangled pairs. The particle inside the event horizon will be feeling much stronger tidi than it's partner. Can they remain entangled under these circumstances?
I doubt it, his impact on theoretical physics isn't that significant and well it's all theoretical with very little chance of being confirmed. That very different than what Einstein did. He will be remembered but it's going to greatly amplified because of his physical disability vs the weight of contribution to science.
Well Einsteins predictions weren't confirmed right away, I mean we are still confirming parts of his theory such as gravitational waves etc. And Hawking was a pretty decent physicist despite being a vegetable as far as promoting and pushing the frontiers of scientific endeavors go.
Fenghuang In his honor we did an animated video explaining his famous hawking radiation theory, if you want for a fun animated yet very educative video you can check our Hawking radiation video in our channel !
This answered me a question tingling me for years, only to open a whole new spectrum of questions. But what's science without tingling questions. :-D Thanks for the breakthrough.
He is like a faraway star, although he is dead his brilliant light will shine on. He has changed the course of time forever and will live on in are hearts inspiring generations to come. We miss you Professor Stephen Hawkins, we always will. RIP
Martín Díaz Cuesta In his honor we did an animated video explaining his famous hawking radiation theory, if you want for a fun animated yet very educative video you can check our Hawking radiation video in our channel !
Thank you very much for this video!!! Just the topic I was looking for for the past month..... Was even going to recommend it in the comments when the sad demise happened
Thanks! On a completely tangential note, there was a chess Grandmaster named Efim Dmitriyevich Bogoljubov (4/14/1889 - 6/18/1952). He even played against Alexander Alekhine for the World Chess Championship - twice (though he didn't win.) 𝕥𝕒𝕧𝕚.
Amazing episode! I cannot wait for a deeper review of Unruh Radiation! Could anyone recommend a text that explains some of the profound implications of it? I do have a rather dumb question: what limits the energy of the radiation produced by a black hole? Could a fluctuation with high enough energy be produced that could, say, create and decay into insane amounts of particles and form an entire planet?
I'm no Stephen Hawking, but what I've seen about it on videos like these indicates that the final evaporation of a black hole, while highly energetic, doesn't contain nearly enough energy to make even something the size of a coin, never mind a planet.
Okay, I'm slightly wrong. Per en.wikipedia.org/wiki/Hawking_radiation, an ideal black hole will radiate energy equivalent to 2.28×10^5 kg of mass during its last second of life, which is 2.05×10^22 J or 5×10^6 megatons of TNT (direct quote). So, more than enough to make a penny, or even a decent-sized car, if it somehow all resolved itself into the appropriate configuration of subatomic particles. As this would represent a spectacular decrease in local entropy, you might get a spontaneous car-sized mass once in a googolplex events or something along those lines.
Well I'm not a physicist but doesn't the energy of a wave depend on it's frequency? If so, and the wavelength (and therefore the frequency as well) is given by the radius, I don't think there are any fluctuations at all.
I could be entirely wrong, but the way I understand it is that the fluctuations are only large enough to produce massless particles over a fairly large range of possible locations, depending on the size of the black hole. I don't think it would be likely that there would be a significant amount, if any, mass produced this way. Just my interpretation though, I'm certainly a little underqualified haha.
If it is quantum field that is distorted by a black hole, doesn't it mean heat glow or radiation is not emerging from black hole itself, but energy of vacuum, meaning there is no loss of mass of the black hole?
9:50. I've heard a theory that Hawking radiation can spawn photons having an energy exceeding the rest energy of the Planck mass. The probability is, of course, very low, given the exponential decline of the Planck distribution. But if such a photon were emitted, it would immediately become a kugelblitz, another black hole. If this same thing happened in vacuum to a photon that remained virtual when it developed its event horizon, then it could not thereafter decay or be annihilated by merging with its antiparticle. It would, instead, detach from our spacetime and begin to occupy a separate spacetime, initially one having only a single point. This state would violate the uncertainty principle, and that one-point spacetime would undergo a change of state where in a singular quantum state became a plurality of quantum states - probably with a vengeance.
Hawking can exist but never escape. There is a finite period of time between generation of the pairs and annihilation . During that time, however small, the particles fall below the event horizon. When they annihilate the resulting radiation cannot escape. I'm surprised no one has pointed this out. Even if the pairs stay separated no particle travels at light speed and would fall back into the black hole.
@@stevelenores5637 Hawking radiation appears as conjugate pairs. They attract each other very strongly. If one member of the conjugate pair falls below the event horizon, all of its potential energy on its partner becomes a general property of the entire black hole and isn't focused on the still-outside partner anymore. It appears to be possible that the gain in (kinetic) energy for this still-outside particle can exceed the gravitational potential energy that binds it to the black hole. In that case, it can escape.
@@Jenab7 I agree it could but it is very unlikely that it will escape. And if it did it would need to reach orbital escape velocity. Orbital velocity near the black hole above the horizon is already near light speeds. Most like if the particle is very very lucky it will orbit a few times and decay back below the horizon. I'm not saying Hawking radiation doesn't exist only it unlikely it will ever be detected. Mathematics and physics shows it can happen, it doesn't prove it can escape for long. IMHO Think it of as POW camp on an island. The prisoners might escape for short period but they will be rounded up and locked back inside again.
@@stevelenores5637 The components of a conjugate pair are opposite in charge, but they are equal in mass. If one of them goes under the event horizon, then the other one gets about its rest energy as kinetic energy, which automatically boosts it to 87% of c relative to its prior reference frame. Also, there's no reason for why that prior reference frame had to be motionless relative to the black hole. It might be travelling, too, at some appreciable fraction of the speed of light. Stephen Hawking did a calculation on the distribution of kinetic energy of particles escaping from the vicinity of a black hole and concluded that it would be a Planck distribution, such that Hawking radiation would mimic a black body having a temperature that depended on the black hole's mass.
Remember particles shed energy quickly at relativistic speeds. They won't stay at 87% C for long, especially fighting the black hole gravity field. Also orbital speed at the event horizon is C. It only drops to 1/2 C when you get the neutron star equivalent radius. Not sure what the distance would be for 87% C orbital speed (probably a consistent multiple of the black hole event horizon but may have an exponent factor). Likely to be much higher altitude than where the particle formed. IMHO Don't ask me to do the math. My textbooks have been in storage since the pandemic.
This is so frustrating, I really am interested in this topic... but I don't understand a word he said. When the last guy who voiced those episodes was talking I was somewhat able to follow but the format just got more difficult and now I am at a total loss.
I am not really having problems with his rythm or his choice of words. To be honest I can understand him better than the previous guy, who talked a tad too fast for my taste. Though English is not my native tounge I understand what he says, though I can not get a grasp on the meaning, not being able to fit the pieces together... that is what is frustrating for me. Yes indeed, it is a really difficult topic and I am amazed on the knowledge he and his team have on it. Truly amazing that there are people out there who, though hard work no less, are able to understand and formulate ideas and new theories out of it.
Of the many tributes that were, and still are, rightly paid to Hawking, this is one of those that touched the deepest: in the absence of a fully unified theory of quantum gravity, with brilliant intuition and an ingenious 'hack', Hawking pushed back the horizons of our knowledge in all directions. And he did this, because, as Matt says, Hawking was "not to be deterred by the impossible"; it is this that lifts him so high, both as scientist and person.
Why is hawking radiation always displayed/assumed that it's the negative charged that goes in and hence evaporates the black hole? why not both mixed and balance that out. What am I missing?
I was sort of wondering myself why that assumption was made. If it's particle/antiparticle pairs, what's saying that the antiparticle can't be the one that escapes? Or does it even make a difference?
I'm not sure that I fully understand it myself, so I hope I'm getting this right, but the matter/anti-matter particles that pop into and out of existence in a vacuum take energy from that vacuum to do it, like the video said. The border where the event horizon is would have a pair of particles pop into existence that should both have belonged to the black hole, but because one popped up on the outside of the event horizon, it got away. Therefore the black hole lost a particle. If this happened often enough on a massive scale (and it likely would), the black hole would leak energy over billions of years, although it would have to take in less stuff than it gave off to evaporate completely.
Actually the black hole is not made of matter. It's what is called a "vacuum solution of GR", which is to say, it's one of the possible ways that spacetime can curve in the absence of matter. Sure it feeds on matter, but it is not itself made of matter. At least in GR. Understanding what exactly it's made of requires quantum gravity, but the important thing here is that Hawking's result does not depend on that. In fact the whole notion of "particles" is a bit sketchy in curved spacetime, but the upshot is: black holes evaporate because they absorb negative _mass._ You may think "well, how can ordinary particles have negative mass?" to which I'd reply "that's one of the reasons you can't think of it in terms of simple particles" :)
I like to think of them as un-particles since they are not antimatter. (which would emit gama rays when they recombine) I can imagine the un-particles flying out into the universe and eating matter without emitting gama rays.
No, CMB is the photons that started their journey about 300.000 years after the big bang when the universe cooled so much that it was no longer plasma. This is the moment when the photons started being able to travel great distances without being absorbed by matter. Also, cosmic redshift made them stretch in wavelength so they are in the radio wave part of the spectrum.
I know what the CMB is supposed to be, what I mean is that if a horizon radiation would create a similar radiation, how do we know what we are measuring is those photones liberated when nuclei and electrons bond together and not a horizon radiation caused by the limit of the observable universe?
Well, CMB is 2.725°K, which means that λmax =~ 1mm (and that corresponds to the schwarzschild radius of the hypothetical black hole). I'm not sure, but this line of reasoning seems sound.
because that limit is observer dependent. An observer falling into a black hole still agrees on the limit thereof. IE; all observers will agree on the point of no return from a black hole, but not all observers will agree on the position of the limit to the observable universe. This is because one of those limits is created by the placement of the observer themselves, while the other is created by the gravitational impact on spacetime of the presence of the singularity at the center of the black hole.
It's hypothesis meaning conjecture that has been modeled in detail capable of being falsified. It makes predictions. If those predictions in observation and/or experiments are not observed then it gets thrown out. It's not like Einstein Relativity which has been in many ways during his life and beyond his life. So yeah. Could all be wrong.
Thank you very much. I thought so, but was not sure. Now. If one were to confirm this radiation, but was (1) unable to detect it in space because eg detectors are not good enough or too much other radiation obfuscating the signal etc. and (2) unable to detect it in the lab, because we are unable to build a small black hole etc. -- would it then be possible to set up an experiment without actually resorting a black hole? Eg. would smaller pertubations in spacetime cause something like a phase-shift between these vacuum-modes mentioned in the video?
There have been analogs of it observed with things known as 'sonic black holes'; these are set up in a lab as drains where a fluid is falling in faster than any wave in that fluid can move. The analog behaves equivalently to a black hole; it stretches fluid waves as they try to escape from it, bends their path and emits Hawking radiation. At the moment while it's speculation there's no good evidence (Or any evidence really) against it. It's also proven very VERY difficult to eliminate from theory. So if it is not observed when it should be something BIG will have to change in physics.
@Steven Moore Oh yes, there are limits. Taken strictly an experiment is only valid for the exact laboratory situation it was performed in. And there are more mundane situations where this restriction is actually necessary. Medications have failed because the mice it was tested on were kept at the wrong temperature, stressing their bodies and altering their responses. Plumbing systems have collapsed because daily pressure variations didn't happen in the setup they were built in. In the end experiments of all kinds are a guide. They never give us certainty, only increased confidence. Often the best thing to do is extrapolate and then ask 'How do we test this prediction?'
They said that in the 1960s. He lived 50 more years to 76, which is pretty good given the average life expectancy at the time. Hawking in his life, did to that saying what he did with so much else; proved it was incorrect and there was something better. Burn bright, burn long. It's been done before.
It's basically saying that virtual anti particles and a particles can appear in the vacuum as quantum fluctuations. These usually annihilate each other but due to the strong gravity of black hole one of the particles falls into it. Energy can't be created out of nowhere so the black hole has to lose the same amount of energy that the escaped particle escaped with
@Steven Moore I think hawking radiation is energy, hence a "virtual" particle. When something is dropped in a blackhole it releases a lot of energy anyway, so the liberation of negative virtual particles may be possible. Either way, I am sure a qualified physicist can give a reasonable explanation because hawking was smart enough to see such an obvious contradiction.
@Steven Moore ah I found the answer I think. The point of no return is the event horizon, but the negative particles don't actually reach that border before they accelerate and escape.
He didn't. That was just a meme through photoshop. From my understanding, he was mentioned in the Epstien files, although as someone who only met Epstien at a physics convention.
@@pokedactyl No he did and was on St Thomas island in March of 2006. He was there with other scientists doing a conference called: Confronting Gravity: A workshop to explore fundamental questions in physics and cosmology. There are pictures of him there as well as the other scientists and spokespeople. I know its hard for some people to imagine this guy on the island but sadly its true.
Hawking was great inspiration even for many ordinary people. He was one of those people whose words could make even my depressed mind to get inspired and look for more information about how things may (or may not) work at scales our common sense fails. I wonder who will be next big celebrity to raise from world of science, there is now great void that will take great person to fill. Rest in peace Hawking.
I'm a huge fan of every PBS channel, but as a foreign, I feel this guy speaks in a veeery low range and with the heaviest accent of them all, he's the one I have more trouble with understanding.. And this is perhaps the most complex channel lol, maybe take this in count so he could speak a little higher? I don't know how strange this is lol
He's not going to change his speaking range or accent. It's not like he's playing a role in a movie. I have no problems understanding him. Just rewind if you miss something.
+ciervo42 Lo siento, mate. It's the Aussie slur...although Pr O'Dowd is also VERY soft-spoken. Still, I would have him any day, as opposed to Gabe (former host) who spouted words at machinegun's speed. :)
His body is in the dirt, but the man himself is up in the stars with Einstein, solving the Theory of Everything to show us all when we finally go to meet them ourselves in the future.
The Casimir effect, the Lamb shift and a certain interpretation of the Einstein coefficient of spontaneous emission all point to the physical reality of virtual particles.
"Black Hole Explosions?" Not only a unique paper by Steven Hawking, but 1974's version of click bait. Hawking ahead of his time in more ways than just physics.
I mean if the black hole is the right size I dont see what else you would call it.
One of the very early papers on black holes (by Wheeler) was called "Black holes have no hair". It's not unusual to give titles like these. ;)
One of the first things you learn about scientific papers is that there's a lot of them. So the challenge is to make other scientitists read _your_ paper. Having an exciting title is one way to do this. The challlenge is of course to actually come up with an exciting title that is still relevant to your work.
Why did the virtual particle cross the event horizon?
...
To get to the other side!
Yep except for the lack of a click, bait goes way back. Titles and short descriptions that get quoted in articles and catalogs sometimes worded to get you to go get the whole thing and read it.
I saw Stephen Hawking speak at Berkeley (around 1989?); he could use his hand to control the speech synthesizer at that time. After the talk there was a Q&A. Some guy stood up and said, "Do you think that general relativity might be wrong, and if so.." "No!" came out of the speech synthesizer. It was hilarious.
DrB1900 Haha I miss his humor
If you use Einstein’s original equations then the answer is yes.
@Steven Moore at the moment we think General Relativity in general is correct.
They're both wrong.
That's a great story, I wonder if a video of that exists somewhere. If parents brought their camcorders to their kids' class plays years before 1989, surely at a talk of Hawking, someone would have brought something there.
I remember watching this video as a high schooler when Stephen Hawking passed away. Understanding nothing, scratching my head. Three years down the line, I am happy I have the chance to revisit these videos and actually follow throw the description as a physics major. Don't worry y'all, you have got this!
I am curious, at what point in your education did you start to understand this?
@@jerrickmarques8777 I dunno but I think that I’m starting to understand this . I’m in 10th grade and love astrophysics and cosmology (astronomy)
I don't. Because I don't study any of this.
But I appreciate that these videos make it quite clear that I'm not getting it. Unlike some other popular science channels that just completely obmit the crux of the topics.
How’s it going now?
yeah i recently gained a passion for space and im a junior in high school and after this video im thinking i needa learn some more building blocks first, i seriously wanna get into astrophysics tho, dedicating my time into studying this💪
Not to distract from the honouring of Stephen Hawking, but I just gotta say: Matt O'Dowd, you are by far one of the best science explicators of our day. Hawking himself would be proud! I never would have gotten the concept of Hawking Radiation so completely without this video. It is so incredibly information-dense, it's almost a singularity in itself! ;-)
[I should give credit also to Graeme Gossel (co-writer) and Grayson Blackmon for his excellent illustrative graphics. But c'mon you two, Matt _is_ an awesome science explicator anyway, even if he got expert assistance from you guys, ain't he? ;-D ]
it is so true
Detract.
@@jerribee1 why should he
Ditto
Honest question: Is he really? Or is he just a model reading a script? I don't know.
“Remember to always look up to the stars and not your feet” Stephen Hawking is one of the main reason as to why I began perusing Quantum and Theoretical Physics. Thank you for everything Dr. Hawking.
It's very important not to look up to your feet. Because if you are looking up to your feet, it means you're upside down and probably about to land on your head. Then again, in that situation, maybe looking up to your feet is a good idea after all, because then maybe the back of your head will strike the ground instead of the top of it straight on, and that may be less traumatic.
How's that doing?
Wait a blazblue player, mainly a Terumi main doing quantum physics and theoretical physics
Are you sure it's not because he couldn't actually look at his feet?
🤣
Actually, looking at your feet is pretty much looking up at the stars, because the Earth is transparent to neutrinos.
"I have noticed even people who claim everything is predestined, and that we can do nothing to change it, look before they cross the road." -SH
"If you believe in determinism (...) then you have 2 choices". Perhaps, however if the universe is deterministic, then you have none.
de Broglie nope its not predetermined.you choose if you want to take the time to check before crossing. Next time you cross the street...stop and think "should a double check first or just walk without looking" I hope u check first.
but not everything is predetermined because of quantum uncertainty affecting very complex systems in an unpredictable way.
Sorry but these words shouldn't belong to someone who had such a great imagination and contributed so much to science. Perhaps, his hate towards "God" made him to desperately deny His existence due to his condition? We'll probably never know.
I mean, what is so difficult to understand that if they don't check the road, it is destiny. If they do, that is also destiny. From his quote, one would think that people who believe in destiny should just sit where they are until they die. But that is not how teaching of destiny works in religious and non-religious belief.
This is the best explanation of reasoning behind "belief in destiny" from a non-religious point of view: th-cam.com/video/o0GN4urbA_c/w-d-xo.html
Nicat Memmedov he actually talks a lot about "God" and not once did he say he hates God. And actually its the other way around. He believed that because of his condition he was able to spend more time thinking about the things "normal" people wouldn't. So I'd say he was not in hatred for god but also based on what he has said, his version god is far from what the religions want you to believe
"I am Matt O'Dowd, this is space time, and its time, for HAWKING RADIATION"
Space-time fans have been waiting for this since so long!!
I know this might sound a little crazy but I've been thinking about this for a long time if matter is mostly empty space then could the universe as a whole be a solid I hope you don't think I'm insane
@@charlesdrury1587 The universe contains matter but it is not matter itself. So it cannot be any state of matter. You could describe it like a web or any other analagous structure, but the universe is not actually made of anything, it just is. A stage has actors but does not recite lines.
Thanks for this episode. It's a nice way to say goodbye to a great guy.
Little Tivor In his honor we did an animated video explaining his famous hawking radiation theory, if you want for a fun animated yet very educative video you can check our Hawking radiation video in our channel !
Nice episode, and big respect for not putting advertising in the episode too. You guys rock!
RIP Dr Hawking.
agreed, that was classy
I would rather watch some ads and be sure this channel keeps existing. I don't see the big problem
@@jonnnnniej bc many of us pay for no ads, and now the channels spend ten plus minutes promoting their sponsors so we can't escape it. Some channels, like psych2go, do their promotion right smack in the middle of their videos.
Hawking did all of this in his head? Goddamn that's impressive.
How so? At the graduate program level all of us learn to do days'-worth of math in our heads. We only write it down so our peers can check our work in real time. Peer reviews are the reason there's still chalkboards in universities. Or if you're working on a problem during a walk, you'd use pencil and paper, snap a pic, and send it off for review. It's really the only time we ever write equations down.
@@HolyGuacamolean wait, really? I can barely remember things just a second after looking at them half the time, and you can remember that many equations at once?
@@noahwilliams8996 Ah. You've got to work your brain 🧠 like a muscle. If you do math with calculators only, you'll experience what a lot of people experience with GPS these days....they know how to drive and the rules of the road, but not how to get there on your own because you were never paying attention to the route and the surroundings. Just the GPS directions.
@@HolyGuacamolean totally true i am probably smarter than dr hawking bc school is soooo hard 👁👄👁
n, nither alone. He had a co-worker writing down everything and discussing with him
Nothing I can say will ever convey what needs to be said... Thanks, Dr. Hawking.
and thanks doctor penrose
What's crazy is the Hawking Radiation episode had already been planned according to recent episodes.
Beautiful.
Your welcome
Not only a great scientist, but also a great communicator LOL
I mean this quite literally when I say Stephen Hawking introduced me to the love of my life. From the day that I snagged "The Universe in a Nutshell" off of my father bookshelf I fell deeply and madly in love with all things physics. The more I researched the more I loved it. The more I learned about Hawking the more I respected him and marveled at all his accomplishments. My life and the life of millions of others will never be the same. RIP Professor Hawking.
That man achieved more from a wheelchair suffering from a progressively degenerative disease than most healthy people do in a lifetime.
RIP
Very confusing
That man also possessed genius far beyond the average person
Cuz we r concerned with dopamine pleasures
@@anom3778 ooooor because he was way smarter than the average person..
Dopamine pleasure is nice to know about, but isn't the reason behind everything..
@@dwiski I understand but if we could create a world where people could study all day and have no other distractions we would have a lot more smart geniuses like hawking einstein and Newton. I think most people have that potential they just don't know it.
That feeling of frustration when u want to understand something soo bad ,but can't....:(
Im sorry :''''''''(
It's been a year. I understand better now :)
@@rajeeshsp8723 Any tips for someone in your shoes when you originally posted?
@@pathayes1757 Read books!! Watch more videos!! It'll be frustrating in the beginning but you'll slowly start recognizing terms and understanding better. I'd also recommend watching kurzgezagt videos. They explain many topics in layman's terms. Read hawking's books as well and if you come across a term you don't understand, stop and find out more about it before continuing. (Ik it's time consuming but if you're really interested, it's worth it!). Hope this helps :)
@@rajeeshsp8723 I agree brother
The best part is that this episode was already planned to come out soon
Lelouch Yagami weird...
Donald Trump it's really you??
Did SpaceTime kill Hawking?????
FOX NEWS
That's the best part? That they raced to release it early in order to ride the wave of sympathy for Hawking's death to get extra views?
Rip hawking
Dead without fear of the unknowable.
Time has stopped for poor decrepit old Hawking, so no more delusions of science fiction to infect the minds of our youth with his self-contradicting drivel. Oh no, Mr Hawking will be instantly transported to the end of time where he will face the Eternal Creator and Judgement for his crimes against humanity. Good riddance stephen, because I cannot imagine eternal life with a repulsive little nutter denialist like you as my neighbor:)
eg. of classic Hawking drivel - "“Because there is a law such as gravity, the universe can and will create itself from nothing,” “Spontaneous creation is the reason there is something rather than nothing, why the universe exists, why we exist. It is not necessary to invoke God to light the blue touch paper and set the universe going.”
BWAHAHAHAHA - like I said, self contradicting drivel from a delusional old fool.
delawarecop
Ah, must be this Christian love, to have fun imagining someone get punished, because he doesn't agree with ones fairy tales.
Crawl back into your hole, troll.
delawarecop 1) The Bible contradicts both science and itself several times on the first page: *In the beginning God created the heavens and the earth.* [a] 2 The earth was formless and empty, and darkness covered the deep waters. And the Spirit of God was hovering over the surface of the waters. 3 Then God said, *“Let there be light,” and there was light. 4 And God saw that the light was good. Then he separated the light from the darkness. 5 God called the light “day” and the darkness “night.”* And evening passed and morning came, marking the first day. 6 Then God said, *“Let there be a space between the waters, to separate the waters of the heavens from the waters of the earth.” 7 And that is what happened. God made this space to separate the waters of the earth from the waters of the heavens. 8 God called the space “sky.”* And evening passed and morning came, marking the second day. 9 Then God said, “Let the waters beneath the sky flow together into one place, so dry ground may appear.” And that is what happened. 10 God called the dry ground “land” and the waters “seas.” And God saw that it was good. 11 Then God said, “Let the land sprout with vegetation-every sort of seed-bearing plant, and trees that grow seed-bearing fruit. These seeds will then produce the kinds of plants and trees from which they came.” And that is what happened. 12 The land produced vegetation-all sorts of seed-bearing plants, and trees with seed-bearing fruit. Their seeds produced plants and trees of the same kind. And God saw that it was good. 13 And evening passed and morning came, marking the third day.
14 Then God said, *“Let lights appear in the sky to separate the day from the night.* (Emphasis on "lights" and "seperate the day from night") Let them be signs to mark the seasons, days, and years. 15 Let these lights in the sky shine down on the earth.” And that is what happened. 16 God made two great lights-the larger one to govern the day, and the smaller one to govern the night. *He also made the stars.* (Emphasis on "also") 17 God set these lights in the sky to light the earth, 18 *to govern the day and night, and to separate the light from the darkness.* (See second bold) And God saw that it was good.
2) If you were born in Nordic times, you would look at lightning, not understand how it works, and then blame it on Thor. Just because we cannot currently explain something doesn't mean that an invisible unicorn-riding leprechaun did it.
3) None of Hawking's work contradicts itself.
delawarecop
It looks like you are dancing on the grave of Hawking and your God will let him but for eternity....
...Christians are so full of love! Bless you!
As an artist and a student of theoretical physics, can I just say YOUR DIAGRAMMATIC ANIMATIONS ARE AMAZINGLY SUPERB!!
I think this was the best tribute to Stephen Hawking. He'll forever be remembered as being one of the great scientists like Einstein. Rip Stephen Hawking
EDIT: I think some people took it the wrong way. Here, when I said "He'll forever be remembered as being one of the great scientists like Einstein" I am not comparing Hawking to Einstein or their ideas. My intension behind that was just that even though he's dead, his ideas will live on and he'll be remembered as one of the great scientists. I am NOT comparing Einstein to Hawking or their ideas.
hawking was great, but comparing him to einstein....hm
I think some people took it the wrong way. Here, when I said "He'll forever be remembered as being one of the great scientists like Einstein" I am not comparing Hawking to Einstein or their ideas. My intension behind that was just that even though he's dead, his ideas will live on and he'll be remembered as one of the great scientists. I am NOT comparing Einstein to Hawking or their ideas.
I think he'll be remembered for a very long time. Like Einstein, as you clarified, no. But like Gauss, certainly. Someone whose name still inspires awe among the informed over a century and a half after he died, but not well known among lay people.
KappaW He will not.
KappaW sure sure just like Aristotle, Buahahahaha
A truly marvelous tribute, remembering Hawking through his incredible work and explaining his ideas with fair detail and rigour. Will always have respect for Hawking and PBS Spacetime.
Ok, let’s try this again.
Every month or two I watch this video telling myself “ *this* time I’ll understand hawking radiation.”
RIP Stephen Hawking. Semiclassical approximations of QFT in curved spacetime is a fantastic legacy for a brilliant man.
zero132132 In his honor we did an animated video explaining his famous hawking radiation theory, if you want for a fun animated yet very educative video you can check our Hawking radiation video in our channel !
FINALLY an explanation that talks about the actual calculation, i.e. transforming the vacuum state between two null surfaces. The interpretation of particle-antiparticle pairs near the horizon is very flawed and little more than an easy-to-understand oversimplification.
My only question is, what about a block hole chomping out a bit of wave makes the universe go, _Hey, you just spat out a particle!_
kindlin, that question demands a bit of a complicated answer. So the key thing to understand here is that this wave is not a "literal" wave. It's an "imagined" wave. If a wave were actually there, it'd behave like that, but we are just imagining. In quantum field theory those "imagined waves" are very important concepts. We call them "modes". In a theory of classical waves, these modes could have any amplitude, but in a quantum theory, they only come in discrete bits, which we call particles.
We borrow the theory of something called the quantum harmonic oscillator to describe particles. For each mode you can talk about objects called "creation" and "annihilation" operators, which are mathematical objects that, as the name says, "create" and "annihilate" particles. There is a state from which you can't remove any more particles with the annihilation operator: that state is called "the vacuum". You can find all other possible states, with all possible numbers of particles, by applying creation operators for the various modes to the vacuum.
The "chomping a bit of wave" by the black hole does something interesting: it changes what kinds of modes exist before and after the black hole forms. This means that if space was empty before, it is no longer empty _after._ Mathematically, this is represented by a relationship between the creation and annihilation operators before, and the creation and annihilation operators after. It's like the presence of the black hole changes what it _means_ for space to be empty.
Essentially the vacuum state is not the same for all observers. You can see that in for accelerating observers (who perceive Unruh radiation) and observers in a gravitational field who are not in free-fall (so essentially in an accelerating frame). Hawking showed that the same is true for black hole geometries for past null infinity and future null infinity.
What is quite brilliant, and somewhat confusing, about this is that unlike the accelerating frame, which can be contrasted to an inertial frame, and the frame of a body hovering above some mass at a finite distance, which exists locally in curved spacetime, the frame of something very far away from the black hole is asymptotically flat. So we see that in Hawking's example, which is a dynamic spacetime in which a horizon had not formed in the past but does eventually form, the existence of a horizon changes the vacuum.
But the best reason for why BHs must have a finite temperature comes from thermodynamics. So think of two cases where some gas with a finite temperature collapses to form a BH, but with the first case you have more gas than in the second case. If BHs have no temperature, then it would appear that black holes are destroying entropy (note that this is DIFFERENT from the BH information paradox!). So to rectify this BHs must have a temperature, which is proportional to the curvature of the horizon, and an entropy, which is proportional to the surface area of the horizon. Bodies with a finite temperature must emit thermal radiation, so there.
Vacuum Diagrams: Thanks for the insightful explanation. Two easy questions: What is a quantum field made of: I know it is a mathematical construct, but it must also exist in the real world in order for modes like particles to come into being.
And what is the difference between a quantum field and a classical field like the EM field? We know the magnetic field is physical because it can move iron filings on a piece of paper. So EM fields must be composed of forces at every point in space or something like that. Can you explain, please?
I'll answer your second question first: what does it mean for something to be a quantum "anything"? Generally, it means that the observable properties of this thing "don't commute". This is mathematical lingo to say that measurement of one quantity _must_ affect a subsequent measurement of the other. For example, if you measure a quantum particle's position, you automatically change its momentum in a random way. So the results of the measurements depend on the order in which they're done, that is, they can't be "switched", or... "commuted". When you see someone use the word "noncommutative" with regards to quantum mechanics, that's what it means.
In a quantum field, there are analogous properties to position and momentum which do not commute. These are, for example, the value of the field, and the "field momentum", which you can think of as proportional to the rate at which the value of the field changes over time, just like momentum is proportional to the rate at which position changes over time.
The specific commutation relations depend on what kind of theory you want to study. Most often (though not always) we use quantum field theory to study relativistic systems, so the recipe we follow is the following: we pick a reference frame, and we select a time in that reference frame (simultaneity is relative, so this time will correspond to a bunch of other times in other reference frames). We then say that almost everything commutes, except for the field value and the field momentum at each given point, where they follow a similar rule as ordinary position and momentum. Then you have to actually think about the dynamics of the theory to see how these commutation relations evolve over time.
This all sounds complicated, but it's actually very reasonable: all it means is that a measurement of the field here couldn't possibly affect a measurement in the andromeda galaxy. But a measurement here can surely affect other measurements here, and my measurement can potentially affect other measurements in my future light cone as well.
So... what is it made of? Nobody knows! Nobody knows even whether that's a sensible question to be asking. It could well be, so I'm not disparaging, but it might not be. All we know is that these are very "delicate" objects, in a sense, which are always affected by measurement in a way we think we understand.
76 With ALS we all should be grateful he was alive for so long while being so sick.
He made us think question doubt everything, he has inspired his successors and will always be known as one of the legends of science.
Yaman just so you know, Stephen hawking was against pretty much everything trump stands for and said so pretty explicitly.
Too brilliant to be expressed in mere words... That's the type of video we need even more! Thank you Matt and spacetime.
Stephen was the subject of my conversation today from Florida to Israel and I couldn't say enough about him. I wish I had this video ready to play. There's always tomorrow.
I don't really understand this, but i'm going to try to anyway in honor of Hawking.
Something about waves.
shatley123 In his honor we did an easy to understand animated video explaining his famous hawking radiation theory, if you want for a fun animated yet very educative video you can check our Hawking radiation video in our channel !
Basically hawking radiation is the release of some sort of energy since black holes lose more energy or mass then they gain so it slowly shrinks down until it collapses on itself.
Even though I am 2 yr late the particles called virtual particle is randomly created from nothing and is formed in pair which annihilate each other a when it is formed near black hole one of the pair like negative one go in it and positive goes away hence the Hawking radiation and black hole will be smaller and smaller or evaporates out until it is no more and for small black hole it takes1*10^60yr and bigger black hole 1*10^100yr
@@APXSTUDIO I've heard that explanation for years and never could understand how the black hole absorbed mostly antimatter instead of absorbing an equal or near equal amount of matter and antimatter.
Remember to look up at the stars and not down at your feet :)
That's beautiful.
I used to do that, then I fell down a flight of stairs.
Wait a minute.... Did your house not have roof as well!!
I doubt anyone will have any problems with that first part. Podiatrists might take issue with that second part though.
With Stephen Hawking no longer in our life it feels like they’re a new found void in the world that no great mind will ever be able to fill in the way he did. Not only was he an amazing physicist, he was also an amazing person. He will be remembered for both his work and person for centuries to come. While his work will remain, his person will be greatly missed by all. ❤️
You are truly performing a service for us all. My hat is off to you and I thank you.
This series of episodes is, in my opinion, a marvel of education. You actually pulled through, and I for one feel enlightened on the subject after decades of hobbying around it. Thank you very much.
*We should make his dreams come true: send nanocrafts to the exoplanet Proxima b within the next 20 years*
We can do it, if we stop invading other continents and attacking every nation that's less advanced as we are ...
NUKE Competition leads to advancements.
dragozal Competition does lead to advance, but sabotaging your adversary doesn't.
dragozal Competition is not the only way to advance. Competition is not necessary.
Nice to meet you here!
I came here from a video suggesting I watch this video first in a playlist, to understand that video...and yet this video also has a playlist to under what this video is talking about...it's playlists all the way down
It's so ironic. On Tuesday afternoon, the day that he passed away, i was telling some friends about the internet rumor that he had died several years earlier. Less than 12 hours later i hear the news.
Stephen Hawking who stood on the shoulders of giants who came before him, now joins them to broaden the surface on which humanity have to stand on. Thank you for your contributions. You will be missed and I hope that those who build on your work in the future sends you a thought of respect every now and then. You were given a bad hand but made more with it than most could ever dream of. I wish I had a fraction of your strength and determination.
We can all learn from your example. Truly, you were one of a kind.
I'm so happy you did a video about Hawking's work this week. Thank you, PBS SpaceTime, and thank you so much for all you shared with us, Dr. Hawking.
Hawking was a supernova, a light house for us all. His passing leaves a black hole.
We really breathed the same air as him...what a guy!! And what a loss!!!
Hawking also gave some sick burns that will live forever.
Julia-6 In his honor we did an animated video explaining his famous hawking radiation theory, if you want for a fun animated yet very educative video you can check our Hawking radiation video in our channel !
I really hope that he isn't remembered only for such reasons on the distant future
how, you actually made me understand Hawking's work a little bit! this is the best tribute to him you could make. thank you.
Oh my goodness, this might be my new favorite youtube channel ❤️❤️❤️
"Empty space seethes with activity" From Beyond, HP Lovecraft
8:45,
It's pretty convenient that only the antimatter particles fall into the black hole, allowing only matter particles to escape.
That's because Hawking started from the assumption of a vacuum evolving forward in time to the infinite future. If you do it in reverse, from the future to the past, you'd find only antiparticles "escaping". Still, the whole derivation is based on math hacks, and while some physicist might tell you otherwise, Hawking radiation is far from a real thing. We've never observed it, and it leads to multiple paradoxes. Usually, paradoxes where thought of as stemming from erroneous assumption (this is basically how Einstein derived special relativity), but for the last 50 years or so paradoxes and infinities have been brushed under the rug with the excuse that our theories are not complete, not that they are based on wrong assumptions. You can thank Bohr and the Copenhagen school for that.
@@FunkyDexter what if the universe contains paradoxes and infinites, and our wrong assumption is that it has none?
@@ffffffffffffffff5840 Then we would have to abandon all hope to make sense of the universe. The whole premise of science is that we can make sense of it, and assuming otherwise is just not constructive.
@@FunkyDexter that's fair. I mean clearly we've made some sense of the universe, since we're both able to use technology to communicate with each other even though we've never met.
A lot of the sense the universe has made has been counter intuitive, so maybe it will get even crazier from here.
Time will tell, the scientists are working on it as we speak
My boy was clapping cheeks, exploring event horizons at epstein Island
My favorite vacation destination
Lmao 🤣
I have watched this and related videos a number of times. It does my head in...
I've watched a few videos just to comprehed hawking radiation, but yours is the best bc u explained instead of leave us think about why
He also disproved time travel by throwing a time traveler party but non turned up he released a press conference about it the day after he had the party...The man is a legend
That only proves no time traveler ever got his invitation...
If I were a time traveller, I wouldn't want to attend a party known for everyone invited not showing up.
Thank you for this video! I have always wondered that why the negative/anti-matter half of the virtual-particle-pair falls in the black hole and not the positive one. Now that you explained it I don't understand it at all, but that's ok, nature does not own me explanations :)
All real particles are have positive mass / energy and obey the usual energy-momentum-mass relations. Black holes have an entropy and non-zero energy, so they have finite temperature. Objects with finite temperature emit thermal radiation. For black holes that's Hawking radiation.
>Now that you explained it I don't understand it at all
That's why I like this channel. It doesn't give me the false sense of having understood a complex topic that I only have a superficial grasp of.
Thank you Stephen Hawking for your discoveries and contributions. May you Rest In Peace.
I was 100% convinced that Hawking Radiation does not evaporate black holes... your explanation along with the visual graphics in this video has demonstrated that it could at least be a possibility, justifying further research into this topic. Well done, you have peaked my curiosity. 🤔👍
The best channel on yt... ever!!!!
Thank You for everything! I learned a lot!!
❤️🏆🏆🏆😎🤓🤓
This guy’s voice puts me to sleep, not because it’s boring but because it’s so damn soothing.
If Hawking radiation can be thought of as quantum entangled matter/antimatter pairs that are being ripped apart, is there any conceivable way to be able to study the particle of the pair that is trapped in the black hole by looking at the one that is outside, thereby sort of "seeing" inside the black hole?
that is pretty much one of the proposed solutions to the information paradox. That the hawking radiation ultimately contains information of all the stuff that fell in, because stuff falling in change its properties.
I was just thinking this same thing. This would make a great SpaceTime episode.
Maybe separation by an event horizon breaks the entanglement???
Good question
Wait a minute
No actual information is transmitted between entangled pairs which is why super luminal communication is not enabled by entanglement.
I wonder though about the effects of gravitational time dilation on the entangled pairs. The particle inside the event horizon will be feeling much stronger tidi than it's partner. Can they remain entangled under these circumstances?
History will remember him as we remember Einstein and all the other great scientists. Forever.
Fenghuang I agree
I doubt it, his impact on theoretical physics isn't that significant and well it's all theoretical with very little chance of being confirmed. That very different than what Einstein did. He will be remembered but it's going to greatly amplified because of his physical disability vs the weight of contribution to science.
Well Einsteins predictions weren't confirmed right away, I mean we are still confirming parts of his theory such as gravitational waves etc. And Hawking was a pretty decent physicist despite being a vegetable as far as promoting and pushing the frontiers of scientific endeavors go.
*Tesla
Fenghuang In his honor we did an animated video explaining his famous hawking radiation theory, if you want for a fun animated yet very educative video you can check our Hawking radiation video in our channel !
Thanks for the special episode Space Time 👍
This answered me a question tingling me for years, only to open a whole new spectrum of questions.
But what's science without tingling questions. :-D
Thanks for the breakthrough.
He is like a faraway star, although he is dead his brilliant light will shine on. He has changed the course of time forever and will live on in are hearts inspiring generations to come. We miss you Professor Stephen Hawkins, we always will. RIP
All of this ties into a theory that plagues me.. If I only knew the math! 😳
I feel your pain, my friend.
There's tons of lectures on youtube.
Stephen Hawking's science will enlight us forever. Farewell, master
Martín Díaz Cuesta In his honor we did an animated video explaining his famous hawking radiation theory, if you want for a fun animated yet very educative video you can check our Hawking radiation video in our channel !
Thank you very much for this video!!! Just the topic I was looking for for the past month..... Was even going to recommend it in the comments when the sad demise happened
Thanks! On a completely tangential note, there was a chess Grandmaster named Efim Dmitriyevich Bogoljubov (4/14/1889 - 6/18/1952). He even played against Alexander Alekhine for the World Chess Championship - twice (though he didn't win.) 𝕥𝕒𝕧𝕚.
Amazing episode! I cannot wait for a deeper review of Unruh Radiation! Could anyone recommend a text that explains some of the profound implications of it?
I do have a rather dumb question: what limits the energy of the radiation produced by a black hole? Could a fluctuation with high enough energy be produced that could, say, create and decay into insane amounts of particles and form an entire planet?
I'm no Stephen Hawking, but what I've seen about it on videos like these indicates that the final evaporation of a black hole, while highly energetic, doesn't contain nearly enough energy to make even something the size of a coin, never mind a planet.
Interesting! Thank you
Okay, I'm slightly wrong. Per en.wikipedia.org/wiki/Hawking_radiation, an ideal black hole will radiate energy equivalent to 2.28×10^5 kg of mass during its last second of life, which is 2.05×10^22 J or 5×10^6 megatons of TNT (direct quote). So, more than enough to make a penny, or even a decent-sized car, if it somehow all resolved itself into the appropriate configuration of subatomic particles. As this would represent a spectacular decrease in local entropy, you might get a spontaneous car-sized mass once in a googolplex events or something along those lines.
Well I'm not a physicist but doesn't the energy of a wave depend on it's frequency? If so, and the wavelength (and therefore the frequency as well) is given by the radius, I don't think there are any fluctuations at all.
I could be entirely wrong, but the way I understand it is that the fluctuations are only large enough to produce massless particles over a fairly large range of possible locations, depending on the size of the black hole. I don't think it would be likely that there would be a significant amount, if any, mass produced this way. Just my interpretation though, I'm certainly a little underqualified haha.
Can quantum entanglement be preserved between two particles after one of them has fallen inside a black hole?
If it is quantum field that is distorted by a black hole, doesn't it mean heat glow or radiation is not emerging from black hole itself, but energy of vacuum, meaning there is no loss of mass of the black hole?
The energy must come from somewhere.
His voice is so freaking relaxing.
Excellent explaination which took my knowledge of Hawking Radiation up a notch, now give me your shirt.
I guess we are just waiting for the next genius to figure out quantum gravity
Well it ain't me! Got enough on my plate as it is...
a next Eisntein, last time we had to wait like 300 years
Paul Austin well society and technology is evolving and developing more than ever so we might not have to wait that long
Agree but sometimes we need an outstanding human being like Galileo, Newton, Einstein to take a big leap, someone who thinks outside the box
reece anley I hope I get to be as good Hawking. Studying physics, I dream to be a scientist one day
9:50. I've heard a theory that Hawking radiation can spawn photons having an energy exceeding the rest energy of the Planck mass. The probability is, of course, very low, given the exponential decline of the Planck distribution. But if such a photon were emitted, it would immediately become a kugelblitz, another black hole.
If this same thing happened in vacuum to a photon that remained virtual when it developed its event horizon, then it could not thereafter decay or be annihilated by merging with its antiparticle. It would, instead, detach from our spacetime and begin to occupy a separate spacetime, initially one having only a single point. This state would violate the uncertainty principle, and that one-point spacetime would undergo a change of state where in a singular quantum state became a plurality of quantum states - probably with a vengeance.
Hawking can exist but never escape. There is a finite period of time between generation of the pairs and annihilation . During that time, however small, the particles fall below the event horizon. When they annihilate the resulting radiation cannot escape. I'm surprised no one has pointed this out. Even if the pairs stay separated no particle travels at light speed and would fall back into the black hole.
@@stevelenores5637 Hawking radiation appears as conjugate pairs. They attract each other very strongly. If one member of the conjugate pair falls below the event horizon, all of its potential energy on its partner becomes a general property of the entire black hole and isn't focused on the still-outside partner anymore. It appears to be possible that the gain in (kinetic) energy for this still-outside particle can exceed the gravitational potential energy that binds it to the black hole. In that case, it can escape.
@@Jenab7 I agree it could but it is very unlikely that it will escape. And if it did it would need to reach orbital escape velocity. Orbital velocity near the black hole above the horizon is already near light speeds. Most like if the particle is very very lucky it will orbit a few times and decay back below the horizon. I'm not saying Hawking radiation doesn't exist only it unlikely it will ever be detected. Mathematics and physics shows it can happen, it doesn't prove it can escape for long. IMHO
Think it of as POW camp on an island. The prisoners might escape for short period but they will be rounded up and locked back inside again.
@@stevelenores5637 The components of a conjugate pair are opposite in charge, but they are equal in mass. If one of them goes under the event horizon, then the other one gets about its rest energy as kinetic energy, which automatically boosts it to 87% of c relative to its prior reference frame. Also, there's no reason for why that prior reference frame had to be motionless relative to the black hole. It might be travelling, too, at some appreciable fraction of the speed of light. Stephen Hawking did a calculation on the distribution of kinetic energy of particles escaping from the vicinity of a black hole and concluded that it would be a Planck distribution, such that Hawking radiation would mimic a black body having a temperature that depended on the black hole's mass.
Remember particles shed energy quickly at relativistic speeds. They won't stay at 87% C for long, especially fighting the black hole gravity field. Also orbital speed at the event horizon is C. It only drops to 1/2 C when you get the neutron star equivalent radius. Not sure what the distance would be for 87% C orbital speed (probably a consistent multiple of the black hole event horizon but may have an exponent factor). Likely to be much higher altitude than where the particle formed. IMHO
Don't ask me to do the math. My textbooks have been in storage since the pandemic.
Genius of our time? I am so old, I remember when Einstein was alive.
Well, I remember when Tesla was alive.
@@쵸스타나크라켄첫템 I remember when Newton was alive.
@4:48 "not to be deterred by the impossible"
Now there's an epitaph for Hawking if I ever heard one.
The very explanation of Hawking Radiation I've been looking for. Thank you!
How did I end up here? I was learning how to finely chop an onion.
Onions have layers, black holes have layers ... one is obviously the other in disguise.
Onions = black holes confirmed‽
Lord American it all makes sense now then.
you know who else has layers?
So onions are black holes are ogres?
The universe led you here.
This is so frustrating, I really am interested in this topic... but I don't understand a word he said. When the last guy who voiced those episodes was talking I was somewhat able to follow but the format just got more difficult and now I am at a total loss.
Yes, his speech cadence totally throws me off.
dont feel bad, this is the most difficult topic in physics and perhaps in all science
I am not really having problems with his rythm or his choice of words. To be honest I can understand him better than the previous guy, who talked a tad too fast for my taste. Though English is not my native tounge I understand what he says, though I can not get a grasp on the meaning, not being able to fit the pieces together... that is what is frustrating for me.
Yes indeed, it is a really difficult topic and I am amazed on the knowledge he and his team have on it. Truly amazing that there are people out there who, though hard work no less, are able to understand and formulate ideas and new theories out of it.
The old guy was fine, but he seemed....youtubey. matt seems a bit more professional. Matt doesnt constantly ask me if hes blowing my mind...
This guy probably watched Jumanji and loved the "smoldering intensity" so much that he does it through this entire video.
Thank you for all those excellent and very informative videos.
Of the many tributes that were, and still are, rightly paid to Hawking, this is one of those that touched the deepest: in the absence of a fully unified theory of quantum gravity, with brilliant intuition and an ingenious 'hack', Hawking pushed back the horizons of our knowledge in all directions. And he did this, because, as Matt says, Hawking was "not to be deterred by the impossible"; it is this that lifts him so high, both as scientist and person.
Why is hawking radiation always displayed/assumed that it's the negative charged that goes in and hence evaporates the black hole? why not both mixed and balance that out. What am I missing?
I was sort of wondering myself why that assumption was made. If it's particle/antiparticle pairs, what's saying that the antiparticle can't be the one that escapes? Or does it even make a difference?
I'm not sure that I fully understand it myself, so I hope I'm getting this right, but the matter/anti-matter particles that pop into and out of existence in a vacuum take energy from that vacuum to do it, like the video said. The border where the event horizon is would have a pair of particles pop into existence that should both have belonged to the black hole, but because one popped up on the outside of the event horizon, it got away. Therefore the black hole lost a particle.
If this happened often enough on a massive scale (and it likely would), the black hole would leak energy over billions of years, although it would have to take in less stuff than it gave off to evaporate completely.
Because scientists are racists
Actually the black hole is not made of matter. It's what is called a "vacuum solution of GR", which is to say, it's one of the possible ways that spacetime can curve in the absence of matter. Sure it feeds on matter, but it is not itself made of matter. At least in GR. Understanding what exactly it's made of requires quantum gravity, but the important thing here is that Hawking's result does not depend on that. In fact the whole notion of "particles" is a bit sketchy in curved spacetime, but the upshot is: black holes evaporate because they absorb negative _mass._ You may think "well, how can ordinary particles have negative mass?" to which I'd reply "that's one of the reasons you can't think of it in terms of simple particles" :)
I like to think of them as un-particles since they are not antimatter. (which would emit gama rays when they recombine) I can imagine the un-particles flying out into the universe and eating matter without emitting gama rays.
Could de CMB be a horizon radiation due to the limit of the observable universe?
RIP Hawking
No, CMB is the photons that started their journey about 300.000 years after the big bang when the universe cooled so much that it was no longer plasma. This is the moment when the photons started being able to travel great distances without being absorbed by matter. Also, cosmic redshift made them stretch in wavelength so they are in the radio wave part of the spectrum.
I know what the CMB is supposed to be, what I mean is that if a horizon radiation would create a similar radiation, how do we know what we are measuring is those photones liberated when nuclei and electrons bond together and not a horizon radiation caused by the limit of the observable universe?
Well, CMB is 2.725°K, which means that λmax =~ 1mm (and that corresponds to the schwarzschild radius of the hypothetical black hole). I'm not sure, but this line of reasoning seems sound.
because that limit is observer dependent. An observer falling into a black hole still agrees on the limit thereof. IE; all observers will agree on the point of no return from a black hole, but not all observers will agree on the position of the limit to the observable universe. This is because one of those limits is created by the placement of the observer themselves, while the other is created by the gravitational impact on spacetime of the presence of the singularity at the center of the black hole.
What I always wanted to know: Has this Hawking radiation been observed, i.e. empirically confirmed somehow or is it "just" speculation?
It's hypothesis meaning conjecture that has been modeled in detail capable of being falsified. It makes predictions. If those predictions in observation and/or experiments are not observed then it gets thrown out. It's not like Einstein Relativity which has been in many ways during his life and beyond his life.
So yeah. Could all be wrong.
Just speculation.
Thank you very much. I thought so, but was not sure. Now. If one were to confirm this radiation, but was (1) unable to detect it in space because eg detectors are not good enough or too much other radiation obfuscating the signal etc. and (2) unable to detect it in the lab, because we are unable to build a small black hole etc. -- would it then be possible to set up an experiment without actually resorting a black hole? Eg. would smaller pertubations in spacetime cause something like a phase-shift between these vacuum-modes mentioned in the video?
There have been analogs of it observed with things known as 'sonic black holes'; these are set up in a lab as drains where a fluid is falling in faster than any wave in that fluid can move. The analog behaves equivalently to a black hole; it stretches fluid waves as they try to escape from it, bends their path and emits Hawking radiation.
At the moment while it's speculation there's no good evidence (Or any evidence really) against it. It's also proven very VERY difficult to eliminate from theory. So if it is not observed when it should be something BIG will have to change in physics.
@Steven Moore Oh yes, there are limits. Taken strictly an experiment is only valid for the exact laboratory situation it was performed in. And there are more mundane situations where this restriction is actually necessary. Medications have failed because the mice it was tested on were kept at the wrong temperature, stressing their bodies and altering their responses. Plumbing systems have collapsed because daily pressure variations didn't happen in the setup they were built in.
In the end experiments of all kinds are a guide. They never give us certainty, only increased confidence. Often the best thing to do is extrapolate and then ask 'How do we test this prediction?'
The more I listen, the more I love it!
That last paragraph was a brilliant bit of writing.
The brighter the star the faster it burns out
RIP DR Steven hawking
Leon Mclaren this one sure took his time tho. The man is an inspiration to ALS patients
They said that in the 1960s. He lived 50 more years to 76, which is pretty good given the average life expectancy at the time. Hawking in his life, did to that saying what he did with so much else; proved it was incorrect and there was something better. Burn bright, burn long. It's been done before.
Nope. I didn't get it. Followed along more than I anticipated though.
It's basically saying that virtual anti particles and a particles can appear in the vacuum as quantum fluctuations. These usually annihilate each other but due to the strong gravity of black hole one of the particles falls into it. Energy can't be created out of nowhere so the black hole has to lose the same amount of energy that the escaped particle escaped with
@Steven Moore I think hawking radiation is energy, hence a "virtual" particle. When something is dropped in a blackhole it releases a lot of energy anyway, so the liberation of negative virtual particles may be possible. Either way, I am sure a qualified physicist can give a reasonable explanation because hawking was smart enough to see such an obvious contradiction.
@Steven Moore ah I found the answer I think. The point of no return is the event horizon, but the negative particles don't actually reach that border before they accelerate and escape.
stephen WHYYYY did you go to the island WHAT DID YOU EVEN GET OUT OF IT DUDE
He didn't. That was just a meme through photoshop. From my understanding, he was mentioned in the Epstien files, although as someone who only met Epstien at a physics convention.
@@pokedactyl No he did and was on St Thomas island in March of 2006. He was there with other scientists doing a conference called: Confronting Gravity: A workshop to explore fundamental questions in physics and cosmology. There are pictures of him there as well as the other scientists and spokespeople. I know its hard for some people to imagine this guy on the island but sadly its true.
Bro was clapping midgets while exploring event horizons
Love this channel👍👍⭐⭐⭐⭐⭐
Keep up the Fantastic work.
Hawking was great inspiration even for many ordinary people. He was one of those people whose words could make even my depressed mind to get inspired and look for more information about how things may (or may not) work at scales our common sense fails. I wonder who will be next big celebrity to raise from world of science, there is now great void that will take great person to fill. Rest in peace Hawking.
Information paradox! Here comes Leonard Susskind! Abbott to Hawking's Costello.
I'm a huge fan of every PBS channel, but as a foreign, I feel this guy speaks in a veeery low range and with the heaviest accent of them all, he's the one I have more trouble with understanding.. And this is perhaps the most complex channel lol, maybe take this in count so he could speak a little higher? I don't know how strange this is lol
You should have seen the guy who did this before. He was like they hired him straight from a shopping channel. I like the calm way of the new guy.
He's not going to change his speaking range or accent. It's not like he's playing a role in a movie. I have no problems understanding him. Just rewind if you miss something.
Not having any trouble with the accent tbh
+ciervo42 Lo siento, mate.
It's the Aussie slur...although Pr O'Dowd is also VERY soft-spoken.
Still, I would have him any day, as opposed to Gabe (former host) who spouted words at machinegun's speed. :)
Turn on subtitles
😅lol
This aged well
His body is in the dirt, but the man himself is up in the stars with Einstein, solving the Theory of Everything to show us all when we finally go to meet them ourselves in the future.
Really good episode. Really enjoyed and appreciated it.
What a beautiful tribute.
Utterly beautiful
Thank you!
Excellent as always. Thank you so much for this.
Amazing, guys. Great video.
This is an underrated video
The Casimir effect, the Lamb shift and a certain interpretation of the Einstein coefficient of spontaneous emission all point to the physical reality of virtual particles.
This is one of the few videos I couldn't wrap my head around. Guess I need to study up some more...
Love this channel!!!!
Could You ask TH-cam to allow more than just one like? You are simply awesome. Keep on.
Well timed video. R.I.P. Hawking!