Q&A: The End of the Universe - with Geraint Lewis
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- เผยแพร่เมื่อ 25 พ.ย. 2024
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Watch the talk: • The End of the Univers...
Geraint F. Lewis is a Welsh astrophysicist at the University of Sydney. He's best known for his work on dark energy, gravitational lensing and galactic cannibalism.
This talk and Q&A was filmed in the Ri on 24 July 2018.
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This is probably one of the best Q&A's I have ever seen.
Brilliant answers to great questions. You done it again Ri
Hey, I want that GR lecture......................bring this guy back, he was very e l u c i d a t i n g............thanks
Awesome professor
The speed of light is not about light. It is about information. The speed of light is the maximum possible speed by which two people (or two anything) can communicate with each other. Light just happens to have this speed. So, the cosmic expansion is not violating the speed of light, because two local areas can't communicate with each other anymore.
why is there such a hard limit to this speed
and what about entanglement?
@@sumilidero in entanglement no actual information can be transmitted
Nobody knows. According to GE if people could communicate faster than the speed of light then it would break causality. But why should that be an issue? Maybe GE is wrong anyway. But, sadly, it was confirmed time and time again to be correct. Anyway, the speed of light is not about light or speed. That is why articles like "4 Things That Currently Break the Speed of Light Barrier" are hilarious. Since they are not breaking the speed at which information is transmitted, they don't violate GE.
Not information, per se... but "causality". It is the fastest that speed that a "Cause" can cause an "Affect".
A star blowing out a gamma ray burst annihilating everything in it's path for thousands of light years can certainly can be thought of as "information" in the technical sort of way that the direction the disassociated atoms take when a planet is vaporized by the blast wave is definitely a bit of datum but ignores the larger picture of what is effectively the delay between cause and affect and "c" (causality), as in E=mc2, is the determining factor in that delay.
Every end have a time, but time have no end.
Could we request that if the microphones aren't working efficiently that we repeat the questions please?
We do brief the hosts and speakers beforehand and make that point, but sometimes people shout before we get to them, or won't repeat the question, or sometimes we forget to ask them to say it again. We try, but sometimes it doesn't work out.
Special relativity does not replace Newtonian gravitational theory. Special relativity replaces Gallielian relativity---only for objects moving close to the speed of light.
Nobody will ever have to complain about the end of univers... aftertward!
Just the religious..when they released theres nothing....
The guy, who directed the questions was so interested, that he had to ask a question himself
can someone fix the second mic? turn it up a bit. have it closer to the face. :D
It is said that energy can sometimes pop in and out of existence. Maybe the big bang happened like this but it failed to disappear afterwords, or something else went wrong. Also, there was an imbalance of matter and antimatter afterwords, maybe as a result. Was the universe an accident? What else went wrong?
So, is the universe expanding multidimensional sphere or is it infinite? And is there a way to know the difference?
Zdravím :)
We do not know since a big sphere can look pretty flat (flat earthers get confused by this fact :D) but as far as our measurements go the universe is flat (no global curvature).
How can it be flat? In 3d nothing should be able to be flat... secondly to me would be strange if flat, when the universe seems to be made of sphere objects, planets moons asteroids sun's etc
@@HomoSapienMan Well, it is the lack of proper terminology for higher dimensions. It is not "flat" in 2D, it is "flat" in 4D (since the time cannot be quite separated from the space).
It is hard to come up with a good analogy, but imagine if the surface of the Earth was space time. the time would go from south pole to the north pole, the space would be parallel to it. Only the space time is probably mapped on 5 dimensional object, it appears "flat" as if it was just a 4 dimensional "plane", but it is also possible (and some might say it is likely), it is a "surface" of 5 dimensional object. The surface of really huge sphere (or some other objects) would be practically indistinguishable from a flat plane on a small local scale. Same goes in higher dimensions, if the 5 dimensional object giving structure to the universe is huge, we cannot tell what it is.
Gravity is a pushing force of sun planets and earth. Earth push is approximately two g.
25:09 "The Americans that beat people on dark roads?" What? (Greetings from Americatown.)
He's saying/joking that people from Detroit shouldn’t qualify as intelligent life. Was it out of left field yeah, but Europeans love making fun of Americans and implying we are crazy when they're not begging us to save them from wars and the accompanying mass killings that start in super intelligent Europe that they cannot stop their own super intelligent selves. We all have our faults and nobody should think they are better than anyone else. Just about everybody today should thank the stars they live in the times they do.
I think he said “meet people on dark roads”, as in deep state X Files vibes
The End Of Time...Perry Como sang that, didn't he?
After all stars die and before matter “dies” why not using dark energy, after all it is a kind of energy.
Stars are constantly being born so why would it end?
Stars are born out of collapsing clouds of hydrogen, which is then used by the star to power fusion reactions, resulting in the conversion of that hydrogen into heavier and heavier elements. Because there's a finite amount of hydrogen in the Universe, the supply will eventually be depleted to the point where no more stars will be able to form.
Can you really kill the big crunch theory if
1. you haven't seen beyond the horizon. There might be effects at the "edge" or the "beginning" of the universe that act differently as the rest of the universe i.e. is denser or w/e other thing comes to mind. During inflation, stuff could've been pushed very densely at the "edge/surface". What odd effects do you have at the "edge/surface" when a star explodes there.
2. the dark energy changes over time. Perhaps it lasts exactly as long as matter holds/generates energy. To extrapolate the characters of dark energy even over 14 B years by observing the galaxies or stars exploding, might not be enough to show its relation to scales such as 10e100 years. Different energy releasing events or "stages" of the universe could have a considerable effect over the dark energy. Its also fun to think that there is a point in our history where dark energy's push has overcome the gravity's pull... Which would actually put into question, how did it ever go past, why did it expand in the first place, right? If you imagine the extremely rapid deceleration of inflation and if that deceleration were caused by gravity, then it would've collapsed right there and then.
3. we don't know the overall structure of the universe or multiverse for that matter.
Wouldn't it be better to hold both theories on the table until there is no "dark" anything.
Not sure should i try to answer with broken English, but i can try to give some short answers. Like he said, there is all kind of theories which may work mathematically, but that's doesn't mean anything he said is an absolute truth, but currently these observations match with mathematics/scientific theories that we have.
It is possible that space isn't isotropic outside our observable universe and/or dark energy/matter may change it's behavior in some point and so on, but the problem is that we can't measure/calculate/test those things to make sure it will match with our observations/scientific theories*, otherwise it is just a theory*
*"Wouldn't it be better to hold both theories on the table until there is no "dark" anything."*
Well, at least we should talk about those things, until someone is able to provide a better explanation/answer or find a better solution that will match our observation.
_*"A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment. Such fact-supported theories are not "guesses" but reliable accounts of the real world."_ en.wikipedia.org/wiki/Scientific_theory
The only trouble with humans is they don`t think of other species being able to survive by moving off the planet. We would need an entire ecosystem running to be able to colonize another exoplanet.
Isn't matter-antimatter annihilation another efficient energy source? What are the possible ways of creating/collecting and storing large amounts of antimatter?
You need energy to create antimatter and to store it. Antimatter can be created with a collider and stored in a magnetic trap basically like the plasma in a tokamak. If you can find some antimatter somewhere, maybe you can trap it and slowly annihilate a bit at a time but I wouldn't count on it.
@@SuviTuuliAllan Yes, you do need energy, but if there's a process in which you put in less energy than you get from annihilation, then problem solved.
One issue is how much useful energy there is in the Universe (before it reaches equilibrium), another is energy density. Because of the expansion, we'd prefer to gather as much energy as possible before it goes beyond the cosmic horizon.
@@czerskip Gathering energy, how?
@@SuviTuuliAllan By storing matter for later use. One scenario would be star lifting to get more red date dwarfs from more massive stars to slow down the energy dissipation, maybe even destructing stars into gas clouds.
Another scenario would be gathering as much matter that's gravitationally bound to us before it passes the cosmic event horizon.
When matter and anti-matter annihilate all the energy corresponding to the sum of their masses is converted into photons. The energy of these photons can be used to do something useful. It's possible to harness some energy source to produce anti-matter with a total mass, less than the equivalent amount of energy available from the energy source. Anti-matter would essentially be like a battery which would allow the energy to be stored in a portable form.
Matter-Antimatter annihilation can never serve as an energy source itself because there's no reservoir of anti-matter in the Universe.
Maybe we could have done without the idiotic question, " why would we be worried about the survival of our own species?".
No question is idiotic!
@@shubhmishra66 almost every disingenuous question is idiotic
The same kid in all the Q&A Videos?
Some of our members come to a lot of our talks!
@@TheRoyalInstitution All of your talks and videos are very interesting! Thank you for sharing them with the world :-*
"what is the economy expanding into?" The universe aka available resources. Cmon ppl. Physicists only pretend 'what the universe expands into' is not a valid question because they have no answer unless it's a contradiction created by them for themselves. Just like how it is the most basic principle that the laws thermodynamics and conservation of energy are unaviodable, but then you have the big bang where everything comes out nothing, which is altogether is the biggest contradiction you can possibly come up with. This is why some logical minded scientist type mathematicians told me they picked math instead of physics when going to the university, from their perspective the whole thing is 50% just silliness.
The “Laws of Physics” are innocuous, given that the world worked very well without them since its beginning. And that: “The Laws of Thermodynamics win all the time”, is total nonsense.
Why should we care about our own species surviving? Cheese, tea, cinnamon toast, and Star Trek must be saved, that's why.
There is no such thing as the end of time. The reason that is IMPOSSIBLE is very simple. WHEN there is no time, that means there IS A TIME when there is NO TIME. Now how in the world can there be no time.... LOL !!!!!!
Dark energy was present at the dawn of inflation then dark energy disappeared and bounced off the edge of the universe and came back to the center and now we’re traveling with it faster and faster
If the universe is going to spend most of the time empty what's the point of it
@@delroyjames9902 It's the Universe, why does it have to have a point?
@@LordLOC because time is always going forward if that makes sense
@@delroyjames9902 But time is mostly a Human construct for events etc. Particles, atoms etc don't much care for time and are the same whether time moves forward or backwards (or sideways lol). So again, in the grand scheme of things, why does the Universe have to have a point to it? Because we exist and can ponder it? That's about it really, no? I hope I'm not coming off as brash, I just studied physics in College back in the day and I love getting into conversations about this stuff.
@@LordLOC I just think it's gave us all this Plus all that space.What a waste
The science is very interesting sad but interesting in this case to have to leave our beautiful planet. I hope that you Love your current political system because say for example on Mars, you wont be able to afford your electric bill, food will have to be supplied to you, to mention just two things so you see .. Love your political system, join it if you dont, and while living on earth fight to preserve our natural resources which are currently fighting pollution. There are two flights to Mars scheduled to take off at the end of 2019.
100% fake
Michael yes sadly this is a fact. We all need to fight to preserve our natural resources as our world wide population continues to increase along with far to few pollution regulations.
The end of time 15.84Gyears, then the collapse.
The weirdest thing that comes to my mind is that how come we exists, how come the universe exists? The very thing of existing is troubling and confusing.
That`s the whole point of astrophysics and theoretical physics, to find out why.
@@biggstavros5876 my personal take is the universe didn't start, I believe that the cause of the universe is from the end. We cannot conceive infinity the notion is too big for our minds, but we can try to imagine it. It is a long long long time. At some point along this path all possibilities would occur, one of those possibilities is for life to occur from nothing. We can't explain how we came to be or the universe or atoms but perhaps we can have faith in that it is possible so since its possible it happened at some point and it only needed once to happen. My second point is what if the causality comes from what we would call the end of time perhaps along infinite there comes a point where a being/s so advanced is able to break the laws of time and actually comes back in time to create the building blocks of the universe as we know it now and what later becomes his conscionous. So he was the cause and effect of himself and it couldn't have been any other way, and it is impossible any other way
When will the new updated school text books be available for students?
kids dont need to know such detailed info.
That's right, they don't need it in so much detail. In Australia, the school's need updated text books that includes all the present day facts and theory.
I dont know about that
2:12 start here to skip the weird boring questions at the beginning. Thank me later
No mention of zero point energy.
Once we really have it, I'm sure they will talk about it non-stop on programs like this. Then we just have to hope we don't blow up the whole solar system with a tiny miscalculation or industrial accident. What did Rodney McKay call it? "Overambitious" even for the Ancients. I once saw a calculation for the potential power conversion of raw space-time and it was something like 10^32 joules per cubic centimeter, like the power output of a whole galaxy.
Still, in an expanding universe, if we could harness it we would have functionally infinite power generation and not even break even with the growth rate of the cosmos. Maybe that's one of those "great filters" that either makes or breaks a developing space-faring civilization and explains the Fermi Paradox. Personally, I'm in favor of trying anyway. Go big!
David Moloney Here’s a little something about zero point energy:
th-cam.com/video/Rh898Yr5YZ8/w-d-xo.html
Cheers
Thanks for the Spacetime reference! Yah, they gave the numbers: 10^112 or 10^-8 ergs depending on which way that issue works out. Also, hopefully, we all know about "Isaac Arthur" channel where he discusses these long-term energy solutions as well, plus other cool futurism topics like space colonization and AI etc. If anyone hasn't seen it yet, I highly recommend his channel.
If there’s a multiverse then the universe has edges
nope. not true
This guy is really bad here. I liked his lectures on other videos, but he's really not explaining things well. Dark matter and dark energy are still not definite as he asserts here but on other lectures he's given he has said as such. Look for other videos of him. He does a much better job.
He also misses on evolution, which does not do what is best or efficient, it does what works. And by what "works" what evolution means is "living long enough to reproduce." Humans have one advantage no other species has had, the ability to use language and particular grammar. And this is inbuilt to humans. We just were lucky enough to have a fluke that allowed us to understand grammar and also live long enough to reproduce. The fact we're able to talk about it, is the result of it, but not the cause, which has no cause.
He also misses on the matter questions. We can calculate the amount of matter in the OBSERVABLE universe. We can observe our universe to about 45 million light years in any direction of any point. So that gives us an approximate radius of 90 million light years in diameter (I've seen some estimates as much as 100 light years in diameter) but beyond that may lie lots of matter. Antimatter may lie beyond that. Nothing may be beyond it. We simply don't know and can't know. And when you're talking on scales so distance in the future one guess is really just as good as the other. To be fair he should speak with these terms and possibilities as conditions.