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Quantum Gravity, String Theory, LHC and Gravity Waves
- Thread starter sayak83
- Start date
Kangaroo Feathers
Yea, it is written in the Book of Cyril...
Yeah? Well if evilution is true, how come the LHC hasn't detected any gravity waves or dark matter yet, huh? Check MATE atheists!Two of the most renowned theoretical physicists...Carlo Roveli and Sean Carroll, have a wonderful and very informative discussion about the advances in developing a theory of quantum gravity...and many other things.
Must hear!
I must say, I'm quite impressed with your ability to watch a 72+ minute video in just under 39 minutes. Good on you, mate!
Kangaroo Feathers
Yea, it is written in the Book of Cyril...
Time is relative, as Einstein tells us.
Wow!?!?! What a disconnect based on a warped agenda!
My player has a speed option. I can watch videos at 2x speed if I want.
Around minute 32 I start to lose grasp of the discussion. When they talk about 'localization' I can understand that these are words but not a lot more. Actually they kind of lost me earlier on when they started talking about 'with respect to' this or that and then chuckled together. That was Math language, so they must have been referring to some quantum rules.Two of the most renowned theoretical physicists...Carlo Roveli and Sean Carroll, have a wonderful and very informative discussion about the advances in developing a theory of quantum gravity...and many other things.
Must hear!
WalterTrull
Godfella
Roveli is saying that properties (or rather their values) are not intrinsic to a physical entity but are only meaningful with respect to its interactions with other physical entities..and compares it to how velocities are of similar nature.
He is also saying that point like locations do not exist or has no physical meaning. Space is granular, to all locations are pixellated in some sense.
Pretty sure Rovelli is a theist though...so lets not mock all theists like that.
He was being sarcastic.
YmirGF
Bodhisattva in Recovery
Nice try, but I never let facts intrude on my thinking. The Good Book is enough!
Theists did probably make Ravioli, yes.
If so the sarcasm was misplaced and not clear.
Photons and hydrogen *do* have gravity (well, they curve spacetime, so produce gravity). Photons have energy and hydrogen has mass. Both produce gravitational effects.
In fact, in the early universe, it is the gravitational effects of light (photons) that dominate over the gravitational effects of matter.
There are two things going on here: one from quantum mechanics and the other from general relativity. Quantum gravity, remember, is trying to reconcile those two theories.
In quantum mechanics, there is the uncertainty principle. There are actually several versions of this principle, but the one they are talking about relates position and momentum. It says that we cannot define both the position and the momentum of something perfectly accurately. One effect of this is that if we attempt to localize something, in other words, determine its position precisely, then the momentum becomes undetermined. The more accurately we attempt to place the particle, the less accuracy we have concerning the momentum of that particle.
Now, momentum and energy are closely related (they aren't the same, but you can get one from the other if you know the mass of your particle). So, the uncertainty of momentum means a corresponding uncertainty in the energy of the particle. But the energy is equivalent to the mass, so there is an uncertainty in the mass of this particle.
So far, this is pretty standard quantum mechanics.
But, from general relativity, gravity is a curvature of spacetime. And mass produces gravity. It curves spacetime around it. So that uncertainty in the mass produces an uncertainty in the curvature of spacetime. In the discussion, they take this to the limit where we want to determine the exact position of the particle, which means a completely undetermined momentum, which means a completely undetermined energy, so a completely undetermined mass, and thereby a completely undetermined curvature for spacetime. This allows for the production of a small black hole (very large curvature).
The problem is that this negates the whole attempt to determine position. A similar thing happens when attempting to determine the time of an event.
The upshot is that the geometry of spacetime itself is undetermined: it has a quantum aspect to it. Which is why we need a quantum theory of gravity (spacetime).