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Physicists discover that gravity can create light

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Re: Physicists discover that gravity can create light

#31

Post by deciplex »

adastra22 wrote: post #23
avmich wrote: post #3

The title is about gravity, but the first line is about wave of gravity. Hmm. We know that gravity alone can create radiation - the Hawking one. We also know that gravitational waves - the spacetime curvature changes with time - carry energy, so can be transformed into light. Do we still know if spacetime alone can create light?.. I'm not sure we know it today. So... we have a great experiment here, which shows somet…

> We know that gravity alone can create radiation - the Hawking one To be pedantic, we don't know this. Hawking radiation has never been observed.

to be even more pedantic, hawking radiation isn't exactly created by gravity

Re: Physicists discover that gravity can create light

#32

Post by scotty79 »

jerf wrote: post #18
Maursault wrote: post #13

Earlier quoted context omitted.

> Isn't gravity just a fundamental force? Not really. Gravity is most accurately described by the general theory of relativity... which describes gravity not as a force, but as the curvature of spacetime, caused by the uneven distribution of mass, and causing masses to move along geodesic lines.[1] [1] https://en.wikipedia.org/wiki/Gravity

You have to remember that General Relativity is wrong. We don't know exactly how it's wrong, but it's wrong. In light of that fact, it's not really a proper answer to say that "General Relativity says it isn't so it isn't." It is true that GR says gravity isn't a force, but the implication doesn't follow. We don't know whether a Grand Unified Theory would have gravity as a force or not. Given that a great deal of the…

We don't have a single test that shows that GR is wrong in any way and we have many tests that show that it is exactly right to any arbitrary precission we can dream of achieving.

Re: Physicists discover that gravity can create light

#33

Post by narag »

habibur wrote: post #11
_8j50 wrote: post #10

Isn't gravity just a fundamental force? Could it be matter reacting to gravity? Light is energy but gravity is not energy and has no mass so how can it create something out of nothing? How is hawking radiation even possible unless something else was involved?

Or gravity is just bending of space around a mass. And not a force.

https://www.youtube.com/watch?v=ZHxoM9lvzVA

Re: Physicists discover that gravity can create light

#34

Post by dogma1138 »

PartiallyTyped wrote: post #28
adastra22 wrote: post #23

Earlier quoted context omitted.

> We know that gravity alone can create radiation - the Hawking one To be pedantic, we don't know this. Hawking radiation has never been observed.

Relevant: https://phys.org/news/2021-02-stationary-hawking-analog-blac...

Not particularly. This isn’t an actual observation, this is just an experiment that attempts to create some analogous phenomena.

Re: Physicists discover that gravity can create light

#35

Post by TheOtherHobbes »

scotty79 wrote: post #32
jerf wrote: post #18

Earlier quoted context omitted.

You have to remember that General Relativity is wrong. We don't know exactly how it's wrong, but it's wrong. In light of that fact, it's not really a proper answer to say that "General Relativity says it isn't so it isn't." It is true that GR says gravity isn't a force, but the implication doesn't follow. We don't know whether a Grand Unified Theory would have gravity as a force or not. Given that a great deal of the…

We don't have a single test that shows that GR is wrong in any way and we have many tests that show that it is exactly right to any arbitrary precission we can dream of achieving.

Now make it work with QFT.

Re: Physicists discover that gravity can create light

#36

Post by chasd00 »

adastra22 wrote: post #23
avmich wrote: post #3

The title is about gravity, but the first line is about wave of gravity. Hmm. We know that gravity alone can create radiation - the Hawking one. We also know that gravitational waves - the spacetime curvature changes with time - carry energy, so can be transformed into light. Do we still know if spacetime alone can create light?.. I'm not sure we know it today. So... we have a great experiment here, which shows somet…

> We know that gravity alone can create radiation - the Hawking one To be pedantic, we don't know this. Hawking radiation has never been observed.

didn't the LHC create a black hole that immediately evaporated due to Hawking radiation? ..maybe it was only a theory that the LHC could do that but i thought it actually did create one.

Re: Physicists discover that gravity can create light

#37

Post by twawaaay »

chasd00 wrote: post #36
adastra22 wrote: post #23

Earlier quoted context omitted.

> We know that gravity alone can create radiation - the Hawking one To be pedantic, we don't know this. Hawking radiation has never been observed.

didn't the LHC create a black hole that immediately evaporated due to Hawking radiation? ..maybe it was only a theory that the LHC could do that but i thought it actually did create one.

No. That's far beyond our capabilities. Somebody calculated that LHC would have to be over 1000 light years in diameter to do this (and then still we would have to wait for thousands of years for particles to get accelerated).

Re: Physicists discover that gravity can create light

#38

Post by twawaaay »

raattgift wrote: post #9
avmich wrote: post #3

The title is about gravity, but the first line is about wave of gravity. Hmm. We know that gravity alone can create radiation - the Hawking one. We also know that gravitational waves - the spacetime curvature changes with time - carry energy, so can be transformed into light. Do we still know if spacetime alone can create light?.. I'm not sure we know it today. So... we have a great experiment here, which shows somet…

The preprint of the paper that is the subject of the (not so great) phys.org article at the top is https://arxiv.org/abs/2205.08767 >. An accessible HTML5 version is available at https://ar5iv.org/abs/2205.08767 > (arxiv->ar5iv, the latter expands to a link within ar5iv.labs.arxiv.org). Hawking radiation is a semiclassical result: the curved spacetime is classical General Relativity and the scalar field (in which Haw…

> The key point though is that their mechanism cannot work in vacuum. It absolutely requires that the light travels significantly slower than the gravitational radiation

I am not a physicist, but I understand we are talking about Universe so early after Big Bang that it wasn't yet transparent to light. There simply wasn't vacuum yet if by vacuum you mean electromagnetic waves being able to travel long distances.

Re: Physicists discover that gravity can create light

#39

Post by Maursault »

TheOtherHobbes wrote: post #35
scotty79 wrote: post #32

Earlier quoted context omitted.

We don't have a single test that shows that GR is wrong in any way and we have many tests that show that it is exactly right to any arbitrary precission we can dream of achieving.

Now make it work with QFT.

It already works. Contrary to vacuous and uninformed popular belief, there is no fundamental incompatibility between QFT and GR.

Re: Physicists discover that gravity can create light

#40

Post by marginalia_nu »

avmich wrote: post #3

The title is about gravity, but the first line is about wave of gravity. Hmm. We know that gravity alone can create radiation - the Hawking one. We also know that gravitational waves - the spacetime curvature changes with time - carry energy, so can be transformed into light. Do we still know if spacetime alone can create light?.. I'm not sure we know it today. So... we have a great experiment here, which shows somet…

If gravity would quantize into photons, that would have very weird implications for the standard model. It would threaten to equate gravity with the electromagnetic force, and mass with charge.
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