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Physicists discover that gravity can create light

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Re: Physicists discover that gravity can create light

#41

Post by mfer »

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.

Not only has Hawking radiation not been observed but the article starts with a "may have" and concludes by pointing out that there aren't conditions to observe the phenomenon described today.

Maybe I'm just not a fan of strong language, making it appear we know something, where we don't.

Re: Physicists discover that gravity can create light

#43

Post by a_wild_dandan »

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…

I'm not seeing how these distinctions are helpful. Maybe there's a miscommunication?

When we say "gravity isn't a force", it's shorthand for "our best understanding of gravity, with the widest explanatory power that most accurately matches experimental results, says that gravity isn't a force." But that's an exhausting, verbose way to talk. Knowing that GR is incomplete doesn't change that.

No falsifiable theory is 100% guaranteed Truth. Not GR, QM, evolution, or any widely accepted future Grand Unified Theory. Science is one big exercise in affirming the consequent, verifying contrapositives, and finding surprises. Maybe all mental models are wrong. Maybe we're brains in vats. Aaaah!...so what?

Evolution naturally developed eyeballs in mammals. My niece just turned 5. The atoms composing me won't rearrange into a facsimile of Abraham Lincoln tomorrow. I'm not going to add "to our best understanding, given the evidence, granting my incomplete knowledge, etc" about these facts in service of reality obviously being unknowable. It's pointless.

Gravity isn't a force. That's a perfectly "proper answer" -- no need to pontificate about philosophical relativism.

Re: Physicists discover that gravity can create light

#44

Post by pa7x1 »

marginalia_nu wrote: post #40
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.

Gravity cannot be exchanged by photons or any other spin 1 particle, for that matter. Spin 1 particles lead to repulsive forces for like charged particles.

This leaves you with spin 0 and spin 2 as the simplest alternatives. Spin 0 doesn't result in light bending and gives a wrong result for Mercury's perihelion precession. Spin 2 gives you General Relativity.

Re: Physicists discover that gravity can create light

#45

Post by nimish »

cocoa19 wrote: post #42
mitthrowaway2 wrote: post #4

We know that light can create gravity, so it stands to reason that there should be a reciprocal relationship!

"We know that light can create gravity" I've never heard of light creating gravity, where did you learn this?

Concentrate enough energy in a small area and baby, you got a black hole going!

Re: Physicists discover that gravity can create light

#47

Post by westurner »

stared wrote: post #14

All quantum fields have their vacuum energy fluctuations. When we change the parameters of the space (e.g. stretch or compress it), the current state is no longer the ground state but becomes a so-called squeezed vacuum state. This effect is used in laser physics to "split photons" in spontaneous parametric downconversion. That is, an intense laser changes the refractive index of a medium periodically. These oscillat…

Is there a corollary SQG Superfluid Quantum Gravity fluidic description of squeezed coherent states?

And what of a Particle-Wave-Fluid triality?

Re: Physicists discover that gravity can create light

#48

Post by antonvs »

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.

What does "gravity alone" mean here? Hawking radiation depends on a black hole that has energy to radiate. The radiation is not due to "gravity alone".

Re: Physicists discover that gravity can create light

#49

Post by westurner »

westurner wrote: post #47
stared wrote: post #14

All quantum fields have their vacuum energy fluctuations. When we change the parameters of the space (e.g. stretch or compress it), the current state is no longer the ground state but becomes a so-called squeezed vacuum state. This effect is used in laser physics to "split photons" in spontaneous parametric downconversion. That is, an intense laser changes the refractive index of a medium periodically. These oscillat…

Is there a corollary SQG Superfluid Quantum Gravity fluidic description of squeezed coherent states? And what of a Particle-Wave-Fluid triality?

[flagged]

Re: Physicists discover that gravity can create light

#50

Post by XorNot »

antonvs wrote: post #48
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. What does "gravity alone" mean here? Hawking radiation depends on a black hole that has energy to radiate. The radiation is not due to "gravity alone".

Hawking Radiation didn't depend on gravity either, it depends on an event horizon. Any phenomenon which would separate virtual particle pairs would produce it - i.e. the edge of the observable universe would do it too.
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