Can light produce weak gravity waves?

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Discussion Overview

The discussion centers around the possibility of light producing weak gravitational waves and the implications of such phenomena, including energy dissipation over cosmological distances. Participants explore theoretical aspects of gravitational effects from light, including interactions between electromagnetic waves and gravitational waves, as well as references to concepts like the tired-light hypothesis.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants propose that light can produce a weak gravitational field, suggesting that antiparallel beams of light should attract each other weakly.
  • One participant argues that a photon cannot emit a graviton, as this would imply superluminal speeds, leading to the conclusion that photons do not produce gravitational effects.
  • Another participant supports the idea that light can produce gravitational waves, citing a source that claims gravitational waves are generated when electromagnetic waves collide.
  • Concerns are raised about the consistency of gravitational wave production with the behavior of photons passing through each other unaffected, questioning whether energy is lost in the process.
  • Discussion includes references to quantum field theory, suggesting that while classical general relativity may not account for photon interactions, quantum gravity theories might allow for graviton production and energy reduction in photons after interactions.

Areas of Agreement / Disagreement

Participants express differing views on whether light can produce gravitational waves and the implications of such production. There is no consensus on the mechanisms involved or the consequences of these interactions.

Contextual Notes

Some claims rely on specific theoretical frameworks, such as classical general relativity and quantum field theory, which may have limitations or unresolved aspects regarding the interactions of light and gravity.

dan_b_
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I have read online that light can produce a weak gravitational field (for example antiparallel beams should, in principle, attract weakly). This made me wonder if light can produce minute gravitational waves. Even if the waves were extremely weak (no disregarding of those high order terms in the applicable equation, whatever equation that may be), could the gravitational waves dissipate energy (on the order that is expected for cosmological redshifts) when light travels across cosmological distances ? I was thinking about the debunked tired-light hypothesis regarding the cosmological redshift, and I wondered if anyone has considered a mechanism whereby gravity waves dissipate energy.
 
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A graviton would travel at the speed of light too. So a photon could not emit a graviton ahead of it. Nor could it emit a graviton to right angles to the direction of a photon, for then it would be going faster than the speed of light, having a velocity c in the direction of the photon plus a velocity c to right angles. These two velocities would add to produce a speed faster than the speed of light and so can not exist. Also a photon could not emit a graviton in the direction opposite a photon. For then that graviton would be at rest, being emitted with -c from a photon traveling at +c. And a graviton cannot exist at rest. So I would have to think that a photon does not produce any gravitational effects.
 
The OP is correct that per GR, anti parallel beams attract. Further, a light beam attracts a particle of matter. Finally, the OP's guess that light can produce GW is correct. The following:

"When electromagnetic waves collide, it appears that gravitational
waves are always generated by the collision. These may be impulsive
waves that occur along the boundaries of region IV only, or they may
appear throughout the interaction region. However, they must always
appear."

is a conclusion from

https://archive.org/details/flooved2797

However, there is no support for any 'tired light' concept, because an EM wave by itself, produces no GW.
 
PAllen said:
"When electromagnetic waves collide, it appears that gravitational
waves are always generated by the collision. These may be impulsive
waves that occur along the boundaries of region IV only, or they may
appear throughout the interaction region. However, they must always
appear." is a conclusion from https://archive.org/details/flooved2797.

I'm not sure how that is consistent with photons passing through each other unaffected. If colliding photons produce gravitational waves, then it seems that the energy of the EM waves (photons) would be decreased by the energy of the gravitational waves that are emitted.
 
friend said:
I'm not sure how that is consistent with photons passing through each other unaffected. If colliding photons produce gravitational waves, then it seems that the energy of the EM waves (photons) would be decreased by the energy of the gravitational waves that are emitted.

Well, this is classical GR. However, in QFT, photons CAN interact with each other via multi-loop interactions (the probability is just vanishingly small). For example, there is computable (exceedingly small) probability that colliding high energy photons can produce positron-electron pair without mediation of another charged particle. Thus, in a quantum gravity theory, it would seem expected that there is a chance of graviton production, and that the photon energy after interaction is reduced.
 
dan_b_ said:
I have read online that light can produce a weak gravitational field (for example antiparallel beams should, in principle, attract weakly). This made me wonder if light can produce minute gravitational waves. Even if the waves were extremely weak (no disregarding of those high order terms in the applicable equation, whatever equation that may be), could the gravitational waves dissipate energy (on the order that is expected for cosmological redshifts) when light travels across cosmological distances ? I was thinking about the debunked tired-light hypothesis regarding the cosmological redshift, and I wondered if anyone has considered a mechanism whereby gravity waves dissipate energy.
Pe
dan_b_ said:
I have read online that light can produce a weak gravitational field (for example antiparallel beams should, in principle, attract weakly). This made me wonder if light can produce minute gravitational waves. Even if the waves were extremely weak (no disregarding of those high order terms in the applicable equation, whatever equation that may be), could the gravitational waves dissipate energy (on the order that is expected for cosmological redshifts) when light travels across cosmological distances ? I was thinking about the debunked tired-light hypothesis regarding the cosmological redshift, and I wondered if anyone has considered a mechanism whereby gravity waves dissipate energy.
Perhaps should you read: "One loop photon-graviton mixing in an em field; part2 arxiv:0710.5572v1, "As has been recognized many years ago... the quantized Einstein-Maxwell theory predicts the process of photon-graviton conversion in an em field..."
 

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