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I've been thinking about energy and how it travels, especially compared to photons. We all know that photons move around at the speed of light in a vacuum.

So, here's my question: Does this idea apply to other forms of energy too, like gravitational potential energy? Could it be that gravitational potential energy also moves at the speed of light, similar to photons? Like we know it takes around 8 minutes for even gravitational force between sun and earth to interact.

So could it be that it is only energy that can travel at the speed of light and nothing else?

I'd love to hear your explanations on this topic.

notephemeral
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  • Possible duplicates: How fast does gravity propagate? and links therein. – Qmechanic Sep 06 '23 at 07:55
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    It is a mistake to think that you can locate potential energy at a specific location. Potential energy is a property of a system as a whole and depends on the configuration of the particles and fields of that system - it does not reside in one element or another, or have a location in physical space. – gandalf61 Sep 06 '23 at 08:33
  • @gandalf61 That makes sense, but why would our earth still revolve for 8 more minutes if the sun disappeared because then there would be no system in which gravitational potential energy for earth could be calculated as the gravitational P.E. depends on both the masses? – notephemeral Sep 06 '23 at 18:43
  • @notephemeral Well, you are going to have to come up with entirely new laws of physics to allow the sun to disappear, so no-one knows what will happen - we are not in Kansas anymore, and all bets are off. – gandalf61 Sep 06 '23 at 19:25

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Photons travel at the speed of light. But photons carry energy, so that means energy (as carried by photons) does indeed travel at the speed of light.

Gravitons and gravity waves also travel at that speed. The waves have been proven to exist but no proof yet on the gravitons.

Photons and gravitons have zero rest mass, which is why they are able to travel at c. Any particle with nonzero rest mass cannot travel at c.

Note here that there are other ways that energy travels from point to point. Inside solids, energy can travel as waves which travel at the speed of sound. Energy can also travel as the random vibrations we associate with heat, in which case the transport mechanism is diffusion.

niels nielsen
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