Do Massless Particles Cause Gravitation?

In summary, while physical bodies with mass are known to cause gravitation, massless particles like photons also have energy and therefore also contribute to the gravitational field. This is due to their non-zero stress-energy tensor, as explained by JA Wheeler's concept of a "geon". However, there are also cases where an "energy" can be attributed to the gravitational field itself, but it does not act as a source of gravitation in the same way.
  • #1
Constantin
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I know physical bodies with mass cause gravitation.
But do massless particles, like photons, also cause gravitation ? I know they're affected by gravity, but would a cloud of photons bend space by itself?

Thank you
 
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  • #2
Yes, photons have energy, and anything with energy causes gravitation.

More precisely, photons have a non-zero stress-energy tensor, which is what acts as the "source" of gravitation. See, for example, this Wikipedia page:

http://en.wikipedia.org/wiki/Stress–energy_tensor

The stress-energy tensor of a source-free electromagnetic field, down the page, would apply to photons.

I add this qualification because there are also cases where an "energy" can be assigned to the gravitational field itself, but this "energy" is not part of the stress-energy tensor and so it does not act as a "source" of gravitation in the above sense.
 
  • #3
JA Wheeler once investigated the idea of a geon. Light traveling in a self perpetuating circle due to its own gravity.

http://en.wikipedia.org/wiki/Geon_(physics )
 
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FAQ: Do Massless Particles Cause Gravitation?

1. What is a massless particle?

A massless particle is a type of particle that does not have any mass. This means that it does not have any physical substance or weight. Examples of massless particles include photons and gluons.

2. How do massless particles cause gravitation?

According to Einstein's theory of general relativity, massless particles such as photons can cause gravitation by creating a curvature in the fabric of space-time. This curvature is what we experience as the force of gravity.

3. Are all massless particles responsible for gravitation?

No, not all massless particles are responsible for gravitation. Only particles that have energy and momentum, such as photons, can cause a gravitational effect. Other massless particles, such as the hypothetical graviton, may also play a role in the theory of gravitation.

4. Can massless particles be affected by gravity?

Yes, even though massless particles do not have any mass, they can still be affected by gravity. This is because they have energy and momentum, which are affected by the curvature of space-time caused by massive objects.

5. Is there evidence to support the idea that massless particles cause gravitation?

There is strong evidence to support the idea that massless particles can cause gravitation. This is based on the success of Einstein's theory of general relativity, which has been extensively tested and confirmed through various experiments and observations. Additionally, the behavior of light around massive objects, such as gravitational lensing, also supports the idea that massless particles can cause gravitation.

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