No Gravity From Photons

[Rev. Green]

A photon has energy. Why does it not generate a gravitational field? Energy = mass.

[Zacs-Master]

Rμν−12gμνR+gμνΛ=8πGc4Tμν

[Atheist]

A photon 'travels' at the speed of light. A particle with mass could not do that; if it had a rest mass, then its light speed mass would be infinite.
I'm unqualified to explain any more. Maybe Jim the scientist could help.

[bobbinwales]

Not sure where your energy = mass comes from ... e = mc squared maybe....
Will attach a link

[Peter Pedant]

well we have a particle physicist on the books so I will let him explain. Photons were once thought to be particles and were boingy
You know those spinning vanes in glass spheres? easy to explain

much more difficult with wave packets

Huyghens 1690 was a the great guy for waves, To explain wave splitting ( easy for waves) newton postulated easy reflection/easy transmission and even tried to measure the relative times !

easy now with particle - wave duality

and whilst youre at it - the energy doesnt dissipate in a vacuum as it travels along - sound for example gets softer and dies away

[Peter Pedant]

eek
answered here
https://usm.maine.edu/planet/i-was-told-light-has-no-mass-i-also-know-gravity-force-between-two-or-more-massive-objects-so#:~:text=A%20photon%20is%20a%20massless,it%20has%20no%20rest%20mass.

[Zacs-Master]

That's why....
In space no one can hear you scweeeeeem!

[bobbinwales]

Not sure where your energy = mass comes from ... e = mc squared maybe....
Will attach a link
https://wtamu.edu/~cbaird/sq/2014/04/01/light-has-no-mass-so-it-also-has-no-energy-according-to-einstein-but-how-can-sunlight-warm-the-earth-without-energy/

[jim360]

"Energy = mass" is sadly misleading. Photons have energy, but an individual photon has no mass. This isn't a contradiction. A more complete statement is something closer to "energy = mass + momentum" (although even this isn't strictly correct, but I don't see a need to be more precise in this conceptual discussion).

Gravity is sourced really from energy, rather than from just mass. So photons are perfectly capable of responding to, and (by symmetry) creating, gravitational fields.

They are, however, tiny in comparison to larger sources. Because the "G/c^4" in Zacs-master's equation is so tiny, you need a *lot* of energy/mass in a given place to have any notable effects.

If you wanted any more details I'd have to do more digging.

[ToraToraTora]

Here's a paper I recently wrote on the subject ☺
https://tinyurl.com/5fx6ukpw

[Rev. Green]

Wow ToraToraTora! That was a difficult paper to read and I couldn't understand the relevance of uncountability. Did I download the correct paper!

[Old_Geezer]

I'm sure T³ will be happy to explain the finer points in his thesis.

[ToraToraTora]

Rev Green, my mistake, try this one:
https://tinyurl.com/4r7w3ary
I do so many it's hard to keep track ☻

[Rev. Green]

Thanks Tora^3, these papers are fascinating, although they appear unrelated to gravity, and I suspect you could be wrong each time you say "every student is aware that...".

[ToraToraTora]

Yeah but you see, gravity does not really exist, it's the curvature of space by massive objects that we often call Gravity. So my papers are focusing on the maths hence gravity is not mentioned.

[ToraToraTora]

have a go yourself it's easy.....
https://thatsmathematics.com/mathgen/

[ToraToraTora]

Hang on Rev I think I found one of yours.....
https://tinyurl.com/2p979yw7

[Rev. Green]

I'd like to claim credit, but I'm not really Rev Green (nor Miss Scarlet!).

[jim360]

As fun as that all is, it's not quite yet at the level of convincing, but certainly fun to see what can be churned out quickly with modern tech :P

[ZebuSanctuary]

// e = mc squared //

There you go jim and Bobbin;

E = mc²

G/c³c¹

No need to thank me guys.

[Old_Geezer]

Is momentum the product of mass and velocity ?