# The Naked Scientists Forum

### Author Topic: Does light emit a gravitational field?  (Read 1021 times)

#### Chondrally

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##### Does light emit a gravitational field?
« on: 01/01/2015 00:36:43 »
Because E=hf and E=mc^2 it seems m apparent= hf/c^2.  Is this correct and does light actually emit a gravitational field at the speed of light, and does light attract itself?

#### alancalverd

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##### Re: Does light emit a gravitational field?
« Reply #1 on: 01/01/2015 10:23:16 »
You can't have your cake and eat it. E/c^2 is the mass that you would create if you converted a photon into a particle, and indeed this is the case.

#### PmbPhy

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##### Re: Does light emit a gravitational field?
« Reply #2 on: 01/01/2015 14:16:44 »
Because E=hf and E=mc^2 it seems m apparent= hf/c^2.  Is this correct and does light actually emit a gravitational field at the speed of light, and does light attract itself?
Note: This is a very good question and as such should have been posted in the Physics Forum.

Yes. Depending on how the light is distributed it usually creates a create a gravitational field. In fact I don't know of a case in which it doesn't. In 1931, Tolman, Ehrenfest and Podolsky published an article in the journal Physical Review called On The Gravitational Field Produced by Light. I put  the derivation here: http://home.comcast.net/~peter.m.brown/gr/grav_light.htm

If you have any questions about it then please let me know.

Quote from: alancalverd
You can't have your cake and eat it.
Actually, in this case you can have your cake and eat it too.

Quote from: alancalverd
E/c^2 is the mass that you would create if you converted a photon into a particle, and indeed this is the case.
In this case if you have, say, a beam of light then it will create a gravitational field. The derivation for the gravitational field of a directed beam of radiation is on my website at:
http://home.comcast.net/~peter.m.brown/gr/grav_light.htm
« Last Edit: 01/01/2015 14:35:58 by PmbPhy »

#### The Naked Scientists Forum

##### Re: Does light emit a gravitational field?
« Reply #2 on: 01/01/2015 14:16:44 »