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jovial01 · 2007-11-21 17:30:02

when i was younger, i was told that gravity only affects objects with mass. Is this correct?

If so, then photons must have mass to be affected by gravity.
Where does this mass come from?
Is it relativistic mass due to their energy that comes from their high velocities? (E=mc^2)? or is the mass due to just their quantum energy (E = hf, therefore hf = mc^2)

If someone could tell me whether im right or wrong id be grateful.
If my reasoning is correct, what then would happen to a photon perfectly stationary in a gravitational field
The nature of gravity is a mystery to me, as theres no evidence of a particle that mediates the gravitational attraction, im sure its a mystery to many people

As im only a first year student, my understanding isnt quite macro yet.

Nicholas · 2007-12-06 02:11:33

If light isn't mass why does it become mass when it is absorbed?

Gravity is a continuum according to Einstein: a space-time curvature continuum.

zozoconde · 2008-02-23 17:04:06

what is a space time curvature

Chris · 2008-02-27 18:38:44

Basically, mass bends space-time. So the path that light travels through space-time will also be bent in the presence of mass.

One of the testaments to the General Theory of Relativity is that it predicted bending light due to massive bodies. This was verified not that long after.

Photons do not "bend" space-time like mass, however.

Nicholas · 2008-03-30 01:08:25

Gravity effects light because light falls. It is effected by space curvature and the slowdown of time.

Mitch Raemsch

Chris · 2008-03-31 16:13:37

Nicholas wrote:
Gravity effects light because light falls. It is effected by space curvature and the slowdown of time.

I wouldn't call it light "falling". But yes, light's path is affected by space curvature because the path itself is affected.

It is not the light qua light that is influenced by gravity. It is the path that changes.

"Slowdown of time" has nothing to do with it.

Nicholas · 2008-04-11 06:31:16

If gravity effects light then what else to call it than falling Chris? I know it must be taken into account that it doesn't fall in the same way as matter does but nevertheless its true. Light is effected by gravity.

The energy of light is effected by the changing timerates of gravitational time that it moves through. Shapiro explains why we must wait on light that falls. It is moving in a slower gravitational time metric.

Mitch Reamsch

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#1 2007-11-21 17:30:02

why does gravity affect light .....

#2 2007-12-06 02:11:33

Re: why does gravity affect light .....

#3 2008-02-23 17:04:06

Re: why does gravity affect light .....

#4 2008-02-27 18:38:44

Re: why does gravity affect light .....

#5 2008-03-30 01:08:25

Re: why does gravity affect light .....

#6 2008-03-31 16:13:37

Re: why does gravity affect light .....

Nicholas wrote:

#7 2008-04-11 06:31:16

Re: why does gravity affect light .....

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