[QUOTE=Frylock]
Does light exert gravitational force?
My guess would be no. But it would just be a guess.
Another way to ask the question is: is it the rest mass of a body that that determines gravity, or is it just its energy?
-FrL-
[/QUOTE]
Yes light can exert a gravitational force but the light system must have a zero momentum frame.
In other words (and simplified) a photon or photons all moving in the same direction have no mass, but a system of two photons moving in opposite directions does have mass.
[QUOTE=Ring]
Yes light can exert a gravitational force but the light system must have a zero momentum frame.
In other words (and simplified) a photon or photons all moving in the same direction have no mass, but a system of two photons moving in opposite directions does have mass.
[/QUOTE]
Here’s an interesting example:
If a sufficiently energetic sphere of photons were heading towards and centered on the Earth we could be inside a black hole right now and not even know it.
ETA assuming the sphere of light was inside it’s Swartzchild’s radius