Gravity Well & Speed of Light: Questions & Answers

[la grange]

Does a gravity well affect the speed of light? I would assume not because I know the speed of light to be a constant and that's how I have always been taught but now I am starting to question this. Also, would gravity wells affect the approximated age of the universe, and if so, by how much?

Thanks for the help guys!
-Grange

 

[muppet]

You may have more luck with this one in the relativity forum Admins move this maybe?
But all observers measure the speed of light to be c. That much I can tell you as fact. As to the age of the universe, I asked a similar question at the end of a lecture at an open day once. The short answer is no, as gravitational effects on time are only significant for very intensely strong fields. It's also worth pointing out that by far the biggest constraint on our estimate of the age of the universe is our uncertainty in the value of Hubble's constant. We think it's around ~70 (km/s)/Mpc, but estimates range over 50-100 (km/s)/Mpc.

 

[blechman]

gravity wells cannot change the speed of light in GR. They can change the trajectory light travels, of course.

 

[A.T.]

Does a gravity well affect the speed of light? I would assume not because I know the speed of light to be a constant and that's how I have always been taught but now I am starting to question this.

Don't confuse gravity wells with relativistic gravitation (http://en.wikipedia.org/wiki/Gravity_well#Gravity_wells_and_general_relativity"). Measured with a local clock the speed of light is constant everywhere. But a local clock runs slower near a mass. So, measured with a faster distant clock light appears to be slower near a mass.