(adsbygoogle = window.adsbygoogle || []).push({}); The Equivalence Principle--bending of light

Hi everyone!

I have learned the general relativity, but I have a few problems which I don't understand. Can someone help me?

I am recently learning the Equivalence Principle and the bending of light. I have read the following paragraphs in a website, and I was quite confused about some questions:

"Consider a rocket undergoing constand acceleration. Light entering one side of the rocket will appear to 'fall' toward the floor as it crosses the rocket. This is because it takes a finite amount of time for light to cross the rocket, and in that time, the rocket has moved. Since it is undergoing constant acceleration, the trajectory of the light will be a parabola. "

"Now by the Eauivalence Principle, this result applies as well as to a stationary frame with a gravitational acceleration equal to the previous rocket acceleration. So light 'falls' in a gravitaional field."

I understand the first part of the quotation that light appears to fall toward teh floor. But, my problem is, when this happens to a stationary frame with gravitational acceleration, why does light fall??? I know that we can apply the Equivalence Principle here, but I just don't think this (light falling toward ground) is possible. I thought that light has no mass and it would not be attracted by gravitational force. Can someone explain this to me? And please do not just say that it is because of the Equivalence Principle......Thanks!

*Quotations from http://www.phys.ufl.edu/~acosta/phy3101/lectures/relativity5.pdf

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# The Equivalence Principle-bending of light

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