Is light attracted by gravity? Answered on Quora by Kip Ingram, PhD in Electrical Engineering, The University of Texas at Austin, Cockrell School of Engineering (1992)
Newton’s theory of gravity would have said “no,” and since Newton’s theory is the most people are generally exposed to in “early physics education” a lot of people walk around thinking that zero mass [light] implies no gravitational activity. This turns out to be incorrect, though for practical day-to-day calculations it’s perfectly good.
Einstein gave us an improved theory of gravity in the early 1900’s, and under his theory any form of energy whatsoever both creates gravitational effects and responds to gravitational effects created by other things. Yes, light follows a curved path through a gravitational field that can be calculated using Einstein’s theory.
Observation of this light curvature was the first “big confirmation” of Einstein’s new theory and was done using a solar eclipse to allow us to see starlight that passed close to the sun on its way to us. Those stars showed up in the “wrong positions,” but precisely where Einstein’s theory told us to expect to see them.