I read that photons are massless. Why then are super massive bodies such as stars able to bend light rays?

Answer 1

Good question. The reason is because gravity isn't actually pulling the light.

Gravity is much like a trampoline. Imagine a bowling ball in the middle. The ball creates an indention. If you rolled a marble across the trampoline, and it traveled into that indention, it would curve around not because the bowling ball pulled it, but because it was following the contour of the trampoline.

This is how mass affects spacetime. The sun or any mass for that matter creates an indention in spacetime. The Earth is traveling in the Sun's spacetime indention, so it isn't the Sun pulling the Earth at all.

When light enters the indented space, it follows the contour of the curved space, which is why it bends.

Answer 2

Although I'm no atrophysicist, I didnt think stars were able to bend light rays.... they emit them. A black whole can though. A black hole's gravity is so incomprehensibly intense nothing escapes it's pull, even massless photons of light. Also a light ray is constructed of much more than a single photon. Many different light rays (at different frequencies like infrared or visible or x or gamma) will have different photonic properties. If a beam of light was pointed directly at or passed close enough to the event horizon of a black hole, it would be consumed. If the same ray was pointed at the sun, it would not bend off course.

Answer 3

One answer is that any particles such as photons of light, move along geodesics in general relativity and the path they follow is independent of their mass. The deflection of star-light by the sun was first measured by Arthur Eddington in 1919. The result was consistent with the predictions of general relativity and inconsistent with the Newtonian theory. Another answer is that the light has energy and momentum which couples to gravity. The energy-momentum 4-vector of a particle, rather than its mass, is the gravitational analogue of electric charge. The corresponding analogue of electric current is the energy-momentum stress tensor which appears in the gravitational field equations of general relativity. A massless particle can have energy E and momentum p because mass is related to these by the equation m2 = E2/c4 - p2/c2 which is zero for a photon because E = pc for massless radiation. The energy and momentum of light also generates curvature of space-time so according to theory it can attract objects gravitationally. This effect is far too weak to have been measured. The gravitational effect of photons does not have any cosmological effects either (except perhaps in the first instant after the big bang). There are far too few with too little energy to make up any noticeable proportion of dark matter.

Answer 4

Because the bodies aren't bending the rays of light. They are bending the medium in which the light travels. This medium, known as Space-Time, is a void in which photons travel. When a supermassive body such as a star is in space-time, it warps it like a bowling ball on a rubber membrane. The photons then follow the new warped path like a marble on the membrane.

Answer 5

Light behaves like two different things, like particles (the photon). and like waves (just energy). Photons do have mass. And that is why they are affected by gravity. An estimate of the upper limit for the mass of the photon is 6×10^−17 eV.

Answer 6

Light acts both as a wave and as a particle. When light passes by an incredibly heavy object, it is attracted to it even though it has no mass. Also, stars and black holes bend the fabric of space.

Answer 7

Supermassive bodies bend the space through which the photons move in a straight line. If the space is bent, the "straight" path is bent.

Answer 8

Light is indeed massless, but it still must follow the geometry (shape) of space. As you probably know, mass determines the shape of space, therefore the path of light through that space will follow its shape.

Answer 9

They have moving mass, but not stationary mass. Good thing or our eyes would fill up with them.

Answer 10

I think they have an effective mass (related to their frequency) although they have no actual mass.