How can gravity affect light?

Question

I know it is only a tiny ammount, because it has a tiny ammount of mass - but how can light have mass, when it travels at the speed of light?

Answer 1

Gravity if the curvature of spacetime, therefore when light travels through curved spacetime, it bends.

but this effect can only be seen when light travels near huge masses like galaxies or planets. bending of light is a phoenomena call gravitational lensing

Answer 2

It's all due to the properties of light itself.
Light is both a wave and a particle at the same time. All particles have a mass. Large masses attract small masses, this is called gravity, so when the light passes by (for simplicity of thought) a planet, the particles making up the light are attracted to the planet and bend towards it.

Answer 3

In general relativity, the effects of gravitation are ascribed to the curvature of spacetime, instead of being a force. Simplistically, these curvatures cause a free falling object to deviate from its geodesic [which is the notion of a "straight line" to curved spacetime; i.e. the world line of particle free from all external force is a particular type of geodesic]. The situation is analogous to setting a bowling ball on a bed; the heavy ball depresses a nearby region of the bed's surface. If you then roll a marble across this "depression" it feels the curvature created by the massive body. The marble thrown onto the bed moves toward the bowling ball. Because its motion is not along a line and its velocity changes, the marble is now accelerating. Therefore it does not matter whether light has mass in order for it to "bend". Now, onto your question. If you look at gravitation as a result of spacetime curvatures and not a force, you'll realize that light can influence a gravitational field since it possesses momentum and energy [by the equation: E^2 = m^2c^4 + p^2c^2]. They're probably not the only reasons, however. Edit: I was wrong, which I realized after reading the above posts. Thanks for the question anyway, made me learn a bit.

Answer 4

Anything with mass creates "gravity". Some items create more gravity like stars and some less to none at all like atomic particles. All very massive bodies, like stars and planets, warp or curve spacetime to create gravity wells. See the Earth, like any object in motion, travels along in a straight line until acted upon by an external force. The external force acting upon the earth to bring it back around the Sun again and again is the curvature of the spacetime around the Sun. Sort of like rolling a marble up a hill. The marble thinks it is going along a straight path, but some force pushes it up. That is all spacetime does to bodies traveling through it, it pushes them along the curves of itself caused by massive bodies. So, even a massless photon will have its path affected by the surface of spacetime it travels along. Usually it travels into the gravity well a bit and then out a continues on, unless it comes to the severely curved space around a black hole. If it doesn't just skim around the event horizon, then it can't escape out of the gravity well.

Answer 5

The speed of light is something measured with a local apparatus in an inertial reference frame, using the same meter stick and clock. A gravitational field has zillions of such 'locally inertial reference frames' which are described by freely-falling observers for short intervals of time and small regions of space. In all of these tiny domains, an observer would measure the same velocity for light as guaranteed by special relativity. To ask what the speed of light is over a domain where gravitational forces make a reference frame 'non-inertial' and not moving at a constant speed, is an ill-defined question in special relativity. As soon as you try to measure the speed of such an impulse, you would be using a clock and a meter stick which would not be the 'proper time and space' intervals for the entire region where the gravitational field exists.

Answer 6

Is it not the other way around in that light speed is the universal constant so gravity exist within the parameters that are set + yes gravity curves spaec-time as light travels through it

Answer 7

It is known from observations that light is affected by gravity, but to understand why you need to delve thoroughly into a modern treatment of Einstein's general theory of relativity. It sounds to me that you presently have a smattering of relativity, eg "the mass of a body tends to infinity as its speed tends to that of light" and that's what has confused you. For a good answer to a similar question see the link, and dig further from there. Good luck.

Answer 8

Gravity is a warping of space, and thus alters the path traveled by light.

Light has no mass and no momentum or inertia.

The solar sail concept uses the solar wind consisting of protons which have mass, not photons of light which do not have mass.

Answer 9

a photon has no rest mass. but travelling at the speed of light it has a momentum, hence the thoughts of things such as solar sails.

As it has a momentum it must have an intrinsic mass, and as such it is affected by graviety. This has been proven my mapping the positions of stars during an eclipise where they appeared in the wrong place, the effect due to the light rays travelling near the sun

Answer 10

honestly one of the best questions. look my friend in order to explain matter we gave it wave properties AND in order to explain waves we gave them matter properties therefore

E= H * f

and E= m*c^2 in the long run come to the play. light moves, therefore is has kinetic energy in my mind it hasd inertia there for it has mass. do not adopt the way of thinking that if i travel with the speed of light my mass converts to energy etc. take a look on the equation that relates the speed of light and the speed of the object under consideration and you will see what the poor man was trying to say.

now as far as the light is concerned a photon traveling next to another photon at the same light "beam" sees it at rest. it travels though with the speed of light.

at the bottom light excess of mass concentration can affect light projectile and as in black whole it can actually "suck" it up due to the enormous forces present.

in the end one should think. is there any mass in light or are the properties only present????????????