Photons do not have mass (that's why they can move at speed of "light").
So, my question is how the gravity of black hole can stop light from escaping?
Tell me more
×
Physics Stack Exchange is a question and answer site for
active researchers, academics and students of physics. It's 100% free, no registration required.
|
|
||||
|
|
|
Black holes affect the causal structure of spacetime in such a manner that all future light cones within a black hole lie within the event horizon of it. Although photons are massless they have energy and have to obey the geometry of a curved spacetime. Since all future lies within the event horizon, photons are trapped inside the black hole.
|
|||||||
|
|
Even though photons have no mass, they are still affected by gravity. That's how we can see black holes - by the way they distort the light going near them. The reason nothing can escape a black hole is because within the event horizon, space is curved to the point where all directions are actually pointing inside. The escape velocity from within a black hole's event horizon is faster than the speed of light, hence light cannot go at that speed and thus cannot escape. |
|||||||||
|
|
The above statement about a photon having no "rest" mass is actually quite contrary to reality. As an object approaches the speed C its mass becomes relatively smaller and smaller, until it reaches the asymptotic light speed and becomes virtually massless, timeless, and spaceless. The more energy the photon has, the smaller the wavelength, higher the frequency, and higher the rest mass. This equation can be given by mv=hf/c. Technically, you yourself (and this entire planet) resemble but a group of photons to some frame of reference (for example, a galaxy going in the opposite direction to ours at a very high speed). I think gravity effects photons because while they are massless (by definition, when it is moving at the speed of light it has no mass) is because they are, even massless, a photonic bundle of energy. |
|||
|
|
|
Gravity is the force which bends the very fabric of Space time. During eclipse scientists have seen the light from distant stars which are near the Sun change their path. So it proves that light is affected by Gravity. Now that you know that light gets affected by gravity, you must also be knowing that the gravitational force of a Black-Hole is immense. As anything on earth needs to have a minimum velocity to overcome the gravitational pull of Earth (which is called escape velocity) is something that Man has been able to achieve, so our space ships and rockets reach Space. But the escape velocity required to overcome the gravitational pull of a black hole is greater than the speed of Light. And as we know that nothing travels faster than light, so Black Hole swallows anything and everything that comes near it including light. |
|||
|
|
|
If we generate a pair of photons entangled in polarisation and seperated the pair sending one photon beyond the event horizon would that produce non-local correlations. We may either observe that both photons cease to exist beyond the event horizon. Or if we suspended one of our entangled photons at near absolute zero, would we be able to communicate from within the singularity? If our entangled photons are without mass at the speed of C then would any observation of our local photon be measurable in mass if our other entangled photon had reached a singularity? Something could then escape in the form of information and maybe only because it had escaped at a speed faster than light. |
|||||
|
