How come light can't escape a Black Hole's gravity? Isn't light an energy?

Edward's answer is fairly close to the mark.

Black holes warp spacetime so much that any particle that crosses the event horizon finds that simply moving forward in time also moves it toward the singularity at the centre of the black hole. The only way anything could escape the black hole would be if it could travel faster than light. You can view an event horizon as being defined to be the boundary between an escape velocity that is lower than c and an escape velocity that has to be greater than c, as Edward indicated.

To understand why light also experiences the warping of spacetime you can imagine a beam of light passing through a rocket with high acceleration. To the astronauts it would look as though the laser beam were travelling in a curve entering the rocket at the nose and leaving it at the tail. As far as the astronauts are concerned the rocket could either be accelerating in free space or sitting on the launch pad on a massive body, they still feel a force pushing them into their seats. They conclude, therefore, that gravity can bend light, just as Edward indicated.

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RE:

How come light can't escape a Black Hole's gravity? Isn't light an energy?

I'm 14, and my Dad questioned cosmologists and physicists on their explanation for what light really is and he said that if light is an energy, how come it gets pulled into a Black Hole? He says that only matter is affected by gravity. And if light is made up of matter, why won't it destroy...

I'll take a swing at giving you a layman's terms explanation, but the words "general relativity" are going to have to be used.

According the Einstein's theory of general relativity (you were warned), gravity causes a curvature of spacetime such that it does affect both mass and light/energy. For example, there's a phenomenon called gravitational lensing, in which light from a star that is directly behind a massive body from Earth's point of view can still be seen because the massive body's gravity bends the light around itself. So light is affected by gravity.

If you take the formula for gravitational escape velocity and plug in the speed of light, you get c^2=2*G*M/R. Hence, if the massive body has a radius R=2*G*M/(c^2) or smaller [called the Schawzchild radius], even light cannot move fast enough to get out of the gravitational field. And that's your black hole.

consider this ok you have a blanket or large peice of cloth right and you drop a ball on to it. The ball causes the cloth to bend inward making a vortex or a well into the center, much like a worlpool. So if you get a large enough gravity pull, say from a supernova, it can even pull in the light. aka a black hole.

light is not made of matter otherwise how would it travel. a sound wave uses the matter by giving it compressions in certain frequencies thus it itself is not matter and light waves have the same characteristics.

You and your dad are thinking of gravity as a force, in a very Newtonian way. And Newtonian physics doesn't allow for black holes. The neat thing about gravity in special relativity, where black holes are possible, is that it doesn't attract matter; it warps space. The light is still going in a straight line, but the straight line isn't straight in a Euclidean geometry, and it's "straight" that gets pulled into the black hole.

I argue that light IS matter, and it does have an EFFECTIVE mass. A photon of light at frequency f has an effective mass of m = h*f/c^2. It just has no REST MASS, but light really doesn't exist at rest.

Light carries energy, does it not? And according to Einstein's mass-energy equivalence principle, energy is mass and mass is energy.

Gravity DOES act on photons of light, we just don't notice it for down-to-Earth observations. Even when distant starlight travels by the sun, we cannot measure it with an unaided eye...BUT, with technology available to astronomers, they CAN detect light deflected by our sun's gravity.

The dual nature theory states that light has a dual nature...

http://en.wikipedia.org/wiki/Wave%E2%80%93particle...

Which deceivingly means that you can consider it as energy/matter according to the conditions of the problem...

Consider a black-hole...Matter immensely dense....enough to weigh tons for a spoonful....a la mammoth sized gravity....poor photons (light particles)....trying too follow a parallel path relative to the black-hole....suck inside at 90 degrees...get the idea??

Now when you say light should destroy things when it passes through them....it actually does...

But normal light in the visible spectrum isn't powerful enough (low intensity)....

Example....LASERs (Light Amplification by Simulated Emission of Radiation) are used for cutting 2 inch thick metal sheets....

Its an Conservation of Energy effect. To move away from the BH the photon must move up the energy slope in the warp of Space-Time. It takes energy to move up the slope. ===> The photon must lose energy. Since it cannot lose velocity, it must lose energy some other way. It loses energy by increasing in wavelength. Consider a neutron star, light from it is strongly "Red shifted." Now keep adding mass. As you add mass the light shifts deeper down the electromagnetic spectrum in to radio waves. At last, it becomes a BH and the photon at the Event Horizon loses it last bit of energy and disappears.

It follows the reasoning for velocity Red Shift. A star is moving away from the earth, why should its light be Red Shifted. Same argument. There must be an energy cost for that motion? For Newtonian Physics we would subtract the relative motion from the photon. But we cannot do that with light the velocity is fixed. We must compensate fir the velocity some how, the motion is subtracting energy ====> The photons lose energy (sort of like loss of KE in Newtonian Physics) by increasing wavelength.

I take it this same train of thought is why people had trouble accepting this back in the late 18th century. You must realize that physics is about asking the question and trying to disprove things by scientific methods.

Quick answer to your question.

Light follows a path determined by the curvature of space. Space is not necessarily a straight line. In the presence of a black whole space is severely curved.

see http://beatificblogs.blogspot.in/2014/04/cant-ligh...