Electromagnetic Force

The electromagnetic force is one of the four fundamental forces. It governs the interactions between charged particles (like charges repel, opposites attract) and is mediated by the photon. All of the quarks, plus the electron, muon, and tauon, all interact with the electromagnetic force. The weak bosons are also charged, and therefore themselves also interact with the electromagnetic force.

Escape Velocity

Escape velocity is a measure of the speed necessary for a projectile to escape the gravitational pull of an object. For example, the earth’s escape velocity is roughly 11 kilometers per second or about 7 miles per second; therefore (discounting air resistance) an object traveling at that speed from the surface of the earth would be able to escape the earth’s gravity and never fall back again.

Event Horizon

If you come too close to a black hole, there comes a point when it is physically impossible to return. The imaginary sphere around a black hole that marks this boundary is called the event horizon. Nothing that crosses the event horizon can ever return, including light; therefore, the event horizon marks the region of space that we perceive as black around a black hole.