Black Hole

Special Relativity Einstein’s special theory of relativity has two parts. –All objects moving at constant velocity have the same laws of physics –The speed of light is constant for all observers The pendulum will swing at the same rate if the car is moving or not.

General Relativity If nothing travels faster than light, how does gravity affect objects? General relativity showed that acceleration acts just like gravity on objects. On Earth, with gravity, objects in the rocket have 1 g pulling down. In space, with no gravity, the engines can create a thrust of 1 g pulling to the floor.

Bending Light Photons, which transmit light, are massless. –Photon energy has an equivalent mass –Photons affected by gravity, which bends the light We picture space as curved by gravity, and light follows the curves like a lens.

Pure Gravity In a neutron star, degenerate neutrons resist gravity. For M ns greater than 3 M  the neutron star collapses. There is nothing left to oppose gravity and the mass collapses to an infinitesimal point.

The gravitational force increases as the distance decreases. –Escape velocity also increases –Escape velocity can exceed the speed of light –No light or matter escapes This is called a black hole. Trapped Light Photon deflected Photon trapped

Observing Radiation Matter which reaches the event horizon is trapped. The acceleration causes radiation before matter is lost. –All parts of spectrum

Black Hole Mass Black holes can keep accumulating mass. –Stars orbit around according to Kepler’s laws –Measure orbit and calculate mass Some black holes have the mass of over a million suns.