Physical Properties
Black holes have three main properties - mass, spin, and electrical charge. The simplest black holes have mass, but no charge or angular momentum (called Schwarzschild black holes). There are three other general types black holes: rotation with charge, no rotation with charge, or rotation with no charge. However, black holes are commonly classified by their mass.
Black holes have three main properties - mass, spin, and electrical charge. The simplest black holes have mass, but no charge or angular momentum (called Schwarzschild black holes). There are three other general types black holes: rotation with charge, no rotation with charge, or rotation with no charge. However, black holes are commonly classified by their mass.
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Event Horizon
A defining characteristic of black holes are their event horizons. These are boundaries in spacetime in which matter and light can only pass inwards to the black hole. Nothing can escape from the event horizon. Event horizons are always approximately spherical in shape. Due to the effect of gravitational time dilation, from an observer's viewpoint, something falling into a black hole seems to slow down as it gets closer to the event horizon and takes an infinite time to reach it, although the object falling into the black hole would not notice this effect. The event horizon gets its name from the fact that information from an event that occurs within the event horizon can never reach an outsider, so it is impossible to determine if that event actually happened. |
Singularity
Described by general relativity, at the center of the black hole lies a gravitational singularity. This is a region where the spacetime curvature becomes infinite. This region can be shown to have zero volume, but can also be shown to contain all the mass of the black hole. Thus, it is though of as having infinite density. The appearance of singularity generally is seen as the breakdown of physics as we know it, and the beginning of quantum effects.
Described by general relativity, at the center of the black hole lies a gravitational singularity. This is a region where the spacetime curvature becomes infinite. This region can be shown to have zero volume, but can also be shown to contain all the mass of the black hole. Thus, it is though of as having infinite density. The appearance of singularity generally is seen as the breakdown of physics as we know it, and the beginning of quantum effects.
Photon Sphere
The photon sphere is a spherical region surrounding the center of the black hole in which the strength of gravity forces the photons to travel in orbit. The photon sphere exists outside of the event horizon and ergosphere. Within this sphere, it would be possible to see the back of your own head, as the photon reflecting the back of your head would orbit the whole and then get intercepted by your own eyes.
The photon sphere is a spherical region surrounding the center of the black hole in which the strength of gravity forces the photons to travel in orbit. The photon sphere exists outside of the event horizon and ergosphere. Within this sphere, it would be possible to see the back of your own head, as the photon reflecting the back of your head would orbit the whole and then get intercepted by your own eyes.
Ergosphere
The ergosphere is a region of spacetime, surrounding rotating black holes, in which it is impossible for objects to remain motionless. According to the theory of relativity, any object around this area will start moving in the direction of the rotation. Sine this region is outside of the event horizon, it is possible for objects within this region to escape the gravitational pull.
The name comes from the Greek word "ergon", meaning "work", because it is theoretically possible to take energy from the take energy and mass from the region.
The ergosphere is a region of spacetime, surrounding rotating black holes, in which it is impossible for objects to remain motionless. According to the theory of relativity, any object around this area will start moving in the direction of the rotation. Sine this region is outside of the event horizon, it is possible for objects within this region to escape the gravitational pull.
The name comes from the Greek word "ergon", meaning "work", because it is theoretically possible to take energy from the take energy and mass from the region.