# Tag Info

12

It is quite correct that a black hole has so much mass that light cannot escape from a region around the black hole. The edge of this region is called the event horizon. If you cross an event horizon you are never coming back. That applies equally to light, and matter. Around the black hole there may be matter in orbit. Since the Black hole has such strong ...

8

The light comes from well outside the black hole event horizon. Matter cannot fall into a black hole without first losing most of its angular momentum (otherwise it would just continue to orbit the black hole). This is accomplished by the outward transfer of angular momentum by viscosity (and other means) in an accretion disc surrounding the black hole. As ...

0

Joe Blow commented about the orbital speed of satellites, correctly. As shown by Aganju, the earth would have to rotate 16 times faster in order to levitate equatorial residents. It's current rotational speed of 0.5 km per sec would then increase to 8 km per s (5 miles/s). We should all recognize this speed as that of orbiting satellites.

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Aganju's answer is excellent, but I'd like to add one thing: The radius used is Earth's radius, which is applicable if you're at the equator. At higher latitudes, the effective radius is smaller by a factor $\cos\theta$, where $\theta$ is the latitude in radians. For iMerchant, who seem to be located in Vancouver at \theta = 49.3^{\circ}\times\pi/180 = 0....

8

If it would rotate fast enough to throw a person off, it would throw everything off - dirt, houses, cars, etc., as the mass of an object is irrelevant - the centrifugal force (pulling out) and the gravitational force (pulling in) are both proportional to an object's mass. Basically the whole thing would explode out at the same time. To calculate we equate ...

7

Straightforwardly no. For a start there are almost no free protons inside a white dwarf. They are all safely locked away in the nuclei of carbon and oxygen nuclei (which are bosonic). There are a few protons near the surface, but not in sufficient numbers to be degenerate. Let us assume though that you were able to build a hydrogen white dwarf that had ...

4

Proton degeneracy is not important, because its effect is much smaller -- much like nuclear particles in theory also are dictated by gravity, but the electromagnetic and nuclear forces are dominating, since they are much stronger. Proton degeneracy is weaker than electron degeneracy due to the far greater mass of the proton compared to the electron. The ...

4

Globular clusters formed whilst the gas of the proto Milky Way was still approximately spherically distributed. The gas forms a dissipative system that loses energy and collapses (within the first billion years) to a disk whilst conserving angular momentum. Formed stars and clusters are essentially collisionless so the halo stars continue to have a ...

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