Event horizon

Back in 1935 a mathematician by the name of Swartzchild showed that if a neutron star were to collapse under its own gravity it would reach a radius at which the escape velocity would exceed the speed of light. At that point it would pass through what has become known as the Swartzchild throat and effectively disappear! The resulting black hole would retain massive gravity.

The event horizon (the radius at which a black hole forms) is defined by the condition ...

.... which for one solar mass is not very big.

Few people took Swartzchild seriously at the time, but subsequent events have shown that black holes not only exist in large numbers, but massive black holes are present in the centers of galaxies.

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