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ably dense matter, its gravitational pull would increase so that a particle would have to be
traveling faster and faster to escape from that gravity (called the escape velocity).
Schwarzschild’s calculations showed that as a massive star collapsed to a single point of infinitely dense matter, its escape velocity would exceed the speed of light. Nothing would escape such a collapsed star. It would be as if the star disappeared and no longer existed in our
universe.
With these calculations, Schwarzschild had discovered the concept of a black hole.
The terms we now use to describe a black hole (event horizon, escape velocity, etc) were all
created by Schwarzschild in 1916. Schwarzschild mathematically “discovered” black
holes, but he didn’t believe they physically existed. He thought it was only a mathematical
exercise.
Fifty years later, astronomers began to seriously search for Schwarzschild’s invisible
collapsed stars. Astronomers realized that, since a black hole couldn’t actually be seen, the
only way to detect one was to track unexplained motion of the stars that they could see and
show that that motion was the result of the gravitational pull of a nearby, unseeable black
hole. (Astronomer John Wheeler coined the name “black hole” in 1970.)
In 1971, calculations by Wheeler’s team confirmed that the X-ray binary star, Cygnus
X-1, was a star circling a black hole. That was the first time a black hole had ever been physically detected.
It wasn’t until 2004 that a black hole was identified in the Milky Way galaxy, by Professor Phil Charles of the University of Southampton and Mark Wagner of the University of
Arizona, this one located 6,000 light years away from Earth in our galaxy’s halo. But it was
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