We know that an object falling to the black hole, as observed from an observer far away, will freeze as it gets closer and closer to the event horizon. So my question is how can a black hole form in the first place? I mean we usually say thing a star collapses into a blackhole. But considering the effect of "time-freezing", how could that be possible in the first place?
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$\begingroup$ See also astronomy.stackexchange.com/questions/8340/… astronomy.stackexchange.com/questions/14399/… $\endgroup$– ProfRobCommented Aug 7, 2016 at 13:45
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After a supernovae explosion from stars whose mass is more than the Chandrasekhar limit, the remaining neutron star is so dense that it collapses into a one single singularity( A point where the density in infinite and is compressed into a point).the only way we can detect a black hole is by the entropy given by the black hole. so at the point of formation the black hole is not taking any matter into it.After the black hole is formed we will see any object going into it as frozen in spacetime
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$\begingroup$ You mean the neutron star is initially already smaller than the event horizon? I think that's not possible. $\endgroup$ Commented Aug 7, 2016 at 11:56
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$\begingroup$ Yes it is actually smaller than the event horizon but the gravitational field is not strong enough because a black hole actually ruptures spacetime.(courtesy: The Theory of Relativity $\endgroup$ Commented Aug 7, 2016 at 11:58
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2$\begingroup$ Sorry, but his is not the correct answer. The collapse of the neutron star begins before it has shrunk below the Schwarzschild radius. The answer is a bit more complicated, but can be found many places. The best explanation I could find searching this site for one minute was this one, which basically says that, yes, a true black hole never forms as seen from our perspective, but what does form is so close to a black hole that for all practical purposes, we can treat it as one. $\endgroup$– pelaCommented Aug 7, 2016 at 12:49