What happens to light and mass in the center of a black hole?

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It's difficult to know what happens on the other side of a black hole, since no information can cross back through the event horizon (the radius at which light and therefore any information can no longer escape). The leading idea is that near the center of every black hole lies a singularity, or a point where the density (and therefore the curvature of space-time) reaches infinity (that is, some amount of mass contained in zero volume).

Any mass which crosses the event horizon will accelerate inwards toward the singularity. When it starts to get close, it will experience tremendous tidal stress. Because the singularity contains the mass of anywhere from one supergiant star to several million of them (or possibly more) and is infinitely dense, the end of the object which is closer to the singularity will experience significantly more gravitational force than the end facing away. This will manifest itself as a gradually increasing stretching of the mass, something colloquially referred to as "spaghettification."

The falling mass will contact the singularity and become part of it in finite time in the reference frame of the mass. To an outside observer, things get a little funny due to the relativistic effects of such a strong gravitational field. Beyond the event horizon, time is essentially frozen, so to anyone watching the black hole, nothing can ever happen inside it. So if an object starts to get close to it and fall in, it will gradually slow down and turn red (the light is red-shifted) and never cross the horizon. The light will get more and more red-shifted until it is infrared, microwaves, radio waves, etc--until it essentially disappears. But you will never observe it cross the horizon. The object itself will cross the horizon normally, however it will still always look like it hasn't crossed the horizon--because all light is rushing down towards the singularity, and none can come back the other way, it will always appear that the horizon is just beyond reach. Looking the other way though, the outside world would appear extremely weird once inside the horizon.

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Annika Peterson
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Annika Peterson

I'm an amateur astrophysicist who is studying at Carnegie Mellon University.

Updated on April 10, 2020

Comments

  • Annika Peterson
    Annika Peterson over 3 years

    I know that black holes are "black" because nothing can escape it due to the massive gravity, but I am wondering if there are any theories as to what happens to the light or mass that enters a black hole and cannot escape.

  • Carson Myers
    Carson Myers over 12 years
    The theory that there is a singularity at the center of a black hole is not the same theory that black holes can create wormholes. A singularity means a point of infinite curvature of space-time, not that it rips a hole in an arbitrary location elsewhere.
  • Spoilt Milk
    Spoilt Milk over 6 years
    This is a good answer but I'd have to disagree with you when you state- "Because the singularity contains the mass of anywhere from one supergiant star to several million of them...". The singularities that we discuss in general relativity are not points in space-time; it’s like the hole in the topology of a manifold. Since a singularity is not even a point on the manifold assigning a mass to the singularity makes no sense...
  • Carson Myers
    Carson Myers over 6 years
    Interesting, thanks! FWIW I wrote this answer on another SE site before it was folded into physics.se, and only had an introductory undergrad physics education
  • axel
    axel over 5 years
    The final paragraph seems to blur the distinction between the event horizon and the singularity. The OP is asking about the singularity.
  • Admin
    Admin over 5 years
    This doesn't really seem like an answer based on any physical theory.
  • Admin
    Admin over 5 years
    According to black hole complementarianism, from the point of view of someone entering a black hole, the event horizon is not a particularly special place in space, and they will pass it without necessarily noticing any change. I assume you mean black hole complementarity. What you say has nothing to do with black hole complementarity. It's just a statement within classical relativity. The second paragraph is about the horizon, but the question is about the singularity, not the horizon.
  • Daniel Turczynskyj
    Daniel Turczynskyj over 5 years
    I'm self taught, so I don't know any theories, and by the way theories are something people think could be true, and a theorem is something that is proven. So even if I did base my answer on theories, it still might not be true. Most of the answers above are all theories. And finally, from what I know, everything I said in my answer is true.
  • Daniel Turczynskyj
    Daniel Turczynskyj over 5 years
    I believe I am the only person who actually answered the question, my answer is true and I said exactly what happens to the matter after it enters the event horizon. And everyone else says they don't know if anything they said was even true, They told you to make up your own answer and said it may be true.
  • Daniel Turczynskyj
    Daniel Turczynskyj over 5 years
    And if one of the answers above says you can make up your own theory, then this is MY THEORY!!!
  • Acccumulation
    Acccumulation over 5 years
    Black hole complementarity says that the first and second paragraph are both valid perspectives on what happens. The second paragraph discusses how from an outside perspective, there is no singularity, other than the horizon. Everything that "falls into" a black hole simply gets smeared across the horizon. There is no "inside".
  • John Duffield
    John Duffield over 5 years
    This answer contains a fatal contradiction. It says "Beyond the event horizon, time is essentially frozen, so to anyone watching the black hole, nothing can ever happen inside it". But it also says "Any mass which crosses the event horizon will accelerate inwards toward the singularity". I would therefore venture to suggest that it's wrong. However since it has most upvotes and it has been accepted, I'd be grateful if anybody can explain why it isn't wrong. @Ben Crowell : perhaps you could assist? I answered a related question of yours on this the other day.
  • Carson Myers
    Carson Myers over 5 years
    I'm no expert but the local time of the matter falling into the black hole is different from the local time of an observer - time keeps passing (seemingly) normally for the falling reference frame, but the observer never sees them actually cross