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Thread: What would we experience if we entered a black hole?

  1. #1
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    What would we experience if we entered a black hole?

    I know that if a human would enter a black hole he would be crushed and trapped. However curiosity gets to me, and I wonder what it would be like if us humans were to survive, and reach the center of a black hole. Are there any theories? If so I'd like to know. Maybe we even could discuss and make logical theories of our own, if the theories we currently have don't satisfy us enough.

  2. #2
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    This?

    But seriously, it would depend on what kind of black hole. A black hole of the same mass as the sun would be about 3 km. The Earth would be torn up before it ever reached the event horizon. Cygnus X-1 has a huge accretion disc, which would again tear up the Earth. A galactic black hole like Sagittarius A* has a rather large event horizon. I believe the number is 44 million km, but I am not sure if this means the event horizon or the accretion disc.

    Making a wild assumption that this is the event horizon (I should feel bad, I am pretty sure it isn't the horizon size), I am not sure if this is large enough not to spaghettify or otherwise damage the Earth. If the Earth could cross the event horizon intact, it wouldn't really experience anything special other than the stars becoming distorted. If the moon was in tow, it would likely take its own path in instead of staying in orbit. This would last until the Earth was compacted in the singularity. I have no idea what that would look like.

    The 44 million km number is kind of interesting. The orbit of the Earth covers about 940 million km, so if the Earth took an ever smaller spiraling path in to the black hole, we would see the stars whip "by", so to speak.
    Solfe

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    Quote Originally Posted by SuperNova View Post
    I know that if a human would enter a black hole he would be crushed and trapped. However curiosity gets to me, and I wonder what it would be like if us humans were to survive, and reach the center of a black hole. Are there any theories? If so I'd like to know. Maybe we even could discuss and make logical theories of our own, if the theories we currently have don't satisfy us enough.
    well if we are in fantasy land then we'd experience a land where everything is chocolate. No the physics breaks down before that. You'd first get irradiated, ripped appart, ionized, then just turned into energy after that who knows and you aren't even at the singularity yet.

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    Quote Originally Posted by SuperNova View Post
    Maybe we even could discuss and make logical theories of our own....
    Big problem: we can't observe anything inside the event horizon. Lee Smolin speculates that black holes house entire other universes in his "fecund universe" idea, which I think is pretty loony. My own speculative but seemingly less loony idea derives from the fact that super-dense white dwarfs are held up by electron degeneracy, super-super-dense neutron stars are held up by neutron degeneracy, and black holes.... we don't know what holds them "together" from collapsing into nothingness, but apparently something does (their gravitational effect is still there). So somewhere inside the event horizon, not the singularity, is a tight ball of super-duper dense matter onto which infallers would be pancaked. A real thin pancake. The state of this matter would be exotic (another term meaning 'unknown'). The very geometry of this 'core' would be shifting and constantly uncertain. Well, you asked for it!
    Everyone is entitled to his own opinion, but not his own facts.

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    So basically the whole Star Trek premise that the black hole is a time travel wormhole is completely wrong. I had already assumed it was already though, it was really far fetched. Otherwise, since a black hole is so strong that even light is trapped in it wouldn't that mean at the singularity everything would just be stuck as trapped energy. So then everything could go on as before, but it'd be much different than it going on outside of the black hole.

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    SuperNova,

    I'm going to argue with some of the ideas Cougar just
    proposed, while hoping you'll find it relevant to your question.

    White dwarfs, neutron stars, and possibly quark stars are
    prevented from collapsing further by forces carried between
    particles at the speed of light. A black hole occurs when the
    minimum speed those forces need to have in order to do their
    thing is equal to or greater than the speed of light. When
    there is no speed faster than the speed of light, no force can
    prevent matter from collapsing in black hole gravity. Nothing
    can prevent it from collapsing to zero size.

    Many people don't like the idea of matter collapsing to zero
    size. The first way to get around it is, as you say, that nobody
    outside the event horizon can observe anything inside it. The
    next step is that anyone falling into a black hole after it forms
    will never see the singularity at the center until he actually
    reaches it. That is of somewhat limited help because, by his
    own clock, he will reach the singularity in a very short time.
    On the other hand, by an outsider's clock, he'll never get there.
    I use an imaginary "God's viewpoint" which can see everything
    everywhere, at every time, in which I consider the gravity well
    of the black hole to be deepening without limit, forever, as the
    matter falls and becomes more and more dense, without limit,
    forever. Again, though, that is from "god's viewpoint", not the
    viewpoint of the infalling matter, which reaches the singularity
    in a very short time. The falling matter doesn't know anything
    about the passage of time in the outside universe, or even just
    higher up inside the black hole. It only knows its own time.

    The next way we might try to prevent matter from collapsing
    to a singularity is via the Heisenberg principle of uncertainty.
    Although no force can stop the matter from collapsing without
    limit, there *is* a limit set by uncertainty on how far it can be
    observed to collapse, apart from the limits set by the finite
    speed of light. Beyond that limit, further collapse may not
    have any meaning. Nothing can prevent it, but it may not
    have any consequences. Certainly the gravity well doesn't
    disappear. The mass doesn't disappear.

    But even if uncertainty doesn't apply -- even if the matter
    collapses to an infinitesimally small volume, or zero volume --
    it will continue to have the same mass and the gravity well
    will continue to exist.

    Anything falling into a black hole eventually is spaghettified,
    not pancaked. It is stretched in the radial direction without
    limit and squeezed in the horizontal direction without limit.
    The atoms are pulled apart in the radial direction, with all the
    bits getting pulled further and further apart from one another.
    So in that direction, the density is actually decreasing. And,
    interestingly, that direction is the future, a direction in time
    rather than space.

    -- Jeff, in Minneapolis

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    One issue my pop-sci understanding gives me with all this is that if the singularity of the BB was at all similar to a BH, how did the first manage to 'break out?' (I suppose the answer is the the BB may not have been a singularity, but that seems to imply either a big bounce that avoided a BH, or brane collisions or whatever...). Your kind clarifications are most welcome.

    ETA: Cougar, would you elaborate a bit on why you think Smolin's idea is loony? (Not that I have a counter-argument; just curious.)
    Last edited by Hlafordlaes; 2014-Aug-11 at 10:23 AM.

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    Quote Originally Posted by Cougar View Post
    Big problem: we can't observe anything inside the event horizon. Lee Smolin speculates that black holes house entire other universes in his "fecund universe" idea, which I think is pretty loony.
    Smolin appears to no longer believe that.

    http://physicsworld.com/cws/article/...nique-universe

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    Quote Originally Posted by Hlafordlaes View Post
    One issue my pop-sci understanding gives me with all this is that if the singularity of the BB was at all similar to a BH, how did the first manage to 'break out?' (I suppose the answer is the the BB may not have been a singularity, but that seems to imply either a big bounce that avoided a BH, or brane collisions or whatever...). Your kind clarifications are most welcome.

    ETA: Cougar, would you elaborate a bit on why you think Smolin's idea is loony? (Not that I have a counter-argument; just curious.)
    You've got the idea. The Big Bang model doesn't actually go back to a singularity. That is extrapolating further then we need to go for that model. The big bang just says the universe started in a hot dense state. Just like, technically, you don't need a singularity at the centre of a black hole to have a black hole. All you need is enough mass in a given region compared to the region around it. In the early universe there where no "wells". If you think of gravity as the ball on a rubber sheet analogy there are none of those bowls. Since the mass/ energy density is so uniform there is no well to fall into. It is just flat. That means there is no one direction where the pull of gravity is stronger, like with a black hole/ planet/ moon or any other body with mass when surrounded by space with very little in it. You need that gradient of gravity going from lower gravity to higher gravity before you get things like event horizons.

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