Q: What happens when you fall into a blackhole?

Physicist: Terrible, terrible things.

The first thing you’ll be likely to notice as you approach the hole is the tidal forces.  Tidal forces are nothing more than the difference in gravitational force between the near and far side of an object, and they aren’t particular to blackholes.  For example, the tidal force of the moon on the Earth causes tides (hence the name).  For any reasonable sized blackhole (less than thousands of suns), the tidal force between different parts of your body will be greater than your body’s ability to stay intact, so you’ll be pulled apart in the up-down direction.  For much more obscure reasons, you’ll also be crushed from the sides.  These two effects combined are called “spagettification”.  Seriously.  Assuming that you somehow survive spagettification, or that you’re falling into an super-massive blackhole (which is ironically much more gentle than a smaller blackhole) then you can look forward to some bizarre time effects.

It’s been established for decades that “time moves slower the lower”.  For example, GPS satellites have to deal with an additional 45 microseconds every day due to their altitude (they move through time faster).  Also, one way to think about gravity is as a “bending” of the time direction downward.  In this way anything that moves forward in time will also naturally move downward.  At the event horizon of a blackhole (the outer boundary) time literally points straight down.  As a result, escaping from a blackhole is no more difficult than going back in time.  Once you’re inside all directions literally point toward the singularity in the center (since no matter what direction you move in will be toward the future).

We don’t experience time moving at different rates or being position dependent, so when we start talking about messed up spacetime it’s useful to look at things from more than one point of view.

From an outsider’s perspective (far from the blackhole): As someone falls in they will move slower and slower through time.  They will appear redder, colder, and dimmer.  As they approach the event horizon their movement through time will halt, as they fade completely from view.  Technically, you’ll never actually see someone fall into a blackhole, you’ll just see them get really close.

From an insider’s perspective (falling into the blackhole): First, torn apart and crushed.  Things farther from the blackhole move through time faster, so the rest of the universe will speed up from your point of view.  As a result the rest of the universe becomes bluer, hotter, and brighter.  The blue shift of the incoming light turns it into gamma rays.  So, right before you pass through the event horizon, you’ll get nuked with a universe’s lifetime worth of starlight and microwave background radiation turned into nuking nastiness.  The event horizon itself is only special from an outside perspective.  If you fall in you should pass right through it.  However, what you see in the moment that you pass through the horizon is dependent on things we don’t know yet.

-If the blackhole lasts until the universe ends (assuming that the universe ends), then you’ll see the entire history of the universe whip by (bluely).  You’ll then find yourself face to face with the singularity.  At that point you go away, according to the math.  However, the universe is slippery like a greased up eel fresh from the bar exam.  It always finds a way to not have singularities where the math predicts it.  So, to be safe, I’ll say “no one knows what happens then”.

-If the blackhole evaporates, then all the matter that (almost) gets to the horizon will be torn apart and reappropriated as Hawking radiation.  If you were to survive, then you would find yourself as close to the horizon as (for uncertainty reasons) it is possible to be, and you would ride it in as it shrinks.  In a blink you’d suddenly find yourself floating around right next to an amazing explosion, as the last of the blackhole evaporates.

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78 Responses to Q: What happens when you fall into a blackhole?

  1. Martin says:

    Ok, if I understand it right, it is impossible to get to the event horizon because time ends due to time dilation just before you get there – there is no “then” you fall into the black hole.
    Likewise, if I’m watching something fall into the black hole, I never see it get there. None of the light from the object gets to me because of gravity redshifts it more and more. So, from a physics point of view, I can’t observe an object passing the event horizon, which is physically equivalent to saying it didn’t happen (the object never passed the event horizon).
    But if this is right, then how can black holes possibly form in the first place? For example, say I’m at the centre of a bunch of gas that I can work out is going to collapse under its own gravity to form a black hole. As the gas gets denser and denser, time dilates and the universe ends before the event horizon forms. Likewise, if I’m watching this happen from outside, I also never see the event horizon form no matter how long I wait – so the black hole never gets created. What gives?
    There are probably ways around this – like if black holes already existed at the moment of the big bang and so were “outside” time and didn’t need to be formed because they’ve always been there – but it makes me pretty skeptical they exist. Has anyone actually seen one being made?

  2. The Physicist The Physicist says:

    No one has observed a black hole being formed, but we have seen black holes themselves.
    Unfortunately, I don’t know details about black hole formation. It’s not an easy thing to study!

  3. clayton says:

    i am in fact still a freshman in college so bare with me. so what you are saying is once you(x) are going near the blackhole or someone who’s watching things go into the blackhole from afar(y), your perception of time changes simply because T=d/s(don’t understand this formula). so something that is much farther from (x) will be faster(if it was possible for your eyes to interpret)….. and if (y) is looking at (x) near the black hole (x) will be moving in slow motion. The thing that i don’t understand is if T=d/(s) and since there is more gravitational force from the black hole that increases (s) wouldn’t that make (T) bigger therefore (x) being the faster object through time and (y) being slower? i am probably wrong about increased speed if closer to (x) so correct me if I’m wrong.

  4. peter says:

    Could you guys make an update for this topic? There seems to be a new theory about a “firewall” directly behind the event horizont (mentioned in this video: http://www.youtube.com/watch?v=XE5PNbsUERE ), which would make the spagettification process theory obsolete…

  5. emanuel gonzalez says:

    luvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv the webpage bro! yeah buddy!

  6. Ali. says:

    I’m Jus An 8th Grader , But There Are A Few Questions I Would Love To Ask

    1.) Will There Ever Be A Time Where A Black Hole Get So Close To Earth To Suck Away Our Sun And Planet ?

    2.) Can You Give Me Any Super Advanced Information About Black Holes …Information.You Will Be told In Collage ?

  7. harry says:

    will we turn into spaghetti in the black hole?

  8. Juan Lopez says:

    Will the world end tomorrow on the date of 12/21/2012? Should I just go out and party hard?

  9. peter says:

    when you fall in black hole you become a god. but still stay in this universe

  10. FrankH says:

    About an observer falling into a black hole, you say: “Things farther from the blackhole move through time faster, so the rest of the universe will speed up from your point of view. As a result the rest of the universe becomes bluer, hotter, and brighter. The blue shift of the incoming light turns it into gamma rays. So, right before you pass through the event horizon, you’ll get nuked with a universe’s lifetime worth of starlight and microwave background radiation turned into nuking nastiness.”

    I think this is not correct. From everything I’ve read, an infalling observer cannot tell from local measurements when she crosses the event horizon, but from what you say they certainly will notice it when they get fried. I think what you say would be true (that you would observe blue shifts and be able to watch the lifetime of the universe) ONLY IF you were using a rocket engine to hover above the event horizon. On the other hand, if you are freely falling into the black hole nothing unusual should happen as you cross the horizon since you are travelling “at the speed of light” as you cross the event horizon and will outrun the infalling light.

  11. lily says:

    there is one thing i have to ask,
    what if someone actually survives being made into spaghetti and all that then what will happen to them? LIKE WILL THEY JUST BE FLOATING IN THE BLACK HOLE AND DOING NOTHING??

  12. Joshua says:

    So it is actually possible to be outside of the Point of no Return and still move forward through time?

  13. The Physicist The Physicist says:

    You always move forward through time from your own perspective, just not from everyone else’s.
    That might not answer your question.

  14. Joshua says:

    Is it Possible for You to go to just out of the Point Of No Return and travel forward through time?

  15. Joshua says:

    Sorry I didn’t notice the “newer comments” and no not really because I watched a movie from Stephen Hawking and he said that it is theoretical that if you go just out of reach of a lack hole you could aproach the speed of light but not actually catch up to it and go forward through time.

  16. Hitesh says:

    if we go inside black hole we will be burnt into ashes.

  17. Hitesh says:

    Even if we go inside we can even go inside other universe

  18. Mehrdad says:

    “an” supermassive blackhole?

  19. Nour says:

    how the center of the black hole looks like?is it mass or just empty dark space?

  20. Bob says:

    It is empty dark space, until you hit the singularity.
    No one knows what happens when you hit the singularity. The math breaks down due to the singularity’s infinite density and infinitesimal size.

  21. Bob says:

    Actually, it would be very light inside the black hole, because of all the starlight, etc. flooding in.

  22. jacob says:

    MY SCIENCE TEACHER SAYS THAT IF YOU GET SUCKED INTO A BLACK HOLE YOU WILL JUST GET VERY LONG LOT AND A LOT, UNTIL YOU ARE LIKE STRING, AND EVENTUALLY DIE.

  23. Niko D says:

    Is it even possible to cross the event horizon? Wouldn’t the sheer number of photons in stable orbit, zap you like a hell laser from a billion death stars?

  24. Xerenarcy says:

    a black hole is the most dense object possible that we know of by definition. it is not a hole in any sense, a better analogy is a woodchipper – all that falls in is crushed, shredded and all identity lost, forever trapped in the subtle ripples of the black hole’s surface… a black hole should distort shape, though slightly, from infalling matter acting on it via gravity, electromagnetism and possibly nuclear forces when sufficiently close to the surface.

    for all intents and purposes a black hole is a tiny, dense, ovoid / sphere (distorted due to rotation and frame dragging) that is more smooth than you can imagine, with virtually all non-smooth impurities dancing around on the surface as remnants of the hole interacting with things as they fell in.

    in short nothing fantastic really happens unless you’re a physicist.

  25. Phillip says:

    As you get infinintely stretched by the gravity of the black hole, it would feel like thousands of years when you get sucked into the black hole because your matters are all accelerating faster than the speed of light, and if one was to move in the speed of light, the time would be “stopped” and everything would look just like a huge photo according to Einstein… So what happens when you move faster than the light. Would it be like what einstein said that you go back in time as you get sucked in (which wouldn’t make sense as back in time, you are farther outside the black hole). If you do, won’t you be creating infininte copies of yourself because you are going back in time as you get sucked in. Causing more matter to be formed in a universe which is known to be impossible. Matters can never be completely gone after all. So what does happen, does the universe pop like an over pumped balloon? Then what happens after the universe “pops”? Whats outside of the popped universe?

  26. Phillip says:

    Would it be an infininte space of vaccum causing every matter in universe getting sucked out to reach equalibrium and makes the universe fall apart? Or like another pne of those universe balloons outside of our universe.

    I apologize for so many questions but I’m only a 7th grader and do not know well. I would appreciate of you answered though ^_^

  27. Avery says:

    I have read a book or two about black holes and also some documentaries. What I get from all of them is that when you approach the actual event horizon someone looking at you will not see you but as you look back or into the black hole, you will see the future of the universe. But before any of that the black hole has to be wide enough not to spagettify but just a little bit. After you past through you would be deposited into a different part of the universe in a different place in time.

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