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.
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?
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!
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.
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…
luvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv the webpage bro! yeah buddy!
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 ?
will we turn into spaghetti in the black hole?
Will the world end tomorrow on the date of 12/21/2012? Should I just go out and party hard?
when you fall in black hole you become a god. but still stay in this universe
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.
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??
So it is actually possible to be outside of the Point of no Return and still move forward through time?
You always move forward through time from your own perspective, just not from everyone else’s.
That might not answer your question.
Is it Possible for You to go to just out of the Point Of No Return and travel forward through time?
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.
if we go inside black hole we will be burnt into ashes.
Even if we go inside we can even go inside other universe
“an” supermassive blackhole?
how the center of the black hole looks like?is it mass or just empty dark space?
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.
Actually, it would be very light inside the black hole, because of all the starlight, etc. flooding in.
COOL
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.
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?
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.
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?
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 ^_^
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.
this is all so interesting. I wish I was more acknowledged about this kind of stuff so I could discuss it more often.
“So what happens when you move faster than the light.”
Light is as fast as things get…at least until we can mathematically demonstrate how particles/objects can move faster, it would be pointless to even assume such a thing. Light is the mathematical constant of EVERYTHING.
“when you get sucked into the black hole because your matters are all accelerating faster than the speed of light”
Matter isn’t accelerating faster than light, it’s simply “falling” towards the singularity because it is simply too powerful. The singularity’s density is INFINITE while light has a FINITE velocity. The most powerful force always wins.
Thinking about it is actually it’s own form of relativity, since you can get so lost in thought trying to wrap your head around how amazing the universe is that hours can seem like minutes. LOL
There are hypotheses about what happens after crossing the event horizon and what happens after matter enters a black hole, but none can be tested. Can’t send a probe because none of the data would make it out. All we can do at this point is imagine. The “multiverse” idea is one of the things that comes from imagining what could happen if matter successfully makes it through a black hole–that they are simply gateways to new universes. Interesting idea, but no way to ever find out.
If NASA would let me and I knew I was going to die shortly I would give my body for science and fly a shuttle into a black hole. If I would even make it there with the after burners and gravitational pull from the multi galaxies nearby. Even if I were to be turned into a floating mass of spaghetti flesh and bone dust I would jump on the opportunity!
That’s my two cents.
I propose a slightly different interpretation of a black hole that is based on the speed of light. It is said that photons experience zero proper time. Another way to say this is that light like paths in spacetime have zero proper time. This means that the interval of the path traveled by a photon is zero. There is no distance between the point in spacetime where the photon is emitted and where in spacetime the photon is absorbed. What we measure as the speed of light is just the ratio of space to time. If an event horizon is a light like surface then the entire surface represents one point is spacetime to there can be no inside. Just a thought.
Lawrence Krauss that said our Universe could be one giant black hole. He reasoned that if a black hole was the size of a galaxy then it would have the density of water and if it were the size of the Universe then it would have the density of our Universe. So maybe we do know what it is like inside a black hole, it just happens to have a diameter of 90 billion light years, give or take a few billion.
I came across this page “http://www.astro.umd.edu/~miller/teaching/questions/blackholes.html” with the goal of answering some of the less complicated questions and give a better understanding of black holes. It didn’t peak my interest as many of the questions were duplicates. However…, question 11 goes as follows. “One day in class Mr. Edwards stated that Dr. Packer calculated when 2 singularities are close enough together, your able to pass through safely. Could that ever be a possibility?” The question has names but not specific by any means. the thing is, it was interpreted as a question about worm holes. Based on the other questions, that may be so. Mine however deals with Lagrangian points. Specifically L1. I’m really trying to get my head around how gravity between 2 black holes would work… in a Lagrangian point the gravitational pull of each black hole would about cancel each other out. allowing you to be past the event horizon without traveling faster than light and still being able to escape. Really it would just be like adding a gravity assist to warp the event horizon or just make it uneven, I guess… any ideas? Is this accurate and more importantly is this potentially useful?
OK, I understand what u said but if a tall object like a our EIFFEL TOWER comes nearer to a black hole will it’s position of centre of gravity change…….???????????
Did i read something wrong?
Something i read said that “once you hit the event horizon of a black hole if anyone were to watch you being pulled into a black hole that they would see you just frozen and never moving again”
Did i read this right?
Thanks “The Physicist” for posting your answer about falling into a black hole. I appreciated your discussion concerning time at the event horizon by saying that “time will halt” there (which also means that during that halted time the universe will experience infinite time which you also discuss). The discussion of warped time is just as important as any discussion about warped space and it is my feeling that time will be our hero at preventing singularities from forming. You said that anyone falling into a black hole will “pass right through” the event horizon and will be “torn apart and crushed” by the singularity. How can that be? Getting closer to the singularity should mean that gravity increases and that should mean that time should go even slower than it does at the event horizon. What kind of time goes slower than halted (zero) time?
I often read that Einstein math says a singularity will form inside a black hole meaning that Einstein math can be used inside a black hole. What does Einstein math say about time inside a black hole? Is that time less than zero?
Physicist says the a particle falling to the centre will see the end of the universe. Now, while much of the interpretation due to Roger Penrose and company remains contentious, the mathematics is not. This predicts a “surface of last influence”, which is essentially a space-time diagram of what can reach the infalling particle before it is anihilated at the singularity. It turns out that the apparent “stopped time” has zero duration in local coordinated, and that nothing that crosses the surface more than a very limited time after the particle crosses the event horizon can ever catch up.
If alternatively, we take the view that proper time truncates at the event horizon, then the final visible time of the external univese is even earlier (for consistency, we would have to relate both times of last visibility to the crossing time of the surface at twice the black hole radius)
Quite a few responses deserve comment – I’ll ration myself
Martin writes: “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).”
I believe you are right about this. But Penrose and his school interpret the maths as allowing the object to penetrate the horizon; as I partially understand it, there are tow prongs to this argument: time only stope for a zero length of time, so it is perfectly possible to penetrate the horizon (a familiar analogy for this is the curve y=x^3); the other is that although we continue to see the object asymptotically approach the event horizon, the object does not receive any information from us after a certain time (the socalled “surface of last influence” – the object has in effect left our universe, and can continue its existence in its own proper time. As I commented earlier, I find this all rather artificial, and it is totally untestable in any case; I believe that when it comes to practicing relativists I am in line with only a minority, but this does include a few eminent mathematical physicists, Roy Kerr not least among them.
Philip writes extraordinarily sensibly on thes difficult matters for a 7th grader, but still think it sensible to put him right on some (not all) of the hteoretical implications:
He writes: “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 ”
This length of time is presicely the reverse of what happens. If we accept Roger Penrose’s view that proper time does not truncate at the event horizon, you can see calculations of the proper time to go from the event horizon to the centre here:
https://www.vttoth.com/CMS/hawking-radiation-calculator
I turns out that even for the largest known black hole it would take you less than 12 days of your time to go from the event horizon to the central region. Time spent within the hole doesn’t even model as time to the external observer: once inside the hole the object is no longer a member of our universe, as the time and space coordinates do not transform into coordinates that exist in our universe. And there is virtually no spaghettification until you fall deep into the hole** – and this will only happen when you are less than 0.0001 hole radii and 0.1 seconds from the centre: you won’t even have time to notice !
In reality your earliest problem would usually be radiation from the accretion zone, which for observed holes would be sufficient to kill you a lifetme before you reach the massive hole. If its a hole whose accretion disc has been destroyed, your biggest problem becomes the blue-shifted CMB, which will fry you a few hours outside to the horizon (and continue until a few hours after crossing if you follow Penrose’s interpetation).
If you are considering smaller holes, the frying times reduce proportionately with the mass (or equally the radius), and the spaghettification durations reduce as the cube-root of the mass.
For holes that are small enough to spaghettify you before you reach the horizon, the only risk of which you can be aware is radiation from the accretion disc: both spaghettification and blue-shifted CMB last for such a short time that you will be dead before you notice.
**This happens in Penrose’s interpretation, but is far from universally agreed
FrankH writes: “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.”
This is unclear, so correct in one sense but incorrect in another. Light that is local to you will be in the same reference frame as yourself, and will outrun you by the speed of light (as you see it). Light that is ahead of you will be in a faaster frame o reference, and you will never catch up. Light that is behind you will be in a reference frame that is slower than yours – and beyond a certin distance it will never catch you up. This effect is referred to as the “surface of last influence”; this is doubtless a real effect, both inside and outside the event horizon. On the hand see my above responses to Martin and Philip for commentary on differences of interpretation.
Peter Cole writes: “I often read that Einstein math says a singularity will form inside a black hole meaning that Einstein math can be used inside a black hole. What does Einstein math say about time inside a black hole? Is that time less than zero?”
No, this is not time that is less than zero, but time that is the square root of a negative number. The closest analogy would be that the transform makes it look mathematically more like space than time; however, id we try to take the full transform (space and time) we end up with dimensions that simply do not exist in the outside universe
Acery writes: “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.”
Many books regurgitate misinterpretations – and these are what happens when nonscientists get little bits of speculation from different physicists., especially when the physicists use slightly different common language to express their ideas.
So:
No you never see the future (forward in time). You do see events that happen between bodies that have aged more than you, but that’s not the same thing. In fact, there is an external time beyond which you will never reeceive any information – your view of the future is drastically restricted. The junk about “being deposited elsewhere” is just that. It is true that local solutions exist that show this condition (albeit not in theform usually picked up by SF writers); however, there is no known way that anything originating in our universe can transition to this situation.
And for Clayton: Yes, the effects you cite are real, but the other contrary effects are larger.
And finally, another comment fo “Physicist”
who writes: “you’ll get nuked with a universe’s lifetime worth of starlight and microwave background radiation turned into nuking nastiness”. Actually, you don’t see anything after a certain extenral time: the period of maximum irradiation is while you are near the event horizon, and the x-ray shift of CMB is only a relatively short time in the external world – much shorter than the time it takes for light to go from twice the event horizon radius to the event horizon. If there is no accretion disc, and you are falling into a stellar black hole you may only get your skin burned; and the onset of spaghettification would be so rapid that you would be dead before you noticed your feet getting heavy.