Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: neilep on 13/03/2009 19:01:15
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50 Billion Suns! -The Biggest Single Object in the Universe
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Scientists have determined the mass of the largest things that could possibly exist in our universe. New results have placed an upper limit on the current size of black holes - and at fifty billion suns it's pretty damn big. That's a hundred thousand tredagrams, and you'll never get the chance to use that word in relation to anything else.
Black holes are regions of space where matter is so dense that regular physics just breaks down. You might think physical laws are immutable - you can't get out of gravitational attraction the same way you can get out of a speeding ticket - but beyond a certain level laws which determine how matter is regulated are simply overloaded and material is crushed down into something that's less an object and more a region of altered space.
While there's theoretically no upper limit on how big a black hole can be, there are hard limits on how big they could have become by now. The universe has only existed for a finite amount of time, and even the most voracious black hole can only suck in matter at a certain rate. The bigger the black hole, the bigger the gravitational field and the faster it can pull in matter - but that same huge gravitational gradient means that the same matter can release huge amounts of radiation as it falls, blasting other matter further away.
Based on this self-regulating maximum rate, scientists at the Harvard-Smithsonian Center for Astrophysics, Massachusetts, and the European Southern Observatory, Chile, have calculated an upper limit for these mega-mammoth masses. Fifty billion suns, that's 100 000 000 000 000 000 000 000 000 000 000 000 000 000 kg, otherwise known as "ridiculously stupidly big" and triple the size of the largest observed black hole, OJ 287.
There are potential problems with this calculation. Based as it is on the radiation outflow from a black hole, new discoveries could change this estimate - though only from "insanely massive" to "ridiculously ginormous."
Source: the Daily Galaxy
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What would that be in elephants or blue whales, the normal units for awfully big things?
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Will we disappear into it?
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...otherwise known as "ridiculously stupidly big"
[:D]
Is that blackhole bigger than J-Lo's bottom?
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Will we disappear into it? [:D]
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Will we disappear into it? [:D]
Did you ask again because no-one answered you the first time?
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No.
It was a reply to:
Is that blackhole bigger than J-Lo's bottom?
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Ah, I see. You tried to make a joke.
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What would that be in elephants or blue whales, the normal units for awfully big things?
A lot of blue whales and even more elephants !
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Will we disappear into it?
Not if we camp just outside it. We can then sing songs and toast marshmallows !
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...otherwise known as "ridiculously stupidly big"
[:D]
Is that blackhole bigger than J-Lo's bottom?
Those scientists got it wrong. Thye forgot to consider the enormity of J-Lo's exit area !..tch tch tch !!
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How come we on one side say that there never will be any mass reaching past the event horizon and on the other treat black holes as growing? Where will all that extraneous mass be if so? Growing and propagating for ever towards a event horizon, that as they also are spinning, creating an enormous frame dragging effect. So what happens if so? You can't assume that this mass building will be 'broken down' in a 'quark gluon soup' as it never reach past the event horizon. And when considering the spin shouldn't this mass outside the event horizon behave somewhat like a stone in a sling, getting 'massed up'? Here is a description of a spinning black hole using the Kerr metric http://www.bun.kyoto-u.ac.jp/~suchii/spinhole.html And here http://www.cosmosmagazine.com/node/873
Read it and ponder.
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How come we on one side say that there never will be any mass reaching past the event horizon and on the other treat black holes as growing? Where will all that extraneous mass be if so?
The mass is inside the event horizon. It can get in, but can't get out again (unless you think Hawking radiation is a real phenomenon). So, there is no dichotomy about "...there never will be any mass reaching past the event horizon" and black holes growing.
In any case, if black holes do indeed contain singularities, then it is just the event horizon that will grow (expand). The singularity would remain a zero-size point.
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The bigger the black hole, the bigger the gravitational field and the faster it can pull in matter - but that same huge gravitational gradient means that the same matter can release huge amounts of radiation as it falls, blasting other matter further away
Hmm... but once the radiation has 'blasted' other matter further away there will be less in-falling matter, so the amount of radiation will drop, letting the matter be drawn back in towards the BH, which is now even more massive than it was before, thanks to the matter it drew in and which caused the radiation that 'blasted' the matter away. So if radiation does have a significant effect re 'blasting' away in-falling matter, it seems to me that we should see an oscillation.
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It would probably happen over millions of years
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As I remember it the mass you're observing will from your perspective always be on its way towards that elusive 'event horizon' never ever reaching it. What you are describing I believe to be the 'former' description where we had mass passing the EV, In that scenario all 'mass' will finally reach a center, but in the one I'm referring to, black holes would have to be 'born' at our spacetimes beginning as the mass never will reach the EV. That is as I've understood it
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You're referring to what's known as "The Blue Curtain", where the time dilation is so great to an outside observer that it appears to stand still and matter seems to accumulate at the event horizon. Light accumulating in this way is infinitely blue-shifted (infinities again grrrrrr).
I'm not sure of the current thinking about this.
That's made me wonder about something else. If the time dilation is that great, would we actually be able to observe the innermost part of the acccretion disk rotating? Wouldn't that, too, appear to stand still?
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It is a very strange thing, a black hole. That's a very interesting question DB, I think we will see it moving, as well as observing the 'frame dragging'. and the way I think of it is like this. If we think of that 'accretion ring' and bends it out. Then we use it as a description of a journey taken by me from Earth to a star and back near 'c'. You stay on Earth watching me at all times with that new super telescope, will you be able to follow my travel at all time? Yes you will. Will there be a 'time dilation' seen? Yes there will be. Did that ship at any point seem to stop moving? No it didn't. If it would have been seen to have stopped, what would the consequences have been for our spacetime. But then again, one can easily lose ones way looking at the possibilities inherent in different scenarios :) So I won't swear to anything, I think :)
Here is another persons headache.. http://alrenous.blogspot.com/search?updated-min=2009-01-01T00%3A00%3A00-05%3A00&updated-max=2010-01-01T00%3A00%3A00-05%3A00&max-results=14
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I think I'll have to read that a couple more times to understand it fully.
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That's a very interesting link yor_on; you are very resourceful. I've quoted below an interesting observation from the link. It reflects on a notion that I have long held. That notion is; electrons cannot possibly be point particles; indeed point particles can not exist.
Similarly, if electrons and other fundamental particles were actually point particles, they would be behind their own Schwarzchild radii and instead of atoms we'd just have a very large black hole. The amount of an electron's charge and mass that is inside a zero-size volume is zero, which is why QCD gets nonsense when it assumes it isn't.
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Yep, it was :) but I take it with a amount of salt, I think.
If you think of a photon, then that is said to be both sizeless as well as massless. That would make for a very strange black hole :)
Here is some other strange ideas. Relating to black holes.
'Ancient Galactic Magnetic Fields Stronger than Expected.'
http://www.spaceref.com/news/viewpr.html?pid=26166
how black holes acquire mass.
http://solarsystem.nasa.gov/scitech/display.cfm?ST_ID=265
Black hole spins at the limit.
http://www.cosmosmagazine.com/node/873
Astronomer Discovers Upper Mass Limit for Black Holes.
http://www.physorg.com/news139839433.html
---Optical Black Holes-
Can we create black holes here on Earth?
http://www.eurekalert.org/pub_releases/2000-03/NS-Cwcb-1403100.php
Black hole event horizon created in the lab.
http://www.newscientist.com/article/mg19726434.800-black-hole-event-horizon-created-in-the-lab.html
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If you think of a photon, then that is said to be both sizeless as well as massless. That would make for a very strange black hole :)
My speculative view of a photon eliminates the strangeness [:)] My photons exist as two plane waves, one electric, and one magnetic, radiating out from central points of maximum electric and magnetic amplitude.
Those were more interesting links yor_on. I suspect though, that artificial black holes can't possibly exhibit the true characteristics of the real critter. They may provide some interesting analogies. That spinning BEC that Hau is working with is fascinating.
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yor-on - Some ineresting links there. I'll read through them thoroughly sometime.
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One of the things to remember when thinking about time-dilation effects near and at the event horizon is that the time-dilation will have consequences on any energy related stuff that occurs there. So, for example, if you release a probe towards an event horizon and the probes flashes a light back to you at a regular interval, the period between the flashes will get longer and longer as the probes gets closer to the event horizon and the degree of time-dilation increases. At the same time though, the light itself will get progressively red-shifted and dimmer and dimmer, so while it may seem to be slowing down what you'll see will also be getting fainter and fainter, and eventually be too faint to detect.
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Still the question remains; how can a black hole gain mass if nothing can get past the event horizon?
I still suspect there is something not yet discovered that prevents anything from reaching the singularity. It will always be approaching it; never reaching it; like repeated instances of getting half way there.
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Still the question remains; how can a black hole gain mass if nothing can get past the event horizon?
I still suspect there is something not yet discovered that prevents anything from reaching the singularity. It will always be approaching it; never reaching it; like repeated instances of getting half way there.
Actually, I'm very much inclined to agree with you. The laws of Physics, as we currently understand them, just don't work beyond the event horizon because gravitational time-dilation means that the rate of time drops to zero at the event horizon, and you can't do physics without time.
The best answer I can come up with is that both space and time get 'stacked-up' and compressed around the event horizon, at a logarithmic rate, effectively allowing room for an infinite amount of space and time at the event horizon itself. To a distant observer though, this all appears to occupy a finite volume of space, so although nothing can ever actually cross the event horizon and fall in to the singularity, the total amount of mass in the observed finite volume of space will have increased.
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There are those infinities again!
Remember, time dilation does not affect the object falling into the black hole. In its own frame of reference it will still fall in at the rate expected. It is only to an outside observer that it will appear to fall slower & slower. That means that in the frame of reference of the falling object, the blackhole does gain mass.
I can't think past that stage at the moment [???] but I'm sure it must have some relevance on the issue at hand. What's tickling my brain about it is the way time & space swap places inside, or at, the event horizon. Let me try to think it through & I'll see if I can come up with any of my normal nonsense.
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There are those infinities again!
Remember, time dilation does not affect the object falling into the black hole. In its own frame of reference it will still fall in at the rate expected. It is only to an outside observer that it will appear to fall slower & slower. That means that in the frame of reference of the falling object, the blackhole does gain mass.
Yes, darn those infinities - I don't like 'em either, but I think you've got that a bit back-to-front. To the observer, the object falling towards the black hole won't appear to move slower and slower, but accelerate, just as things appear to do when we drop something here on Earth. Nothing that occurs outside of the event horizon is any different to what happens with non-black hole sized gravity wells; it's just a matter of degree.
If the observer is watching something time-based happen on the falling object though, it will appear as though that thing will be happening more slowly. However, to the object itself, in it's local frame of reference, time will seem to be passing at the normal rate and it's everything else that seems to be changed.
The most important thing to remember is that the conditions for the observer do not change throughout this, but they do for the falling object.
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If the observer is watching something time-based happen on the falling object though, it will appear as though that thing will be happening more slowly. However, to the object itself, in it's local frame of reference, time will seem to be passing at the normal rate and it's everything else that seems to be changed.
That's what I meant. Maybe I phrased it badly.
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" A Lenticular Galaxy Reveals Spinning Black Holes "
And "The X-ray glow of those iron atoms is so intense that gravitational heating alone cannot explain it. What that unassuming little graph may represent is the detection of a new source of cosmic energy, one predicted a quarter century ago but never before observed"
Cool heh :)
http://discovermagazine.com/2008/whole-universe/09-a-lenticular-galaxy-reveals-spinning-black-holes
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Very interesting link yor_on; spinning black holes; I'm guessing that we will find that all black holes are spinning. If they are born of stars that are spinning, the angular momentum must be conserved. So the black hole would be a disk.
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You're referring to what's known as "The Blue Curtain", where the time dilation is so great to an outside observer that it appears to stand still and matter seems to accumulate at the event horizon. Light accumulating in this way is infinitely blue-shifted (infinities again grrrrrr).
That's puzzling - when an object falls into a black hole, it's falling into an increasingly deep gravity well, effectively accelerating away from external observers - light escaping from the edge of the event-horizon should therefore surely be increasingly red-shifted. The photons emitted have the same energy, but it's spread out - stretched in space-time, so should become fainter and redder. By the time apparent movement stops, shouldn't the light be infinitely red-shifted as it takes infinitely long to climb out of the gravity well (although still at C) ??
Please resolve my conundrum.
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You may have an unresolvable conundrum. But you may have spotted a good measure of a black hole. It seems true that if we observe a black hole we should see red-shifted matter radiating back to us as it plummets inward toward the black hole. That should be a signature of a black hole.
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Well whether the conundrum is unresolvable or not, surely someone can explain why the light is said to be blue-shifted, as if it somehow gains energy emerging from the gravity well, or as if the object falling in is accelerating towards us [???]
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It's not emerging, it's heading in. I'm not sure of the mechanics behind it, I just read about it. If I recall correctly it's more to do with time dilation.
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Does this mean that Disney's Black Hole (http://en.wikipedia.org/wiki/The_Black_Hole) is not authoritative ?
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Disney's black hole is good theatre. I suspect it represents very little similarity with reality. We are still guessing when it comes to the true nature of black holes.
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Does this mean that Disney's Black Hole (http://en.wikipedia.org/wiki/The_Black_Hole) is not authoritative ?
Well, old Walt was always more of a biologist than a physicist.
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Does this mean that Disney's Black Hole (http://en.wikipedia.org/wiki/The_Black_Hole) is not authoritative ?
Well, old Walt was always more of a biologist than a physicist.
But look what he did to Bambi's mum. Killed her, he did. Killed her stone dead! Poor Bambi.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fbestsmileys.com%2Fcrying%2F2.gif&hash=6f40ed49d250203da654520072aa4687)
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It's not emerging, it's heading in. I'm not sure of the mechanics behind it, I just read about it. If I recall correctly it's more to do with time dilation.
The object is heading in, sure - but the light it emits must be heading out, otherwise we wouldn't see it. ISTM the time dilation that makes the inward fall and the timeframe of the object appear to slow, will surely increase the wavelength of the light it emits - and the same number of photons over a longer period at longer wavelengths will make it correspondingly dimmer...? [I'm considering this independently of the radiation emitted by the frictional heating by tidal forces of infalling matter from the accretion disk]
DoctorBeaver do you remember where you read about this? My curiosity is aroused now - I'm going to have to find out :-)
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Aha, found it - on Wikipedia (Falling Into A Black Hole (http://"http://en.wikipedia.org/wiki/Black_hole#Before_the_falling_object_crosses_the_event_horizon")):
...From the viewpoint of a distant observer, an object falling into a black hole appears to slow down, approaching but never quite reaching the event horizon: and it appears to become redder and dimmer, because of the extreme gravitational red shift caused by the gravity of the black hole. Eventually, the falling object becomes so dim that it can no longer be seen, at a point just before it reaches the event horizon. All of this is a consequence of time dilation: the object's movement is one of the processes that appear to run slower and slower, and the time dilation effect is more significant than the acceleration due to gravity; the frequency of light from the object appears to decrease, making it look redder, because the light appears to complete fewer cycles per "tick" of the observer's clock; lower-frequency light has less energy and therefore appears dimmer, as well as redder.
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I read it in a book by John Gribben, the author of many science books. I borrowed it from a library about 4 years ago.
Looking through his list of books I found "Unveiling the Edge of Time: Black Holes, White Holes, Worm Holes ". It could have been that 1.
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DB, here is the link to that those 'new' BH I was referring too. As I read it over a year ago and also found that it then was quite supported by a lot of physicists, it made me wonder where it had gone. http://www.physorg.com/news101560368.html "what is controversial about the new finding is that "from an external viewer's point it takes an infinite amount of time to form an event horizon and that the clock for the objects falling into the black hole appears to slow down to zero," said Krauss, director of Case's Center for Education and Research in Cosmology."
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I read it in a book by John Gribben, the author of many science books. I borrowed it from a library about 4 years ago.
Oh yes, Gribben - I've got some of his - 'In Search Of Schroedinger's Cat', 'Schroedinger's Kittens', 'the Matter Myth'. He's usually pretty good.
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The evidence for Black Holes seems rather overwhelming :)
But when it comes to those spinning at almost 'c' I can't help wondering over how this framedragging expresses itself. First you have the sheer mass in itself, in a non rotating black hole (Schwarzschild geometry) you will have a point of no return at the EV. And with a spinning BH (Kerr metric)it seems to me that this 'point of no return' should be seen even further out, before reaching any EV (event horizon)? Shouldn't this move the EV? And also 'collect' the matter falling in into a concentrated 'density' dragging it around that BH as all matter has an 'inertia'?
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I think I've remembered what that Blue Curtain thing is all about. It's from the perspective of an observer falling into the EH. Does that sound better?
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If we have light emitted from a object falling into a spinning BH, that light will have to make its way back up the 'gravity well' to the observer, will it then do that 'both' ways, as seen thinking of that spin? I mean, being reflected going against that spin will give it a extreme redshift, but when reflected as light when 'spinning' towards you shouldn't it get a blueshift and because of that have a 'easier' way out from that BH, still being redshifted due to the gravity well but not as much as the light reflected seen from that other angle? But then again it will only have one way to go and that is searching the easiest path out, which will be a spiral, ah, forget it, the light can only go one way :)
And 'red blue shift' will be 'equalized' as it moves around I suppose?
Or, will it? Depending on where its finally comes from meeting your observer??
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This Site is nice too:)
http://chandra.harvard.edu/resources/flash/bh_truth.html
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And 'red blue shift' will be 'equalized' as it moves around I suppose?
Or, will it? Depending on where its finally comes from meeting your observer??
It seems that a spinning black hole should appear as both red shifted and blue shifted depending upon the circumference observed. My guess is a galactic black hole would be spinning in the plane of galaxy in the centre of a huge accretion disk. I doubt that black holes exist as a singularity for the same reasons cited in yor_on's link. You can never get completely there because of the relativistic behaviour of light and matter.
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I think I've remembered what that Blue Curtain thing is all about. It's from the perspective of an observer falling into the EH. Does that sound better?
That sounds reasonable.
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I think I've remembered what that Blue Curtain thing is all about. It's from the perspective of an observer falling into the EH. Does that sound better?
I don't see it myself [;)]
If you're falling towards the EH, you're accelerating. You'll be accelerating away from everything further out, so if you look back, it will all be red-shifted. Everything in front of you (toward the EH) is accelerating away from you into the BH, so that should be red-shifted too. So where does the blue light come in? Maybe if you were stationary at the EH, you'd see stuff coming in toward you as blue-shifted...
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dlorde - I don't remember the details of it. It was at least 4 years ago and I didn't know much about physics in those days (I still don't, but I knew even less then). It didn't really sink in.
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dlorde - I don't remember the details of it. It was at least 4 years ago and I didn't know much about physics in those days (I still don't, but I knew even less then). It didn't really sink in.
OK, I was just curious.
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"That's a hundred thousand tredagrams, and you'll never get the chance to use that word in relation to anything else."
It's a lot less than a googleplex though, and there is one of those in Mountain View. I've been in Mountain View a few times; it's no big deal.
It's late, but my scratch paper gives about 10^(-8) grams /m^3. Air at sea level is on the order of kg/m^3.
I have wondered whether the universe should be considered a black hole. Nothing escapes unless it is evaporating, its size is unknown but much larger than 50 billion suns, and the usual Schwarzschild interior solution is dubious.
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I think I've remembered what that Blue Curtain thing is all about. It's from the perspective of an observer falling into the EH. Does that sound better?
I don't see it myself [;)]
If you're falling towards the EH, you're accelerating. You'll be accelerating away from everything further out, so if you look back, it will all be red-shifted. Everything in front of you (toward the EH) is accelerating away from you into the BH, so that should be red-shifted too. So where does the blue light come in? Maybe if you were stationary at the EH, you'd see stuff coming in toward you as blue-shifted...
You've got to remember the time-dilation effects too.
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The Event Horizon is a region around a black hole that marks the boundary where light closer in can never exit the black hole. Why does that fact give the boundary special properties? The natural laws should still apply. A steel rod part way past the EH should still allow its internal construct to follow a force on the outside part that pulled it out of the EH.
I think we globally describe the event horizon then in our minds, give it special properties that the General theory of Relativity does not give it.
We like to say that, once past the event horizon, nothing can escape. Maybe that should be modified to say that nothing operating under its own momentum can escape.
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You've got to remember the time-dilation effects too.
OK, please explain, I don't see how time-dilation would cause an observer falling into the BH to see blue-shifted light.
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The Event Horizon is a region around a black hole that marks the boundary where light closer in can never exit the black hole. Why does that fact give the boundary special properties? The natural laws should still apply. A steel rod part way past the EH should still allow its internal construct to follow a force on the outside part that pulled it out of the EH.
I think we globally describe the event horizon then in our minds, give it special properties that the General theory of Relativity does not give it.
We like to say that, once past the event horizon, nothing can escape. Maybe that should be modified to say that nothing operating under its own momentum can escape.
Yes, there is no special property at the EH, it's simply the point at which the escape velocity is > c. An observer falling through the EH wouldn't notice anything - assuming the BH is large enough that tidal forces don't rip him apart [;)]
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That was my thinking exactly. However, we seem to be thinking of the EH as the singularity itself. It seems to me that the EH would be some distance from the singularity.
Wiki article explaning the Schwarzschild radius (http://en.wikipedia.org/wiki/Schwarzschild_radius)
In 1916, Karl Schwarzschild obtained an exact solution[1][2] to Einstein's field equations for the gravitational field outside a non-rotating, spherically symmetric body (see Schwarzschild metric). The solution contained a term of the form 1 / (2M − r); the value of r making this term singular has come to be known as the Schwarzschild radius. The physical significance of this singularity, and whether this singularity could ever occur in nature, was debated for many decades; a general acceptance of the possibility of a black hole did not occur until the second half of the 20th century.
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Apparently you don't actually need a singularity for an event horizon to form. If the mass is spread over a large enough area you could still get an EH. I've seen this theory proposed for the universe. It was referred to as a brown hole (sounds a bit dodgy, that).
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The Event Horizon is a region around a black hole that marks the boundary where light closer in can never exit the black hole. Why does that fact give the boundary special properties? The natural laws should still apply. A steel rod part way past the EH should still allow its internal construct to follow a force on the outside part that pulled it out of the EH.
I think we globally describe the event horizon then in our minds, give it special properties that the General theory of Relativity does not give it.
We like to say that, once past the event horizon, nothing can escape. Maybe that should be modified to say that nothing operating under its own momentum can escape.
The event horizon isn't a region but a boundary. It doesn't occupy a volume of space but separates two regions of space that have different characteristics. In the region of space outside the event horizon the rate of time is greater than zero but reduces as one gets closer to the event horizon. Exactly at the event horizon, the rate of time reduces to zero. What happens on the other side of the event horizon is anyone's guess, and a guess is all anyone can give you, but one thing for sure is that you couldn't poke a steel rod through it.
It's debatable that the steel rod could even actually reach the event horizon, for if space is distorted just as time is, there may be an infinite amount of space compressed around the event horizon, in which case you could fall forever and never reach the event horizon, not only from your point of view, in a slow time-frame, but also from the point of view of an observer, who would seem to see you perpetually receding from them, both shrinking and fading from sight. Like I said though, this interpretation of the distortion of space-time around a black hole is open to debate.
However, one thing is for sure, if the rate of time reduces to zero at the event horizon we cannot talk of anything happening inside it for there appears to be no time, from our point of view, on the other side of the event horizon for anything to happen within.
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You've got to remember the time-dilation effects too.
OK, please explain, I don't see how time-dilation would cause an observer falling into the BH to see blue-shifted light.
Although light produced closer to the event horizon than the observer is red-shifted, effectively reducing it's frequency when viewed by the observer, the time-dilation experienced by the observer means that less time has passed for the observer, which has the effect of raising the frequency of the light.
Also, iirc, I think the main factor for the Blue curtain effect is that matter falling into the BH produces gamma frequency light, which after the red-shift and time-dilation factors are taken in to consideration, ends up as blue in the visible spectrum. Or something like that.
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However, one thing is for sure, if the rate of time reduces to zero at the event horizon we cannot talk of anything happening inside it for there appears to be no time, from our point of view, on the other side of the event horizon for anything to happen within.
Are you sure about this? It seems that time should be zero at the singularity. How does time get to be zero at the Event Horizon?
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However, one thing is for sure, if the rate of time reduces to zero at the event horizon we cannot talk of anything happening inside it for there appears to be no time, from our point of view, on the other side of the event horizon for anything to happen within.
Are you sure about this? It seems that time should be zero at the singularity. How does time get to be zero at the Event Horizon?
Have a look at:
http://en.wikipedia.org/wiki/Gravitational_time_dilation#Outside_a_non-rotating_sphere (http://en.wikipedia.org/wiki/Gravitational_time_dilation#Outside_a_non-rotating_sphere)
for the simplest solution (outside a non-rotating sphere). The formula is pretty simple and it shows that at the Schwarzchild radius you end up with 0.
Interestingly, there's another solution just below, for inside the event horizon, but it doesn't deal with how anything can actually pass that zero-time boundary, and while the outside solution might be provable, the inside solution isn't; if someone were to be able to get inside to prove it, they couldn't convey that proof back to us.
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Thanks for the link LeeE. I notice that the Schwarzchild radius is part of the equation. It is not immediately obvious to me that t = 0 at that radius. I don't doubt that it might, I just notice that many folks think that t = 0 closer in toward the singularity. I'll have to do some arithmetic. [:)]
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The event horizon isn't a region but a boundary. It doesn't occupy a volume of space but separates two regions of space that have different characteristics.
In the region of space outside the event horizon the rate of time is greater than zero but reduces as one gets closer to the event horizon. Exactly at the event horizon, the rate of time reduces to zero. What happens on the other side of the event horizon is anyone's guess, and a guess is all anyone can give you, but one thing for sure is that you couldn't poke a steel rod through it.
Not really - the time dilation experienced by objects at the EH is relative to the outside observer. Because of the extreme curvature of spacetime, external observers can't see beyond the event horizon in space or time, but the only thing special about spacetime at that point is the amount of curvature it has. From outside, we can't see inside because at that point the curvature is too great, but the curvature is smooth. If the black hole is sufficiently large (e.g. 10 million x solar mass), the curve will be shallow enough at the EH that an observer falling through the EH would not be ripped apart by the tidal forces, and would, in principle (ignoring radiation, etc) be able survive for some time on the other side before being pulled apart.
It's debatable that the steel rod could even actually reach the event horizon, for if space is distorted just as time is, there may be an infinite amount of space compressed around the event horizon, in which case you could fall forever and never reach the event horizon, not only from your point of view, in a slow time-frame, but also from the point of view of an observer, who would seem to see you perpetually receding from them, both shrinking and fading from sight. Like I said though, this interpretation of the distortion of space-time around a black hole is open to debate.
Again, that's not accurate, there is no special discontinuity at the EH - the singluarity sits at the bottom of almost infinitely deep gravity well - we don't know what's near the bottom or if there is one, but spacetime is being effectively stretched down into this well. Space-time may be compressed at the singularity, but no-one knows. But outside the singularity tidal forces will pull objects apart in the direction of travel and compress them across it (spaghettisation) as the gravity differentials across them strengthen as space-time stretches. Other than that (ouch), and some odd visual distortions, not a lot is different.
However, one thing is for sure, if the rate of time reduces to zero at the event horizon we cannot talk of anything happening inside it for there appears to be no time, from our point of view, on the other side of the event horizon for anything to happen within.
That doesn't mean that an observer falling through the EH experiences that time distortion. It is possible to predict what they might experience right up until they approach the region of singularity. In 'The Emperor's New Mind' (pp 433,434), Roger Penrose describes what an observer B, falling into a BH, away from an observer A outside the EH, would experience:
".. It should first be pointed out that there will be nothing whatever noticeable by B at the moment of his crossing the horizon. He glances at his watch ... and he sees the minutes pass regularly by. He can look back at A, and will find that A remains continuously visible the whole time. He can look at A's own watch, which appears to be proceeding in an orderly and regular fashion. Unless B has calculated that he must have crossed the horizon, he will have no way of knowing it. ... The second law [of thermodynamics] will hold sway just as much inside a BH as it does elsewhere. The entropy in B's vicinity is still increasing, right up to the time of his final crunch." Penrose should know - he helped Hawking develop the physics of BHs.
ISTM that in principle, it would be possible to drop down a cable or tether across the EH from orbit around a BH - but of course, you couldn't pull it back. In practice, the tether would have to be incredibly strong, and if it didn't break, it would start pulling you in towards the EH well before it got there. Once it reached the EH, you'd have to let go or be pulled in with it.
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Detailed studies of the properties of ordinary nuclei reveal strongly repulsive interactions between neutrons.
[See: "Neutron repulsion confirmed as energy source", Journal of Fusion Energy 20, 197-201 (2003)].
http://www.omatumr.com/abstracts2003/jfe-neutronrep.pdf (http://www.omatumr.com/abstracts2003/jfe-neutronrep.pdf)
These studies show that neutron-emission from a neutron star "may release up to 1.1%-2.4% of the nuclear rest mass as energy". By comparison, only about 0.8% of the rest mass is converted to energy in Hydrogen fusion and only about 0.1% of the nuclear rest mass is converted to energy in fission.
Therefore massive, energetic celestial objects are probably not black holes at all, but neutron stars that are highly energized by repulsive interactions between neutrons.
With kind regards,
Oliver K. Manuel
http://www.omatumr.com/ (http://www.omatumr.com/)
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Another good link on falling into a Black Hole (it's not habit forming [;)]) : Fall Into A Black Hole (http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/fall_in.html)
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There's a problem with your link. You got http:// twice. Try editing it.
It's an interesting article but I'll have to read it a few times to fully absorb it.
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DoctorBeaver,
Thanks for your comment. Try this link to: "Neutron repulsion confirmed as energy source", J. Fusion Energy 20 (2003) 197-201,
www.omatumr.com/abstracts2003/jfe-neutronrep.pdf (http://www.omatumr.com/abstracts2003/jfe-neutronrep.pdf)
If it doesn't work, see: "Nuclear systematics: III. The source of solar luminosity", Journal of Radioanalytical & Nuclear Chemistry, Vol. 252, No. 1 (2002) 3-7
www.omatumr.com/abstracts2001/nuc_sym3.pdf (http://www.omatumr.com/abstracts2001/nuc_sym3.pdf)
With kind regards,
Oliver
www.omatumr.com/index.html (http://www.omatumr.com/index.html)
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Another good link on falling into a Black Hole (it's not habit forming [;)]) : Fall Into A Black Hole (http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/fall_in.html")
It seems to still not work when edited.
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Ah, Vern, wrong dude :)
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Well; I don't know; the link did have, http://http://, doubled like that. But I fixed it in the quote and the link still didn't work. However the home site is really nice [:)]
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Sorry guys, it's fixed now. Looks like this forum software adds the http prefix automatically.
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The event horizon isn't a region but a boundary. It doesn't occupy a volume of space but separates two regions of space that have different characteristics.
In the region of space outside the event horizon the rate of time is greater than zero but reduces as one gets closer to the event horizon. Exactly at the event horizon, the rate of time reduces to zero. What happens on the other side of the event horizon is anyone's guess, and a guess is all anyone can give you, but one thing for sure is that you couldn't poke a steel rod through it.
Not really - the time dilation experienced by objects at the EH is relative to the outside observer. Because of the extreme curvature of spacetime, external observers can't see beyond the event horizon in space or time, but the only thing special about spacetime at that point is the amount of curvature it has. From outside, we can't see inside because at that point the curvature is too great, but the curvature is smooth. If the black hole is sufficiently large (e.g. 10 million x solar mass), the curve will be shallow enough at the EH that an observer falling through the EH would not be ripped apart by the tidal forces, and would, in principle (ignoring radiation, etc) be able survive for some time on the other side before being pulled apart.
While the degree of time-dilation is relative to the observer, as it must be unless when compared with a hypothetical space-time frame outside of our universe, it doesn't mean that the effect is not real. Experiments, both with moving clocks and with clocks in different gravitational potential, show that different amounts of time have passed for the two separated clocks when they are subsequently brought back together. The difference in the duration of time that has passed for the two separated points of view is not illusory. Thus, as something approaches an event horizon, the absolute amount of time that passes for the approaching object is less than the absolute amount of time that has passed for a distant observer, and when the approaching observer reaches the event horizon zero time will pass for it. At this point, the ratio between the rate and duration of time for the approaching observer and that for the distant observer becomes infinite, and from that point onwards, physics breaks down. Yes, the approaching observer will not be aware that time is running slow, at least from their point of view, in their own space-time frame; they will not 'feel' that they are running slow, and neither, when/if they reach the event horizon, will they realise that no time is passing for them, because everything will have stopped. Even though the difference can only be expressed in relative terms, if one set of values equals zero the difference is absolute.
If the approaching observer only closely approaches the event horizon, and then returns to the distant observer, their two space-time frame can be reconciled because the difference between the rates and durations of time that have passed for both of them will be finite. If the approaching observer were to be able to actually reach the event horizon, however, the difference between the two rates and durations cannot be reconciled because for the approaching observer, they will both be zero.
I think that the other two points you raise are dependent upon your first point.
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Thanks for the link LeeE. I notice that the Schwarzchild radius is part of the equation. It is not immediately obvious to me that t = 0 at that radius. I don't doubt that it might, I just notice that many folks think that t = 0 closer in toward the singularity. I'll have to do some arithmetic. [:)]
This is the equation:
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fupload.wikimedia.org%2Fmath%2F1%2F2%2Fb%2F12b6af8d31abe31378245988a0e74f66.png&hash=38131a4a68c8978cbb927449fe35c2a2)
cutting straight to the shortened form, to save time, when the distance r from the center of the object is equal to the Schwarzchild radius r0, we get 1 - 1 = 0.
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Just a thought. according to the Schwarzchild metric the inside of the EV (event horizon) will, if observed from the inside, be almost limitless in distance if I understand it right. When we have a spinning black hole using the Kerr metric I presume the same. But then we have the spin too? That must add to the distances as seen from the inside, won't it? Won't all geodesics become infinitely long there as it forms a spiraling motion?? Not that you would notice it while being in there, but if one could observe it from the outside? (I know you can't though, still?:)
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Okay; I am a convert [:)] According to the accepted equations t = 0 at the event horizon. But it seems now that nothing could ever reach the event horizon. I think mostly in terms of computer simulation since that is what I've done most of my life, and I can't imagine a program that could simulate something getting past the event horizon.
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While the degree of time-dilation is relative to the observer, as it must be unless when compared with a hypothetical space-time frame outside of our universe, it doesn't mean that the effect is not real.
Certainly it's real, the external observer measures the time of the infalling observer slowing, and their image dimming and reddening. From the external observer's POV, the faller never reaches the EH.
Thus, as something approaches an event horizon, the absolute amount of time that passes for the approaching object is less than the absolute amount of time that has passed for a distant observer, and when the approaching observer reaches the event horizon zero time will pass for it.
Yes - from the POV of the distant observer. This is relativistic physics at the extremes, but it only breaks down completely at the singularity.
Yes, the approaching observer will not be aware that time is running slow, at least from their point of view, in their own space-time frame; they will not 'feel' that they are running slow, and neither, when/if they reach the event horizon, will they realise that no time is passing for them, because everything will have stopped.
Only with respect to the distant observer. The approaching observer will notice no change in time in his local vicinity, as my quote from Penrose describes.
Even though the difference can only be expressed in relative terms, if one set of values equals zero the difference is absolute. If the approaching observer only closely approaches the event horizon, and then returns to the distant observer, their two space-time frame can be reconciled because the difference between the rates and durations of time that have passed for both of them will be finite.
And the visitor to the edge of the EH would have aged considerably less than the outside universe - the distant observer and his planet would probably be ancient history by the time he returned (all depending on how close the observer got to the EH).
If the approaching observer were to be able to actually reach the event horizon, however, the difference between the two rates and durations cannot be reconciled because for the approaching observer, they will both be zero.
I'm with Penrose on this one - he developed the physics of BHs. I can't pretend to have the maths to work it out myself, so when he says the EH is simply the point where the curvature of spacetime routes light into a circular path, and that an approaching observer can, in principle, fall through it without noticing significant change, I'll take his word - unless, of course, there have been developments in BH physics in the years since, that have changed that description - but I haven't heard of any.
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Vern:
I think that whether something can actually reach the event horizon or not depends upon how space is warped in the region of the BH.
If space is linear in the direction of the BH, that is, along a straight line passing through the center of the BH, and is only warped around the BH so that an orbit feels like a straight line, then I can't see any reason why something could not reach the event horizon. In this case, the distance traveled, as measured by both the approaching object and the distant observer would agree. This would be akin to an observer on Earth* a distant observer agreeing with an observer in the ISS that the ISS was at the same altitude above the Earth.
If space is non-linear along that line though, then moving say, one metre nearer as viewed by a distant observer, might actually equate to moving more than one meter for the approaching object. If this is so, and the amount of spatial warping matches the amount of temporal warping, then it seems to me that at the point where the rate of time drops to zero the amount of space becomes infinite and the object can never reach the event horizon. In this case, an observer in close orbit around a BH would disagree with a distant observer regarding their altitude above the event horizon.
As time is non-linear along a path through the center of the BH, I'm inclined to believe that space is non-linear along that path too.
* Oops!
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dlorde:
Outside of the event horizon, physics is no different to any other gravity well and just as something accelerates as it falls in to the Earth's gravity well, it will accelerate as it falls towards an event horizon; it will not seem to slow down. The only slowing that will be apparent to a distant observer is if the falling object is periodically sending a signal back to the observer at a constant rate i.e. the falling object flashes a light once every second. Then you will find that the amount of time between successive flashes increases, showing that the rate of time for the falling object has slowed.
The reduced amount of time that passes for the falling object is not just from the point of view of the distant observer. If this were so, then two synchronised clocks, one staying with the distant observer and the other traveling close to the BH before returning, would show the same elapsed time when the traveling clock returned; the clock experiments that have been performed, both moving and in different gravitational potentials show that this is not so and there is an absolute difference in the amount of time that has passed for the two clocks.
You then seem to go on and agree that different amounts of time will pass for the two different locations, so I can't see how you can say that it will only be from the POV of the distant observer.
As much as I respect Penrose, I have to work stuff out for myself, and if I come to different conclusions, so be it.
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Just a thought. according to the Schwarzchild metric the inside of the EV (event horizon) will, if observed from the inside, be almost limitless in distance if I understand it right. When we have a spinning black hole using the Kerr metric I presume the same. But then we have the spin too? That must add to the distances as seen from the inside, won't it? Won't all geodesics become infinitely long there as it forms a spiraling motion?? Not that you would notice it while being in there, but if one could observe it from the outside? (I know you can't though, still?:)
Yes, the equation for inside the event horizon is interesting, but it's even more hypothetical, and imo, more questionable than the conditions outside it. However, if both equations actually do apply, then they must be reconcilable with each other; the implications of one must be accounted for in the other because they are both dealing with the same single object.
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... If this is so, and the amount of spatial warping matches the amount of temporal warping, then it seems to me that at the point where the rate of time drops to zero the amount of space becomes infinite and the object can never reach the event horizon.
If an object approaching the BH can never reach the event horizon, doesn't this suggest that a BH, once formed, will not increase in mass, as no mass can reach it... ? Wouldn't this lead to a dense shell of mass trapped at the EH ?
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The reduced amount of time that passes for the falling object is not just from the point of view of the distant observer. If this were so, then two synchronised clocks, one staying with the distant observer and the other traveling close to the BH before returning, would show the same elapsed time when the traveling clock returned; the clock experiments that have been performed, both moving and in different gravitational potentials show that this is not so and there is an absolute difference in the amount of time that has passed for the two clocks.
You then seem to go on and agree that different amounts of time will pass for the two different locations, so I can't see how you can say that it will only be from the POV of the distant observer.
Different amounts of time will pass in each location *relative to the other*.
As much as I respect Penrose, I have to work stuff out for myself, and if I come to different conclusions, so be it.
Fair enough.
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... If this is so, and the amount of spatial warping matches the amount of temporal warping, then it seems to me that at the point where the rate of time drops to zero the amount of space becomes infinite and the object can never reach the event horizon.
If an object approaching the BH can never reach the event horizon, doesn't this suggest that a BH, once formed, will not increase in mass, as no mass can reach it... ? Wouldn't this lead to a dense shell of mass trapped at the EH ?
Yes, so it would seem, or rather, just outside the EH. For the distant observer though, the amount of mass inside that volume of space, which appears to be finite from their point of view, would appear to increase.
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The reduced amount of time that passes for the falling object is not just from the point of view of the distant observer. If this were so, then two synchronised clocks, one staying with the distant observer and the other traveling close to the BH before returning, would show the same elapsed time when the traveling clock returned; the clock experiments that have been performed, both moving and in different gravitational potentials show that this is not so and there is an absolute difference in the amount of time that has passed for the two clocks.
You then seem to go on and agree that different amounts of time will pass for the two different locations, so I can't see how you can say that it will only be from the POV of the distant observer.
Different amounts of time will pass in each location *relative to the other*.
If you're just comparing two different rates, of anything in fact, one rate can be related to another different rate, but with time we're dealing with something having a rate that is always either positive, or zero, and once it's zero any comparison seems to be absolute and not relative.
As much as I respect Penrose, I have to work stuff out for myself, and if I come to different conclusions, so be it.
Fair enough.
Just to be clear, I'm not saying that I'm right and he is wrong, just that until I can see where I've made a mistake I have to work on the basis that I'm right. I've been wrong plenty of times, so won't be surprised if I find that I'm wrong again, but it won't be until I can see where I'm wrong. I think that's the same for most people, really.
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Serious readers of this forum may want to consider:
1. Evidence from Case Western Reserve University [Science (21 June 2007)] that Black Holes do not exist:
http://sciencenow.sciencemag.org/cgi/content/full/2007/621/1 (http://sciencenow.sciencemag.org/cgi/content/full/2007/621/1), and
2. A 2007 discussion published in Nature about interactions between neutrons in massive celestial objects:
blogs.nature.com/news/blog/2007/05/the_biggest_bang_of_them_all.html (http://blogs.nature.com/news/blog/2007/05/the_biggest_bang_of_them_all.html)
In my opinion, repulsive interactions between neutrons:
a.) Rule out the existence of Black Holes, and
b.) Explain otherwise "mysterious" explosions of massive cosmic objects.
With kind regards,
Oliver K. Manuel
Emeritus Professor
Nuclear and Space Studies
myprofile.cos.com/manuelo09 (http://myprofile.cos.com/manuelo09)
www.omatumr.com/ (http://www.omatumr.com/)
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Thanks for the link LeeE. I notice that the Schwarzchild radius is part of the equation. It is not immediately obvious to me that t = 0 at that radius. I don't doubt that it might, I just notice that many folks think that t = 0 closer in toward the singularity. I'll have to do some arithmetic. [:)]
This is the equation:
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fupload.wikimedia.org%2Fmath%2F1%2F2%2Fb%2F12b6af8d31abe31378245988a0e74f66.png&hash=38131a4a68c8978cbb927449fe35c2a2)
cutting straight to the shortened form, to save time, when the distance r from the center of the object is equal to the Schwarzchild radius r0, we get 1 - 1 = 0.
LeeE, You are right in that Schwarzchild metric defines time as being zero as seen from a 'stationary observer' being at the event horizon. But to me that seems more of a theoretical limit? As I understand it, this is a situation that won't exist as there is no way to place an observer stationary at the EV, the definition of a EV is a 'point of no return'. When you're there you won't be able to 'hover' without expending a lot of energy in the opposite direction, and from the point of the in-falling observer there is nothing stopping him from falling further in towards that black hole. If I was observing him I expect that there would be a 'last moment' where light was reflected from that person, falling in.
That light I would expect to be both distorted and redshifted, but, it would still hit my retina at 'c' so that image wouldn't, as some imply, 'freeze' at that EV (event horizon). There is no 'hovering' allowed there, neither for the person falling in, nor for any light obeying spacetimes geodesics. So that last 'reflection' will arrive to the 'stationary observer' outside and then there would be no more reflected light emitted from that in-falling person.
From the situation of the person falling in it seems trickier though, one might argue that, as seen from the point of the in-falling observer, time would would 'slow down' allowing the universe to 'die' before he ever reached that EV. But that won't hold from our stationary observers point of view I think. He will observe this person disappearing from our view and so draw the conclusion that he have passed what he saw as the EV.
Why I think so goes back to my thought experiment with a 'stationary' relative Earth super-telescope watching a our spacecraft leave earth toward a star and then come back. That spacecraft, even if being extremly close to light speed in space, will have the same 'time dilation' as we observe at a black hole, you could say that the ship represents the in-falling observer and our telescope represents the observer outside the gravity well (black hole). To say that the observer of the in-falling person would observe, from his frame of reference, that this person would freeze in space due to the time dilation caused by the black hole seems to me to be equivalent to expecting that our spacecraft, as observed from our super telescope, would 'freeze' in space.
If that was a fact, I believe that this ship never would be able to make that journey, as seen from the telescopes (stationary observers) point of view. And all discussions about length contraction seems then to be a exercise in futility as any 'stationary observer' only would experience that spacecraft passing it at near 'c' as being frozen in time. So I expect the in-falling 'observer' to pass, what the 'staionary observer' outside the gravity well will observe to be, the Event Horizon.
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When it comes to the Kerr metric for a spinning black hole there will be framedragging added to the situation though. But we're not talking about that as I understands it? Anyway :) I might be wrong in my 'comparison' between those two situations, but even without that 'comparison' I see no real problem for the guy at the EV to keep falling as that is the only way he can take, as seen from his frame of reference.
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I think I'll just waddle off somewhere and eat worms.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.freesmileys.org%2Fsmileys%2Fsmiley-scared008.gif&hash=480858ba98e5fc4081db59cb3c5c0810) (http://www.freesmileys.org)
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om:
I had a look at the first article you mentioned, and found: "As Einstein demonstrated in his Theory of General Relativity, a passenger inside a spaceship traveling toward a black hole would feel the ship accelerating, while an outside observer would see the ship slow down."
Which is just wrong. A passenger falling towards a gravity well doesn't feel acceleration. What Einstein pointed out was that when someone falls off a roof they feel nothing until they hit the ground. Apart from the increasing speed of the air passing by them, they feel nothing. Well, perhaps fear too.
As viewed by a distant observer, the ship will only appear to slow down (while it's actually accelerating) if space is compressed along the path of the craft, so that while the craft may actually travel, say 100m, a distant observer will measure that amount of space as less than 100m. If this is so though, then we're back to a potentially infinite amount of space around the event horizon, which then can't ever be reached. In fact, rather than slow down, the craft would appear to recede from the distant observer, as it is actually getting further away.
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Yor_on:
in that Schwarzchild metric defines time as being zero as seen from a 'stationary observer' being at the event horizon
It's the other way around; the observer at, or close to, the event horizon won't be aware of any slowing. Rather, from their point of view, they will seem to be running at 'normal' time and everything else in the universe will seem to speed up.
Actually, I think that trying to work out what happens directly at the event horizon may not be the best way to find the answer. Working out some solutions outside the event horizon will show the direction that things are going without having to deal with any zero values anywhere - all the physics will be 'normal'.
So instead, let's imagine sending a craft on a sling-shot voyage around the BH so that it returns back to the distant observer. Now, when both the traveling craft and the distant observer are back in the same frame of reference, we find that less time has passed for the traveling craft. They've started from the same frame of reference and ended in the same frame of reference, but different periods of time have elapsed for them.
Although it requires calculus to find the actual elapsed time for the traveling craft, because the rate of time will be changing during it's voyage, we can see that the elapsed time will relate to the degree of time-dilation that it experiences, and we know that if it's path is closer to the event horizon the degree will be greater and if it's further away it will be less, which is all that the equation tells us, so all we really need do is to plot several values for r to see which way t0 is going.
We can then try reducing r to be infinitely small, so that the craft comes as close to the event horizon as possible without actually touching or crossing it. When the craft returns from this journey to compare the elapsed times, what are we going to find?
Yes, I agree that there won't be a frozen image of them - that's just silly.
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I think I'll just waddle off somewhere and eat worms.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.freesmileys.org%2Fsmileys%2Fsmiley-scared008.gif&hash=480858ba98e5fc4081db59cb3c5c0810) (http://www.freesmileys.org)
Watch out for worm-holes [;)]
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I think I'll just waddle off somewhere and eat worms.
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.freesmileys.org%2Fsmileys%2Fsmiley-scared008.gif&hash=480858ba98e5fc4081db59cb3c5c0810) (http://www.freesmileys.org)
Watch out for worm-holes [;)]
Stop picking on me [:-'(]
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I may have got it all backwards then?
Sorry LeeE, I got the impression that you said that the in-falling observer wouldn't get past that EV? But here you seem to say exactly the same as I think too "from their point of view, they will seem to be running at 'normal' time " and so they will, as seen from their frame of reference, just keep falling in. What I reacted on was the statement that "t = 0" at the eventhorizon. How exactly do you see that idea?
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wow!!! would this formula has anything to do with this?
Fg=GMm
r2
where G=6.67*10^-11
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Not sure, you are talking about the gravitational force between two frames of reference I presume? Why don't you enlighten me :)
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yes, [:D].
that is how we calculate the force of attraction between bodies. That is what my teacher said. But how did the scientific people like you figured out this??
and how is this other equation:
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fupload.wikimedia.org%2Fmath%2F1%2F2%2Fb%2F12b6af8d31abe31378245988a0e74f66.png&hash=38131a4a68c8978cbb927449fe35c2a2)
related to this one [???]
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Tell me Eric, what is your point here?
To ridicule others by what ability you might have with manipulating numbers?
Or do you have a a 'cleaner' agenda with those formulas?
Like proving some point you haven't bothered to mention perhaps?
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I may have got it all backwards then?
Sorry LeeE, I got the impression that you said that the in-falling observer wouldn't get past that EV? But here you seem to say exactly the same as I think too "from their point of view, they will seem to be running at 'normal' time " and so they will, as seen from their frame of reference, just keep falling in. What I reacted on was the statement that "t = 0" at the eventhorizon. How exactly do you see that idea?
Yes, they'll think that time is running normally for them, but at the point where t0 = 0, they'll stop thinking; their rate of thinking will slow and stop, so they won't be aware that they've stopped thinking.
Go back to close paths outside the event horizon; the traveler isn't aware that less time has passed for them when they return to the same frame of reference as the distant observer, even though the absolute amount of time that has passed for both is different. The only difference is that instead of the absolute difference being finite, if they could return from the point where t0 = 0, the absolute ratio would seem to be infinite.
I think this just actually complicates the issue though. The actual reason that I think they couldn't reach the event horizon is that it may be infinitely far away in spatial terms, regardless of how time-dilation effects the relative energy that's seen to be expended, say by a battery powered light inside the craft, by both the local and distant observers.
Energy is highly time dependent and the amount that seems to be being used should differ between the observers due to time-dilation, so for example, if the craft were to hover above the event horizon, expending energy to maintain it's position against gravity, the amount required should seem different to the observers even though the amount should be absolute and just dependent on the masses and distances involved.
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Tell me Eric, what is your point here?
To ridicule others by what ability you might have with manipulating numbers?
Or do you have a a 'cleaner' agenda with those formulas?
Like proving some point you haven't bothered to mention perhaps?
I was wondering that too. We're discussing time-dilation, not forces. I fail to see the point.
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50 Billion Suns! -The Biggest Single Object in the Universe
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Scientists have determined the mass of the largest things that could possibly exist in our universe. New results have placed an upper limit on the current size of black holes - and at fifty billion suns it's pretty damn big. That's a hundred thousand tredagrams, and you'll never get the chance to use that word in relation to anything else.
Black holes are regions of space where matter is so dense that regular physics just breaks down. You might think physical laws are immutable - you can't get out of gravitational attraction the same way you can get out of a speeding ticket - but beyond a certain level laws which determine how matter is regulated are simply overloaded and material is crushed down into something that's less an object and more a region of altered space.
While there's theoretically no upper limit on how big a black hole can be, there are hard limits on how big they could have become by now. The universe has only existed for a finite amount of time, and even the most voracious black hole can only suck in matter at a certain rate. The bigger the black hole, the bigger the gravitational field and the faster it can pull in matter - but that same huge gravitational gradient means that the same matter can release huge amounts of radiation as it falls, blasting other matter further away.
Based on this self-regulating maximum rate, scientists at the Harvard-Smithsonian Center for Astrophysics, Massachusetts, and the European Southern Observatory, Chile, have calculated an upper limit for these mega-mammoth masses. Fifty billion suns, that's 100 000 000 000 000 000 000 000 000 000 000 000 000 000 kg, otherwise known as "ridiculously stupidly big" and triple the size of the largest observed black hole, OJ 287.
There are potential problems with this calculation. Based as it is on the radiation outflow from a black hole, new discoveries could change this estimate - though only from "insanely massive" to "ridiculously ginormous."
Source: the Daily Galaxy
so if we use the mass of the blackhole(M) and the mass of the sun(m) put it into that formula tadadata = the force of gravity, and by having this we might calculate the time that will take the sun to get there. And since the distance from the earth to the sun is almost nothing compare to the distance from the sun to the black hole (assumption [::)]) we will get there ~ the same time. [:D] [:D] and since that black hole has the biggest force of attraction nothing else would be in our way . [::)] or does the time changes because of the speed?? idk Im confuse now [V]
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You mean that by calculating the gravitational force between the sun and Earth we will find out how fast it would take us in time to get to, let's say, our closest BH?
I'm not sure how you think here. So, I'll guess if that's ok with you:)
Are you looking at gravity as a 'propagating force'?
And wondering of how big a black hole would need to be to have the same 'gravitational force' relative Earth, and perhaps if it then would take the same approximate time, as seen from the frame of someone traveling, to get from Earth to that BH (black hole).
To me gravity is what creates the 'geometry' in our 'three dimensions' of 'space', and the least 'energy craving' path would then define the shortest to my eyes. That's how the photons seems to travel as they 'bend' around great masses.
So when you calculate that 'gravitational force' you are in fact looking on how 'space wrinkles'. To have a black hole or a quasar that strong would be quite a feat, and we would all 'fall' into it. We are in fact traveling towards something called the "Great Attractor" at a breakneck speed of 22 million kilometers (14 million miles) per hour. That's our Milky Way traveling btw with tens of thousands of other galaxies too. http://en.wikipedia.org/wiki/Great_Attractor
If it is this you were thinking of:)
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I may have got it all backwards then?
Sorry LeeE, I got the impression that you said that the in-falling observer wouldn't get past that EV? But here you seem to say exactly the same as I think too "from their point of view, they will seem to be running at 'normal' time " and so they will, as seen from their frame of reference, just keep falling in. What I reacted on was the statement that "t = 0" at the eventhorizon. How exactly do you see that idea?
Yes, they'll think that time is running normally for them, but at the point where t0 = 0, they'll stop thinking; their rate of thinking will slow and stop, so they won't be aware that they've stopped thinking.
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I think this just actually complicates the issue though. The actual reason that I think they couldn't reach the event horizon is that it may be infinitely far away in spatial terms, regardless of how time-dilation effects the relative energy that's seen to be expended, say by a battery powered light inside the craft, by both the local and distant observers.
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Ok LeeE:)
I thought that it was this you said after all, but still, isn't that just a measure of what coordinate system you use? In this one you are using 'Scwarzschild coordinate time' where as you say, according to the equation(s), time will stop to 'zero' at the EV. But it seems to exist other coordinate systems too? http://en.wikipedia.org/wiki/Gullstrand-Painlev%C3%A9_coordinates.
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I'm not familiar with Gullstrand-Painlev coordinate systems - interesting name though - but as there's an absolute difference in the elapsed durations if the clocks are reconciled when the traveling clock returns to the same reference-frame as the observer, I can't see it making much difference because whatever coordinate system they're in, it will apply to both but won't cancel the difference.
I might have misunderstood you there though.
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You mean that by calculating the gravitational force between the sun and Earth we will find out how fast it would take us in time to get to, let's say, our closest BH?
I'm not sure how you think here. So, I'll guess if that's ok with you:)
I meant to say that we will be suck by that BH around the same time that the sun(yeah rigth [;D]). idk if we can apply the free falling equations when talking about planets, but if we can get the gravity from the BH-Sun and use it instead of 9.8m/s^2 we can calculated the time in which the sun will bounce the floor(BH). [::)]
Are you looking at gravity as a 'propagating force'?
And wondering of how big a black hole would need to be to have the same 'gravitational force' relative Earth, and perhaps if it then would take the same approximate time, as seen from the frame of someone traveling, to get from Earth to that BH (black hole).
no
So when you calculate that 'gravitational force' you are in fact looking on how 'space wrinkles'. To have a black hole or a quasar that strong would be quite a feat, and we would all 'fall' into it. We are in fact traveling towards something called the "Great Attractor" at a breakneck speed of 22 million kilometers (14 million miles) per hour. That's our Milky Way traveling btw with tens of thousands of other galaxies too. http://en.wikipedia.org/wiki/Great_Attractor
If it is this you were thinking of:)
yeah this is!! [:)] [:)]. so is this BH bigger than the GA
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I'm not familiar with Gullstrand-Painlev coordinate systems - interesting name though - but as there's an absolute difference in the elapsed durations if the clocks are reconciled when the traveling clock returns to the same reference-frame as the observer, I can't see it making much difference because whatever coordinate system they're in, it will apply to both but won't cancel the difference.
I might have misunderstood you there though.
I see it as there will be a time dilation too LeeE, between the observer outside the BH and the observer at the Eventhorizon (traveling clock) but that time change depends on them being in different 'spheres' of place and time. And as my view says that 'time' as observed by you, wherever you might be, only can come to a standstill as seen from your own perspective (traveling clock) at 'c' then time can't stop for you, as long as you are made of matter.
Another thing is that, no matter how near 'c' you might put yourself traveling, I still expect you to observe your own frame of reference and time coordinates to behave as usual (biological clock), even though red and blueshift and spatial 'distortions' will appear as observed when comparing 'frames of reference'. And that experience will hold true for a black hole too, as I see it.
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Although when falling into a black hole the gravitational forces will be accompanied by time-dilation and as you there will be in a accelerating system as I understands it your 'biological clock' will be dispersed in a undecidable number of 'time zones' :) So this depends on how you define your system I think. But given a 'clock' small enough one might expect it to be able to 'transit' in between those different 'timezones'. On the other hand, if time is a flow :) then perhaps gravity could be seen so too? And in that case there will be an 'infinity' of 'timezones' to fall through and there will be no possibility to create a smallest 'clock' transitioning those 'timezones' created by the black holes gravitywell.
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Thinking of why some expect to see that redshifted image of the 'traveling clock' frozen at the Eventhorizon I think they are seeing it as that redshifted light having to traverse out of a gravitywell it also will have to take it a immense time walking back up that 'slope' :) As you could see a redshift depicting a stretched wave in time, looking at it this way its not the wave that becomes longer, its rather the timedimension that 'stretches out' taking the wave with it. But that information received by the redshift is not the object so you could, as I see it, disregard it as a 'optical illusion' caused by time expanding.
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This one describes both 'metrics' http://www.mysearch.org.uk/pdfFiles/6Science/Schwarzschild.PDF , one might possibly say with a slight bias towards the Schwarzschild metric.
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I think I'm getteing neare to what you think Eric.
You write "if we can get the gravity from the BH-Sun and use it instead of 9.8m/s^2 we can calculated the time in which the sun will bounce the floor(BH)."
The force of gravity on Earth is decided by its mass, if you were standing 'on' the sun your weight would be twenty seven time that amount approximately. http://www.exploratorium.edu/ronh/weight/ . That tells you that the mass of the sun should be around twenty seven Earths put together.
What those two masses do with the space between them is to 'wrinkle' it. Is it this 'wrinkling' you would like to describe as some kind of 'constant'? If so then you just use the objects mass and relative velocity as compared to some other 'frame of reference' (Sun contra Earth).
You will also have to know if it is a 'accelerating' system or a uniformly moving system. A uniformly moving system might be two frames of reference uniformly moving, as when compared to each other, sharing the exact same 'time zone' and physical laws, and so being possible to define together as a 'inertial frame' http://en.wikipedia.org/wiki/Inertial_frame_of_reference
I don't know if there is some such 'constant' being able to be found, but as spacetime seems a 'sliding system' where everything you do to a parameter seems to affect the others, there just might be one. Perhaps others here have a better suggestion how to search? still, a very nice idea Eric :)
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accelerating system or a uniformly moving system.
[:o]
[:D] thanks for the help my knowledge is increasing exponentially!! [:D] [:D].
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Well Eric, considering that I still don't know if I've been anywhere near what you might think of?
Ah, whatever :)
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don not worry a table is always good to hide under
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Serious readers of this forum may want to consider:
1. Evidence from Case Western Reserve University [Science (21 June 2007)] that Black Holes do not exist:
My problem with the referenced article is this statement:
"a passenger inside a spaceship traveling toward a black hole would feel the ship accelerating, "
A passenger inside a spaceship following a geodesic should be weightless.
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[xx(]
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Sorry Yor On, I think that I really misunderstood the topic and please forgive if I wasted your time. [V]
although I learned about initial frame of reference and the great attractor thanks [:)]. from now on I will only post concise and understandable questions not cross disciplinary assumptions. [;)]
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What would that be in elephants or blue whales, the normal units for awfully big things?
Don't be bloody stupid, it's measured in OSSP's these days (Olympic Sized Swimming Pools) which replaces the Tri-Mega-Litre"