Slashdot Mirror
Spinning Black Hole's Edge Rotates At Nearly the Speed of Light
astroengine writes "Astronomers have directly measured the spin of a black hole for the first time by detecting the mind-bending relativistic effects that warp space-time at the very edge of its event horizon. By monitoring X-ray emissions from iron ions (iron atoms with some electrons missing) trapped in the black hole's accretion disk, the rapidly-rotating inner edge of the disk of hot material has provided direct information about how fast the black hole is spinning. Astronomers used NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) — that was launched into Earth orbit in June 2012 — and the European observatory XMM-Newton measured X-ray radiation as a tool to directly infer the spin of NGC 1365's black hole. 'What excites me is the fact that we are able to do this for the very massive black holes at the centers of galaxies but we can also make the same measurement for black holes in our galaxy ... black holes that resulted from the explosion of a star ... The fact we can extend this from billions of solar masses to 10 solar masses is pretty cool,' Fiona Harrison, professor of physics and astronomy at the California Institute of Technology, Pasadena, Calif., and principal investigator of the NuSTAR mission, told Discovery News."
i love how this summary explains what an ion is, but assumes i know the definitions of black hole, x-ray, and solar mass. great writing, folks!
Have they shown that the black hole is rotating near c, or just that the accretion disk is rotating near c at the event horizon? The accretion disk and the black hole are not necessarily spinning in sync. If they mean the accretion disk, then, like DUH: if it wasn't rotating near c, it would fall straight in and there wouldn't be a disk.
Could the near light speed rotation of the SMB be equivalent in some way to having extra mass at the core of the galaxy? In other words, does this change how much dark matter there must be?
I come here for the love
The speed of light is influenced by gravity?
The speed of light in a vacuum is a constant. It never changes.
Time, on the other hand, is different almost everywhere. My hypothesis is that the the speed of light and time have switched places in someones private universe.
You might as well say it's because they are made of rainbows and ponies unless you have math to support your theory.
Gravity certainly bends light. But as far as slowing it down, I always thought was a constant represented by the letter "c".
They are obviously made of strawberries and unicorns.
"Lack of speed can be overcome. In the worst case by patience." --Znork
I had a Honda Civic that could go the speed of light. It sucked because nothing ever showed up in the rear view mirror.
Let's make like a bird... and get the flock outta here.
http://helios.gsfc.nasa.gov/qa_sp_gr.html
" Yes, light is affected by gravity, but not in its speed. General Relativity (our best guess as to how the Universe works) gives two effects of gravity on light. It can bend light (which includes effects such as gravitational lensing), and it can change the energy of light. But it changes the energy by shifting the frequency of the light (gravitational redshift) not by changing light speed. Gravity bends light by warping space so that what the light beam sees as "straight" is not straight to an outside observer. The speed of light is still constant."
Dr. Eric Christian
Speed is distance over time. If time slows down, then light will appear to slow down to an observer in another frame of reference. However, speed is unaffected, it takes the same amount of time to cover a set distance within the same frame of reference - it just appears to be slower to an outside observer.
In my limited understanding of these things, (mostly from articles meant for mass consumption, not scholarly journal papers), I imagine a black hole to be so massive not even light can escape its gravitational pull. Which technically means the escape velocity is the speed of light. So anything at the event horizon should be at the speed of light. This is of course, a naive view. The escape velocity is based on Newtonian, not Relativistic, physics.
sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
So many people (a number of whom who should know better) get this totally wrong because you always here that a black hole has "such powerful gravity that not even light can escape!!!111!!!"
This is another failing of Science Channel styled science shows*. They neglect to tell you that light doesn't escape because the gravity well created by a black hole warps space, not because photons are pulled on by gravity. It may sound like I'm splitting hairs since the overall end result is the same but a lot of people mistake it as meaning that light is sucked in to the black hole because particles with mass are also sucked in. This also doubtlessly leaves people scratching their head over the misconception that maybe the gravity is forceful enough to actually attact the light.
* Yeah, I'm the guy who complained about definitions being used too often in another thread.
it is just that our warp tech is not yet caught up with your honda civic.
c is a constant represents the theoretical maximum speed of light. The problem is that the speed of light is not constant. Light slows down in a medium.
Learn to love Alaska
do black holes blend?
It may sound like I'm splitting hairs since the overall end result is the same but a lot of people mistake it as meaning that light is sucked in to the black hole because particles with mass are also sucked in. This also doubtlessly leaves people scratching their head over the misconception that maybe the gravity is forceful enough to actually attact the light.
Light has momentum (which "require" mass in more classical thinking). Light is "moved" by gravity (which indicates mass). If mass distorts space so that it makes light and particles behave the same, then why is it a misconception to think of light as a particle? It's both a particle and a wave, thus *is* a particle.
Learn to love Alaska
If it's anything like my last Honda Civic, that's because the mirror fell off and is sitting under the passenger seat.
Learn to love Alaska
Doesn't the light have a constant speed for all observers but it's frequency is shifted for an observer in a different frame of reference ?
You seem to regard science as some kind of dodge... or hustle.
Not a physicist of any kind, but I had thought that information could not cross the event horizon? If that is true, then how can we construe that the speed of matter near the event horizon indicate the speed of rotation of the black hole? Wouldn't it only indicate the speed of that particular matter? Educate me if I'm wrong!
Most of the Science Channel-style science shows I've seen that cover the issue not only cover that light doesn't escape the gravity well because the gravity of the black hole warps space, but also covered that that's how all gravity works, not just a special variation related to "black holes" as the source or "light" as the affected entity. (As do the more technical, less Science-Channel-ish, works that I've seen addressing the same subject matter.)
The "sucked in" analogy is exactly as accurate (or inaccurate) applied to light as it is to "particles with mass".
Which actually is correct (except for "here" instead of "hear" :-)). What's wrong is the imagination that this is because the light is slowed down when going outwards (actually in some sense the light is slowed down, because the time as seen from outside is slowed down; but that's independent of the direction, and of course locally it is still going with c). The real reason is that the spacetime (not space, spacetime) is curved in a way that there's no way out when going at light speed or below. That is, the outward-going light is still going with light speed, but will not get out, but eventually reach the singularity. Yes, that seems paradox, since the singularity is "in the middle" (which isn't entirely accurate either; for a non-rotating black hole it is actually in the future), but that's because we are not very good in imagining curved four-dimensional spacetimes.
The Tao of math: The numbers you can count are not the real numbers.
Oliver's law of assumed responsibility: If you're seen fixing it, you will be blamed for breaking it.
No, time is the same everywhere, too. Only the length of timelike paths depends on how you move. But ultimately it is not too different from the fact that the length of spacelike paths depends on the way you take. Except that for spacelike paths, the direct path is the shortest, while for timelike paths, the direct path is the longest.
The Tao of math: The numbers you can count are not the real numbers.
TFA mentions a fact that I'd read about before, that the black hole's rate of rotation increases as it collapses due to the conservation of momentum. But since no matter can actually mover faster than the speed of light, is the collapse limited by this maximum rotation rate? Would the black hole cease collapsing when the rotation rate neared the speed of light?
-----
Sorry, I'm only a 1336 h4x0r.
In some mediums, light moves faster than it does through a vacuum.
No, it doesn't. Not only does such a material not exist, it is proven beyond any reasonable doubt to be impossible.
c is the speed of light in a vacuumm
Hey! You got something right!
not the "theoretical maximum speed of light"
And right back to wrong. Nothing can travel through space (empty or otherwise) at faster than c, that is the central concept of relativity.
If conservation of momentum is preserved (and arguing that it isn't would... well, quite an extraordinary claim) black holes, and the stuff falling into them, are going to be rotating. Unless, I suppose if everything collapsed absolutely, completely, perfectly symmetrically; to an accuracy 1 part in several millions of billions). And even then, as soon as matter starts flowing in the rotational momentum is going to start climbing.
People have it in their heads that since science is wrong in the past, science will be just as wrong in the future. But there are certain things that just aren't going to change, and the laws of conservation of mass/energy and momentum are one of them.
And you're always adjusting the in-dash clock.
Tic-Tac-Toe, Global Thermonuclear War, and relationships all have the same winning move.
FTA:
Imagine a sphere more than 2 million miles across - eight times the distance from Earth to the Moon - spinning so fast that its surface is traveling at nearly the speed of light. Such an object exists: the supermassive black hole at the center of the spiral galaxy NGC 1365.
If it were a rigid body,
Rotation Rate omega = Tangential Speed nu / 2pi * Radius r = 186 280 mi/s / 6.2832 * 2e6 mi = 0.014824 cyc/sec = 0.88942 cyc/min
Roughly one revolution per minute. Not an amazing rotation rate for objects of scales we're used to, but for something 2 million miles across it's pretty impressive.
Now, an event horizon is anything but a rigid body, so I could be waaaaay oversimplifying. But the article says "imagine a sphere..."
Anyone care to extend the math to apply to something other than the theoretical physicist's favorite imaginary object?
I can see the fnords!
They are obviously made of strawberries and unicorns.
I can't prove they're not, so it must be true! </sarcasm>
!#@%*)anks for hanging up the phone, dear.
If I were to build a disc with its inner ring located near (but not inside) the event horizon of this black hole, and an outer ring located a few million kilometers away, at what speed would the outer section of the disc spin? What would happen along that outer edge?
!#@%*)anks for hanging up the phone, dear.
Time and space are influenced by gravity, and speed depends on both.
Three dimensions.are mind boggling enough, once you are inside the BH, light is bent such that all directions are pointing towards the "middle", it's sort of like the 3D equivalent of asking which way is north when you are at the south pole.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
Black holes are not made from particles. Black holes are vacuum. Curved vacuum, that is. Yes, that's hard to understand, because our brain was not made to deal with this. But that's what the mathematics says.
A charged particle does emit light radiation when going faster than light. This can be observed in a medium (e.g. water) where the speed of light is slower than in vacuum, so particles there can indeed go faster than light (but still not faster than the vacuum speed of light). That radiation is known as Cherenkov radiation. It is the optic analogue of the sonic boom. If the particles could go faster than light in vacuum, they'd emit that radiation also in vacuum.
Uncharged particles would not emit Cherenkov radiation, however uncharged particles don't emit light radiation no matter what their speed is.
The Tao of math: The numbers you can count are not the real numbers.
Probably the CNN question would be if supermassive black holes are caused by global warming or maybe that they started to rotate so fast due to global warming. Anyway, small things after they ask if the bing bang was caused by global warming.
In some mediums, light moves faster than it does through a vacuum.
No, it doesn't. Not only does such a material not exist, it is proven beyond any reasonable doubt to be impossible.
That depends on what exactly you mean with the "speed in the medium".
You certainly can have a phase velocity larger than c, and AFAIK you also can have a group velocity larger than c. What you cannot have is a signal velocity larger than c.
The Tao of math: The numbers you can count are not the real numbers.
Actually it is already a misconception that particles are sucked in. Particles can fall in, but they also can orbit the black hole (as long as nothing else is in the way), just as they can orbit earth. If they get too close they no longer can orbit the black hole for the simple reason that they would need to go faster than light to do so.
The Tao of math: The numbers you can count are not the real numbers.
For a non-rotating black hole in Schwarzschild coordinates, the radial vector inside the horizon gets timelike, that is, the singularity is not really "in the middle" but "in the future". This quite intuitively explains why you cannot go "outward": The "outward" direction is actually the past direction.
Now, Schwarzschild coordinates are not the full story, but neither are Eddington-Finkelstein coordinates (which obviously are what you had in mind). The complete structure of the Schwarzschild solution can only be seen in Kruskal coordinates, where you on one hand quite literally see that the singularity is in the future (for any world line starting outside the black hole and entering it), but you would still be able to evade it if you could travel faster than light (while in Schwarzschild coordinates it looks as if you'd have to travel backwards in time).
Anyway, light is not "bent towards the middle", that's only the result of non-ideal coordinates where the singularity appears spacelike while it is actually timelike.
For rotating black holes, things are more complicated (there are two horizons, the singularity is spacelike, but not a point, and inside the black hole there occur closed timelike curves).
The Tao of math: The numbers you can count are not the real numbers.
Well, at the big bang, it was extremely hot everywhere in the universe. So how could that have happened except by global warming? :-)
The Tao of math: The numbers you can count are not the real numbers.
Are they sure they're not seeing the light-speed reflections of another source? If I shine a laser at the moon and wiggle it, I can make the dot "move" really fast.
Please explain time, please explain whether it is continuous or not. And if you have time explain further relative to this case :)
thanks
Don't you just love armchair physicists!!!
My karma is bad. Don't get too close!!!
Light has momentum (which "require" mass in more classical thinking). Light is "moved" by gravity (which indicates mass)
Also light has energy which is mass in Relativistic thinking, and is moved by (and moves other things by) gravity which is due to it's energy (same as mass).
This is confusing because people think of "mass" as the things photons don't have and matter does (which is true if we mean intrinsic mass), but also think of "mass" as the thing which effects/is affected by gravity and makes objects resist acceleration, when that's actually the relativistic mass (= energy).
It's both a particle and a wave, thus *is* a particle.
A photon is a quantum mechanical particle, which is a thingie which behaves kinda like a classical particle and kinda like a classical wave but not exactly like either.
However the key thing about quantum mechanics is that stuff is quantized... like particles are. So we call them particles. There is no misconception in doing so.
The enemies of Democracy are
In some mediums, light moves faster than it does through a vacuum.
No, it doesn't. Not only does such a material not exist, it is proven beyond any reasonable doubt to be impossible.
Your statement would seem to be contradicted by this theory on faster-than-c speeds between 2 Casimir plates.
It does not. It only looks that way due to the reactions with electrons.
You must also think that light travels in a straight line?
c is a constant represents the theoretical maximum speed of light. The problem is that the speed of light is not constant. Light slows down in a medium.
meh, you are almost right.
C is a constant that represents the maximum speed of light *in a vacuum*.
That "in a vacuum" piece is quite important. The medium itself has no effect on the constant c ( constant is a constant), but each medium has its own value of light propagation speed which is *always* less than c.
Think of 'c' as the speed of reality.
I take your reasonable doubt and counter it with un-reasonable doubt.
Thats more than enough for many people, sadly.
If they get too close they no longer can orbit the black hole for the simple reason that they would need to go faster than light to do so.
So you are saying that the singularity curves time-space so much that you'd have to travel infinitely far to be able to leave a black hole, and speed is irrelevant. The light orbits the singularity inside the event horizon, and will never leave, nor contact the singularity itself. Or something like that.
Learn to love Alaska
You must also think that light travels in a straight line?
Light thinks it does, just like standing on a trampoline and rolling a ball, the ball travels in a straight line, in a curve around you. Gravity curves space such that light travels in a straight line, and the universe curves around it.
Learn to love Alaska
C is a constant that represents the maximum speed of light *in a vacuum*. That "in a vacuum" piece is quite important.
If there is no material in which light travels faster than C, then your clarification is irrelevant.
Learn to love Alaska
If the matter on the outer edge of the disc is spinning near the speed of light, and if that matter is gravitationally bound to the rest of the disc and the black hole itself, then eventually the outer edge of the disc should act as a brake on the entire black hole's spin rate (because it can't exceed c). If it were to experience additional imparted momentum, what would happen to spacetime at the edge? I'm curious what the frame-dragging implications of this are.
Is this simply a matter of the amount of energy needed to approach c is so large that even galactic-sized energies aren't significant?
My God, it's Full of Source!
OUTSIDE_IP=$(dig +short my.ip @outsideip.net)
Objects in Mirror are closer than they appear.
The only place the light can fully orbit the black hole is exactly at the event horizon, and it is an unstable orbit that would be destroyed by any other near by matter. Once inside the event horizon, light cones all point inward to the point that even at the speed of light, you could not remain at a constant radius from the center.
So light slows down inside singularity? Because at the speed of light, it would be in a stable orbit at the event horizon, right?
And an unstable orbit is an orbit, still a "full" orbit.
Learn to love Alaska
Objects in Mirror are bluer than they appear.
FTFY
USE HOT GRITS WITH STATUE OF NATALIE PORTMAN (NAKED AND PETRIFIED)
"speed of light" is meaningless -- because it's not a constant. Might as well talk about the "speed of a honda civic".
I thought "the speed of a honda civic" was "fast and furious"... :)
Excuse me, wtf r u doin?
So light slows down inside singularity? Because at the speed of light, it would be in a stable orbit at the event horizon, right?
Yes and no. Light doesn't actually slow down. Time does. If a photon, at 300.000 km/s, gets close to the event horizon time slows down, so while it may still move 300.000 km in a second, that second takes longer and longer to pass. At the event horizon it takes an infinite amount of time.
Therefore if you are looking at it from the outside (and if the light you are using to look with doesn't have these pesky relativistic effects we are talking about) you'd think the photon has stopped.
[/armchair physics without much official education in the direction]
Well, I might have a way, but it only works on a semi spherical planet in a vacuum.
I've switched to plastic iron ions. Much cheaper.
Well, I might have a way, but it only works on a semi spherical planet in a vacuum.
Someone's been watching a bit too much Friendship Is Magic...
We know it's rotating at some fast rate because the swirling of space puts stress on the matter and causes it to emit radiation. Swirling is caused by rotation.
Spinning at "nearly the speed of light" is o.k.
Note: Anything faster will certainly not be approved.
Signed,
A. Einstein
Chief relativity supervisor
If time slows to zero at the event horizon, then no matter could ever enter a black hole, right?
Learn to love Alaska
The problem is that uneducated people hear terms and take them in the non-scientific meaning, which often conflicts with reality. Science is like all tech fields. Nobody outside the field knows or cares about the terminology. 10 Gbps fiber is "baseband" and 128kbps DSL is "broadband" from the original definitions. But idiots misused the terms so much that the field gave up and neither term has any meaning anymore beyond "broadband" means "feels fast" and "baseband" means the floorboard that holds your carpet in place, or whatever "regular" people think of when they hear it.
The current scientific models seem agree that nothing can be accelerated from below the speed of light to above it, nor decelerated from above the speed of light to below it. There is nothing that indicates that nothing may travel faster than the speed of light, just corollaries that indicate that if anything is, we'd never be able to detect it. That you don't understand that (or are lying about what you believe) doesn't change reality, or what it's widely considered to be.
Learn to love Alaska
The next question that brings up is, "What is the minimum energy of a photon?"
Learn to love Alaska
I don't know the book (I hope I don't have to hand in my geek card because of this :-)), but if the Lifestone is a bit in the future, shouldn't you be a bit too early? If I arrive at the place where an event shall happen, and the event is ion the future, I'm too early. If I'm too late, the event is already in the past.
Anyway, in the Schwarzschild solution, the singularity being in the future means you will get to it, because you simply cannot avoid going to the future.
The Tao of math: The numbers you can count are not the real numbers.
Well, in General Relativity time is continuous, and it is a dimension of spacetime. Spacetime is four-dimensional, with three space dimensions and one time dimension. Actually the time dimension only differs from the space dimensions by the sign in the metric (which basically means that as soon as time is involved, things are often reversed to what we are used in space, but the important part is that it makes it impossible to rotate the time dimension to a space dimension or vice versa; the metric is basically an onject which tells us how to measurte distances and angles). Also, while there are three space dimensions, there's only one time dimension (this makes it impossible to just turn around in time, as we can do in space). Note that this doesn't mean there's only one time direction; you can rotate the time axis in spacetime. That's known as boost; it's exactly what you do if you accelerate. Note that this is even true if you use a Newtonian spacetime, as one can easily convince oneself by simply drawing the world lines (i.e. the line describing at which place an object is at each point in time; to draw it, you certainly have to remove at least one spacial dimension). What's new in Special Relativity (which basically is a special case of General Relativity, namely the case of flat spacetime) is that also the space axis is turned on a boost, and in a way that the speed of light is the same in both systems. The time which elapses for you between two events is just the length of the world line (measured with the space time metric, with the different signs for space and time coordinates). Due to the different sign, the direct way is the one which takes the most time (unlike in space, where a detour makes the way longer). That's basically because if you detour in space, the change in the orthogonal direction adds to the distance, while for time, it gets subtracted (actually it's in the square of the distance where this addition/subtraction occurs, but the qualitative effect is the same: Moving in other dimensions at the same time adds to a length of a spacial path, but subtracts from the elapsed time, which is the length of the world line). This difference is generally known as twin paradox (the travelling twin makes the detour, and therefore he needs less time, and thus is younger than the waiting twin when he returns).
Now General Relativity adds to the mix that the spacetime is curved (and the curvature depends on the energy and momentum of the matter inside). That works in principle the same way as for example the curvature or earth's surface. For example, imagine two people meet somewhere at the equator, and one goes 5000 km west, and then 5000 km north, while the other first goes 5000 km north, and then 3535.5 km west. Then they get (approximately) to the same place, although the second one has gone a shorter distance. Quite similarly, someone going closer to the black hole and then remaining there will need less time than someone first waiting far away from the black hole and only then going close to it to meet the other one.
Note that the analogy goes even further: After going first north and turning west, to keep going west you have to constantly turn right (i.e. to accelerate in the direction of the pole). If you just went straight on, you'd start moving southwards, as if the pole would push you away. The acceleration causes you to keep at fixed distance from the pole. Similarly, the observer going close to the black hole (assuming he does not orbit it) has to accelerate away from it to not fall in; again this is the effect of curvature (of spacetime in this case). However spacetime around a black hole is curved in a way to make unaccelerated motion go towards it instead of away from it, thus the acceleration has to go away from it (orbiting is another way to keep from falling in; this option is not available in the earth surface analogy).
The Tao of math: The numbers you can count are not the real numbers.
The enemies of Democracy are what?
"Nine times out of ten, starting a fire is not the best way to solve the problem." - my wife
Light in a vacuum is the fastest speed
Light between the Casimir plates is less c
Some particles can move through a medium faster than light can move through said medium
The particles are not moving faster than c, just faster than light in that medium.
Strange stuff still happens, but still does not violate c.