What is Digg?181 Comments
- 0260, on 10/31/2008, -2/+79Another great post. Learned a few new things.
- AgentMull, on 11/01/2008, -0/+32They’re spheres. And they’re definitely not funnel shaped.
Who the hell thought black holes were funnel shaped. I didn't think the bed sheet analogy was that hard to understand. - superflydugg, on 11/01/2008, -0/+28science is sexy.
- cosmicastaway, on 10/31/2008, -2/+27So mindblowingly interesting. Anyone who likes this stuff should check out Phil's book, Death from the Skies! It's goooood.
- YEEK, on 11/01/2008, -3/+28Just a crazy thought, but...
What if a black hole grew so large that it's density was equal to our present Universe? If that's possible, then, perhaps our universe actually is an enormous black hole. As its mass continually increases, its event horizon expands outward, and its density decreases. Distance increases between galaxies inside the event horizon. The view from inside our black hole would look exactly like the expanding universe we see around us. - quiggibub, on 11/01/2008, -4/+27I already knew these things, but Dugg for explaining things fairly well without leaving out the science parts.
- Disgod, on 11/01/2008, -0/+17Huh, wow, that's an interesting thought. The only problem would be it doesn't explain the Big Bang. If it was a black hole then all the matter in the Universe would have had to been put into that black hole at once for it to occur as the evidence shows, rather than accreted over a long period of time, like what we would expect from a black hole.
But damn, that's possibly one of the most interesting questions I've seen raised on digg. - TSK05, on 11/01/2008, -1/+14"If this is true, consider my mind blown." - in that case, consider your mind blown. Side note though is that when people discuss radius of a blackhole, they mean the radius of the event horizon, not the radius of the singularity (which is 3 solar masses worth compressed into a space less than the diameter of an electron).
- staffa, on 11/01/2008, -0/+11Not only could they pack 3 solar masses into that size, they can pack a billion solar masses or any amount really.
That mass has size is just an illusion, a result of the forces of nature preventing different particles of mass from having the exact same location.
As you probably know, a wood table is 99.99% empty space, the eletromagnetic force keeps your hand from passing through it. At even smaller scales, different forces prevent matter from occupying the same space. A black hole occurs when gravity gets strong enough to overcome all the other forces of nature. - coolian, on 11/01/2008, -3/+14This pic: http://www.spitzer.caltech.edu/Media/mediaimages/s ... never ceases to fascinate me. There is nothing - NOTHING - special about us if you look at it. We are just some microscopic, random, boring part of the Milky Way. And that's just in our galaxy. Factor in hundreds of billions of galaxies in the observable universe and, jeez, we are ridiculously insignificant. Incredible stuff.
- TheMidnight, on 11/01/2008, -1/+12Fly 14,000 light years in the direction of Cygnus X-1 and tell us what you see.
- DrZmobie, on 11/01/2008, -0/+9Excellent article. Black holes are crazy!
- doublefelix, on 11/01/2008, -0/+9"At some point, the collapsing core will be smaller than an atom, smaller than a nucleus, smaller than an electron. It’ll eventually reach a size called the Planck Length, a unit so small that quantum mechanics rules it with an iron fist."
Maybe someone with a grasp on this can give me the movie pitch version - does this mean the empty space between all the ***** swirling around in a single atom is so great that you can pack 3 times the mass of the Sun into it? If this is true, consider my mind blown. - inactive, on 11/01/2008, -1/+1011. I used mine as a purse.
- sho76und3wd, on 11/01/2008, -0/+9Excellent article. I would love to see more like this on digg.
- outreach417, on 11/01/2008, -0/+7Whoah
- LarianLeQuella, on 10/31/2008, -1/+8Even if you think you know a lot about Black Holes, this is well worth the read! Even regular readers of Dr. Plait's blog are learning things here! And I second cosmicastaway, get the book.
- yournightmare, on 11/01/2008, -2/+811. Black holes are pink on the inside.
- andypop481, on 11/01/2008, -1/+7this is why i love digg. this ***** is awesome.
- wilhoitm, on 11/01/2008, -4/+10Did you know that Black holes originate from civilizations that are advanced enough to build their own Large Hadron Colliders (LHC) in the quest to find the GOD particle.
- mastercosby, on 11/01/2008, -2/+812. It can make that special part of the male body larger!
- TSK05, on 11/01/2008, -0/+6You're right, fermions can't occupy the same space and quantum state together.
But you're wrong that the article is wrong. Have you heard about electron degeneracy pressure? This pressure is actually the pressure resisting the changing of the quantum state into a higher level. So when this pressure is overcome, a higher level is achieved and fermions DO occupy the same space but have a different quantum state. Then the star collapses into a neutron star. And if it has enough mass to overcome neutron degeneracy pressure, it'll collapse into a blackhole.
Here is a bit of reading: http://en.wikipedia.org/wiki/Electron-degenerate_m ... - Disgod, on 11/01/2008, -0/+5We've got photographic evidence of stars orbiting around the exact center of our galaxy at a significant fraction of the speed of light. The only way this can only be explained by a incredibly massive object at the center of the Milky Way, on the order of millions of Suns. That means a super massive black hole.
So it's not photographs of an actual Black Hole, but it is incredibly persuasive evidence towards them.
Further more, if we see direct imagery of the Milky Way Black hole starting to "feed" at some point; the Milky Way would become an "active galaxy" which would be direct evidence of a super massive black hole. Feeding just means that large quantities of matter are falling into the black hole. Active Galaxies are galaxies which have incredibly massive jets of matter being shot out of the center of the galaxy at incredibly high energy levels, aka incredibly hot. These jets can only be explain by super massive black holes. The jets are formed by matter actually escaping the black hole's gravitational field before it hits the event horizon.
Finally, we can look for something called "gravitational lensing". Gravitation lensing is when light is bent around a super massive object. If the lensing occurs in some area which has no stars which could account for the lensing we might have found a regular black hole. I think they may have found evidence of this, but it has been years since I remember reading about this. - Exzhaton, on 11/01/2008, -1/+6Celestial Goatse - Pwning the entire universe.
- TSK05, on 11/01/2008, -1/+6Sure...except it's not in the optical band. I can't find one right now but look for data from systems like Cygnus, they've got "pictures" of blackholes. Sort of. They've got pictures of the gas swirling around them. Obviously you can't actually see a blackhole because it emits no light and reflects no light, but I suppose you can see the absence of light.
- TSK05, on 11/01/2008, -6/+11Well.....as an astronomy major I knew all of those but who cares :P
"It’s not their mass, it’s their size that makes them so strong." - Meh. True for stellar mass black holes but not true for supermassive black holes and intermediate black holes. His example is just saying that blackholes are so powerful because their density is large (mass per unit volume, with volume being 4/3 pi r^3, notice that r^3). Newton's law of gravitation: Force of Gravity (9.81 for Earth for example) = (G(universal constant, just a number)*Mass1(of object being attracted)*Mass2(of object doing the attracting like a blackhole))/r^2 - that r is the distance between the objects. So he's saying if the density of the blackhole is large, the radius of the blackhole is decreased (from first equation) then radius between the two objects can decrease because the object being affected can come closer to the blackhole and thus (by newton's law of gravitation) the gravity of the blackhole increases.
This is only true for stellar mass blackholes, the density of supermassive black holes can be quite small. This is actually #10 on his list and the strength of blackholes there is their mass, not their size (by what I said above). - JohnFlux, on 11/01/2008, -0/+5The particles aren't packed next to each other, they exist on top of other.
A neutron star ( http://en.wikipedia.org/wiki/Neutron_star ) is what you can when the particles (neutrons in this case) are packed as closed together as you can get. This is a type of collapsed star which is prevented from collapsing just because of the principle that 'two fermions cannot exist in the same place at the same time' (A popular misconception of this that I've heard in films is that 'two objects cannot exist in the same place at the same time'. This is false)
So anyway, if the mass is large enough, the fermions (neutrons in this case) are forced to combine to form bosons. Multiple bosons are allowed to exist at the same place at the same time, and so the object can continue to collapse forever, into a black hole. - Disgod, on 11/01/2008, -0/+5I think it is because it is difficult to picture the bed sheet analogy three dimensionally. Also, they might have the idea it looks like a flat disc, due to images of black holes with accretion discs around them.
- YEEK, on 11/01/2008, -0/+4Inside a black hole, who knows how time and space manifest itself. The rules we see around us would not apply. Perhaps our universe started off as a typical black hole, with all matter inside a singularity. Then, as the black hole's mass increased, and the event horizon expanded, and density dropped at an ever increasing rate, the nearly infinitely massive singularity exploded to fill the void inside the event horizon- hence the big bang.
- inactive, on 11/01/2008, -1/+5No they're not. I'll divide you by zero.
- Rigman, on 11/01/2008, -2/+6Dugg for Bad Astronomy Blog... and the great article pic. Loved that movie when I was a kid!
- CuriousDan, on 11/01/2008, -0/+4Here's another fact: there's a black hole which emits a Bb note 57 octaves below C4: http://www.nasa.gov/centers/goddard/universe/black ...
- JohnFlux, on 11/01/2008, -0/+4The pauli exclusion principle only applies to fermions. For example electrons, neutrons etc. The pauli exclusion principle is what keeps a neutron star from collapsing. A neutron star is a collapsed star where the gravity is so heavy that it has squeezed all the particles as close as possible. If this was the end of the theory, then radu would be correct.
However if you increase the mass, eventually gravity 'overcomes' even the pauli 'pressure'. The neutrons are forced to join in a way that turns them from a fermion into a boson. Bosons are not restricted by the pauli exclusion principle and are allowed to overlap. Thus the star can collapse indefinitely, forming a black hole.
So basically the pauli exclusion principle isn't outdated, but only applies to fermions and there is a 'loophole' that fermions can turn into bosons. - Sornos, on 11/01/2008, -1/+511. Aliens can hide in them.
- MtheoryX, on 11/01/2008, -0/+4I really just like the clear, introductory explanations he gives in the article. I'll definitely be picking up the book for more.
- Disgod, on 11/01/2008, -1/+5To those in the center of the galaxy, no. But to us, who would be moving much faster relative to them, yes it would appear time would be marginally slower, but not by much.
To actually be able to see a major difference in times you need to be going at a fairly signification percent of the speed of light. We're only orbiting at 719,000 km/hr, and the speed of light is 1,079,252,848,800 km/hr which is 0.000000666% the speed of light.
/hope I got that right. I think I did, but feel free to correct. - nicejai, on 11/01/2008, -0/+4We measure things by bouncing other things off of them. We see because light bounces off things and enters our eyes. This is no problem in the large world because photons can't really move a basketball (for example) much when they hit it. If we want to see really small things, we need can't use photons of visible light because their wavelengths are simply too big. Think of wavelength like the pixels in your digital camera. The smaller they are, the higher the resolution they give us. The thing that sucks is that generating small wavelengths requires boatloads of energy.
Since light is just an oscillating magnetic field, you can think of it like taking a regular magnet, and flipping it upside-down and back again, then upside-down again, then back again, etc etc... billions of times a second. You can imagine how it would take more energy to flip it faster to generate the short wavelengths that you'd need.
So, if you want to see anything small (quantum-level small) you'd need a really high-energy wave. However, whatever you hit with that beam is going to change whatever it is you wanted to look at. Not only that but there will be a limit to the strength of your beam. Because, there will be a point when your beam becomes so strong, that once it hits something the energy density will become so high that it will theoretically create a mini black-hole and suck back the beam/particle you were expecting to bounce off the thing. You would reach this limit if you could generate a electromagnetic wave with a wavelength equal to the planck length.
That is why the planck length is the smallest we could ever measure anything with certainty. Any smaller, and we wouldn't know because the bounce-back signal we'd need for measurement would simply disappear into a miniature black hole.
... in theory. - championchap, on 11/01/2008, -0/+4You could fill a Black Hole with all the things I don't know about Black Holes.
- antoniuk, on 11/01/2008, -3/+7Everything I need to know about Black Holes i learned from SG1 And Lieutenant Colonel Samantha Carter.
- Plasmodia, on 11/01/2008, -0/+4WARNING: After reading the following excerpt, your mind will implode on itself.
"A billion solar mass black hole (big, but we see them this big in galaxy centers) would drop that density by a factor of 1 x 1018. That would give it a density of roughly 1/1000 of a gram per cc… and that’s the density of air!" - layzice, on 11/01/2008, -0/+4Vote Blackholes in '08, for real change.
- Disgod, on 11/01/2008, -0/+4err to make myself more clear
No time would not seem slower for a person near the center of the galaxy. However, If we could look at something in the center of the galaxy with enough precision from our point of view there would be a really small, but noticeable slowdown in the speed of time at the center of the galaxy.
and
.... Which means we're only traveling at 0.000000666% the speed of light relative to the center of the galaxy. Which translates into a very small relativistic effect.
/sorry I'm high - Farik, on 11/01/2008, -1/+4"Out here, we’ll never know for sure. We can’t see in, and it sure enough isn’t gonna send any info out."
Not entirely true, Hawking Radiation is (theoretically) emitted from black holes and through quantum entanglement could technically "send" information out. - playaj20008, on 11/01/2008, -0/+3Brown noise?
- JohnFlux, on 11/01/2008, -0/+3Hi,
Yes, time would run slower in the center than out here. Disrod's information is correct if you consider only special relativity, but it seems that he has not studied general relativity (which isn't surprising - it's not even covered in most undergraduate physics degrees).
Time slows down due to gravity. Even for GPS satellites orbitting above us they have to take this into account.
The gravitational time dilation ( http://en.wikipedia.org/wiki/Gravitational_time_di ... ) due to a supermassive black hole at the center of our galaxy (it seems that there is one) would be significant. - outreach417, on 11/01/2008, -1/+4Dugg for "black holes suck"
- JohnFlux, on 11/01/2008, -0/+3Virtual pairs of particles are created and destroyed continually in the vacuum of space all around us. They exist for only tiny amounts of time before they collide again and destroy themselves. So normally we never notice them.
Near a black hole however, if a pair is created and one crosses the event horizon but the other does not, they cannot join up again to destroy each other. So the one that managed to escape the black hole goes off on its merry way across the universe. But this particle has mass and energy so to conserve the total amount of energy in the universe, the particle that fell into the black hole must have negative mass and energy. Thus the black hole decreases in mass, and so shrinks. - tallphil, on 11/01/2008, -0/+3Another way of thinking about the Planck Length is as follows:
In quantum physics there exists a law called the Heisenberg Uncertainty Principle, which stipulates that there are certain values or properties of a system that cannot both be known with unlimited precision. A popular example is the relationship between momentum and position: if I know where a particle is with infinite precision, then I will find it impossible to tell how fast it is going.
Another such relation is between energy and time. Such a relationship allows things like 'virtual particles', which can come into existence by 'borrowing' energy from the vacuum as long as it is payed back quickly enough. The more energy that is borrowed, the faster it must be payed back.
Obviously, if the time over which energy is being borrowed is small enough, the range over which this borrowed energy has influence is very small. Very large amounts of energy can be borrowed, but it only affects a very tiny amount of space, such as the distance designated as the Planck Length.
The energy can be so great as to warp spacetime as per Einstein's equations of General Relativity (but remember this is only on a very small scale, and for a very small amount of time). The result of all this energy being borrowed and payed back on a small distance scale is 'Quantum Foam' which can be imagined as a bubbling, frothing sea of spacetime, which averages out to zero at larger distance scales.
When the black hole has collapsed to sizes where quantum foam comes into play, we can no longer claim to know what is happening, because spacetime is so messed up.
I'm not entirely sure looking back that i've answered the question, but I hope this was interesting to read. If I'm wrong about anything here (a distinct possibility), I would be glad to have my errors pointed out to me. - manogamez, on 11/01/2008, -1/+4For anyone interested I would recommend reading "Death By Black Hole" by Neil DeGrasse (the dude who's on discovery a lot).
- cannonball, on 11/01/2008, -1/+4your logic divided by zero is an undefined joke.
-
Show 51 - 100 of 183 discussions
Check out the new & improved 
© Digg Inc. 2009
— Content created and posted by Digg users is