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Posted
by
timothy
from the that's-an-immense-candy-bar dept.
ChazeFroy writes: "A black hole with a mass of more than 2 million suns has been pinpointed at the center of the Milky Way. Scientists used triangulation based on the acceleration of infrared images of three stars and to find the center. CNN has the story here."
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Got news for you dude. Nature doesn't care about mathematics.
I hate to break it to you dude, but Nature cares very deeply about mathematics. This is why she chose to base all of creation on it.
The fact is people didn't invent mathematics, we merely discovered it.
Look at the whole fiasco over the discovery of irrational numbers and "imaginary" numbers.
No one wanted these, they were forced into accepting their existence. ---CONFLICT!!---
You can lower the cable near the horizon to take measurements, but if you lower it into the horizon the cable will snap. Tension will increase without bound if you try to keep it from snapping.
Why? If the tension increases without bound, does that mean there is an infinite gravitational gradient?
Is it impossible for a solid object to be partly within and partly outside the event horizon? Why?
For the love of god man! we're all going to be sucked into a black hole that will negate exsistance as we know it! Panic now! avoid the rush! we've only got a few billion years left!
Uhm, you DO know that not only is the universe expanding, it is ALSO accelerating !
Edwin Hubble realized that galaxies were rushing away from each other at a rate proportional to their distance, i.e. the farther away, the faster the recession
The rate is called the "Hubble constant" which you can read about it here:
What I like about these astronomical-black-hole-sun posts, is that you know what to excpect when you look at the forum - first 10 posts (highests scores first) will be *Funny*. Any lame joke will get propagated on top of the list. People, what's up with that? Or is astronomy is way funnier than Napster? hmm..
Check out recent work by Susskind and 't Hooft (the guy who pretty well invented Gauge Theory) - in particular the stuff on the Holographics Hypothesis (this *isn't* the cheesy holographic universe thing in some popular physics book). Susskind had an article in SciAm about a year ago - otherwise, if you have a physics background, try searching xxx.lanl.gov. They, and others, suggest that the event horizon isn't the well behaved place classical general relativists say it is. You may no the classical result that a black hole has no hair. The opposite seems to hold in quantum gravity - the event horizon actually has lots of quantum information concentrated near it. I am sympathetic towards their controversial outlook (I did black holes and strings for a few years before and during my PhD). Who knows though - *none* of this stuff is founded on anything rigorous.
--
If you take the Schwartzschild radius, the point where the escape velocity equals the speed of light, it's radius would be about 3000km. Compared to the size of the Milky Way, that's a pinpoint;)
The Schwartzschild Radius is 2 * gravitational constant * mass of sun / (speed of light^2 )
Righty, here is a basic explanation. Some of the bits will pobably be slightly inaccurate but that's okay, you're all understanding people.
Stars are big and hence they have a big gravitational field. What prevents the star from collapsing is basically the heat and light it produces by fusing lighter elements into heavy ones. When the star runs out of available hydrogen to burn it then starts to burn helium and so on up/across the periodic table until it reaches iron which it can't fuse because the released enegy per nucleon is negative.
(non-MS)ie. It don't produce any heat.
The star then begins to collpse. There are various thing that can happen, depending on the mass of the star. If it is big enough, the whole shebang colapses until the core is hyper-compact and reaches the exclusion-principle limit. The outer layers rebound at a fair old fraction of the speed of light (10%???) producing a supernova (I forget which type, IIa???). If it is still above a certain mass, the Chandrasekhar limit IIRC, then it collapses further until the curvature of space around it becomes infinite (as per Gen'l Relativity).
Gravitational lensing has never been and will never be used to detect the presence of a black hole.
The reason? It's not that gravitational lensing does not exist, or even that it's not dramatic enough to detect. The reason is that no black hole is close enough for us to use parallax to know the true positions of stars behind it. The way gravitational lensing works is by being able to detect when stars are out of place (not where they should be) due to their light being bent by a super-massive black hole. We would never know where these background stars should be so we can never figure out if they have moved.
So you just demonstrated how horribly uniformed on the tremendous size of the universe you are, and how that results in us not being able to use gravitational lensing to detect black holes.
i now realize
that we will all simply
boil alive in a horrible,
galactic nuclear
holocost.
Oh, don't worry about that either. As the sun
revs up over the next
billion years, all of the
water on Earth will
evaporate and we'll all
die of dehydration.
T. M. Pederson
"...and so the moral of the story is: Always Make Backups."
yeah, that's not a great choice of comparison for distance. the radius of a one solar mass black hole is about 3 km, and it just scales linearly with mass, so you're looking at no more than 8 million km for a 2.6 million solar-mass BH. By comparison, the radius of our Sun is about 700,000 km, and the Earth orbits at about 150 million km from the Sun.
of course, the above numbers are upper limits on the radius; a BH can always be *smaller* than the Swarzschild radius, but never larger.
All we need is an object bigger than the black hole, to plug it up.
As an aside, do things in the northern hemisphere of the universe flush one way down a black hole, while in the southern hemisphere, they flush the other?
To attempt to illustrate it's denseness further, if you could place a cubic inch of this black hole on the floor, it would shoot straight to the earth's core. That's dense!
For those that haven't read it, Stephen Hawking's "A Brief History of Time" is an excellent book that covers black holes.
Typical, but a little on the small side, as supermassive black holes go. A black hole at the center of M87, in Virgo, might have a mass as large as three billion suns, for example.
See this article [space.com] at space.com for more info.
um, that'd just generate an error. I think what you mean is
cat center.galaxy.txt >/dev/null
but even that wouldn't do what you wanted, because center.galaxy.txt would still exist, and doing
cat/dev/null > center.galaxy.txt
wouldn't be the same either, because then it's the black hole going into the galaxy, not the other way around.
I think what you're looking for is
alias 'blackhole=rm -rf'
blackhole center.galaxy.txt
A black hole isn't just a homogeneous mass. Theoretically, all the mass collapses to a singularity. The "boundary" of a black hole is the event horizon, or the distance where light can no longer escape the black hole's gravitational pull.
1) how come more negative (un-, if you wish) than positive particles are attracted?
Both particles are equally attracted by the gravity of the hole, but they have different initial velocities. One might exceed escape velocity while the other does not. It takes a lot of luck, but given enough time, it's bound to happen to some particles.
Positive particle do get sucked in just as often as the negative ones. The difference is that normal matter loses potential energy when falling, whereas "negative matter" gains energy as it falls. This is the magic that allows the remaining particle to become "real"... Sounds a little fuzzy, I admit.
1.1) how come gravity works the same on unparticles? Shouldn't they be repelled?
Fair question. I don't know.
2) why does this happen at a faster rate for small black holes (I understand that rate of evaporation is inversely proportional to mass)
The smaller the hole is, the greater the tidal forces at the event horizon. Stronger tidal forces mean that pair of virtual particles is more likely to be ripped apart, just like you'd be ripped apart if you got near the event horizon of small black hole.
1. There is no preferences, and it is not un-particle, but anti-particles.
I made up the word "unparticle". There may be a better term, but I wanted to make it clear that they are not anti-particles. Anti-particles are identical to regular particles, except that they have the "wrong" charge. For example, a positron is an electron with a positive charge. If a positron and an electron were to suddenly appear near a black hole, the universe would object strenuously, because that would violate conservation of energy. However, electrons and "un-electrons", i.e. electrons with negative energy, can come and go as they please, because the sum of their energy is 0.
Does anyone know what the term for a particle with negative energy actually is?
I can't beleive you guys want to spend more of my hard earned dough on your Wasp Rap devices. I think you white folks need to remember that rap is the language of the people. I'm so tired of you whitees thinking that you can just change all our artforms into your bastardized propaganda for white rule. Power to the people. The revolution will not be televised. Next time you drive around in your $200,000 Chevys, listening to that Warper Eminem, remember that we're taking names and plates, boy. You best watch your back.
The impact of the woman's head on the window is from the acceleration of that window toward her head. (Just another way of phrasing your point about her linear inertia.)
After her body came to rest against the window and the door, she was experiencing centripital acceleration in the literal sense. (Although the car is not a string, and she is not a yo-yo (I dont know her), the factors are the same. The car is keeping her on the arc of a circle.)
[i]Before saying things like it's just Math, you'd better not forget that quantum theory and GR are quite successfull, so if they predict that something happen, well, it has quite a chance to happen "for real".. [/i]
Okay, first off, it's not a matter of chance. Something is real, or it isn't. The theory is either real to the world in this respect or it isn't. There is no way to measure what the "chances" are that it's correct, and as we all know, if you can't measure it, it's not science.:)
And a theory can be completely and totally correct in every respect except one, and still be wrong.
Also, note that I don't thing it's incorrect here, I just don't see how you can get the particle/unparticle explanation from the math of it. Seems like that's a made up explanation for mass comsumption.
This just in: Finding that there was a previously undiscovered black hole at the center of our galaxy, the RIAA sued them for copyright infringement. "We thought we had sued everything in the known universe for violating our artists' rights," said a RIAA spokesman. "Thanks to the tireless efforts of NASA and Lars Ulrich though, we have continued to make the universe safe from free music." Reports also indicate the MPAA will sue the Big Bang next week for, "Making the creation of DeCSS possible through its own reckless acts of creation."
So, we're now sure there's a blackhole at the center of the milkyway. But what is there at the center of the blackhole? What are the physics like inside? What's it like to fall in? How many dimensions inside? What would it look like to stand inside and look out at the light falling in? What's it feel like to be a blackhole?
These are the things we still don't know, and I'm afraid we'll never know them within my lifetime.
If (by the greatest of all possible spaces) you are using the min distance Mars-Sun as the diameter of a sphere of space, you can use 4/3*pi*r^3 to get a V of 4.62*10^24 km^3. Sol's V is 1.412*10^18. You can only fit 3.3 million suns in there.
If you just take the linear distance, you can only fit 308 suns in there.
Either way, that is a shit-load of suns in a relatively small space (compared to the normal distance between suns).
I think the original post made that classic geometry error we have probably all made, and substituted radius for diameter. If his calculations are correct, you can fit 26 million inside the sphere measured out by mars, but the quote implied that the _diameter_ of the sphere is about the distance between the sun and mars.
That's just a little too close for my comfort. Anyone else care to start up an expedition to move a little farther out in the galaxy before It's too late?
First it was the flouride in the water, then it was the ozone layer, currently it's like "oh no, we'll all be killed by the Asteroid!". Next big thing will be "We're all going to be swallowed up by the black hole!".
You're right! That is the error I made. I went back and re-read the quote, and although the original quote is not (IMHO) clear, i believe you are correct. Thanks for pointing that out. My misunderstanding arose the comparison of the mass of the black hole relative to the mass of our sun, which put me in a heliocentric frame of mind. Once there, my mind was not prepared to discuss the size of an celestial body as a diameter measured as a radius outward from our sun.
At least i know i was not alone in my mistake...this time.;-)
Rather impossible. If that were so, we'd be inside the event horizon, and therefore we'd be falling into that black hole. Now, even though science fiction has all sorts of time-dilation motifs inside the event horizons of black holes, I tend to doubt that my existence to this point has been a few seconds on the way into a singularity.
Sorry, but that's a little too rough. Particles are not ripped in two. Rather, at the event horizon, just like everywhere else, virtual particle/antiparticle pairs are constantly being formed and annihiliated as allowed by the uncertainty principle (they don't last long enough to be detectable, so they don't violate any conservation laws). However, being at the event horizon, some of these pairs get formed, and then one of the two particles gets trapped by the black hole, and its partner does not annihilate undetectably quickly, but rather sticks around long enough to collide with other matter or decay or both, thus producing Hawking radiation.
... however, Hawking radiation is immeasureably faint, and has nothing to do with how we detect black holes. People spout off about this every time black holes are mentioned on Slashdot, so much so that it makes me wonder if they're just trolling.
Actually, I have one other quibble with your explanation: the virtual particle pairs are not particle/anti-particle pairs. They're more like particle/unparticle pairs. Anti-matter just has a negative charge (relative to normal matter); the stuff that we're talking about actually has negative energy. The difference is that when particles and anti-particles annihilate, they leave a huge amount of energy, whereas when a virtual particle pair annihilates, it leaves absolutely nothing. 1 + (-1) = 0
News flash: The scientists found the black hole in space where it was lost by mistake over twelve billion years ago. The achievement is astonishing if you consider the the hole is only two million times the mass of our parent Sun.
The CNN article [cnn.com] says: The black hole could hold 2.6 million stars the mass of the sun inside a relatively tiny area -- less than the distance from the sun to Mars.
That shouldn't be at all shocking. Even if we take the minimum orbital distance of Mars (~206.7e6 kms), you can fit the equivalent of 26,193,511 Sol volumes within that space. (given the radius of Sol to be 6.96e5 kms)
So, even NOT counting on compression from the incredible amount of mass, you could fit 26 million stars the mass of the sun into the "relatively tiny space".
Given that the numbers match so closely, except for the decimal place, i suspect one of two things:
1) The article writer is amazed you can fit the volume of a marble into the volume of a basketball.
or
2) The article writer put the decimal in the wrong spot, and discovered you can put volume "V" into the space of volume "V"
Is that really nougat in a Three Musketeers? I thought nougat was stickier... gooier... and tan. Three Musketeers seems to have kind of a nougat foam in the middle. Weird.
Yup.
Science in schools, both here in the UK and in the US, has gone down the tubes.
Example: 'Which planet are we sending this (the HST) to?'. Senator Albert Gore.
Elgon
Being a Brit living abroad I was delighted to find that America had Milky Ways and Mars Bars. I was less than delighted to find out they were not the same as the British originals. Same name different product:-(
The black hole at the center of our galaxy is typical for a galaxy like ours. M31, the great galaxy in Andromeda, has a slightly larger one. Both the Milky Way and Andromeda are rather large spiral galaxies.
But neither black hole can hold a candle to the hole at the center of M87, the giant elliptical galaxy at the center of the Virgo cluster. This titan weighs in at several billion suns, and emits relativistic jets of matter from its poles.
Astronomers are very close to demonstrating that the phonemenon known as quasars, are nothing more than an active black hole, swallowing matter at a prodiguous rate in young galaxies that have undergone a burst of star formation. Our galaxy is likely to have shown quasar properties in times past. But as the concentration of matter near the center of a galaxy decreases as it is consumed by the black hole, the quasars turn off.
Astronomers are also gaining new insights into the role of central black holes in the formation of galaxies. It appears that the galaxy and the hole evolved together - the hole provides the gravitational anchor, pulling in nearby gas clouds, which collapse to form stars. We may have never come to exist were it not for the galaxy-forming propensity of massive black holes.
The Next Generation Space Telescope is expected to answer these questions one way or another. It is hoped that it will be able to image very young galaxies in the process of formation, or perhaps even find evidence of naked black holes just beginning to draw in the surrounding primordial gas. That would be quite a find, since it would imply that the black holes came first, and raises the question: from what? Were the created somehow in the maelstrom of the Big Bang, or was there a very early era of star formation that preceeded the era of galaxy formation?
"The theory goes (extremely roughly) that as individual particles reach the "edge" (event horizon?) of the black hole (crossing this line means you never come back), some of them are torn apart, half of the particle going in, half going out, and some energy is released during this fission"
Sorry, but that's a little too rough. Particles are not ripped in two. Rather, at the event horizon, just like everywhere else, virtual particle/antiparticle pairs are constantly being formed and annihiliated as allowed by the uncertainty principle (they don't last long enough to be detectable, so they don't violate any conservation laws). However, being at the event horizon, some of these pairs get formed, and then one of the two particles gets trapped by the black hole, and its partner does not annihilate undetectably quickly, but rather sticks around long enough to collide with other matter or decay or both, thus producing Hawking radiation.
Now someone can correct my rough explanation and eventually we'll get this straight...
It measures speed. Velocity is a vector, described by speed plus direction. The earth is constantly accelerating towards the sun, but the earth maintains a constant speed (if you treat its orbit as a circular instead of elliptical).
Anyone remember the URL to that cool site that had the animations of computer simulations of various relations to black holes? orbit around a black hole, falling into the event horizon, watching a star or planet falling into the event horizon, etc.
We didn't find there to be a black hole in the center.. we knew that already
If you read the article you would note that we pinpointed it's location in the milky way
Read the article, then post.
[phpwebhosting.com] nerdfarm.org
Here's a test: On a *snap* basis, figure out what the difference is between acceleration and speed.
Most people won't think about the difference, as most folks think speed=acceleration.
Try it out - go around and ask 5 average folks (you may have a few around) what 'acceleration' means... betcha they all say 'how fast something is going'.
Black holes can be detected (in theory of course) by looking for the emissions they give off. The theory goes (extremely roughly) that as individual particles reach the "edge" (event horizon?) of the black hole (crossing this line means you never come back), some of them are torn apart, half of the particle going in, half going out, and some energy is released during this fission. It is these fissions at the edge that make a black hole appear to give off energy, and make it detectable.
That type of radiation is called Hawking Radiation (after Stephen Hawking, naturally). However, this isn't what lets us detect black holes, as Hawking Radiation is ridiculously faint. Black holes can be detected by the X-Rays that they "inadvertantly" produce. When matter is falling into a black hole it is accelerated, heated, and compressed to such a degree that it gives off large amounts of X-Rays. I believe the first black hole we detected (again, assuming black holes exist), was Cygnus X-1 (or cygnus something), and we detected it by the x-rays it gave off.
Another method of detecting black holes is to look for graviational lensing effects. Because black holes are so massive, they bend the fabric of space time. (Imagine a sheet suspended in the air. Place marbles on the sheet. The marbles make depressions on the sheet, like stars make "depressions" in space-time. A black hole is so heavy, it's like dropping something that is the size of a marble but with the weight of a bowling ball onto the sheet. The sheet bends A LOT, and it actually will have a hole where the singularity is.) Light travels in a straight line, so if space-time curves, light also curves with space-time. Gravitational lensing was proved during a solar eclipse. Astronomers observing the eclipse noted that they were able to see stars that should have been blocked by the eclipsed sun. The sun's gravitational field caused enough "lensing" so that stars directly behind the star could be seen to either side of the star. So, if we find something out in space that is causing a LARGE amount of gravitational lensing, but we can't see anything, there's a chance it's a black hole. At that point we normally observe it more to determine if it is or isn't a black hole.
"Black holes are so dense they create gravity so strong that even light cannot escape their surface, making them nearly impossible to see. Kormendy said the black hole at the center of the galaxy is not pulling in other stars.
Even if it's not pulling in other stars yet, I'll bet it'l suck the fillings out of my great,great,great,great,great,great,great,great,gr eat,great,great,great,grandkids teeth... Wonder why it's not eating stars yet, the density there should be high enough for some motion..
So, even NOT counting on compression from the incredible amount of mass, you could fit 26 million stars the mass of the sun into the "relatively tiny space".
Given that the numbers match so closely, except for the decimal place, i suspect one of two things:
1) The article writer is amazed you can fit the volume of a marble into the volume of a basketball.
or
2) The article writer put the decimal in the wrong spot, and discovered you can put volume "V" into the space of volume "V"
I vote for option 3), 4), or a combination of the two:
3) The amount of space is "tiny" compared to the amount of space taken up by stars in the rest of the galaxy. Stars are seldom packed one against the other.
4) The writer is using copy from descriptions of smaller black holes. The even horizon's radius grows in linear proportion to a black hole's mass, if I remember correctly.
This means that volume grows far faster than mass. Black holes with the mass of a mountain are smaller than an atom; a black hole the mass of the sun have a radius of about 3 km. More massive black holes, however, have less density. In fact, if the universe is closed (i.e. returning to a "Big Crunch"), it would be the perfect example of a very sparse black hole - transplant a sufficiently large chunk of it to a reasonably flat space, and an observer outside of the transplanted chunk would see an event horizon surrounding it.
oh whew, for a minute there i thought we were all going to be ripped apart that the atomic level by a force we could niether understand nor control. i now realize that we will all simply boil alive in a horrible, galactic nuclear holocost. Man i was worried there for a second
Well, she's right, from a certain point of view. (Luke, I am your father.:)
'Centrifugal force' is a force defined from a non-Newtonian reference frame, and as such, is not a true force. A force can only be defined from within a Newtonian reference frame, so your implication that she is incorrect is correct. (Does that make sense?)
What your wife is actually feeling (aside from the bump) is her linear inertia taking her in a straight line while the car turns away from that line. So, she bumps into the window.
When she asks you what she is feeling ("I'm feeling something, so what is it, Mr. Smary-Pants?"), you can tell her that what people typically call 'centrifugal force' is actually the other side of 'centripetal force'. Centripetal force is the tension in the string when you swing a Yo-Yo over your head; centripetal force keeps an object traveling in a circle.
Try this, Newton's first law of motion says that it takes force to move something or change it's straight line motion at constant speed (in Newton's world being at rest and traveling with a constant velocity are the same thing, the first glimpse of relativity), and you are traveling in your car in a straight line, with constant speed. You turn the wheel and the car starts turning, which means that acceleration is being applied to the car to change it's velocity. This acceleration is called centripetal acceleration.
In conclusion, there is no centrifugal force, although it appears to be a force, but it is measured from the wrong reference.
I dunno, wouldn't that cubic inch of 2-million sun black hole actually be more massive than the entire Earth?
So it would be more likely that the Earth would get "eaten" by that cubic inch. Then again, if that chunk of black hole is too small to maintain its integrity, it may just evaporate violently and blow everything in the immediately spacial environment to plasma...
Take a Windows 2000 server, link it up by some radio connection, and place it near the event horizon of a black hole.
The effect of time dialation would decrease the MTBF dramatically, with only a minor change in processing speed (slow down a Windoze server by a factor of 1E9 and I doubt anyone would notice).
[Unfortunately, there would still need to be a sysAdmin sleeping next to the server to handle the occaisional (every 10,000 years) crash, but then again, that's probably the best use of someone with an MCSE anyway.]
This dramatic improvement in reliability could be a "hole" new marketing angle for MS. Maybe we could put the entire.NET infrastructure INSIDE a black hole to make the Internet REALLY safe...
True. He got quantisation of non-abelian gauge theory to work. As theoretical physics today seems to be nothing but quantising non-abelian gauge theories (at least that's what almost all the theoretical physicists in my mathematics department did!) it makes him a pretty important guy - which is what I really should have said (ie. he's not a crackpot).
--
What I find far more disturbing is that really long distances are now measured in football fields, as football seems to be more common than both kilometers and miles.
In case you're not kidding: In the same way that a pound of gold is smaller than a pound of feathers, a 2-million-sun black hole is much smaller than 2 million suns. It's dense. Actually, it's more-or-less infinitely dense, since a black hole forms a singularity, a one-dimensional object, a pin-point, like the article said. The thing that confused me was that they also said it was the size of the distance from the sun to mars. Did they mean the event horizon was that size? Seems small to me, not that I would know.
I never understood the "evaporation" thing. If particle/antiparticle pairs are ripped apart by the event horizon, with one of them going in, aren't half of the "things" going in going to be particles and the other half antiparticles, effectively canceling each other out?
Or is one more likely to fall into a black hole than the other?
I thought that a black hole was just a star that collapsed on itself because there was no matter trying to escape, and therefore just started to,
uhh, suck.:-)
Not exactly. Stars enter other phrases before dying. See The Death of a Star [syr.edu].
What you say is true, but this isn't what the group mentioned in the article was doing. More germane, maybe, is that another way of "detecting" BHs, and actually quantifying how massive they are, is to look at the motions of objects around them -- if, eg, stars are moving very quickly, then the mass around which they orbit must be quite large. The technique described in the Nature article sorta, kinda, has to do with this, but the goal was (I think) to pinpoint position more than anything else. We were already pretty sure Sag A was a black hole.
Gravity doesn't work that way. It's only a function of mass (and space). Two objects of the same mass and the same vollume will produce the same distortion in the space-time continuum and will appear indistinguishable. It doesn't matter what goes on inside the black box (in this case, the black hole).
But what is there at the center of the blackhole?
If you go along with general relativity - ignoring quantum mechanics - we have a fairly good mathematical model of the inside of a black hole - at least in terms of its gravitational field. The problem is at the very centre where the mathematics goes a bit haywire and we have a 'singularity'. That's just a way of saying the solution to the equations goes to infinity and the equations aren't valid at this point.
What are the physics like inside?
In principle. Similar to outside. One twist is that time and radial distance are flipped. What this means is that instead of particles taking an inexorable path into the future from the past they take a path that is confined to travelling towards the singularity. (This is for a non-spinning black hole, spinning black holes are more complex but this is a slashdot post not a book on general relativity).
What's it like to fall in?
As you approach the event horizon you're going to have more and more stuff falling in behind you. Much of that stuff is light that whacks in behind you. That light will have been converted to gamma rays by gravitation blue shift. You'd get frazzled before reaching the event horizon.
How many dimensions inside?
Same as outside according to the theory.
What's it feel like to be a blackhole?
Try 'As She Crawled Across The Table' by Jonathan Lethem:-)
Personally I think there's a lot of evidence that ignoring quantum effects is wrong. There is a lot of evidence that interesting quantum effects take place at the event horizon so that the laws of physics we currently have break down well before the singularity. Connecting quantum mechanics and general relativity is the biggest challenge facing theoretical physics right now but I home we see some glimmer of understanding within your lifetime!
If you're really Louis Wu, why don't you use the puppeteer hyperdrive to have a look at the galactic core like Beowulf Schaeffer did, instead of reading Slashdot?
Maybe it's just browsing at 1 that did it, but I was expecting at least 90% of the replies to this post to be jokes based around "probing the inside of a black hole". Instead, people actually gave semi-thought-out answers to the original post! Not a probing joke in sight. Consider this to be in lieu of every bad joke you can think of...
...or alternatively, just imagine a beowulf cluster of those...
For the ones interested, the uncertainty principle variant for this situation is:
dE * dt >= h-bar,
where
dE = the pair's energy, meaning the amount of energy that is "borrowed" from vacuum in order to create it
dt = the amount of time the pair lives
h-bar = Planck's constant divided by 2*pi
Actually, you're not entirely correct on this one. We can do relatively complete simulations of what it looks and "feels" like to fall in toward and past the event horizon of a black hole. Based on what I remember of these results, your perception of the outside stars and starts to contract behind you until it basically becomes a single pinpoint of light and you are otherwise surrounded entirely by darkness. I.e. your effective horizon of vision of light falling in contracts down to a pinpoint, I believe at a point in time after you've fallen through the event horizon. But my memory of these things has faded somewhat, you can probably pull some of this stuff out of some books on black holes. Of course it's all rather useless since tidal forces will tear you to pieces before you get close enough to enjoy the view (i.e. the delta in gravitational force exerted on your head versus your feet assuming you are falling in lengthwise... depending on the size of the black hole, you could get torn apart long before you get close to the event horizon.
Well if you deem it important to develop superlightspeed flight in order to save mankind/our replacements, then you would acknowledge a much more pressing need to make a lightsaber.:)
The Schwarzchild Radius is the radius that if a mass is compressed to within, the escape velocity exceeds the speed of light. The Event Horizon is the border between the region where an observer can 'observe' 'events' occuring near a black hole and where the observer can no longer 'observe' 'events'. Current theories suggest that these two only coincide for a non-rotating black hole as if the black hole is rotating, the space around the black hole is dragged along with it (Frame dragging) and the Event Horizon decreases in size.
However, the Event Horizon cannot ever reach a size of zero (exposing the Naked Singularity) as that would mean that the Black Hole would have an angular velocity equivalent to an energy of infinity!
How massive is this blackhole compared to others? Is this impressive in any way besides that it's neat that they were able to 'prove' that there's a blackhole at the center of our galaxy?
A Snickers is peanuts & caramel wrapped in chocolate. It used to be called a Marathon in the UK until the early 90s.
A Milky Way in the UK (and Australia) is just that fluffy stuff wrapped in chocolate. In the USA, a Milky Way also has a layer of caramel over the fluffy stuff. NO peanuts.
I have this on good authority, as an Englishman working in the states - I just asked the guys in the office.
The black hole is not more then million suns in size, but *MASS*. That is what makes a black hole: an almost infinite mass in a very small (relatively speaking) radius.
A third! Where did you find that published? I'm pretty amazed it's that popular given the lack of experimental success. I personally think string (or M) theory isn't a great *physical* theory but I don't care as I think it's the most beautiful thing to come out of physics ever.
Of course you can't make a clean split between gauge theory and string theory and you can quantise strings as a gauge theory.
Maybe some of the experts here can answer this random question... a thought experiment, if you will:
Suppose you had a platform or spaceship or something orbiting a small black hole, just above the event horizon. Now, that platform would be moving at just under light speed, but so what.
Now, what if you lowered a cable down towards the event horizon, while simultaneously extending a cable upwards to keep everything balanced out. This is pretty much the standard "space elevator" concept.
Why couldn't you be able to get the bottom end of the lower cable down into the event horizon, and measure the Hawking radiation effects directly? Then, you could pull the cable back out when you were finished the experiment - The end of the cable would then be escaping from the black hole.
I think the only problem (remember, this is a thought experiment) would be making a cable strong enough to withstand the gravitational pull. Would this be fundamentally impossible?
When a star collapses the matter begins to implode upon a point, eventually crossing the point where the escape velocity becomes greater than the speed of light and a black hole is formed. The edge of this black hole is what we call the event horizon - anything passing within the event horizon cannot ever escape. The simple solution is described by the Schwartzchild metric.
The matter however is still collapsing to a point at the centre of the black hole. According to general relativity there is nothing to stop this collapse and we end up with a point of infinite density and zero volume - a singularity.
However when you come to rotating black holes (described by the Kerr metric) there are differences. The angular momentum of a collapsing star is conserved, and this causes the black hole's event horizon to bulge out along the equitorial plane, much like the Earth has a slight bulge around its equator. Indeed, the central singularity itself forms a torus rather than a point when the black hole is rotating.
As angular momentum is increased this bulge gets bigger and the polar size of the event horizon shrinks, until eventually you are left without an event horizon at all, but just a torus-shaped singularity, which is said to be "naked".
Of course, whether a naked singularity can ever exist is an open question. There is something called the "Cosmic Censorship Principle" which states that the laws of physics will never allow a naked singularity to form, but the final answer is "we don't know".
Also of interest is that since the naked singularity would be in the shape of a torus you could theoretically pass through the centre of the torus and find yourself somewhere completely different, possibly even in another universe!
For a fairly technical intro to black holes and singularities, see this article [suite101.com] at suite101.
A joint team of network specialists, consisting of employees from Cisco Systems, Hewlett-Packard, 3Com and others have located an immensive Troll Hole on the Internet, centered directly on the popular weblog Slashdot. While the presences of the hole has long been suspected, today's announcement has confirmed its status as the largest Troll Hole on the Internet.
Experts say the Slashdot Troll Hole has been continually drawing hundreds of trolls to the site for over three years. "It seems to present an incredible attractive force to individuals with an abundance of spare time," explained Michael Czekjum of the Internet Engineering Task Force. "Once drawn, they find themselves compelled to inundate comments with disguised obscene hyperlinks, single-minded knee-jerk insulting replies and vacuous first post attempts."
While today's pinpointing of the hole represents a great triumph, officials stress there is still much to learn. Early analysis seems to suggest it is expanding. Datapoints from Slashdot's founding in late 1997 show an almost complete lack of trolls. Since then, their numbers have expanded at a geometric rate. The types of individuals being attracted is also being studied. "While traditional text-based trolls are still in the majority, the past six months have seen a great increase in graphical trolls, using primitive ASCII representations," wrote Ari T'teyel of Sun Microsystems in a paper published last week. "In addition, the hole's effect on other individuals, such as karma whores, is as yet unknown."
The Troll Hole draws in
Gravity is caused by matter (and energy, but that's usually only in infintesimal amounts - see E=mc^2).. the force of gravity given off by an object is directly proportional to its mass. If we sent an object into a black hole, it couldn't change its gravity (or that of the entire hole) without destroying or creating matter, which is impossible.
I assume your thoughts about ripples are along the lines of having an object split up inside the black hole, so that there would be two little masses instead of one big one.. But outside the event horizon, the black hole acts like a point source of gravity, no matter how split up things were inside. --
I read about this in a newspaper already. Remember those? A newspaper is that thing you have to unfold to read... those things that never used to get their news to me before/. could...
I don't know what to do! I may have to go to ZDNet or do something equally dumb.
[i]However, this leaves a few questions
1) how come more negative (un-, if you wish) than positive particles are attracted?
1.1) how come gravity works the same on unparticles? Shouldn't they be repelled?
2) why does this happen at a faster rate for small black holes (I understand that rate of evaporation is inversely proportional to mass)[/i]
You're taking the particle/un-particle pair too seriously. While that's the conventional explanation, it doesn't quite fit the math. In fact, the math admits of no explanation. It's just mathematics.
Anyway, having looked hard at the math until my head buzzed, I couldn't see how the standard particle/un-particle explanation fit. However, I also couldn't see any 'real world' explanation that fits either.
It's not pulling in the other stars because the stars still have plenty of momentum from the Big Bang. Eventually, that'll change.
It's kinda like how 'constant velocity' actually means 'just enough acceleration to offset drag, gravity, and every other force acting on the body in motion'
That'd be my theory. It's just as valid as any scientist's theory, because when you get right down to it, we're all just guessing.:-)
Well here we are again. Anyways, if you were sucked into a black hole what would happen?
Black holes have immense gravity. As a "matter" of fact the mass of them is so high that the gravity is practically immeasurable. Now, with gravity comes time, as clearly shown in our favorit Einsteinian theory. Yup, the theory of relativity. Now if you all studied and di your homework(did you) then you would know that TIME IS RELATIVE! As a matter of fact time is pretty arbitrary by humans standards, but that is a completely different story.
Anyways, you get sucked into a black hole. Since the gravity IS higher(duh!) then time would slow for you. Things outside would appear to mvoe faster, if there was anything to look at then you would see things going REALLY fast. Since the time is relative you could see the whole universe ending, only because we have not determined how long black holes exist. This poses another question. If the time is slowed down immensely, then black holes must exist long enough so that the universe ends, or the time dialation is not as heavy as theorized and you get sucked in well before the end of the universe. It is also said that you get "stretched" when you go into a black hole because of the difference in gravity between the event horizon and the lip. Well, at a certain point time and space theories as of now are thrown out of the water and well, your fucked. The point of singularity breaks down everything we know about the universe. You would probably also be torn apart atom by atom. The time change would also appear as if you were moving slow to the outside world. This is truly fucked up.
The velocity, or speed of the stars [...] , had been roughly measured, but the UCLA team took it a step further by using the infrared images of three stars to measure their acceleration -- or how fast the stars were speeding up
Thanks for the definitions. It really helped out those of us who have never owned, driven, or ridden in an automobile before!;) --
When the Mars candy company created the Milky Way and Three Musketeers bars, somehow along the way they messed up the packaging. The Milky Way bar was meant to be the bar with a creamy, non-nutty center that eventually became the Three Musketeers bar, and vice-versa. The Milky Way ended up with three main layers (Peanuts, Nougat, and Chocolate). Three layers, Three Musketeers, get it? Yes, I'm sure you do.
Yeah, a life would be in order, but I'm too busy munching down on the Milky Way and filtering the world's Tequila supply with my liver. Oh, well.
Wonder why it's not eating stars yet, the density there should be high enough for some
motion..
For the same reason that the earth hasn't fallen into the sun yet. From a distance, a black hole is just another gravitational body. Any object orbiting that body is safe, provided it stays well away from the event horizon.
A black hole with a mass of more than 2 million suns has been pinpointed at the center of the Milky Way.
.. but if something is the size of more then two million suns, then how exactly is it 'pinpointed?' Wouldn't it make more sense if it was 'two million suns pointed'? Just how big of a pin are you guys using here?!
Assuming that gravity behaves like quantum forces (no sure bet at this time), you could imagine an experiment like those that "detect" quarks without actually separating them from each other.
Assume we can fling massive (order of the black hole itself) objects about at near light speed. No problem:-)
Fling such an object past the black hole at a close distance, and observe the path of the object, plus the gravity waves from it and the black hole.
What I don't know is what current theory would predict about the results of this experiment: would it let you observe the internal structure of the black hole indirectly -- in a sense, would you hear how it rattles, and know what's in the box?
The paradox for me is that the gravitons (again assuming they exist) would travel at the speed of light, and thus not escape the event horizon any better than anything else, but still the existence of the event horizon depends on the effects of the gravitons. Huh?
Once again, the Slashdot moderators have messed up the facts again. As stated (url: http://www.mars.com/facts.asp?op=milkyway [mars.com]) here [mars.com], the center of the MilkyWay is not a black hole.
THE FACTS: The MilkyWay is often consumed into what may be considered a black hole. However, if this were indeed a black hole, the black hole would not appear to gain mass.
For instance, one 40-year-old male who had taken part in the study, funded by the United States Food and Drug Administration [fda.gov]. Where a black hole would compress the matter to a mere geometric point, the black hole referred to in the study actually appeared to expand when the chocolate-malt product was consumed. When enough MilkyWay are regularly consumed, the subject will experience an increased capacity to eat; the capacity increasing with each sitting.
More concerned are the exercise professionals. "Those who consume too much of the product will put personal trainers out of business," suggests Jed Smith, Editor, American Human Body Focus. "People," he adds, "will no longer see a need to keep their bodies fit. Consumers are putting millions of professional trainers at risk of losing their job."
Cynthia Lamon, of the Maximum Performance Association of Athletic trainers (MPAA), has vowed to encourage US Congressional support of the Diet Manipulation Consumption Act (DMCA), currently a bill which was introduced and passed by the House. Pending the approval of the Senate, the President would then be asked for his approval.
The DMCA, if passed, require the millions who consume the MilkyWay chocolate-malt bar to accept the planned licensing agreement displayed on the outside of the packaging. Additionally, if the licensing provisions state so, those who wish to consume the sacred bar will be required to slice the bars only with Mars-KitchenWare utensils. Such sets of tools are alleged to offer technological advantages over traditional fork and knife sets.
The food items will also contain Crafted Structured Starch (CSS) technology, which would make splitting the food fibers impossible without the KitchenWare tools, which are able to unbind the additives which ensure the foods are sanitized.
...oh, great. Even though most Slashdotters are smarter than this, people are probably going to start panicking, if only for a brief time.
The Earth is in no danger whatsoever of being sucked into this black hole. The reason: the black hold has a mass of roughly 26 million suns. That's a finite mass, even if it is of near-infinite density. Expand that into a star with that mass. This star has the same mass as the black hole, and therefore has the same gravitational pull as the black hole. No more, no less.
So then why don't we get sucked into the star? Because gravitational pull is inversely proportional to the square of the distance, not from the surface of an object, but the center of gravity of the object. When the star collapses into the black hole, its center of gravity stays in about the same spot.
What this means is that, once you're further away from the black hole than the radius of the original star, the black hold has no more gravitational pull on you than the original star did. It's when you go inside that radius that the hole's pull gets really strong. So, if our sun were to collapse into a black hole at this very instant (which it can't do, but let's say it does for the sake of argument), we would be in no more danger of falling into the black hole than we were of falling into the sun. We'd be screwed anyway, due to the loss of solar energy and the X-ray bombardment, but we wouldn't fall into the black hole.
This is important, because studies have shown that the solar system is moving further away from the center of the Milky Way, not closer to it. Therefore, the Earth is perfectly safe from this new "threat."
Well, I think they concluded that the radio source is the same as the black hole.
To quote John Kormendy (quoted in the article) "'And the nice thing is they intersect right on top, almost exactly, of this radio source, Sagittarius A, which people have long suspected is a black hole.'"
Re:Almost Infinite, Literally! (Score:1)
I think you mean the whole "Cantorian" rap.
Georg Cantor is the guy who came up with major portions of the theory of infinite sets.
---CONFLICT!!---
Re:-1, Snotty (Score:1)
--
Re:Black hole experiment (Score:1)
I hate to break it to you dude, but Nature cares very deeply about mathematics. This is why she chose to base all of creation on it.
The fact is people didn't invent mathematics, we merely discovered it.
Look at the whole fiasco over the discovery of irrational numbers and "imaginary" numbers.
No one wanted these, they were forced into accepting their existence.
---CONFLICT!!---
Re:It's progress, but it doesn't go far enough (Score:2)
Is it impossible for a solid object to be partly within and partly outside the event horizon? Why?
Damn, I have to get a good book on this stuff.
Torrey Hoffman (Azog)
OH MY GOD! (Score:2)
--
Re:Black Holes (Score:2)
Maybe you were readin this one?
> but how eventually when the expansion halted
Uhm, you DO know that not only is the universe expanding, it is ALSO accelerating !
The rate is called the "Hubble constant" which you can read about it here:
Cheers
Re:Internet Troll Hole Pinpointed at Slashdot.org (Score:1)
Connah
Funny Posts (Score:1)
Re:It's progress, but it doesn't go far enough (Score:2)
--
Re:Now, I'm No Scientist.. (Score:1)
Re:I thought... (Score:1)
Stars are big and hence they have a big gravitational field. What prevents the star from collapsing is basically the heat and light it produces by fusing lighter elements into heavy ones. When the star runs out of available hydrogen to burn it then starts to burn helium and so on up/across the periodic table until it reaches iron which it can't fuse because the released enegy per nucleon is negative.
(non-MS)ie. It don't produce any heat.
The star then begins to collpse. There are various thing that can happen, depending on the mass of the star. If it is big enough, the whole shebang colapses until the core is hyper-compact and reaches the exclusion-principle limit. The outer layers rebound at a fair old fraction of the speed of light (10%???) producing a supernova (I forget which type, IIa???). If it is still above a certain mass, the Chandrasekhar limit IIRC, then it collapses further until the curvature of space around it becomes infinite (as per Gen'l Relativity).
Voilà. Black hole. (All corections welcome:-)
Elgon
Re:Detecting black holes (Score:1)
Gravitational lensing has never been and will never be used to detect the presence of a black hole.
The reason? It's not that gravitational lensing does not exist, or even that it's not dramatic enough to detect. The reason is that no black hole is close enough for us to use parallax to know the true positions of stars behind it. The way gravitational lensing works is by being able to detect when stars are out of place (not where they should be) due to their light being bent by a super-massive black hole. We would never know where these background stars should be so we can never figure out if they have moved.
So you just demonstrated how horribly uniformed on the tremendous size of the universe you are, and how that results in us not being able to use gravitational lensing to detect black holes.
Re:OH MY GOD! (Score:1)
Oh, don't worry about that either. As the sun revs up over the next billion years, all of the water on Earth will evaporate and we'll all die of dehydration.
T. M. Pederson
"...and so the moral of the story is: Always Make Backups."
Re:Heh (Score:2)
of course, the above numbers are upper limits on the radius; a BH can always be *smaller* than the Swarzschild radius, but never larger.
Re:Star suckers (Score:1)
We can stop the destruction (Score:1)
As an aside, do things in the northern hemisphere of the universe flush one way down a black hole, while in the southern hemisphere, they flush the other?
--
Re:Now, I'm No Scientist.. (Score:1)
For those that haven't read it, Stephen Hawking's "A Brief History of Time" is an excellent book that covers black holes.
--------------------------------------------
Re:size? (Score:2)
Re:English as a language (Score:1)
Re:Galaxy runs linux! SHOCK HORROR (Score:1)
cat center.galaxy.txt >
but even that wouldn't do what you wanted, because center.galaxy.txt would still exist, and doing
cat
wouldn't be the same either, because then it's the black hole going into the galaxy, not the other way around.
I think what you're looking for is
alias 'blackhole=rm -rf'
blackhole center.galaxy.txt
Re:Heh (Score:1)
Re:Detecting black holes (Score:2)
Positive particle do get sucked in just as often as the negative ones. The difference is that normal matter loses potential energy when falling, whereas "negative matter" gains energy as it falls. This is the magic that allows the remaining particle to become "real"... Sounds a little fuzzy, I admit.Fair question. I don't know.The smaller the hole is, the greater the tidal forces at the event horizon. Stronger tidal forces mean that pair of virtual particles is more likely to be ripped apart, just like you'd be ripped apart if you got near the event horizon of small black hole.
Re:Stupid moderators! (Score:2)
Does anyone know what the term for a particle with negative energy actually is?
Oh my golly gee. Whitey's at it again. (Score:1)
Re:centrifugal force (was - Re:Not to be pedantic) (Score:1)
After her body came to rest against the window and the door, she was experiencing centripital acceleration in the literal sense. (Although the car is not a string, and she is not a yo-yo (I dont know her), the factors are the same. The car is keeping her on the arc of a circle.)
Oh man, if that's true (Score:1)
Re:Are we really this dumb? (Score:1)
Have no sense.
You tried to be funny with this?
Re:Are we really this dumb? (Score:1)
And jerk (a parameter I've only seen referred to once) is the derivative over time of acceleration
Re:Time Dialation (Score:1)
Re:Stupid people! (Score:2)
Okay, first off, it's not a matter of chance. Something is real, or it isn't. The theory is either real to the world in this respect or it isn't. There is no way to measure what the "chances" are that it's correct, and as we all know, if you can't measure it, it's not science.
And a theory can be completely and totally correct in every respect except one, and still be wrong.
Also, note that I don't thing it's incorrect here, I just don't see how you can get the particle/unparticle explanation from the math of it. Seems like that's a made up explanation for mass comsumption.
---
Black Hole Sued For Copyright Infringement (Score:3)
It's progress, but it doesn't go far enough (Score:1)
These are the things we still don't know, and I'm afraid we'll never know them within my lifetime.
Re:2.6 million stars in that space? try 10x that! (Score:1)
If (by the greatest of all possible spaces) you are using the min distance Mars-Sun as the diameter of a sphere of space, you can use 4/3*pi*r^3 to get a V of 4.62*10^24 km^3. Sol's V is 1.412*10^18. You can only fit 3.3 million suns in there.
If you just take the linear distance, you can only fit 308 suns in there.
Either way, that is a shit-load of suns in a relatively small space (compared to the normal distance between suns).
Re:2.6 million stars in that space? try 10x that! (Score:1)
Huh? (Score:2)
Re:We knew the black hole was there.. (Score:2)
First it was the flouride in the water, then it was the ozone layer, currently it's like "oh no, we'll all be killed by the Asteroid!". Next big thing will be "We're all going to be swallowed up by the black hole!".
Re:2.6 million stars in that space? try 10x that! (Score:1)
At least i know i was not alone in my mistake...this time. ;-)
Re:Great Barrier (Score:2)
Kierthos
Re:Detecting black holes (Score:2)
Actually, I have one other quibble with your explanation: the virtual particle pairs are not particle/anti-particle pairs. They're more like particle/unparticle pairs. Anti-matter just has a negative charge (relative to normal matter); the stuff that we're talking about actually has negative energy. The difference is that when particles and anti-particles annihilate, they leave a huge amount of energy, whereas when a virtual particle pair annihilates, it leaves absolutely nothing. 1 + (-1) = 0
At least, that's the way I heard it.
Oh, Yeah! (Score:2)
2.6 million stars in that space? try 10x that! (Score:5)
That shouldn't be at all shocking. Even if we take the minimum orbital distance of Mars (~206.7e6 kms), you can fit the equivalent of 26,193,511 Sol volumes within that space. (given the radius of Sol to be 6.96e5 kms)
So, even NOT counting on compression from the incredible amount of mass, you could fit 26 million stars the mass of the sun into the "relatively tiny space".
Given that the numbers match so closely, except for the decimal place, i suspect one of two things:
1) The article writer is amazed you can fit the volume of a marble into the volume of a basketball.
or
2) The article writer put the decimal in the wrong spot, and discovered you can put volume "V" into the space of volume "V"
Re:Huh? (Score:2)
Is that really nougat in a Three Musketeers? I thought nougat was stickier... gooier... and tan. Three Musketeers seems to have kind of a nougat foam in the middle. Weird.
Re:Are we really this dumb? (Score:1)
Re:actually.. (Score:1)
Being a Brit living abroad I was delighted to find that America had Milky Ways and Mars Bars. I was less than delighted to find out they were not the same as the British originals. Same name different product
Re:size? (Score:3)
But neither black hole can hold a candle to the hole at the center of M87, the giant elliptical galaxy at the center of the Virgo cluster. This titan weighs in at several billion suns, and emits relativistic jets of matter from its poles.
Astronomers are very close to demonstrating that the phonemenon known as quasars, are nothing more than an active black hole, swallowing matter at a prodiguous rate in young galaxies that have undergone a burst of star formation. Our galaxy is likely to have shown quasar properties in times past. But as the concentration of matter near the center of a galaxy decreases as it is consumed by the black hole, the quasars turn off.
Astronomers are also gaining new insights into the role of central black holes in the formation of galaxies. It appears that the galaxy and the hole evolved together - the hole provides the gravitational anchor, pulling in nearby gas clouds, which collapse to form stars. We may have never come to exist were it not for the galaxy-forming propensity of massive black holes.
The Next Generation Space Telescope is expected to answer these questions one way or another. It is hoped that it will be able to image very young galaxies in the process of formation, or perhaps even find evidence of naked black holes just beginning to draw in the surrounding primordial gas. That would be quite a find, since it would imply that the black holes came first, and raises the question: from what? Were the created somehow in the maelstrom of the Big Bang, or was there a very early era of star formation that preceeded the era of galaxy formation?
Composition of Black Hole is really... (Score:1)
It's all true! ±5%
Re:Detecting black holes (Score:5)
"The theory goes (extremely roughly) that as individual particles reach the "edge" (event horizon?) of the black hole (crossing this line means you never come back), some of them are torn apart, half of the particle going in, half going out, and some energy is released during this fission"
Sorry, but that's a little too rough. Particles are not ripped in two. Rather, at the event horizon, just like everywhere else, virtual particle/antiparticle pairs are constantly being formed and annihiliated as allowed by the uncertainty principle (they don't last long enough to be detectable, so they don't violate any conservation laws). However, being at the event horizon, some of these pairs get formed, and then one of the two particles gets trapped by the black hole, and its partner does not annihilate undetectably quickly, but rather sticks around long enough to collide with other matter or decay or both, thus producing Hawking radiation.
Now someone can correct my rough explanation and eventually we'll get this straight...
Your speedometer doesn't measure velocity (Score:2)
Re:It's progress, but it doesn't go far enough (Score:2)
We knew the black hole was there.. (Score:2)
If you read the article you would note that we pinpointed it's location in the milky way
Read the article, then post.
[phpwebhosting.com]
nerdfarm.org
Re:Are we really this dumb? (Score:3)
Here's a test: On a *snap* basis, figure out what the difference is between acceleration and speed.
Most people won't think about the difference, as most folks think speed=acceleration.
Try it out - go around and ask 5 average folks (you may have a few around) what 'acceleration' means... betcha they all say 'how fast something is going'.
Detecting black holes (Score:4)
That type of radiation is called Hawking Radiation (after Stephen Hawking, naturally). However, this isn't what lets us detect black holes, as Hawking Radiation is ridiculously faint. Black holes can be detected by the X-Rays that they "inadvertantly" produce. When matter is falling into a black hole it is accelerated, heated, and compressed to such a degree that it gives off large amounts of X-Rays. I believe the first black hole we detected (again, assuming black holes exist), was Cygnus X-1 (or cygnus something), and we detected it by the x-rays it gave off.
Another method of detecting black holes is to look for graviational lensing effects. Because black holes are so massive, they bend the fabric of space time. (Imagine a sheet suspended in the air. Place marbles on the sheet. The marbles make depressions on the sheet, like stars make "depressions" in space-time. A black hole is so heavy, it's like dropping something that is the size of a marble but with the weight of a bowling ball onto the sheet. The sheet bends A LOT, and it actually will have a hole where the singularity is.) Light travels in a straight line, so if space-time curves, light also curves with space-time. Gravitational lensing was proved during a solar eclipse. Astronomers observing the eclipse noted that they were able to see stars that should have been blocked by the eclipsed sun. The sun's gravitational field caused enough "lensing" so that stars directly behind the star could be seen to either side of the star. So, if we find something out in space that is causing a LARGE amount of gravitational lensing, but we can't see anything, there's a chance it's a black hole. At that point we normally observe it more to determine if it is or isn't a black hole.
Star suckers (Score:2)
Even if it's not pulling in other stars yet, I'll bet it'l suck the fillings out of my great,great,great,great,great,great,great,great,g
Wonder why it's not eating stars yet, the density there should be high enough for some motion..
Re:2.6 million stars in that space? try 10x that! (Score:4)
Given that the numbers match so closely, except for the decimal place, i suspect one of two things:
1) The article writer is amazed you can fit the volume of a marble into the volume of a basketball.
or
2) The article writer put the decimal in the wrong spot, and discovered you can put volume "V" into the space of volume "V"
I vote for option 3), 4), or a combination of the two:
3) The amount of space is "tiny" compared to the amount of space taken up by stars in the rest of the galaxy. Stars are seldom packed one against the other.
4) The writer is using copy from descriptions of smaller black holes. The even horizon's radius grows in linear proportion to a black hole's mass, if I remember correctly.
This means that volume grows far faster than mass. Black holes with the mass of a mountain are smaller than an atom; a black hole the mass of the sun have a radius of about 3 km. More massive black holes, however, have less density. In fact, if the universe is closed (i.e. returning to a "Big Crunch"), it would be the perfect example of a very sparse black hole - transplant a sufficiently large chunk of it to a reasonably flat space, and an observer outside of the transplanted chunk would see an event horizon surrounding it.
Re:OH MY GOD! (Score:2)
--
Proof positive (Score:2)
"This galaxy really does suck."
centrifugal force (was - Re:Not to be pedantic) (Score:2)
'Centrifugal force' is a force defined from a non-Newtonian reference frame, and as such, is not a true force. A force can only be defined from within a Newtonian reference frame, so your implication that she is incorrect is correct. (Does that make sense?)
What your wife is actually feeling (aside from the bump) is her linear inertia taking her in a straight line while the car turns away from that line. So, she bumps into the window.
When she asks you what she is feeling ("I'm feeling something, so what is it, Mr. Smary-Pants?"), you can tell her that what people typically call 'centrifugal force' is actually the other side of 'centripetal force'. Centripetal force is the tension in the string when you swing a Yo-Yo over your head; centripetal force keeps an object traveling in a circle.
Try this, Newton's first law of motion says that it takes force to move something or change it's straight line motion at constant speed (in Newton's world being at rest and traveling with a constant velocity are the same thing, the first glimpse of relativity), and you are traveling in your car in a straight line, with constant speed. You turn the wheel and the car starts turning, which means that acceleration is being applied to the car to change it's velocity. This acceleration is called centripetal acceleration.
In conclusion, there is no centrifugal force, although it appears to be a force, but it is measured from the wrong reference.
Louis Wu
"Where do you want to go ...
Re:Now, I'm No Scientist.. (Score:2)
So it would be more likely that the Earth would get "eaten" by that cubic inch. Then again, if that chunk of black hole is too small to maintain its integrity, it may just evaporate violently and blow everything in the immediately spacial environment to plasma...
Windows on the event horizon (Score:2)
Take a Windows 2000 server, link it up by some radio connection, and place it near the event horizon of a black hole.
The effect of time dialation would decrease the MTBF dramatically, with only a minor change in processing speed (slow down a Windoze server by a factor of 1E9 and I doubt anyone would notice).
[Unfortunately, there would still need to be a sysAdmin sleeping next to the server to handle the occaisional (every 10,000 years) crash, but then again, that's probably the best use of someone with an MCSE anyway.]
This dramatic improvement in reliability could be a "hole" new marketing angle for MS. Maybe we could put the entire
Re:It's progress, but it doesn't go far enough (Score:2)
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That's nothing (Score:2)
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Re:Now, I'm No Scientist.. (Score:2)
Re:Detecting black holes (Score:2)
Re:I thought... (Score:2)
not too relevant in this case (Score:2)
Re:Probing the inside of a black hole? (Score:2)
Re:It's progress, but it doesn't go far enough (Score:2)
Personally I think there's a lot of evidence that ignoring quantum effects is wrong. There is a lot of evidence that interesting quantum effects take place at the event horizon so that the laws of physics we currently have break down well before the singularity. Connecting quantum mechanics and general relativity is the biggest challenge facing theoretical physics right now but I home we see some glimmer of understanding within your lifetime!
--Re:centrifugal force (was - Re:Not to be pedantic) (Score:2)
If you're really Louis Wu, why don't you use the puppeteer hyperdrive to have a look at the galactic core like Beowulf Schaeffer did, instead of reading Slashdot?
All I gotta say... (Score:2)
Re:Probing the inside of a black hole? (Score:2)
Re:Detecting black holes (Score:2)
For the ones interested, the uncertainty principle variant for this situation is:
dE * dt >= h-bar,
where
dE = the pair's energy, meaning the amount of energy that is "borrowed" from vacuum in order to create it
dt = the amount of time the pair lives
h-bar = Planck's constant divided by 2*pi
Flavio
Re:It's progress, but it doesn't go far enough (Score:2)
Re:Saving the species. (Score:2)
Devil Ducky
Schwarzchild Radius (Score:2)
size? (Score:3)
Re:Huh? (Score:2)
A Snickers is peanuts & caramel wrapped in chocolate. It used to be called a Marathon in the UK until the early 90s.
A Milky Way in the UK (and Australia) is just that fluffy stuff wrapped in chocolate. In the USA, a Milky Way also has a layer of caramel over the fluffy stuff. NO peanuts.
I have this on good authority, as an Englishman working in the states - I just asked the guys in the office.
Re: Now, I'm No Scientist.. (Score:3)
--weenie NT4 user: bite me!
Re:It's progress, but it doesn't go far enough (Score:2)
Of course you can't make a clean split between gauge theory and string theory and you can quantise strings as a gauge theory.
--Are we really this dumb? (Score:2)
"images of three stars to measure their acceleration -- or how fast the stars were speeding up--" [emphasis mine]
Was it really necessary to define acceleration? Are people in general really this illiterate?
Zipwow
Re:It's progress, but it doesn't go far enough (Score:2)
Suppose you had a platform or spaceship or something orbiting a small black hole, just above the event horizon. Now, that platform would be moving at just under light speed, but so what.
Now, what if you lowered a cable down towards the event horizon, while simultaneously extending a cable upwards to keep everything balanced out. This is pretty much the standard "space elevator" concept.
Why couldn't you be able to get the bottom end of the lower cable down into the event horizon, and measure the Hawking radiation effects directly? Then, you could pull the cable back out when you were finished the experiment - The end of the cable would then be escaping from the black hole.
I think the only problem (remember, this is a thought experiment) would be making a cable strong enough to withstand the gravitational pull. Would this be fundamentally impossible?
Torrey Hoffman (Azog)
Re:Are we really this dumb? (Score:2)
Re:Black Holes (Score:2)
When a star collapses the matter begins to implode upon a point, eventually crossing the point where the escape velocity becomes greater than the speed of light and a black hole is formed. The edge of this black hole is what we call the event horizon - anything passing within the event horizon cannot ever escape. The simple solution is described by the Schwartzchild metric.
The matter however is still collapsing to a point at the centre of the black hole. According to general relativity there is nothing to stop this collapse and we end up with a point of infinite density and zero volume - a singularity.
However when you come to rotating black holes (described by the Kerr metric) there are differences. The angular momentum of a collapsing star is conserved, and this causes the black hole's event horizon to bulge out along the equitorial plane, much like the Earth has a slight bulge around its equator. Indeed, the central singularity itself forms a torus rather than a point when the black hole is rotating.
As angular momentum is increased this bulge gets bigger and the polar size of the event horizon shrinks, until eventually you are left without an event horizon at all, but just a torus-shaped singularity, which is said to be "naked".
Of course, whether a naked singularity can ever exist is an open question. There is something called the "Cosmic Censorship Principle" which states that the laws of physics will never allow a naked singularity to form, but the final answer is "we don't know".
Also of interest is that since the naked singularity would be in the shape of a torus you could theoretically pass through the centre of the torus and find yourself somewhere completely different, possibly even in another universe!
For a fairly technical intro to black holes and singularities, see this article [suite101.com] at suite101.
Internet Troll Hole Pinpointed at Slashdot.org (Score:5)
Experts say the Slashdot Troll Hole has been continually drawing hundreds of trolls to the site for over three years. "It seems to present an incredible attractive force to individuals with an abundance of spare time," explained Michael Czekjum of the Internet Engineering Task Force. "Once drawn, they find themselves compelled to inundate comments with disguised obscene hyperlinks, single-minded knee-jerk insulting replies and vacuous first post attempts."
While today's pinpointing of the hole represents a great triumph, officials stress there is still much to learn. Early analysis seems to suggest it is expanding. Datapoints from Slashdot's founding in late 1997 show an almost complete lack of trolls. Since then, their numbers have expanded at a geometric rate. The types of individuals being attracted is also being studied. "While traditional text-based trolls are still in the majority, the past six months have seen a great increase in graphical trolls, using primitive ASCII representations," wrote Ari T'teyel of Sun Microsystems in a paper published last week. "In addition, the hole's effect on other individuals, such as karma whores, is as yet unknown."
The Troll Hole draws in
Re:Probing the inside of a black hole? (Score:2)
I assume your thoughts about ripples are along the lines of having an object split up inside the black hole, so that there would be two little masses instead of one big one.. But outside the event horizon, the black hole acts like a point source of gravity, no matter how split up things were inside.
--
I'm Upset (Score:2)
I don't know what to do! I may have to go to ZDNet or do something equally dumb.
Devil Ducky
Precise definition of Hawking radiation (Score:2)
Re:Detecting black holes (Score:3)
1) how come more negative (un-, if you wish) than positive particles are attracted?
1.1) how come gravity works the same on unparticles? Shouldn't they be repelled?
2) why does this happen at a faster rate for small black holes (I understand that rate of evaporation is inversely proportional to mass)[/i]
You're taking the particle/un-particle pair too seriously. While that's the conventional explanation, it doesn't quite fit the math. In fact, the math admits of no explanation. It's just mathematics.
Anyway, having looked hard at the math until my head buzzed, I couldn't see how the standard particle/un-particle explanation fit. However, I also couldn't see any 'real world' explanation that fits either.
Virtual particles are tricky bastards.
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Re:Why does Kormendy say, (Score:2)
Time Dialation (Score:2)
-1, Snotty (Score:2)
Thanks for the definitions. It really helped out those of us who have never owned, driven, or ridden in an automobile before!
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actually.. (Score:5)
scientists have triangulated it's ooey gooey goodness using several rats and a nougascope.
FluX
After 16 years, MTV has finally completed its deevolution into the shiny things network
Re:actually.. (Score:2)
Actually...
When the Mars candy company created the Milky Way and Three Musketeers bars, somehow along the way they messed up the packaging. The Milky Way bar was meant to be the bar with a creamy, non-nutty center that eventually became the Three Musketeers bar, and vice-versa. The Milky Way ended up with three main layers (Peanuts, Nougat, and Chocolate). Three layers, Three Musketeers, get it? Yes, I'm sure you do.
Yeah, a life would be in order, but I'm too busy munching down on the Milky Way and filtering the world's Tequila supply with my liver. Oh, well.
Re:Star suckers (Score:2)
Now, I'm No Scientist.. (Score:3)
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CitizenC
Re:Probing the inside of a black hole? (Score:2)
Assume we can fling massive (order of the black hole itself) objects about at near light speed. No problem
Fling such an object past the black hole at a close distance, and observe the path of the object, plus the gravity waves from it and the black hole.
What I don't know is what current theory would predict about the results of this experiment: would it let you observe the internal structure of the black hole indirectly -- in a sense, would you hear how it rattles, and know what's in the box?
The paradox for me is that the gravitons (again assuming they exist) would travel at the speed of light, and thus not escape the event horizon any better than anything else, but still the existence of the event horizon depends on the effects of the gravitons. Huh?
So, what would this experiment do?
Error in original post! (Score:2)
Once again, the Slashdot moderators have messed up the facts again. As stated (url: http://www.mars.com/facts.asp?op=milkyway [mars.com]) here [mars.com], the center of the MilkyWay is not a black hole.
THE FACTS: The MilkyWay is often consumed into what may be considered a black hole. However, if this were indeed a black hole, the black hole would not appear to gain mass.
For instance, one 40-year-old male who had taken part in the study, funded by the United States Food and Drug Administration [fda.gov]. Where a black hole would compress the matter to a mere geometric point, the black hole referred to in the study actually appeared to expand when the chocolate-malt product was consumed. When enough MilkyWay are regularly consumed, the subject will experience an increased capacity to eat; the capacity increasing with each sitting.
More concerned are the exercise professionals. "Those who consume too much of the product will put personal trainers out of business," suggests Jed Smith, Editor, American Human Body Focus. "People," he adds, "will no longer see a need to keep their bodies fit. Consumers are putting millions of professional trainers at risk of losing their job."
Cynthia Lamon, of the Maximum Performance Association of Athletic trainers (MPAA), has vowed to encourage US Congressional support of the Diet Manipulation Consumption Act (DMCA), currently a bill which was introduced and passed by the House. Pending the approval of the Senate, the President would then be asked for his approval.
The DMCA, if passed, require the millions who consume the MilkyWay chocolate-malt bar to accept the planned licensing agreement displayed on the outside of the packaging. Additionally, if the licensing provisions state so, those who wish to consume the sacred bar will be required to slice the bars only with Mars-KitchenWare utensils. Such sets of tools are alleged to offer technological advantages over traditional fork and knife sets.
The food items will also contain Crafted Structured Starch (CSS) technology, which would make splitting the food fibers impossible without the KitchenWare tools, which are able to unbind the additives which ensure the foods are sanitized.
Re:Not to be pedantic. . . (Score:4)
Of course, if I did that less often she might be able to think more clearly about classical mechanics...
Before panic sets in... (Score:2)
The Earth is in no danger whatsoever of being sucked into this black hole. The reason: the black hold has a mass of roughly 26 million suns. That's a finite mass, even if it is of near-infinite density. Expand that into a star with that mass. This star has the same mass as the black hole, and therefore has the same gravitational pull as the black hole. No more, no less.
So then why don't we get sucked into the star? Because gravitational pull is inversely proportional to the square of the distance, not from the surface of an object, but the center of gravity of the object. When the star collapses into the black hole, its center of gravity stays in about the same spot.
What this means is that, once you're further away from the black hole than the radius of the original star, the black hold has no more gravitational pull on you than the original star did. It's when you go inside that radius that the hole's pull gets really strong. So, if our sun were to collapse into a black hole at this very instant (which it can't do, but let's say it does for the sake of argument), we would be in no more danger of falling into the black hole than we were of falling into the sun. We'd be screwed anyway, due to the loss of solar energy and the X-ray bombardment, but we wouldn't fall into the black hole.
This is important, because studies have shown that the solar system is moving further away from the center of the Milky Way, not closer to it. Therefore, the Earth is perfectly safe from this new "threat."
IANAP - I Am Not A Physicist.
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well... (Score:2)
Re:We knew the black hole was there.. (Score:2)
Well, I think they concluded that the radio source is the same as the black hole.
To quote John Kormendy (quoted in the article) "'And the nice thing is they intersect right on top, almost exactly, of this radio source, Sagittarius A, which people have long suspected is a black hole.'"