View Full Version : Black Holes
In what I expect will be a useless attempt to get people to stop bothering me about black holes, I would like to explain a bit about forces, black holes, and CERN.
*Gravity is a very weak force. You might not have realized this because the common conception is that gravity is a "law of nature we can't break"; you can't fly off the Earth, thus gravity is super duper strong. Well, this is not really true. I will quote a number for you, and then give a real life example. There are four (depending on how you count) basic types of forces that we know about. Gravity is the weakest. Another commonly know force is the electromagnetic force (electricity from the wall, magnetism from a magnet, etc). The electromagnetic force is 10^39 times stronger than gravity. That's the same ratio as the mass of the sun to the mass of 1 grain of salt.
"Bah, numbers!" you say. "Who cares about them!" Well consider this: There's probably a book within reach of you right now. Try to pick up the book. Did it work? Do you realize you just overcame the gravitation force of *the entire earth* with just a small bit of electromagnetic force (you probably can't even tell that your hands have electric charge at all). Gravity is very very weak. It only seems strong because you can lump a bunch of mass together a lot easier than you can lump a bunch of charge together.
*The gravitation (=force of gravity from a specific object) of an object is not affected by its shape. Think of the sun. It's a big sphere of some size. If we imagine shrinking the sun down to half its size, then the force on the earth from the sun would be exactly the same. If we expanded the sun to be twice as large, the force on the earth from the sun would be exactly the same. If somehow (and it's impossible as far as we know) the sun suddenly became a black hole, the force on the earth from the black hole sun (hehe) would be exactly the same.
Likewise, the gravitation of two protons on the rest of the earth is quite small. It doesn't matter how much you squish them together. In fact, if you packed those protons so tightly that they became a black hole, you could hold that black hole in your hand, since the gravitation <<< electromagnetic repulsion.
*Black holes have a certain density. That is, a certain amount of mass per volume. You can equally think of this as a certain energy per volume (e=mcc). The reason some people claim black holes will be formed at CERN is because we are smashing a lot of energy into a small space. (Even though the science does not support the conclusion of creating the black holes). However, with what you have just learned, you should feel safe in knowing that even if such a black hole were to be created, it could make no trouble. In fact, it would just evaporate in less than a second.
Rest easy,
Z
But... but... the anti-matter! Dan Browne proved it!
Kidding, thanks for the info, interesting, I didn't know that.
That was very interesting. I'm assuming you work on the Collider which some newspapers (Ie- the Daily Mail) would have us believe is going to end the world.
Interesting that you have time to play Eq though, reminds me of a Frankie Boyle comedy sketch.... "Cure cancer? Auch no... I want to see how many fruit pastels it takes to choke a Kestrel"
:D
Genadine
06-01-2010, 00:39
So, why does light get pulled into a Black hole? I was under the impression that light being an electromagnetic wave would be able to run away but the very thing 'black' hole is or was thinking because light cannot escape from it.
Genuine question btw if you can explain it to me would be cool.
G
The gravitational field of a black hole (hence the reason its black) is so strong it can capture light waves. Due to wave-particle duality, even electromagnetic waves have, at least a theoretical, mass. If something has sufficent gravitational field to attract even light it is by definition a black hole. Therefore to have that amount of gravitational force, it requires a large mass. Hence the impossiblity of a black hole on the scale of 2 protons.
I understand it this way.
The real dangerous black holes have the gravity field of several suns.
So when you shrink our sun to the size of a tomato it still would have the same gravity field and would do nothing to us regarding the gravity. It is just hard to see, the tomato I mean. So something could fly into the gravity field of the tomato and will be trapped there.
The huge black holes (not huge in size, they can also be a tomato) are the result of many, many, many shrunken suns. More and more stars fall into this trap and squeeze more and more. So in the end you have a tomato with the force of 10000000 of suns and those swallow all light, other planets and things that come to close to the Event Horizon.
So to create something so dangerous that it would destroy our earth you would have to collect several suns and make a tomato out of them.
Correct?
We're all dooooomed ! :grimmrun:
You should work at CERN Jolene
But i still wanna cyber you about your job.. it is the only fun I have since Rigs retired :(
So, why does light get pulled into a Black hole? I was under the impression that light being an electromagnetic wave would be able to run away but the very thing 'black' hole is or was thinking because light cannot escape from it.
Genuine question btw if you can explain it to me would be cool.
G
It is indeed a good question, and confused many physicists for years. Photons have no mass. How can they possibly experience a force from a black hole then!! Isaac Newton, who came up with the first theory of gravity, explained gravity as a force like any other. Force = Mass of object / (distance from object)^2 . According to this theory of gravity, light could escape no matter how great the mass of a black hole.
However, Einstein (a smart guy) refined the theory of gravity with what is now called the General Theory of Relativity. In his theory, the force of gravity is a geometrical force. (The math here is really complicated so I have to make some bad analogies). You can think of it like this, take a sheet with stripes. The stripes are the paths that a photon would follow (straight lines). Now drop a large weight onto the sheet. It will deform the sheet.
Now if you look at the lines, it appears that they bend toward the mass. This is the geometrical nature of the force. Mass warps "spacetime" and that forces the straight line paths of photons (these are called geodesics for anyone wanting to study more math!) to bend toward the mass.
Now if you drop a bunch of large masses onto the sheet, they will all end up in the same area (if they are close enough together). If they are heavy enough, they will rip through the sheet. The mathematical term for this is called a "singularity" and it is a point of infinite bending of the "spacetime" sheet. That is a blackhole. All the stripes on the sheet entering the "black hole" get stuck there because of the rip in the sheet. They have no path to follow back out.
As I said, it's a bad analogy. You can prove from the math that you need to travel faster than the speed to escape, but I was never good at General Relativity and so I cannot remember how to prove this at the moment :>(
The gravitational field of a black hole (hence the reason its black) is so strong it can capture light waves. Due to wave-particle duality, even electromagnetic waves have, at least a theoretical, mass.
Momentum, not mass! :grimmrun:
I understand it this way.
.....
Correct?
Absolutely correct. I also like the bit about the tomatoes.
My tomato example ))
The "Raumzeitkrümmung" "Spacetime bending" is like you put many tomatos on a blanket and they make a dent into the blanket, when you imagine billions of billions of billions tomatos on the blanket (universe) you come to the conclusion that the whole universe has to be round.
A wormhole also called the Einstein-Rosen-Brücke is also some kind of spacetime bending.
You could (COULD) travel from one spot to another one that is million of lighttravel years away in no time. It bends the universe, the squeezed tomatoes aka black holes do the same. They bend the spacetime and everything is falling into it towards the middle, so light also will not go straight anymore it will follow the bending towards the squeezed tomatoes (now called ketchup)
Ah yes and what Zorland means is what Hawkins said ?? That the flee space has to be faster than light and since nothing is faster than light nothing can flee also not the light. And the gravity is unmeasuerable big, and my tomatoe isn't existing anymore, there is no mass anymore, it is so small that it doesn't exist. The space is bended towards 0.
As I said, it's a bad analogy. You can prove from the math that you need to travel faster than the speed to escape, but I was never good at General Relativity and so I cannot remember how to prove this at the moment :>(
I'll let you know after we get next selo upgrade.
Momentum, not mass! :grimmrun:
Surely if they have momentum p = mv implies a theoretical mass
(no symbol font on here so had to use p)
P=Mv is a large object approximation. The photon momentum is derived from another one of Einstein's equations...
E^2 = (pc)^2 + (mc^2)^2
In the case of a photon (m=0) this reduces to
E=pc
It's pretty crazy, I admit, to think of something with non-zero momentum yet zero mass.
What I said none existent ketchup p ))
Genadine
06-01-2010, 18:30
How can something exist if it has no mass?
Everything must be made up of something else?
Or is there multiple items that simply 'exist' and we have no clue atm how to prove them?
How can something exist if it has no mass?
Everything must be made up of something else?
Or is there multiple items that simply 'exist' and we have no clue atm how to prove them?
This is a very good question. Why do some particles have mass and yet others don't? In the current theory of particle physics (the standard model) it is the Higgs Field (which is two words for a lot of fancy math). Are we certain this is the way it works? No! We have yet to see the Higgs boson, which is usually just refered to as the higgs. Where might we see the higgs? We hope in our detectors at the LHC. The higgs search is one of the most interesting parts of the research going on at CERN.
Mephistopheles
07-01-2010, 15:22
Geek Alarm ;)
http://img98.imageshack.us/img98/6382/20071128geek.jpg
:sadolf: Hello I am a Higgs, they all search for me but hahahaha I have my methods to hide !!!!!
Geek Alarm ;)
Well in that case...
Heisenberg is speeding down the road, and a cop pulls him over. The cop says "Sir, do you have any idea how fast you were going?" Heisenberg says "No, but I know exactly where I am."
LOL or the question could be, I know how fast I was but I have no idea where I am.
Well that is something that made Einstein uses his famous words. God don't play a dice.
But he does !!!
Grynoldy
30-07-2010, 14:35
This is the accelerator Zorland is working on now!!! :grimmrun:
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Quorthon
01-08-2010, 00:46
I (and (directly or indirectly) my taxes) are so glad we're fannying around with stuff like this instead of spending time worrying about stuff like war, famine , disease, poverty and death in the world.
I mean come on,
Time travel-
If it were to become possible in the future, what's the first thing you'll do?
You'd pop back to 2010 and wtfpwn this board and 10 gazillion like them with 2nd year students and their "theories" about inside-out toilet roll tubes and such like pish.
I'd also go back to the 1982 and put every bloody penny I had on Grittar to win the national at (initial) sp of 66/1.Or last weeks lottery numbers.
You'd certainly wouldn't (I'd hope) sit on your arse and laugh as X million people die to massive disaster XYZ that could plausibly be avoided with a bit of forewarning.
Co-existence, parrallel universes etc-
Just like when you were 9 and flicked straight to the "shower" section of the Freemans catalogue, first thing you'd do would transmorgify into the bathroom of that ginger lass from Dr.Who's bathroom/bedroom for a wee sneaky look.
probably.
Joking and flippancy aside, there surely is more important things in 2010 to fret about that wee bits of stuff shooting around a glorified scalectrix track.
Isn't there?
Renewable power sources, drought resistant crops, "cures" for cancer and HIV would figure significantly higher on my list to start with, and I'd view "scientific boffin's" time best spent in this direction.
/peace, waves and no apologies for spelling/logic/sense mistakes as just back from pub :)
Q
And since no one came back and owned this board and no one came back to win the lottery, or to stop a war, or to save the icebears, it never will be possible. Very easy. If it would ever be possible, we would have some kind of tourism already. But we don't.
Klorch Bashlight
01-08-2010, 01:37
Ahhh time travel.
Thank you Mr Q for bringing that on.
To back up that Lady over there with the lovely hairstyle, I'd mumble the names of those sci fi authors who imagined the concept of the Watchers : invisible time travelers who cannot interact with their surrounding.
Surely you heard about the tremendous amount of sci fi novels and movies which tried to toy with the quite confusing time travelling concept.
Besides, if time travelling was possible, I would have travelled back in 1990 and tell a certain Lady to go to hell.
But that's another story.
Cheers,
Klorchy
The people at Cern obviously do NOT have a clue what they are doing. If they did the Cern project whould allready be an sucess.
"The prostitute rest"
Fingalf.
Mephistopheles
02-08-2010, 12:10
Haha, good one Q.
Truth be told tho, even if the money wasn't wasted (depends how you look at it i guess) it would probably go to some other random_huge_money_eating_useless_project_#32424 or to some private accounts
This is a very good question. Why do some particles have mass and yet others don't? In the current theory of particle physics (the standard model) it is the Higgs Field (which is two words for a lot of fancy math). Are we certain this is the way it works? No! We have yet to see the Higgs boson, which is usually just refered to as the higgs. Where might we see the higgs? We hope in our detectors at the LHC. The higgs search is one of the most interesting parts of the research going on at CERN.
Energy has no mass, yet it exists! It's mass in another form.
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