# Please answer My Many New Bee questions on a Black hole.

1. Jan 14, 2009

### wannaknow4995

What is a Black Hole? Does it suck even energy? When a black hole sucks something, what happens to that substance?

When a black hole appears, does it even suck empty space?(<-Sorry, if this last question sounds stupid and absurd to the reader. But, hey! No scientific question is foolish for the questioner!)

Does a black hole have mass and energy? We all Know that a good absorber is also a good emitter... Can a black hole be a good emitter of heat too? Does it have a magnetic field around it like earth? What is its density? What is its composition?

Last edited: Jan 14, 2009
2. Jan 14, 2009

3. Feb 3, 2009

### doctormath

I want to ask you one question? What is an empty space? [wannaknow4995]

4. Feb 3, 2009

### nicksauce

A black hole is a spherical region of space, such that light inside the space cannot escape. If the region of space is of radius R, then the mass inside must be M >= c^2R / 2G.

Black holes "suck" no more than any other spherical object of the same mass. For example, if the sun turned into a black hole of the same mass tomorrow for some reason, it would still exert the same gravitational force on the earth.

I'm not sure what you mean by, "does it suck even energy?". But, by special relativity energy<->mass, and black holes exert a gravitational force on mass.

When a black hole "sucks" something, then it becomes inside the black hole. It may or may not reach the centre of the black hole in a finite time, and then no one knows what happens to it.

Yes a black hole certainly has mass and energy.

Black holes do emit radiation, called Hawking radiation. For a solar-mass black hole their temperature would be, I believe, equivalent to 0.1 nanokelvin. It takes an extremely small black hole to have a significant temperature. (Temperature is inversely proportional to mass for black holes).

Rotating black holes presumably have magnetic fields.

A black hole's density is its mass divided by its volume.

There is a theorem called the no-hair theorem that says that black holes are only distinguishable by their mass, charge and angular momentum. Therefore one might say that their composition is irrelevant. Others might say that its composition is what ever went into making it, and this information is eventually retrievable via Hawking radiation.

5. Feb 8, 2009

6. Feb 9, 2009

### SighNoSnsLeft

Black holes are insane. Ive only taken one astronomy class but when i learned that light wasnt faster then the required escape velocity to get out of a black hole and thats why we couldnt see what was inside...I was just sitting there for a moment like...wow...its interesting stuff to sit there and think about sometimes.

7. Mar 3, 2009

### Saturni

Black holes.
Black holes cannot be seen, but in my thesis, if you ever lived to go through one, you would be "sucked" or "transported" into another dimension.
Fact is that there IS other dimensions out there.
And somewhere out there, extinct creatures still roam, astral speaking.
EX: When you walk down the pavement and to a two way road, you turn left, but you actually turn both ways.. It's hard to explain. Do some researching.

8. Mar 4, 2009

### Chronos

No proof of other dimensions has been offered. This claim is unsubstantiated, IMO.

9. Mar 4, 2009

### Saturni

Actually, it has been proved that there ARE other dimensions out there. It's even on basic forums, and even the History channel.
Tuesday night 8, 9 pm.

Try watching.

10. Mar 4, 2009

### BoomBoom

It's probably best that you don't believe everything you see in a documentary (or at least to assume it is "proven"). They are in the business of entertainment, so they will naturally present some of the most fringe ideas out there in order to entertain you.

It took some time for me to clear all the misconceptions from my head that were placed there by documentaries.

11. Mar 22, 2009

### Kopachris

You're thinking of parallel universes, not extra dimensions. Extra dimensions (in addition to our four (3 spacial + 1 temporal) that we live in) are predicted by string theory. Up to 26 total (in the bosonic case). The most commonly given explanation is that these extra dimensions are curled up extremely small (on the order of the Planck length). Supposedly, gravity leaks into these extra dimensions, which is why it appears so much weaker than the other fundamental forces here on our end.
The parallel universes thing is a product of quantum mechanics. For every possible outcome, one universe is created where that particular outcome becomes true. For instance, if you want a hot beverage and you decide between tea or coffee, you'll have coffee in one universe and tea in another. For each of those, you'll have it with sugar in one, with only cream in one, and without in another. For each sugar and cream, you'll have the opposite in one and not in another.
For another example, think about the classic thought-experiment of SchrÃ¶dinger's Cat. There's a cat in a box with a bottle of poison within striking range of a hammer connected to a Geiger counter that is reading a radioactive sample. If the Geiger counter detects that a particle has decayed, the hammer will smash the bottle of poison and kill the cat. If the Geiger counter doesn't detect that a particle has decayed, the cat will live. When we're about to open the box, we don't know if the cat is dead or alive. In one universe, the cat will be dead, and in another, it will be alive. We don't know which universe this one is until we open the box, so the cat is simultaneously dead and alive, but now I'm getting off topic.

12. Mar 23, 2009

### Chronos

Documentaries are fun and speculative, as BoomBoom noted. The commentators do not claim any evidence of extra dimensions, they merely speculate as to what they may be like should they exist. I may be a bit out of date so feel free to link any peer reviewed papers asserting 'proof' of extra dimensions. In the mean time, stay in the wading pool until you learn how to swim.

13. Mar 24, 2009

### Kopachris

Yeah, we're still waiting to see if the LHC manages to "unravel" the extra dimensions (if they exist). I personally hope they don't find the unraveling of extra dimensions. Right now, string theory is purely mathematical, with no physical evidence of it being true. I also hope they don't find the Higgs boson. I think that would be fun.

14. Mar 25, 2009

### Chronos

Even the most optimistic string theorists concede the LHC has only a slight chance of achieving the energy densities necessary to affirm or deny predictions. This is no great surprise given binary neuton stars and quasars yield no discernable results to date.