A few questions on newtons law and black hole

[arnob54]

1. We know from Newton's 1st Law that every body tends to continue its state of inertia unless acted by an external force. Now we know that when Big Bang took place, before that the whole universe was concentrated in a singularity. and since "everything" was inside this singularity and there couldn't be anything "outside" or "external", then why did big bang take place? i mean there wasn't any external agent which trigerred the motion of universe from rest!

2. We know that Black hole is something uses the force of gravitation to suck everything in the universe. Then, can there be any body analogous to black hole, but which uses a different force? ( say electromagnetism? )

3. By Kirchoff's radiation law, we know that a good absorber is also a good emitter. since black hole absorbs everything in the universe, shouldnt it also emit all sort of powerful radiation as well? but then again i heard its impossible to detect a black hole because they never emit anything, is it not a violation of kirchoffs law?

[tanvirab]

1. This question is banned form the scientific community. This is a question for religion and philosophy. Science only works on things that we can observe and try to explain them. Anything that was before the universe or is outside the universe is not the concern of science.

2. There could be. Say, if there is a huge negative charge somewhere than it might act like a black hole for all positive charges (of course it will repel all negative charges). But the problem is, as this negative charged black hole sucks positive charges, it's force gets weaker since positive charges cancel the negative charges. So, this black hole will not survive for very long. On the other hand, gravitation has no polarity; so the more it sucks the stronger it gets. It might be possible for other forces to create black holes as well, by the same priciple; i.e. if the force gets big enough.

3. Kirchoff's law assumes that light is not affected by force. So, you cannot apply that to black holes, because black hole's gravitation affects light.

[arnob54]

thankss for the info bhaiya!

i had one general question, can you explain to me one of the basic principles of relativity? that speed of light is independent of frame of reference?

[tanvirab]

The basic principle is that "Laws of physics are the same in all inertial frame of reference".

This implies that the speed of light is constant, since Maxwell's laws of electromagnetism depends on the speed of light.

[rakeen]

Hey, I thought blackhole DOES emmits light(and all sorts of radiation)!!! But then it isn't called 'black hole'. Like, sun emmits all sorts
of radiation. So that's a perfect black body. But at a time it will turn into a blck hole(I know sun won't! it is for those who is 2.4 times
heavier than sun); and then it'll absorb all sorts of radiation. _howzzat?

oh! and 1 thing more. Kirchoff(I've never heard this name!) is verry smart. He first assumed that light is NOT affected by
any sort of force. If that is true then his law prevails. But, THAT is NOT True. So Kirchoff should be wrong. Right?

[murshid]

i heard its impossible to detect a black hole because they never emit anything

That's not entirely true. See Hawking Radiation: http://en.wikipedia.org/wiki/Hawking_radiation
.

[tanvirab]

Black holes do emit (Hawking radiation); but it is not light.
Hawking radiation has never actually been detected. It's too faint to be detected by current tools.
At the moment the only way to see a black hole is by it's gravitational effect on other objects.

[tanvirab]

Also, Hawking radiation is technically not emitted by a black hole. The actual event is a black hole absorbing negative Hawking radiation, which an observer outside the black hole views as black hole emitting positive Hawking radiation.

[tanvirab]

Hmm.. so it is important to realize that no information from the black hole can actually be in Hawking radiation, since it does not actually come form the black hole. So, even if we can detect Hawking radiation, we can only know that a black hole exists, but we cannot get any information about the black hole from Hawking radiation.

[murshid]

Black holes do emit (Hawking radiation); but it is not light.
Hawking radiation has never actually been detected. It's too faint to be detected by current tools.
At the moment the only way to see a black hole is by it's gravitational effect on other objects.

I agree. And black holes can be detected by gravitational lensing.

Anyway, I enjoyed reading your posts. I've learned quite a few things from the posts. So, thank you!
.