# Big bang question

1. Nov 29, 2009

### edpell

If all mass of the universe was in a region 1mm in extent then was it a black hole (escape velocity greater than c)? Now 13 billion years later the universe is bigger. What is the escape velocity now? Did it change from >c to <c?

Last edited: Nov 29, 2009
2. Dec 2, 2009

### Matterwave

The big bang is an odd phenomenon. Singularities are a problem for current physics. I don't think you can really think of the big bang having arisen out of a black hole (Current Physical laws don't seem to work at the moment of the big bang or before, only something like 10^-42 seconds afterwards). There is no escape velocity for the universe, as far as I know you can not leave the universe...

3. Dec 3, 2009

### Jolb

Since the Schwartzchild radius tells the maximum radius a given mass could have to be a black hole, we can calculate the minimum mass of a 1mm black hole.
$$R_{Schwarzchild}=\frac{2GM}{c^2}\approx 3km(\frac{M}{M_{sun}})$$

So setting the Schwarzchild radius equal to 1mm, we get 7*10^23 kg, about a tenth the mass of the Earth.

Really, the smaller a black hole you can achieve (good luck overcoming degeneracy pressure), the less mass you need. (A massive body becomes a black hole depending on the density.)

However, there's a much more important issue here. The Schwartzchild radius describes black holes in space. The big bang was not an explosion in a background of space. The big bang involves spacetime itself expanding from a single point. The universe (which may or may not be infinite) has always had a nearly homogenous and isotropic mass distribution.

In addition, it might interest you that the big bang had excruciatingly low entropy while black holes have the highest possible amount of entropy in a given region of space.

Last edited: Dec 3, 2009
4. Dec 3, 2009

### fatra2

Fact is that just after the BigBang, matter did not exist. There was something like a soup of plasma more or less seethrough. It took "very long" for matter to form.

Therefore, you cannot think in the sense of compressing matter into a very small volume. You need to see the Big Bang as a release of energy that eventually formed elementary particles, that eventually formed nuclei, that eventually formed atoms, that eventually contracted to form the matter as we know nowadays.

Cheers

5. Dec 6, 2009

### Bethann

Does your collective thinking believe that the LHC can create a Little, Big Bang?

If yes, then that is a lot of bucks for the bang! ... or will it answer the \$4.5B question! Is the Higgs Boson the end of the question? What is the next question?

OR, if the answer is no, then 1.) another failed attempt? , or 2.) WHAT? "We came, we saw, we conquered, we left suddenly!"

6. Dec 7, 2009

### fatra2

By just taking a quick look at the CERN's website makes you realize that they are not focusing on just one particular field. The CERN is a research center open to all research team around the world.

Some of their projects, like the ATLAs has a very specific focuse, and they will use part of the beam. But other research are always welcome to apply for beam time.

Cheers

7. Dec 14, 2009

### edpell

Bethann, I enjoy your sense of humor "we left suddenly" :)

Fatra2, I do not think it "matters" (sorry for the pun) if the stuff is energy or matter I get the impression these are about the same as far as gravitational effects are concerned.

Jolb, your remarks about a "hole in space" versus "spacetime itself expanding" contains so many ideas I do not know where to being and many of the ideas I do not understand. I would ask when can we talk about holes in space? How big does the universe need to be? If a 1mm black hole is about a tenth the mass of the earth then using 10^55kg as the mass of the universe we can make 1.6x10^30 black holes. If they are all packed next to each other than there was a time when the universe was about 11,000km in radius it "contained" 1.6x10^30 black holes packed cheek to jowl. How do you think about this? At what point do we move from expaning spacetime to hole in space?