# Big bangs & macroquantic - two questions

1. Jul 25, 2012

### skepsys82

hi everybody.

1) i read that the diameter of the observable universe is about 93 billion light years. But the age of it is 14.3 billion light years.
how could the universe expand itself at a speed larger than the speed of light? is it possible that the universe started not by
one singe big bang, but by several sepparated big bangs that banged together in a chain reaction, distanced from eachother, like
wwII sea mines?

2) at quantic level, our laws i know dont apply, but is there a field of physics dealing with the laws that apply at the macromacrocosmos?
i would imagine that if at a very small level laws change, so should they at a very large scale...

thanx.
Andrei

2. Jul 25, 2012

### Mark M

Remember that the universe has expanded since the big bang. If the universe wasn't expanding, then the observable universe would only grow by one light year per year, as new areas of the universe would become visible to us. Then, you would be correct that the observable universe would have a radius of 13.7 billion light years, and a diamter of 27 billion light-years. However, remember that space expands in between ever galaxy. So, the observable universe also grows in this manner. This results in a total radius of 46.5 billion light years, and 93 billion light years in a diameter.

That idea doesn't make sense, and you can see why. Remember that the big bang was NOT an explosion. It was te extremely hot and dense state the ENTIRE universe was in. The universe expanded from every point, and more dense regions of the primordial gas attracted less dense regions, forming galaxies. These don't expand. So, the space in between galaxies continues to expand, from every point.

The word you're looking for is 'quantum' not 'quantic'. Over very large distances, the universe follows the rules laid out by general relativity. The solution to the Einstein field equations that corresponds to our universe is the FRW metric.

3. Jul 25, 2012

nice.
thanx :)