## Sunday, August 16, 2009

### What Major Problems In Physics Were Resolved By The Big Bang?

(Someone following the blog felt that more than LDS people are interested in these questions and that the title "Letters To The LDS Community" seemed as if I was only concerned about answering LDS' peoples questions. Because of this, and not wanting to give a feeling of exclusion to non-LDS people, I am changing the title of these things to "Answers To Science Questions". LDS people can still take comfort in the fact that this title echos a series by a man named Joseph Fielding Smith. :) Almost the perfect name to have.)

Dear science community
,

If there were infinitely many stars in the universe that has existed forever, as physicists used to believe, major problems occur. There are three issues I want to discuss that were very troubling before the Big Bang was proposed:

1. Olbers' paradox. The night sky should not be dark but very bright! Every single direction you look you should see a star since a.) given an infinite number of stars there should be one there and b.) even if light has a finite speed, given "forever" the starlight should have arrived here by now. The top picture describes what you should see. As time progresses, more and more starlight from an infinite number of stars should shine on the earth producing a blazing night sky to gaze at, not a dark one.

Another way to think about this is mathematical: Set up an infinite sky with infinitely many stars shining brightly forever and ask how many photons should be at any given point. The answer is every point in the universe should eventually be flooded with photons from every direction so that there isn't a dark spot anywhere.

The Big Bang made us give up the idea that the number of stars is infinite and that the universe, in the form it is today, has been around forever solving Olbers' paradox.

2.) Universe Is Not In Thermodynamic Equilibrium: Take a pan of cold water and throw a hot object inside and what will happen? Given enough time, the pan of water and the object will become the same temperature. This is called thermodynamic equilibrium.

If the universe has existed forever it should be in thermodynamic equilibrium by now. Infinitely many stars producing heat for an infinite amount of time would heat up the whole universe to be the same temperature as themselves. However, the majority of the universe is cold, not hot like the stars.

Take away the infinite time, as the Big Bang does, and the thermodynamic equilibrium problem goes away.

3. Stars are no more than 12-13 billion years old. We have ways of measuring how old stars are. (Will blog on this later.) Surprisingly, we can't find any stars older that 12-13 billion years old. Maybe you say stars like creatures die and give rise to new stars. Okay, where are the infinity many dead stars, and why are all the "dead stars" we know about still no older than 12-13 billion years old?

It turns out the Big Bang should have happened ~13.7 billion years ago and it would take ~1 billion years for most types of stars to form after such an event. Thus the Big Bang resolves this problem with physics too.

Now, I don't believe I touched on every problem solved by the Big Bang. (Minus the predictions.) I'm sure others will know more problems so please share them in the comments.