The Big Bang Theory

The Big Bang Theory

The universe began as a single cosmic explosion about 14 billion years ago.

After the Big Bang

• Gravity pulls matter into small clumps• Clumps become huge clouds of dust and gas• Clouds become solar systems and galaxies

Major Piece of Evidence #1: Background Radiation

• Energy left over from the Big Bang is evenly spread throughout the universe.

• This background radiation is observable!

Major Piece of Evidence #2: Expanding Universe

• Every object in the universe is moving away from the center.

• Think of waves spreading out from where you drop a pebble into a pond.

• Except . . .

Expanding Universe• Objects near the very edge of the universe are

the oldest• The most distant known objects in the universe

are over 12 billion light years from the Earth

Major Piece of Evidence #3: Temperature

• The temperature in deep space is around 3° K.

• Leftover heat from Big Bang keeps space just above absolute zero

Let’s look at that first picture again

What Happens Next?• Big Bang theory leads to two possible futures

for the Universe:1.Open Universe2.Closed Universe

Open Universe: The End• The universe will continue to expand. All stars

will die as the last of their energy is released. Eventually, all matter will be reduced to single atoms moving away from each other. There will be nothing left.

• The end.

Closed Universe: Collapse

• Gravitational attraction between objects will cause the expansion of the universe to slow and, eventually, come to a halt. Gravity will then begin to pull everything back to the center of the universe.

• Kind of like a rebounding bungee cord.

Closed Universe: Déjà vu

• Eventually, all matter and energy will again condense into a single point, possibly no larger than a dime. Another Big Bang will occur and the formation of the universe will begin all over again.

In any case . . .• Whatever happens to the

universe, we are pretty lucky here on earth.

• We have the two main requirements for life:– Liquid water– Protection from UV radiation

• Perhaps elsewhere in the universe, other planets or moons do, too