2. The Big Bang Theory
big bang
The universe began as a single cosmic explosion about 14 billion years ago.

3. After the Big Bang Gravity pulls matter into small clumps
Clumps become huge clouds of dust and gas
Clouds become solar systems and galaxies

4. 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!

5. 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 . . .

6. 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
furthest objects measured

7. Major Piece of Evidence #3: Temperature
The temperature in deep space is around 3° K (-454° F).
Leftover heat from Big Bang keeps space just above absolute zero

8. What Happens Next?
Big Bang theory leads to two possible futures for the Universe:
Open Universe
Closed Universe
Fate of the Universe Part 1

9. 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.

10. 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.

11. 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.
May occur every billion years.

12. 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
Fate of the Universe