1. The Big Bang Theory

2. In science, a theory is an explanation of a big idea for which there is a lot of scientific evidence.
A scientific theory can be supported by new evidence. New evidence might modify or disprove a scientific theory. A scientific theory can never be proven like a scientific law (we can never be 100% certain).
The Big Bang Theory explains how our universe was formed based on all the scientific evidence.

3. The Big Bang occurred about 14 billion years ago.
All the matter of the entire universe was in a small, extremely hot mass that expanded quickly outwards under tremendous pressure.
This “beginning” is called time zero. What happened before this is not known.

4. All known matter, dark matter, and energy was formed in the Big Bang.
All matter, all atoms in the universe were formed.

5. The Big Bang simplified

6. Hubble Ultra Deep Field Image

7. Evidence to Support the Big Bang Theory
Expanding Universe
Astronomer Edwin Hubble observed that distant galaxies were moving away from our Milky Way galaxy.
How did he know this, and what did it mean?

8. Redshift and Blueshift of light from stars and galaxies
Light and sound travel as waves. Red light has longer wavelengths than blue light.

9. When an object is moving, the waves (sound or light) will be either compressed or stretched. This is called the Doppler Shift.
When an object is moving towards the earth, the light from objects will be compressed and shifted towards blue light (shorter wavelengths). This is a blueshift.

10. When an object is moving away from the earth, the light from objects will be stretched and shifted towards red light (longer wavelengths). This is a redshift.

11. The wavelengths of light coming from almost all galaxies we can see is getting longer (redshifted).
This means they are moving away from our Milky Way galaxy. If the galaxies are moving away from each other, the universe must be expanding.
The farther away the galaxy is from us, the faster it moves. This is called Hubble’s Law.

12. Expanding Universe Raisin Bread Analogy
The farther away the galaxy is from us, the faster it moves. This is called Hubble’s Law.

13. Cosmic Background Microwave Radiation
According to the Big Bang Theory, enormous amounts of energy were given off from the initial explosive event that sent radiation out in all directions.
After billions of years of cooling of the universe, and of the radiation from the Big Bang event traveling through space, the entire universe is still “glowing” like a piece of firewood continues to glow after the fire is put out.

14. This radiation, particularly in the microwave frequencies, can be detected today using radio telescopes, telescopes that can detect electromagnetic waves outside of the visible range.
This radiation is called Cosmic Background Microwave (CMB) Radiation.

15. Image of the Cosmic Microwave Background (CMB) Radiation of the early universe – bright spots correspond to higher temperatures

16. What is the Big Bang Theory?
13.7 billion years ago the universe formed when an infinitely dense point suddenly and rapidly expanded in a single moment.