1. THE BIG BANG THEORY

2. HOW IT ALL BEGAN Scientists hypothesize that approximately 13.7 billion years ago, a rapid expansion created the universe, producing energy and all the material from which the stars, planets, satellites, and all other objects formed. (ATOMS & ELEMENTS) This theory is known as ‘The Big Bang Theory’ Like all scientific theories, theories about the origin and evolution of the Universe must constantly be tested against new observations and experiments. Current theories began with observations made less than 100 years ago.

3. THE EXPANDING UNIVERSE It is believed that the Universe was once microscopically small Since the Big Bang, the size of the universe has been increasing rapidly. The universe is billions of times larger now than it was early in history. Near the end of the 1920’s, Edwin Hubble first observed that other galaxies are moving away from us. Hubble’s Law states that the farther a galaxy is from us, the faster it is moving away from us. About 200 million years after the Big Bang, the first stars and galaxies formed.

4. THE EXPANDING UNIVERSE Using Hubble’s observations, astronomers have been able to determine that the universe is expanding. The expanding universe can be thought of as a raisin cake rising in the oven. If you were able to sit on one raisin, you would see all the other raisins moving away from you. Similarly, galaxies in the universe are moving farther away from each other due to the expansion of the universe.

5. COSMIC BACKGROUND RADIATION In 1965, Arno Penzias and Robert Wilson using a radio telescope detected cosmic background radiation Cosmic background radiation: radiation (energy) uniformly detected from every direction in space; considered a remnant of the big bang. Astronomers believe that cosmic background radiation formed shortly after the big bang. The background radiation has cooled after the big bang, and is now about 270°C below zero.

6. RIPPLES IN SPACE Maps of cosmic background radiation over the whole sky show ripples. These ripples are irregularities caused by small fluctuations in the distribution of matter in the early universe, and may indicate the first stages in the formation of the universe’s first galaxies.

7. DARK MATTER About 23% of the universe is made up of a type of matter that does not give off light but that has gravity. This type of matter is called dark matter. Analysis of the ripples in the cosmic background radiation shows that the matter that humans, the planets, the stars and the matter between the stars makes up only 4% of the universe.

8. DARK ENERGY Most of the universe is made up of an unknown material called dark energy. Scientists think that dark energy acts as a force that opposes gravity. Many scientists think that some form of undetectable dark energy is pushing galaxies apart.

9. TIMELINE OF THE BIG BANG