The Expanding Universe THE BIG BANG THEORY How

The Expanding Universe THE BIG BANG THEORY

How the Universe Formed • Astronomers theorize that the universe began billions of years ago. • At that time, the universe we now see was no larger than the period at the end of this sentence. • It was very hot and dense. • It then EXPLODED. • Scientists call this the BIG BANG THEORY.

What is the Big Bang Theory? • The universe formed in an instant, billions of years ago, in an ENORMOUS explosion.

If the big bang theory is accurate, what evidence might you expect to find in today’s universe? • That the matter hurled by a huge explosion would still be moving apart. • Evidence of energy from the explosion.

What did Hubble discover? • Hubble’s Law: the farther away a galaxy is, the faster it is moving away from us. • This supports the Big Bang Theory.

Cosmic Background Radiation • Penzias and Wilson observed faint radiation on their radio telescope. • It appeared as a mysterious glow from all directions in space. • This glow is the leftover thermal energy from the BIG BANG.

Formation of the Solar System • A cloud of gas and dust formed a spinning disk. (This is called a solar nebula. ) • Gas in the center of the disk collapsed to form the sun. (Gravity caused this. ) • The remaining gas and dust formed the planets. • The solar system includes the sun, planets and belts of rock, ice and dust.

If the universe continues to expand, what might happen to galaxies? • They will spread farther and farther apart. A major breakthrough in our understanding of the universe took place in the 1920's thanks to American astronomer Edwin Hubble. For centuries, astronomers believed that the Milky Way made up the entire universe. Hubble was among the first to show that the fuzzy patches in the sky seen through telescopes were other galaxies, not distant parts of the Milky Way. By looking at the spectra of these galaxies, he concluded they were speeding away from us - that the universe was expanding!

What evidence supports theory that the universe might expand forever? • Galaxies appear to be moving apart faster now than they were in the past.

STEADY STATE THEORY Matter is being continually created at the outer parts of the universe & is being condensed into galaxies This theory is not generally accepted today because the amount of helium observed in the universe & the discovery that galaxies were more crowded together in the past further discredit the Steady State theory.

Today’s Views • Will the universe expand forever? • Data collected shows that the expansion of the universe is accelerating