1. What is the Universe Like? Chapter 31

2. The universe is everything…all matter and all energy The universe is everything…all matter and all energy The universe is expanding. The evidence is the “red-shift” of the light from most galaxies The universe is expanding. The evidence is the “red-shift” of the light from most galaxies red-shift: a shift toward the red end of the spectrum in the observed spectral lines of stars or galaxies. Known as the “Doppler Effect.” red-shift: a shift toward the red end of the spectrum in the observed spectral lines of stars or galaxies. Known as the “Doppler Effect.”

3. If the universe is expanding now, this implies that it was once smaller. If the universe is expanding now, this implies that it was once smaller. If we imagine what the universe was like about 15 billion years ago, everything would have been in one spot. If we imagine what the universe was like about 15 billion years ago, everything would have been in one spot. So, about 15 billion years ago, the universe began expanding. This is called “the big bang” So, about 15 billion years ago, the universe began expanding. This is called “the big bang” big-bang theory: a scientific theory that states that the universe began 10 to 20 billion years ago in an enormous explosion. big-bang theory: a scientific theory that states that the universe began 10 to 20 billion years ago in an enormous explosion.

4. If the big-bang theory is correct, we should see evidence of the explosion about 15 billion light-years away. This evidence was discovered in 1965. It is called “cosmic background radiation.” If the big-bang theory is correct, we should see evidence of the explosion about 15 billion light-years away. This evidence was discovered in 1965. It is called “cosmic background radiation.” There are three possibilities of how the universe might end: There are three possibilities of how the universe might end: The universe might expand forever The universe might expand forever The expansion of the universe might slow down and the universe will stay one size The expansion of the universe might slow down and the universe will stay one size The universe might begin shrinking, eventually collapsing into a “big-crunch.” The universe might begin shrinking, eventually collapsing into a “big-crunch.”