AST 248: The Search for Life in the Universe

PLEASE TYPE YOUR ANSWERS.

1. What is the difference between Dark Matter and Dark Energy?
2. What are two kinds of astronomical observations that indicate that the vast majority of the universe is made up of dark matter and/or dark energy, i.e., most matter/energy is not visible or observable as ordinary matter such as gas, stars or galaxies?
3. Suppose a rock formed 4.47 billion years ago and it contained ⁴⁰K and ²³⁸U nuclei in equal proportions.
   1. Today, which nucleus is more abundant in the rock?
   2. Originally, the abundance ratio of these two nuclei was 1. Today, the ratio is about (choose one answer and show work) 1.2, 3.4, 5.9, 7.8 or 9.2.
4. Pretend that the Geologic Time Chart was made into a 24-hour clock. If the Earth was formed at 00:00, the Earth's atmosphere became oxidizing 2.5 billion years later, or at approximately 13:11 on the 24-hour clock.
   1. What time on the clock corresponds to the age of the oldest evidence (from carbon isotopes) for life?
   2. What time on the clock did dinosaurs become extinct?