Physical Principles
1. What would happen to the Earth's orbit if the mass of the Sun were instantaneaously doubled? Would the Earth move closer to or further from the Sun?

2. What if a giant trash compactor in the sky came and compressed the Sun to half its current volume? What would happen to the Earth's orbit then?

3. If the Moon's angular momentum were cut to less than a third of what it is now but the mass remained the same: How would the Moon's orbit change?

4. Which exerts a stronger gravitational attraction on you, your friend standing 3 meters away from you or the planet Jupiter? (Relevant info about Jupiter is in table 8-1 of your book, page 182.)

5. Draw a thermal radiation curve (intensity versus wavelength) of an object that is at a temperature of about 6000 degrees K. Where is the high frequency end on your graph? What happens to the peak of the curve as you heat the object?

6. Which releases more microwaves: a star at 6,000 degrees Kelvin or a star at 10,000 degrees Kelvin?

7. Two stars are the same color. Star A is 9 times fainter than star B. Which is further away? How much further?

8. The atom at right just absorbed a microwave photon.
What does the conservation of energy say must happen to the electron?

9. A moment later, the electron drops to the ground state. The conservation of energy says that a photon must be released by the atom. Is that photon shorter or longer than a microwave?

10. Helium is the second element in the periodic table. It has two protons and two neutrons, and two electrons. If you add an extra neutron, is it still helium? If you take away one of the electrons, is it still helium? If you add an extra proton, is it still helium?