Which of the following is required for helium fusion as compared to hydrogen fusion?

 Which of the following was an important reason why most ancient Greeks rejected the notion that the Earth orbits the Sun?

If the Sun’s surface were cooler, how would its appearance change?

Hydrogen fuses into what heavier element in the core of the Sun, a main sequence star?

What kinds of atomic nuclei were present when fusion ceased at the end of the era of nucleosynthesis?

 How do we know that quasars are very distant objects?

Kepler’s third law states: p2 is proportional to a3

What kind of pressure prevents a white dwarf from collapsing?

Which of the following is an example in which you are traveling at constant speed, but not at constant velocity? (Velocity has both magnitude and direction).

Why would we expect WIMPs to be distributed throughout a galaxy’s halo, rather than settled into a galaxy’s disk?