18 polaris the north star doesnt appear to move in

18. Polaris, the North Star, doesn't appear to move in the sky because
* a) it lies directly over the northern axis of the Earth
b) the stars are fixed relative to each other
c) it is too nearby for the motion to be discernible
d) it is located directly overhead of everyone on Earth
19. The gravitational force between two bodies is:
20. The Doppler effect causes light emitted from a body moving away
from the observer to be
21. Electromagnetic emissions in the ultraviolet part of the spectrum have
22. The Sun is primarily composed of
a) liquid hydrogen
* b) hydrogen gas
c) helium gas
d) oxygen and nitrogen
23. Explain any one of Kepler's laws of planetary motion in terms of
Newton's law of gravitational force. 10 points
24. Name three astronomical observations made by Galileo. Why were
each important?
25. Show the three nuclear reactions which convert 6 protons
into Helium 4 (2 protons plus 2 neutrons) plus 2 protons.
Why do these processes cause energy in the form of heat
to be produced?
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