Which planet (besides Earth) has been visited by the largest number of robotic spacecraft?
A) Mars B) Venus C) Jupiter D) Saturn
Question 2
If the rest wavelength of a certain line is 600 nm, but we observe it at 594 nm, then
A) the source is getting 1 hotter as we watch.
B) the source is spinning very rapidly, at 1 of the speed of light.
C) the source is receding from us at 10 of the speed of light.
D) the source is approaching us at 1 of the speed of light.
E) the source is approaching us at 0.1 of the speed of light.