How long would it take a message sent as radio waves from earth to reach mars when farthest from earth (401 million km apart)?

Which statement is true? a. kepler's laws apply only to the motion of earth. b. kepler's laws can be used to predict eclipses. c. kepler's laws are true for a central force that is directly proportional to distance. d. kepler's laws can be deduced from newton's laws of motion and gravity.

Observations show that interstellar clouds can have almost any shape and

Often called simply "velocity," this is the velocity of an object at a particular moment in time.