Describe how light radiation leaves a star, travels through the vacuum of space, and finally is seen by someone on earth.

The of a machine determines its "usefulness." a. input force b. output force c. mechanical advantage

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.

The difference between a red shift and a blue shift has to do with wavelength frequency. t or f