Suppose that in the distant future astronomers build a telescope so powerful they can see aliens on a planet that is 10 light-years from earth. One day they observe the aliens board a spaceship and blast off toward earth. According to earth clocks, the ship and its alien crew arrive at the earth exactly one week later. Assuming the velocity of the ship was constant during almost the entire trip, find its velocity ratio \(\beta=v / c\) in earth's frame, valid to three significant figures. (Note that \(v / c<1\).)