Use Einstein's special-relativity equation Upper R Subscript a Baseline equals Upper R Subscript f Baseline StartRoot 1 minus left parenthesis StartFraction v Over c EndFraction right parenthesis squared EndRoot , which gives the aging rate of an astronaut, Upper R Subscript a, relative to the aging rate of a friend, Upper R Subscript f, on Earth. In this formula, v is the astronaut's speed and c is the speed of light. Suppose an astronaut is moving at 40% of the speed of light. Substitute 0.4c for v, the astronaut's velocity, in the equation. What is the aging rate of the astronaut relative to a friend on Earth? If the astronaut was gone for 92 weeks, approximately how many weeks have passed for the friend?
What is the aging rate of the astronaut relative to a friend on Earth?