Consider a trip by the Starship Enterprise from the Earth to a star located 12 l
ID: 1698918 • Letter: C
Question
Consider a trip by the Starship Enterprise from the Earth to a star located 12 lt • yr away according to earth-bound observers. (1 lt • yr is the distance light travels in one earth-year.) The Enterprise moves at a speed of v = 4/5 c relative to the Earth, where c is the speed of light (c = 1 lt • yr/yr). The Enterprise makes a brief stop at the star, then returns to Earth at the same speed. You can neglect the time spent in decelerating, visiting the star and accelerating back toward earth.a. According to observers on Earth, how long did the Enterprise take to travel to the star and return to earth?
b. According to the passengers and crew of the Enterprise, how long did the journey take?
c. At the time the journey began—when the Enterprise was still near Earth—a light signal was transmitted to the star to announce the impending visit to the inhabitants of a planet near the star. How much time did residents living on a planet near the star have to prepare for the arrival of the spaceship?
d. Communications between the Enterprise and Earth are carried out using pulses of laser light. The wavelength of light transmitted by the lasers on Earth and on the Enterprise are the same according to observers at rest with respect to the lasers. Which statement below best characterizes the wavelength of the communications signals received on Earth and the Enterprise during the course of this journey?
1. The wavelength of light received by each will be the same as that of their respective transmitters.
2. The wavelength of light received on Earth is always longer than what is received on board the Enterprise.
3. The wavelength of light received on Earth is always shorter than what is received on board the Enterprise.
4. The wavelength of light received by each will be longer than that of their respective transmitters on the outbound journey and shorter on the return trip.
Explanation / Answer
Given: