75) Here we are asked to find the time it takes light to travel between the two objects. This problem is a tricky one. The spaceship is moving at a speed of c/2 and light moves at speed c, where c ≈ 3 * 10^8 m/s. Many people would think that since they are moving towards each other, the light is traveling at a speed of c/2 + c = 3c/2 ≈ 4.5 * 10^8 m/s.
And, using the equation above, those people may think the light will reach the ship 4.5 * 10^8 meters away in 1 second.
This may be true because of relativity; however, with light this rule does not apply. According to Einstein’s postulates of special relativity, which holds true to this day, light will always travel at a speed of c ≈ 3 * 10^8 m/s. The speed of the spacecraft doesn’t matter and is irrelevant information included to throw you off. Instead the light travels at 3 * 10^8 m/s and will reach the ship, which is 4.5 * 10^8 meters away, in 1.5 seconds.
Answer: C
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