Question

Halley’s Comet comes near Earth every 75 years as it travels around its 22 billion km orbit at a speed of up to 700,000 m/s. If it were possible to put a clock on the comet and read it each time the comet passed, which part of special relativity theory could be tested? What would be the expected result? Explain.

a) Time dilation; The clock on the comet would run slower compared to a stationary clock on Earth
b) Length contraction; The distance between the ticks on the clock would appear shorter
c) Mass dilation; The mass of the comet would increase as it moves faster
d) Gravitational time dilation; The clock on the comet would run faster compared to a stationary clock on Earth

Answer 1

If we were able to read a clock on Halley's Comet each time it passed near Earth, we could test time dilation, predicting that the comet's clock would run slower than a clock on Earth due to special relativity.

Step-by-step explanation:

If a clock were placed on Halley's Comet, as it travels at speeds of up to 700,000 m/s, the part of the special relativity theory that could be tested would be time dilation. According to Einstein's theory of special relativity, as the velocity of an object increases, time as measured by a clock on that object will run slower compared to a clock that is in a relative state of rest. Thus, the expected result would be that the clock on Halley's Comet would run slower compared to a stationary clock on Earth (option a).

This can be related to the way clocks on satellites, which move much faster than clocks on Earth's surface, tick more slowly by about 7 millionths of a second per day. However, this effect is incredibly small due to the relatively low speeds when compared with the speed of light. Consequently, over the comet's 75-year orbit, the cumulative effect would be detectable but very minuscule.