A deep space probe is positioned halfway between two stars, A and B each 1 light
ID: 233610 • Letter: A
Question
A deep space probe is positioned halfway between two stars, A and B each 1 light year away. These stars are near the end their life cycle and are each due to become supernovae soon. A scientist in a space craft is traveling from star A to star B. Just as the scientist passes the probe he sees both stars supernova at the exact same time. What a coincidence! Each star must have exploded precisely one year ago. He also decides to down load the probe's data. To his astonishment the probe reports that the stars did not explode simultaneously. Use your understanding of relativity to carefully explain how this is possible.
Explanation / Answer
When a star explodes as a supernova, most of its matter is blown away into space to form a nebula. The ultra-dense remnants of the imploding core which are left behind are known as a neutron star. The gravitational force on a massively dense neutron star is about a million million times fiercer than on the Earth, and a projectile would need to attain almost half the speed of light in order to escape its gravity. Under conditions of such powerful gravity, Sir Isaac Newton’s Law of Universal Gravitation (which generally works well enough in our own Solar System) becomes redundant, and Albert Einstein’s General Theory of Relativity is needed to expain. Clocks on a neutron star would run 10 - 20% slower than those on Earth, and any light from its surface would be so strongly curved , thus the time taken from star to probe is different although the distance is same.