In 1945, Albert Einstein wrote a letter to one of his sons in which he explained links between his theory of relativity and the atomic bombs that were dropped on Japan. This letter has been sold for $62,500 at a recent auction.

This letter is one among 27 letters that Einstein wrote; the 27 letters were auctioned by Profiles in History on Thursday. On the whole, over $420,000 was fetched by selling the letters including two that were written by him in the 1940's; in these two letters, he explained his opinions on God to a man who had asked the question. The two letters fetched $28,125 and $34,375, respectively.

In other letters that were auctioned, Einstein has explained his thoughts on McCarthyism, Nazism and personal matters.

The letters consists of notes written on the margins of the pages. The transaction had been in cash for a big amount and it has not been revealed that who has acquired it.

In Albert Einstein's theory of general relativity, the laws of physics have been explained that are no different for all non accelerating observers, in addition to that the speed of light in a vacuum was not dependent on the motion of all observers. This theory of special relativity was explained in 1905.

Einstein included the acceleration in the theory after spending 10 years researching on it. After that he published his theory of general relativity in 1915. He found that massive objects led to a distortion in space-time that is felt as gravity.