German physicist Albert Einstein's letter which is a reply to the queries of a science teacher in 1953 has been sold for USD 53,503 at an auction.
Einstein penned the letter in reply to a two-page questionnaire submitted by Arthur Converse, a science teacher from Iowa, concerning electrostatic theory and special relativity.
The letter, with an opening price of USD 15,000, was bought by an unidentified person.
It had been in the Converse family's possession for many years, said Sam Heller, a spokesman for the Nate D Sanders Auctions auctions that sold the letter.
The envelope of the letter indicated that it was sent from 'Room 115' of the Institute for Advanced Study in Princeton, New Jersey, on September 7, 1953.
The letter seems to answer questions about Einstein's theory of relativity and how to reconcile the theory with experiments, 'Live Science' reported.
Converse was a science teacher and had sent Einstein a questionnaire regarding experiments with electroscopes, which are charge-measuring instruments.
"It is clear to the reader that Einstein was interested in Converse's questions and generous in his considerate response," said Nate Sanders, owner of Nate D Sanders Auctions.
"These documents provide a rare glimpse into Einstein's generous nature and willingness to help teachers better understand and communicate his theories," Nate said.