In 1946, a Wisconsin student wrote to Albert Einstein. Einstein's reply is now at auction

Nearly 80 years ago, a New London high school senior wrote Albert Einstein a question about the famous scientist's special theory of relativity — and got a brief answer.

The result is one of the few times Einstein wrote out his most famous equation: E=mc², which describes how mass and energy are the same physical entity. Along with other theories, this equation is key to understanding nuclear reactions.

The original writer, Jack Monsted, consigned the letter to Boston-based company RR Auction. Since the listing went live Jan. 19, the maximum bid for the letter has risen to nearly $30,000. Before the sale closes, the price could rise even higher.

In an age before search engines, a New London high school senior went right to the source

When Monsted consigned the letter to RR Auction, he included the stamped envelope addressed from Einstein and a letter of provenance, or a written statement about where Einstein's letter came from.

According to the letter of provenance, Monsted said he was curious about Einstein's special theory of relativity when learning about the atom bomb in his high school physics class.

At the time, the first atom bombs were very recent history; Monsted sent his letter in early April 1946, less than a year after the bombings of Hiroshima and Nagasaki.

But Monsted, then a high school senior, wanted to know what the units of measurement in Einstein's famous equation actually were. He also asked Einstein if the special theory of relativity meant a yardstick would shrink as it approached the speed of light.

Two weeks later, Monsted received a short, typed reply.

Dated April 21, 1946, the letter from Einstein read: "Dear Sir: Your informations do not seem to be quite reliable to me. But there is no time to correct them. In the formula E=Mc², M is measured in gram, E in erg and c in cm/sec.” He signed the letter "A. Einstein."

RR Auction executive vice president Bobby Livingston said of Monsted, "For him to actually reach out to Albert Einstein and ask him to explain — it shows the fascination of that generation with physics. That speaks so much to the inquisitiveness of the consignor as a young person."

Monsted's letter one of the few times Einstein actually wrote out his famous equation

RR Auction, which has sold rare manuscripts, autographs and historic artifacts since 1976, has consigned plenty of Einstein memorabilia, Livingston said.

Most notably, these include a letter to a colleague explaining the special theory of relativity and the scientist's personal copy of a famous 1951 photo showing Einstein sticking out his tongue.

But, according to Livingston, Monsted's letter is unique for several reasons.

First, as a German scientist, Einstein usually wrote using the German language, but in Monsted's letter he used English. Second, since Einstein wrote the letter on Princeton University stationery, the authenticity of the letter is more immediately obvious.

Finally, it's one of the "very rare" times Einstein writes out the equation E=mc², which for him was the "chalkboard" way of describing his special theory of relativity, Livingston said.

All these factors, Livingston said, make the letter "very displayable" for collectors of Einstein memorabilia or famous autographs.

What will happen to the letter now?

The letter is currently for sale in an online-only auction at the RR Auction website, with 35 bidders and the highest bid at $28,204 as of this writing. The highest bidder at around 7:30 p.m. ET on Feb. 22 will win the auction.

Typically, consignors reach out to RR Auction to have their items evaluated, authenticated and sold. Bidders, on the other hand, pay a 25% buyer's premium on the hammer price once they've won an auction, according to the website.

RR Auction has also auctioned off other historical items, like an electric guitar Johnny Ramone used onstage, a watch worn on the moon during the Apollo 15 mission, love letters from Bob Dylan to his high school sweetheart and an Apple II manual signed by Steve Jobs.

Rebecca Loroff is an education reporter for the USA TODAY NETWORK-Wisconsin. Contact her with story tips and feedback at 920-907-7801 or rloroff@gannett.com. Follow her on X (formerly Twitter) at @RebeccaLoroff.

This article originally appeared on Appleton Post-Crescent: A Wisconsin man wrote to Albert Einstein. His reply is up for auction