![](http://www.ecns.cn/hd/2021/05/24/f1a1ad54877f4c6893687185733e12bc.jpg)
This handout photo released by courtesy of RR Auction shows a handwritten letter from Albert Einstein to Polish-U.S. physicist Ludwik Silberstein, dated October 26, 1946, in which Einstein wrote out the equation "E = mc2" (top R) in German. The letter was sold for $1,243,707 during the auction from May 13 to 20, 2021. (Photo/Agencies)
![](http://www.ecns.cn/hd/2021/05/24/46941cc1d9c241d494cc95523e4bf267.jpg)
This handout photo released by courtesy of RR Auction shows a handwritten letter from Albert Einstein to Polish-U.S. physicist Ludwik Silberstein, dated October 26, 1946, in which Einstein wrote out the equation "E = mc2" (top R) in German. The letter was sold for $1,243,707 during the auction from May 13 to 20, 2021. (Photo/Agencies)
![](http://www.ecns.cn/hd/2021/05/24/045fde8e8d434935a789404b2f876002.jpg)
This handout photo released by courtesy of RR Auction shows a handwritten letter from Albert Einstein to Polish-U.S. physicist Ludwik Silberstein, dated October 26, 1946, in which Einstein wrote out the equation "E = mc2" (top R) in German. The letter was sold for $1,243,707 during the auction from May 13 to 20, 2021. (Photo/Agencies)