Einstein's love letters prove that E=MCP

Albert Einstein could well defy his own laws of physics by turning in his grave next month when his family secrets go under the hammer in New York.

Christie's hope to raise around $2m (pounds 1.3m) by selling an archive of some 400 letters between the great scientist and the family he abandoned. The auction is advertised as "the most important and expensive group of letters of Albert Einstein ever to come to market".

Not only does the consignment include the steamy letters which when published recently revealed he had an illegitimate daughter by his first love, Mileva Maric, whom he subsequently married.

It also contains a treasure trove of unpublished material which shows the callous way in which the genius dispensed with Mileva to marry his cousin Elsa. One letter written around 1918 says: "I am very eager to see which will take longer, the war or our divorce."

"These letters show Einstein washing his hands of Mileva and sending her away. Initially they are very bitter as he tries to divorce her to marry his cousin," says Robert Schulmann, co-author of Albert Einstein - Mileva Maric: The Love Letters, who plans to publish the new material next year.

Eventually, he says, Mileva "accepts the fact that she cannot have Einstein any more and he tries to make his peace with his sons who he feels she has poisoned against him".

The fortunes of these sons in adulthood could not be more diametrically opposed. The elder, Hans Albert, became a distinguished academic and hydraulic engineer who enjoyed discussing the problems of his field with his father. The younger, Edward, became a schizophrenic who was institutionalised on the death of his mother in 1948.

The sale is a money-raising exercise by Mileva's heirs, who kept the archive under lock and key in a Los Angeles bank vault until 1986, when they started revealing its contents to scholars.

Einstein was only 17 when he met Miss Maric in 1896, when they were both studying at the federal technical high school in Zurich. She was three-and-a-half years his senior. Described by one academic as "darkly handsome" but prone to limp from a congenital hip dislocation, she was remarkable in being one of the earliest female students to enter such a male preserve.

Soon Albert was besotted, calling her his dearest "pussy cat", "kitten" and "doll." One letter in the sale has him saying how much he misses "your two little arms and that glowing mouth full of tenderness and kisses". Another describes her as his "shrine . . . of all people, you understand me the most and love me the best". The correspondence - spanning the years 1897 to 1955 - also charts how Einstein defied his family in (initially) sticking with Mileva against their wishes. Tactlessly he describes to Mileva how his mother threw herself on to her bed and wept at the news that he had committed himself to his love: "By the time you are 30 she is an old witch," Einstein quotes his mother as saying.

Things started going wrong for Mileva in July 1900 when Einstein passed his exams but she failed. Then in 1901 she became pregnant during a holiday at Lake Como. When their daughter was born in January 1902, Einstein was far away. Although Einstein eventually plighted his troth to Mileva in 1903, the marriage was doomed. After their daughter contracted scarlet fever that year, all references to her cease. Scholars - who had no idea of the girl's existence until recently - now believe that she died or was given away for adoption.

Whatever the truth, Mrs Einstein gradually became more brooding and remote. In 1914 Einstein struck up the liaison with Elsa and started asking for a divorce.

All these dramas took place while Einstein was making some of his most important breakthroughs in physics. According to Christie's expert Christopher Coover, several of the love letters are written on the back of scientific notes. In November 1915, as he is putting the finishing touches on his General Theory of Relativity, he writes to Hans Albert, then aged 11: "I have just completed the most splendid work of my life."