PASSIONATELY hoisting his young secretary up against the blackboard, her legs wrapped around his waist, Albert Einstein was hell-bent on proving he was no stranger to experimenting.
But when she later turned him down for a threesome with his wife, the brilliant physicist grumbled in his diary: “Perhaps triangular geometry is not as simple as I would like it to be.”
These days Einstein has a rock-solid reputation as a wild-haired visionary, but it was a different sort of chemistry that drove his younger days.
Women swooned at his “sensuous mouth”, “broad-shoulders” and “thick, curly hair”.
Even Marilyn Monroe fell for his charms at a dinner party when she cooed into his ear: “I want to have your child. With my looks and your brains, it will be a perfect child.”
Grinning, he purred back: “But what if it has my looks and your brains?”
Now a new TV series, starring Geoffrey Rush as Einstein, is set to blow the lid off the brainbox image of the 20th-century thinker with a host of steamy scenes.
It will show that while he was brilliant at understanding nuances of nuclear fission, he was a cold-hearted pleasure seeker when it came to sex.
Mileva was a fellow physicist who walked with a limp.
Einstein was her toyboy and, despite having three kids with her, he went on to describe her as “an employee whom I cannot fire” as he set his sights on Elsa.
They divorced 1919.
A flirting and fickle lover who enjoyed as many as ten mistresses, Einstein was a callous husband twice over and a distant father.
Oscar-winning film-maker Ron Howard, who directs the series, called Genius, said: “Einstein’s private life is way more complicated and dramatic than I realised.
"He loved the world and women — and he felt that was a real energy force in the universe.”
After bad-mouthing his missus to his first cousin Elsa, Einstein began an affair with her while he was with Mileva.
Despite the fact Einstein fancied Elsa’s daughter, the pair tied the knot in 1919.
He then had a fling with a pal’s neice.
Elsa died in 1936.
Alternatively, as one of Einstein’s friends remarked at the time, “he acted upon women as a magnet acts on iron filings”.
His ladykilling began soon after he moved from Germany to Zurich, Switzerland, in 1896, aged just 17, to study maths and physics.
He fell in love with the only girl in his class, shy Hungarian Mileva Maric, who was four years older than him and walked with a limp.
Even then, as it would later, temptation got the better of him.
While on holiday with his mum, he enjoyed trysts with Anneli Schmidt, a beautiful 17-year-old innkeeper’s daughter.
On his return to Zurich, Mileva announced she was pregnant, but both families ruled out marriage as they were practically broke.
Einstein loved the world and women — and he felt that was a real energy force in the universeRon Howard
Their illegitimate daughter, Lieserl, was born in January 1902. It is thought she was either put up for adoption or died of scarlet fever as a baby.
Six years later, after Einstein found a job at Bern University, he married Mileva.
They had two sons, Hans Albert and Eduard, who was diagnosed with schizophrenia at 20 — much to Einstein’s horror — and spent much of his life in institutions.
He did not remain in Mileva’s bed for long, sticking to a belief that: “People are like bicycles. They can keep their balance only as long as they keep moving.”
In 1912 he began an affair with his recently divorced first cousin Elsa Lowenthal.
A giggling, curvy blonde with a fraction of his intellect, she was everything the serious-minded physicist Mileva was not.
Einstein complained to Elsa in one letter that his wife was an “unfriendly, humourless creature” and in another wrote: “I treat my wife as an employee whom I cannot fire.”
As his marriage became increasingly toxic, in 1914 he wrote an extraordinary memo to Mileva setting out the conditions under which he would go on living with her for the sake of their sons.
The demands included telling her to keep his rooms tidy, bring him three meals a day and stop talking at his request. He also told her to expect no intimacy.
These were Einstein’s terms for moving back with his wife, which he hoped would lead to a permanent split.
A. You will make sure:
1. That my clothes and laundry are kept in good order.
2. That I will receive my three meals regularly in my room.
3. That my bedroom and study are kept neat, and especially that my desk is left for my use only.
B. You will renounce all personal relations with me insofar as they are not completely necessary for social reasons.
Specifically, you will forego:
1. My sitting at home with you.
2. My going out or travelling with you.
C. You will obey the following points in your relations with me:
1. You will not expect any intimacy from me, nor will you reproach me in any way.
2. You will stop talking to me if I request it.
3. You will leave my bedroom or study immediately without protest if I request it.
D. You will undertake not to belittle me in front of our children, either through words or behaviour.
Soon afterwards he moved with his family to Berlin — where Elsa lived. A disgusted Mileva eventually headed back to Zurich with his sons.
In exchange for agreeing to divorce in 1919, Einstein promised Mileva the Nobel Prize money he was expecting to win for his pioneering work in theoretical physics.
However, before he could hand over a penny when he won in 1921, he lost most of it on the stock market.
My wife is an unfriendly, humourless creature... I treat her as an employee I cannot fire
The divorce left the door open to marry 44-year-old Elsa.
Yet out of the blue, Einstein, who was 47, noticed how gorgeous her 20-year-old daughter Ilse had become and announced he would marry either of them — and they should decide which.
In a panicked letter to a friend, Ilse said: “I know that A(lbert) loves me very much, perhaps more than any other man ever will, he also told me so himself yesterday.”
Ilse eventually told Einstein she loved him only as a father. He married her mum.
That relationship was far from smooth, unsurprising for a man who described the institution of marriage as an “unsuccessful attempt to make something lasting out of an incident”.
Within just four years he was having a fling with Betty Neumann, the niece of one of his best friends who worked as Einstein’s secretary.
Elsa is said to have grudgingly given her permission to their year-long affair, although Betty ended up dumping Einstein.
Unperturbed, as his fame grew, so did his pulling power.
Letters published in 2006 show how he described his affairs in letters to Ilse and Elsa, who died in 1936.
The spy who loved Einstein was the wife of a Russian sculptor, whose next commission was a statue of the man having it away with his beloved.
Not that he knew it at the time, but the affair came with added risk.
It emerged in 1998 that Margarita was a Soviet spy.
It would have taken a genius to work that one out.
In 1933 Einstein, a Jew, left Germany for the US — where he would die, aged 76, in 1955 — after Hitler’s rise to power made it impossible to remain.
He kept a keen eye for the ladies and in his sixties the widowed physicist had a fling with the wife of Russian sculptor Sergei Konenkov.
They met after Sergei was commissioned by Einstein’s employer, Princeton University, to make a statue of him.
The affair could have landed Einstein in deep trouble as it emerged in 1998 that the woman, Margarita Konenkova, was a Soviet spy.
But Einstein was no more able to live without distracting female company than he was to stop the wheels of his genius mind from turning.
As he said himself: “When a man sits with a pretty girl for an hour, it seems like a minute.
“But let him sit on a hot stove for a minute — and it’s longer than any hour. That’s relativity.”
— Genius is on the National Geographic Channel at 9pm from April 23.