"My dear kitten, '' Albert Einstein wrote, in 1901, to his first wife, the physicist Mileva Maric. "I just read a wonderful paper by Lenard on the generation of cathode rays by ultraviolet light." The romance didn't last. By 1914, Einstein had presented a list of "conditions" under which he could consent to remain in his sour marriage. Among them was a demand to have three meals a day delivered to his room. There was also this: "You are neither to expect intimacy nor to reproach me in any way.''

By then, Einstein was having an affair with his cousin Elsa Löwenthal, who soon became his second wife (and who, it is often said, remained his second wife by permitting him to "meet" with Betty Neumann, the niece of a friend, twice a week for nearly a decade). The divorce from Mileva was bitter, but it generated one of the more unusual legal agreements in the history of science: Einstein assumed that he would eventually win the Nobel Prize, so he instructed his lawyers to make the money part of the divorce settlement.

Visitors to the Einstein exhibit that opened last week at the American Museum of Natural History may be inclined to skip lightly over the panels dedicated to his complicated personal life, but it is strangely comforting to see that the man who created the modern world was so frequently befuddled by it. His relationships often failed. He fled one country and lived uneasily in another. He hated totalitarianism but was opposed to capitalism. He barely knew his sons.

Einstein's thoughts are often portrayed as too complex for mortals to master. That turns out to be untrue. In the exhibit, the curator, Michael Shara, explains how light travels, why time warps, what makes stars shine. Walk in the door and you are immediately greeted with a view of yourself as seen through a black hole. (It is not a pretty sight.) Shara had access to the collection of Einstein's papers at Hebrew University, and he has made exquisite use of them. "Everything you have ever thought about space and time is wrong," he says. "Absolutely wrong." Shara never cheats on the science, but, because many of us are at least a tiny bit afraid of physics, he and the graphics team, led by Stephanie Reyer, have provided a series of interactive aides to penetrate the complexity of Einstein's world. For instance, they present some amusing scenarios to illustrate Einstein's discovery that the faster you travel the slower time passes: the cosmonaut Sergei Avdeyev spent more than two years on the Russian space station Mir; Mir was moving faster than the earth, so Avdeyev is two-hundredths of a second younger than he would be if he'd never been in space. (The exhibit makes it clear that much faster trips, say, at nearly the speed of light, produce rather more dramatic results.)

Shara doesn't simply explain what E=mc2 means; he demonstrates that, under the right conditions, the mass of a single penny could be converted into enough energy to fuel New York City for two years. He also notes that the temperatures required for such a procedure would be well in excess of those found inside the sun. So, for the moment, we are stuck with Con Ed.

In 1905, at the age of twenty-six, Einstein published four papers that provided the blueprint for much of the modern experience. Pages from those papers are displayed together. It is still hard to believe that Einstein's work in that single year led to the discovery of, among other things, X-ray crystallography, DNA, the photoelectric effect, vacuum tubes, transistors, and the mechanics of the information age. Unfortunately, it also laid the groundwork for the atomic bomb.

The bomb hovers over the exhibit as it has over life itself since the Second World War. The most chilling exchange of letters is one between Einstein and Franklin D. Roosevelt-never before displayed together-in which Einstein informed the President that the Germans were on the verge of creating an atomic weapon. He urged Roosevelt to get there first. "Some recent work by E. Fermi and L. Szilard, which has been communicated to me in manuscript, leads me to expect that the element uranium may be turned into a new and important source of energy in the immediate future,'' Einstein wrote. His letter led to the Manhattan Project, and in later years he often wondered whether he'd made a mistake writing it and what might have happened if he had not. When the bomb was dropped on Hiroshima, Einstein's immediate response was "Vey iz mir," and Shara presents the phrase, under a picture of the mushroom cloud, with the translation: "Woe is me." By the end of his life, Einstein was a pacifist, his creations having slipped well beyond his control.