hat are you up to, you frozen whale, you smoked, dried, canned piece of soul?"

So did Albert Einstein, then a 26-year-old patent clerk in Bern, Switzerland, begin a letter to his pal Conrad Habicht in the spring of 1905.

Whatever Habicht, a math teacher in Schaffhausen, had been up to was not much compared to his irreverent friend, who had been altering the foundations of physics during the few free hours left to a young father, husband and government worker. As he related to Habicht, Einstein had just finished writing three major physics papers.

One showed how the existence of atoms, still a debatable proposition, could be verified by measuring the jigglingof microscopic particles in a glass of water, a process known as Brownian motion; in another, his doctoral dissertation for the University of Zurich, he deduced the size of molecules. In still another, which he described as "very revolutionary," Einstein argued that light behaved as if it were composed of particles, rather than the waves that most physicists thought.

That paper, which won him the 1921 Nobel Prize, helped lay the foundation for quantum theory, a paradoxical statistical description of nature on the smallest subatomic scales that he himself later rejected, saying that God did not play dice with the universe.

But he wasn't done. There was a fourth paper, he told Habicht, still just a rough draft that employed "a modification of the theory of space and time."

That, of course, was relativity, the theory that set the speed of light as the universal speed limit and loosened space and time from their Newtonian rigidity, allowing them to breathe, expand, contract and bend, and led to the expanding universe and the apocalyptic marriage of energy and mass in the famous equation E=mc2.

Any of those papers would have made a young man's reputation, or even a career. Taken together they amounted to an "annus mirabilis" or miracle year for the young physicist, a remaking of physics at the beginning of the still-young century.

Einstein has been dead for 50 years this April, but he is still the scientist most likely to have his picture on the front page of the newspaper, perhaps famously sticking out his tongue. It is still Einstein's universe, and in honor of his "miracle year" in 1905, physicists, universities and governmental organizations have laid on a gantlet of celebrations, conferences, books, concerts, contests, Web sites, lectures, games and a controversial intercontinental light show.

As Dr. Gerald Holton, a professor of physics and the history of science at Harvard who is the dean of Einstein scholars, put it, "There's a typhoon headed our way" before heading off to Berlin to give the keynote address at a conference last week called "Einstein for the 21st Century" - the first of many stops on his itinerary this year.

The International Year of Physics, as the United Nations has officially designated 2005, has already had its zany moments of physics fun, with more to come. This month, Ben Wallace, 18, a professional stunt cyclist, flew off a ramp in the London Science Museum and did a back flip 12 feet in the air while folding his bicycle sideways - a maneuver designed by a Cambridge physicist who said she was inspired by a tale that the 26-year-old Einstein had invented his theory of relativity while riding a bicycle.

Never mind that there is no evidence that Einstein even had a bicycle as a young man. Never mind that the "Einstein flip" itself, as complicated and carefully plotted as it was, relies strictly on the old-fashioned laws of Isaac Newton.

If bicycle stunts aren't your cup of tea, perhaps you would take in "Constant Speed," a ballet inspired by relativity, which the Rambert Dance Company will perform in London starting May 24. Maybe you would like to download the rap song "Einstein (Not Enough Time)" by DJ Vader, adopted by Britain's Institute of Physics for an educational computer game, or the Einstein@Home screen saver, which will allow your computer to process signals from the cosmos for the twitches and vibrations of space-time known as gravitational waves.

Or maybe you would like to try the Pirelli Group's contest for the best five-minute multimedia explanation of relativity. (The prize is 25,000 euros, or about $32,500.)

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The point of all this, physicists freely admit, is not to glorify Einstein, who hardly needs it, but to promote physics and impress its importance and relevance to young people who have been drifting off into other pursuits even as physics becomes more and more essential to grapple with problems like climate change, nuclear proliferation, a looming energy crisis and missile defense.

"The great contributions of physics to the development of science and technology and its impact on our society might still be evident to us physicists, but no longer to everybody," Dr. Martial Ducloy, a physicist at the University of Paris and the chairman of the physics year steering committee, said in an e-mail message. He noted that the number of physics students had declined drastically worldwide.

The party has actually been going for a while.

A museum exhibition organized by the Hebrew University of Jerusalem, repository of Einstein's papers and artifacts; the American Museum of Natural History; and the Skirball Cultural Center in Los Angeles has been touring the world since 2002. In August the Aspen Institute summoned academics, thinkers and writers like the Caltech Nobelist Murray Gell-Mann and the author E. L. Doctorow to the Rockies for a three-day exploration of Einstein and his legacy, from physics and arms control to morality and spirituality and even modern art.

Festivities kicked into higher gear this month with Mr. Wallace's safe landing and a conference titled "Physics for Tomorrow" at the Paris headquarters of Unesco.

It continued in Berlin, where last week Chancellor Gerhard Schröder pronounced 2005 "Einstein Year" in Germany, a nice twist of fate, since, although Einstein was born in Germany, he had been chased out by the Nazis in 1933. The party will move on to London, Tenerife, Tel Aviv, Munich, Vienna, Bern and Durban, South Africa, among other places.

Much of the action, however, will happen on a smaller scale, at universities and schools and museums.

"We're reaching out to the 10-year-olds and 14-year-olds who don't know what physics is," said Helen Czerski, the Cambridge physics graduate student (and springboard diver) who designed the Einstein flip.

On April 18, the 50th anniversary of Einstein's death, Princeton, N.J., where he lived for his last 22 years, will unveil a new statue of him by the sculptor Robert Berks. (A listing of events, country by country, can be found at www.wyp2005.org.)

The Einstein year is also likely to mean a surge in sales of T-shirts, mugs, calendars, action figures and the like, to the benefit of Hebrew University. Einstein left his papers and his copyright to the university, which he helped found, and which licenses the use of Einstein's image through the Roger Richman Agency of Beverly Hills, Calif., famous for representing dead celebrities.

Dr. Menachem Magidor, president of the university, said that Einstein royalties had brought in more than $10 million to the university over the years.

Presumably the amount could have been even greater, but the university is mindful of Einstein's image and so, for example, recently turned down a proposal for an Einstein vodka, Dr. Magidor said.

Einstein's miracle year was only the beginning of his legend. Einstein topped himself in 1915 when he extended relativity to gravity in his general theory of relativity, which predicted the expansion of the universe and black holes (somewhat to his befuddlement).

When the theory was supported by observations of light bending during a solar eclipse in 1919, he became an international celebrity.

By then, Einstein, who was born in Ulm, Germany, in 1879, was living in Berlin, but he fled Hitler in 1933 and took a post at the new Institute for Advanced Study in Princeton where he wandered the streets, a sockless living legend and reminder of cosmic mystery.

A lifelong pacifist, he lent his prestige to the development of an atomic bomb only to see it dropped on Hiroshima and Nagasaki, to his lasting dismay. He spent much of his later years campaigning for nuclear disarmament and civil liberties. By the time he died in 1955, he had gone from being the human face of mystery and science to being the human face of humanity.

This year's festivities are the biggest planned since the centennial of his birth, and since then much has been learned about Einstein, the man and the physicist, partly as a result of a vast effort by Hebrew University and Princeton University Press to collect and publish Einstein's 50,000 pieces of correspondence and other papers.

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The first of a projected 30 volumes, which was published in 1987, contained newly discovered love letters that the young Einstein had written during his college years to his classmate, sweetheart and future wife, Mileva Maric, disclosing, among other things, the existence of an illegitimate daughter, Lieserl, now lost to history.

The letters showed scholars a side of Einstein they hadn't seen before, as a passionate and energetic young man, a flirt and a poet.

"We hadn't thought of Einstein as a gorgeous sort of fellow in that sense," Dr. Holton said.

The result has been a wave of new biographies in recent years (including one by this writer).

Dr. Ducloy said he had proposed making 2005 the World Year of Physics back in 2000, when he was elected president of the European Physical Society. The proposal was formally approved by the General Assembly of the United Nations last July.

As with the Einstein flip, however, success has its price. Take, for example, the Einstein light relay. The idea, as developed by Dr. Max Lippitsch and Dr. Sonja Draxler of Karl-Franzens University Graz in Austria, is an illuminated version of the wave made familiar by sports fans.

On the night of April 18, the 50th anniversary of Einstein's death, lights are to go on in Princeton and then in a sequence, like the bulbs on a Christmas tree, all the way across the United States.

The lights will then the leap the Pacific to Japan and China and follow a pair of tracks, north and south, across Asia, reconnecting in Austria, crossing Europe and then jumping across the ocean to arrive in back in Princeton 24 hours after it left: a sort of cosmic cheer for the memory of Einstein.

The proposal was opposed, however, by astronomical groups like the International Dark Sky Association, dedicated to fighting light pollution that can ruin deep space observations. While harmless in itself, the light relay would set a bad precedent, they say.

"We think it is a bad thing for people to splash light around without considering the consequences," said Dr. Robert Kirshner, an astronomer at the Harvard-Smithsonian Center for Astrophysics and president of the American Astronomical Society.

In response the light relay has been modified. The new rules specify that participants turn off the lights 10 minutes before the light arrives so that a "flash of darkness" accompanies the flash of light, and to make sure they point their lights along the path of the relay and not into the sky.

Dr. Lippitsch said he thought emotions had calmed.

"In the U.S.A., the number of registered participants is rather low so far," he admitted in an e-mail message, "but we are confident that a project designed to overcome the vastness of Siberia or the deserts of Iran will not break down in the country with the best infrastructure and the highest number of physicists."