Changing Planet

EINSTEIN Part I: The Pi in ‘π-day’


Between 1931 and 1933 Einstein spent three stints at Oxford University's Christ Church College. The photo was taken in 1931 when Einstein gave a pair of lectures. Two of the young members of Christ Church who served as ushers at the event were Erwin Schrödinger, who would receive the Nobel Prize in Physics 1933, and John Eccles, who would receive the Nobel Prize in Medicine or Physiology in 1963)

Among physics students, March 14 is known as “π-Day” (“Pi-Day”) the day that Albert Einstein was born in Ulm, Germany in 1879. The venerable physicist is known for changing the very paradigm of physics, rejecting the three “fundamental undefinables” of length, mass and time as invariant, and positing in their place the speed of light as the unique invariant. (Thus, measuring the speed of a light beam while traveling in the same direction as the beam, and measuring it while traveling in the opposite direction would yield precisely the same relative velocities; this in distinction to common sense, which would call for adding and subtracting the speed of light from the speed of the observer.) The ramifications of this shift in paradigm lead to fascinating effects at relativistic speeds — including, a contraction of length, an increase of mass, and the slowing down of time. Lying down in the direction of motion in a rocket ship traveling at 50% of the speed of light, a 6′ man would shrink to 5’3”; if his weight were 180 pounds normally, it would increase to 207 pounds. And if he traveled for one earth-year, he would age 47 days less than if he had remained stationary. Launched on March 14, 2012, and brought back one year later, on March 14, 2013, it would be only January 25, 2013 for him. Einstein’s special theory of relativity was published in 1905, and the far more complex general theory of relativity in 1915. Special relativity gives the equivalence of energy and mass in the most famous equation in science, E=mc^2. General relativity, based on the equivalent effects of gravitation and acceleration, leads to explanations of the large-scale universe — a violent universe that has its origin in a “Big Bang” 13.7 billion years ago; of light bending around massive bodies such as stars and galaxies; of stars that collapse into black holes; of “worm holes” that connect different locations of space-time in the universe. Isaac Newton’s dynamics, formulated two centuries earlier in the Principia are still valid, but at relativistic velocities they have to be modified. Einstein’s work has to be regarded as buttressing Newton’s physics and not in any way subverting it. A spaceship can still be sent to land on the moon with Newton’s physics, but Einstein’s corrections would make it a softer landing.

Ink drawing by the author, inspired by a Yousuf Karsh photo hanging in the Physics Department at Princeton University


Late in 1999, the editors of Time Magazine, used to selecting the “Individual of the Year,” found themselves with a much more difficult task — selecting the individual of the century. After what must have called for considerable deliberation, they made their announcement. It would not be a spiritual leader, such as Pope John Paul II, Gandhi or Mother Teresa. And it would not be a political leader, such as FDR, Stalin or Churchill, in a century that had seen two World Wars. The editors’ choice for the “Individual of the Century” would be Albert Einstein. They explained the reasoning in their selection: the 20th century had been the ‘Century of Science’ and Albert Einstein was its greatest practitioner, and the very symbol of science.


π is the symbol for the irrational number representing the ratio of the circumference of a circle divided by its diameter. To seven places after the decimal, its value is 3.141 592 7 As an irrational number π cannot be expressed exactly by the ratio of two numbers; however, elementary school students are often taught 22/7, as a crude approximation. It yields 3.142 857, good to two places after the decimal. A much better approximation is 355/113, a ratio that equals 3.141 592 9, good to six places. A better approximation still comes from the mnemonic, “How I need a drink, alcoholic of course, after the heavy lectures involving quantum mechanics,” 3.141 592 653 589 79… Good to 15 places, it comes from counting the letters in each successive word. (For children, substitute “pepsicola” for “alcoholic”.)


Bulent Atalay, a scientist, artist and author, has been described by NPR, PBS and the Washington Post as a “Modern Renaissance Man.” He is the author of two successful books on the intersection of art, science and mathematics, with Leonardo, the pre-eminent Renaissance man, serving as the foil. His best selling book, "Math and the Mona Lisa," (Smithsonian Books, 2004) has appeared in 13 languages. Professor Atalay's academic background is in theoretical physics. He travels around the world lecturing at academic institutions and on cruise ships on the "A-subjects," art, archaeology, astrophysics, atomic physics and Ataturk, confessing that he knows much less about the "B-subjects," business, banking, biology and botany... He is the President of the Ataturk Society of America (ASA), dedicated to promoting Ataturk's ideals of science and reason over dogma and superstition, of a secular state with full equality of genders. For more details click on Bulent Atalay
  • Bob A

    Once again, Bulent Atalay explains things in such a way that neophytes can understand. In other words, now we can get a piece of the π.

  • Bob, thank you for the kind words, and the pun!

  • Alice Calaprice

    Bulent, I can never pretend to understand relativity theory, but your explanations get me a bit closer. Looking forward to reading the anecdotes. You may know that a charming little German book, “Liebes Hertz” (Birkhaeuser 1994), is full of amusing ones–and some are even true! “Hertz” is of course a reference to Heinrich Hertz and a play on the German word Herz for heart.

  • Alice, 25-30 years ago, I was on a flight from DC to NY, grading a batch of nuclear physics tests, when a young woman sitting next to me, asked, “Are you a mathematician?” I told her I was physicist, and that physics was irreversibly married to mathematics. She replied by offering an enigma, “My great grandfather was a famous physicist, and his name is on every radio in the world, but no one knows who he is.” There is another reference to Heinrich Hertz. Regarding π-day celebrations at Princeton, sitting next to Freeman Dyson at the book signing, his foreword complementing your book, “The Ultimate Quotable Einstein,” you must have sold all the copies on hand, and indeed I hope that Professor Dyson signed them also. It’s a definitive book on an individual as quotable as Winston Churchill and Yogi Berra. Thank you for the comment.

  • Rochele HC Hirsch

    On March 6-7 this year, it was reported that particles from the Sun’s recent Solar Storm were traveling towards us at 1300 miles / second. Seems very fast until we compare it with the speed of light, 186,282 miles / second. Einstein truly moved us from “what is real” according to our 5 senses into a different paradigm of reality at the speed of light. Thanks, Bulent, for helping us to know more about this man and the “bigger picture” he drew for us.

  • Laura Rickard

    Reading your article made me feel like I was back in your Physics class again. I am happy to see that the world has now become your classroom.

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