Bending the mind around five dimensions This may seem difficult to visualize after spending a lifetime thinking in the four dimensions we call home. Additional dimensions of space may be present but have gone undetected if they are curled up to small sizes. In one description of a possible fifth dimension, our world is confined to a four-dimensional sheet floating in the fifth dimension. Some forces can be limited to traveling in the familiar four dimensions while others can travel through the extra dimensions. Such dimension-jumping forces arenāt known for sure, but Arkani-Hamed thinks one of them may be one of the most familiar in the universe: gravity. Unlike the other basic forces of nature ā the strong and weak forces that operate at the atomic level, and electromagnetism that keeps our electronic society humming ā gravity is familiar to virtually everyone who has ever seen a leaf fall or dropped their keys. Familiar though it is, gravity is something of a puzzle to physicists. One problem is that, compared with the other forces, gravity is extremely weak. It takes the gravity exerted by a huge body like the Earth to keep small creatures like us from floating off into space. Meanwhile, a common magnet smaller than your fist has no trouble overcoming gravity and picking up a paperclip. Arkani-Hamed believes that extra dimensions may hold the answer to gravityās weakness. If gravity is able to act in fifth, sixth, and higher dimensions, that could effectively dilute the force of gravity in our four dimensions and explain its apparent weakness. Exotic answers to exotic questions Arkani-Hamedās journey to Harvard began as a high school kid in Toronto, where he first became interested in theoretical physics. Physics excited him, he said, by explaining natureās basic forces in ways he could not only understand, but also use to predict what will happen in specific cases. He received a bachelorās degree in math and physics from the University of Toronto in 1993 and a doctorate in physics from the University of California at Berkeley in 1997. From there, he became assistant and associate professor of physics at Berkeley, and then in 2001, he became a visiting professor at Harvard. Arkani-Hamedās theories on extra dimensions and gravity stimulated a lot of excitement among experimental physicists, who began working to confirm his theories, said Physics Department Chair Professor Gerald Gabrielse.
