![]() ![]() The problem is we don’t know which page is the right one, and the number of pages has grown fantastically in the last few years. Literally, I could write out a book and turn page by page and show you different shapes for the extra dimensions that people have mathematically determined as being possible. What is the current status of string theory research? We have a range of possibilities for the shape of the extra dimensions. ![]() The dream in the 1990s was to find the shape of the extra dimensions and then calculate the values of all those properties that experimenters have found. The energy depends on how its little string can vibrate, and the string vibrates in a manner that depends on its environment, so it depends on the shape of the extra dimensions. An electron weighs what it does because it has a certain internal energy, and that energy, according to Einstein, equals mc². So if you asked me, “Why does the electron have its charge or its particular mass?” the answer in string theory would be because the extra dimensions have the shape that they do. How can we envision these extra dimensions, and how would they manifest themselves in our seemingly three-dimensional world? The shape and size of the extra dimensions would affect the properties of particles. Nevertheless, it’s an idea that string theorists take seriously, because that’s where the math leads, and math has proved itself to be a very sure-footed guide to how the universe works. It required nine dimensions, and when you add in time it gives you 10 dimensions, which is an astoundingly bizarre idea. When people stared at the mathematics governing the motion of these little filaments, they found, remarkably, that the math didn’t work in a universe that has only three dimensions of space. They could exist in either little loops of filament-tiny loops of energy-or little snippets of energy, open strings as we call them. How does string theory create a single worldview that applies everywhere-and what exactly is a string, anyway? The fundamental idea is that the elementary constituents of matter-electrons, quarks, and so forth-might not be dots of no size, which is the traditional image, but rather little filaments. In reality, both sets of laws are meant to work everywhere. It’s uncomfortable to have two laws of physics, each claiming that the other somehow doesn’t work. But when you try to meld the two, there is an incompatibility, a hostility. What is the major problem string theory attempts to solve? Our current theory of gravity-Einstein’s general theory of relativity-and our current theory of the behavior of atoms and subatomic particles-quantum mechanics-both work fantastically well in their respective domains: general relativity for big things, quantum mechanics for small things. Greene talked to DISCOVER about how string theory has evolved, the attempts to find supporting evidence through new experiments, and the challenges of making science exciting to the general public. In 2008 he cofounded the World Science Festival, an annual event that brings together scientists, artists, and ordinary people who are simply interested in the great questions of the universe. He has provided insight into the topology of those additional dimensions, and in 1999 he introduced the theory to nonscientists in a best-selling book, ![]() That may seem wildly counterintuitive, but many scientists agree it is the most promising approach to explain the laws of physics.Ĭolumbia University physicist Brian Greene has become the public face of string theory. At that level, according to the theory, lies the foundation of all the particles and forces in the universe: one-dimensional strands of energy, or “strings,” vibrating in nine dimensions. ![]() String theory explains what you might see if you zoomed in without limit, past the cells that constitute your body, past the atoms that make up those cells, past even the electrons and gluons that those atoms are made of, all the way to the scale of a billionth of a trillionth of a trillionth of a centimeter. It could be the elusive theory of everything, a set of universal laws governing everything from the smallest quark within the atom to the largest cluster of galaxies, from the Big Bang to this moment. Now many scientists believe an improved version of his conjecture, known as string theory, may do more than merely explain the atom. In the 1960s, Italian physicist Gabriele Veneziano developed a theory to explain the inner workings of the atom and failed-at first. This article is a sample from DISCOVER's special Extreme Universe issue, available only on newsstands through March 22. ![]()
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