String theory

But we can t be too smug. We must avoid the mistake of the physicist who, as the twentieth century began, stated confidently that we knew all there was to know about physics, that science just needed to clean up a few dusty corners. Then came relativity, quantum theory, the Big Bang, and now dark matter, dark energy and string theory. Similarly in the life sciences, the more we learn, the better we understand how little we really know. There remains a vast landscape to explore, with great questions remaining. 

The observation of atomic spectra stimulated physicists in the early 19th century to develop the theory of quantum mechanics. This theory sets out to explain all physical phenomena at an atomic scale and atomic spectroscopy is an important validation. Quantum mechanics is flawed, however, notably in the description of gravity, but it is the best theory at present (although super string theory promises well) for the description of the structure of nuclei, atoms and molecules. 

Super string theory The theory of cosmology that attempts to unite gravity and the other forces of nature. 

Langone, John. Theories for everything an illustrated history of science from the invention of numbers to string theory. Washington, D.C. National Geographic, 2006. 

In heterotic string theory... the right-handed bosons (carrier particles) go counterclockwise around the loop, their vibrations penetrating 22 compacted dimensions. The bosons live in a space of 26 dimensions (including time) of which 6 are the compacted real dimensions, 4 are the dimensions of ordinary space-time, and the other 16 are deemed interior spaces —mathematical artifacts to make everything work out right. 

String theory may be more appropriate to departments of mathematics or even schools of divinity. How many angels can dance on the head of a pin How many dimensions are there in a compacted manifold thirty powers of ten smaller than a pinhead Will all the young Ph.D.s, after wasting years on string theory, be employable when the string snaps ... 

String theory is twenty-first century physics that fell accidentally into the twentieth century. 

In some string theories, the loops of string move about in ordinary three-space, but they also vibrate in higher spatial dimensions perpendicular to our world. As a simple metaphor, think of a vibrating guitar string whose notes correspond to different typical particles such as quarks and electrons along... 

As technically advanced as superstring theory sounds, superstring theory could have been developed a long time ago according to string-theory guru Edward Witten, a theoretical physicist at the Institute for Advanced Study in... 

Princeton. For example, he indicates that it is quite likely that other civilizations in the universe discovered superstring theory and then later derived Einstein-like formulations (which in our world predate string theory by more than half a century). Unfortunately for experimentalists, superstrings are so small that they are not likely to ever be detectable by humans. If you consider the ratio of the... 

So complex is string theory that when a Nobel Prize-wining physicist was asked to comment on the importance of Witten s work, he said that he could not understand Witten s recent papers therefore, he could not ascertain how brilliant Witten is ... 

Unfortunately, there are so many different ways to create universes by compactify-ing the six dimensions that string theory is difficult to relate to the real universe. In 1993, researchers suggested that if string theory takes into account the quantum effects of charged mini black holes, the thousands of 4-D solutions may collapse to only one. Tiny black holes, with no more mass than an elementary particle, and strings may be two descriptions of the same object. Thanks to the theory of mini black holes, physicists now hope to mathematically follow the evolution of the universe and select one particular Calabi-Yau compactification—a first step to a testable theory of everything. ... 

Some trivia Gabriele Veneziano, in the late 1960s, worked on string theories. However, interest in his particular version of the theory faded when other physicists showed they would only work in twenty-six dimensions. Also, some researchers believe that all known elementary particles have unseen symmetric twins called sparticles. 

M-theory in eleven dimensions gives rise to the five competing string theories in ten dimensions (two heterotic theories, Type I, Type IIA, and Type IIB). When the extra dimension curls into a circle, M-theory yields the Type IIA superstring. On the other hand, if the extra dimension shrinks to a line segment, M-theory yields one of the heterotic strings. 

Note that string theory says little about the space in which strings move and vibrate. A relatively new mathematical model known as loop quantum gravity represents an alternate approach in which the rules of quantum mechanics are applied directly to Einstein s description of space and time. In this model, space itself comes packaged in... 

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