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His infinite curiosity

  • Stephen Hawking took on the most challenging questions, and brought humanity several steps closer to true understanding. Courtesy photo / Discovery Channel

  • The universe remains a place of discovery and mystery. Courtesy photo



Friday, May 11, 2018

Stephen Hawking wasn’t finished, but what an amazing and productive life he had till the very end. In his notes and in an unfinished technical paper, he thought that something called “M-Theory” is our best bet for a complete theory of the universe.

But I thought we understood the universe pretty well. What’s not complete? What is this so called M-theory? Google search to the rescue.

We have all heard of Einstein’s theory of general relativity, and a few may even understand it. The theory is quite accurate in describing a planet’s orbit or galaxy dynamics. If we work hard enough, he suggested, we will eventually find the elegant and simple rules that underlie the entire universe.

Delve into the other direction, into the infinitely small world of atoms and particles, described by quantum mechanics, …concepts some may have heard of but very few understand. Missing however, glaring for its absence, is an expression for the interaction of gravity. A consistent theory of gravity should be valid at any scale and should take into account the quantum nature of fundamental particles.

M-theory?

OK, hold on to your hats because it gets crazy from here, especially if you’ve never heard of string theory. To understand the basic idea of M-theory you have to go back to the ‘70s when scientists realized that, rather than describing the universe based on point like particles (protons, neutrons, quarks, etc) you could describe it in terms of tiny oscillating strings (tubes of energy). Tiny, as in about 10^-33 centimeters, or about a millionth of a billionth of a billionth of a billionth of a centimeter. This new way of thinking about the fundamental constituents of nature turned out to solve many theoretical problems. And unlike the standard theory of gravity, string theory can describe its interactions mathematically without getting weird and strange results. Gravity was finally included in the unified framework. Scientists were ecstatic, but there is a problem. It’s all purely mathematical and you can’t prove it. Even stranger is the striking feature that string theory requires the existence of 10 spacetime dimensions. I can’t explain it, I can’t envision these extra dimensions but it doesn’t seem to bother the smartest intellects, these scientists and mathematicians. The extra dimensions are “compactified” on such a small scale that we wouldn’t notice.

But there was a problem, a big problem. A thorough classification showed the existence of five different consistent string theories. I smile to myself to continue because it does seem “way out there,” but these incredible geniuses believe it. In 1995, a physicist proposed that the five consistent string theories are actually only one, just different faces of a unique theory that lives in 11 space-time dimensions. OK, I said that with a straight face. This is known as M-theory. It includes each of the string theories in different physical contexts, but it is still valid for them all. That last statement is very important, and it leads to the so-called “theory of everything.”

Most great physicists and cosmologists are driven by a passion to find that beautiful, simple description of the world that can explain everything. And although they are not quite there yet, they wouldn’t have a chance without the sharp, creative minds of people like Hawking.

David Buren lives in Peterborough.