For the last three weeks, I have waded through Brian Greene’s The Elegant Universe, a book that explains string theory and its role in physics. Now that I have finished the book, I wanted explore its contents with you in the hopes that you and I will have a better understanding of the universe.
As I have mentioned in earlier posts, physics and anything close to it have never been a forte of mine. I have never formally studied the field, finding it intimidating. I finally decided to be brave and learn more. While I am glad I did, the book definitely left me with questions. But first let me explain to you a little bit more about what it’s about.
It starts with Albert Einstein and his theories of special and general relativity. Einstein’s theory of special relativity says that our perceptions are relative, or, in other words, no one will see force-free motion the same way. These motions are also only meaningful in comparison with other individuals or objects. For every day events, we don’t really see these differences in perception, because daily motion is incredibly slow compared to the speed of light. But the distortions of space and time are clouded, though, by these perceptions. There are two constants to special relativity: the speed of light never changes and the laws of physics must be absolutely identical.
The theory of general relativity is compatibly with special relativity that explains gravity as a force that warps both space and time. Objects with any mass, including you and I, curve the spatial dimensions around us. This is space’s response to our presence. Larger masses warp space more.
Green quotes the physicist John Wheeler on gravity as saying, “mass grips space by telling it how to curve, space grips mass by telling it how to move.”
Time is also warped by gravity. The stronger the gravitational field, the slower time passes. This concept makes me think of Star Wars. I imagine the tractor beam on a giant star ship pulling in Han Solo and the Millennium Falcon. But I am not exactly sure time actually slows down for those on the Falcon.
Now on to the next concept. Quantum mechanics.
Quantum mechanics looks at microscopic particles and how they behave, using mathematical equations. These complex calculations can predict the probability an outcome, such as the location of an electron, will occur. They can’t predict the actual outcome of experiments. This gives rise to the uncertainty principle, which says that the position and velocity of a particle cannot be precisely determined. Things are pretty chaotic on the microscopic level. Quantum mechanics also has shown that all matter has wave-like properties.
The theory of general relativity and quantum mechanics attempt to explain different aspects of our universe. Both theories have been experimentally tested and confirmed multiple times separately. Yet, physicists haven’t been able to make them work together to create a unified theory. General relativity’s smooth spatial curves are violently killed by the chaos of quantum mechanics.
Greene writes, “Calculations that merge the equations of general relativity and those of quantum mechanics typically yield one and the same ridiculous answer: infinity. Like a sharp rap on the wrist from an old-time schoolteacher, an infinite answer is nature’s way of telling us that we are doing something that is wrong.”
Enter string theory.
String theory in short says that at the most basic level particles are tiny loops of string. These strings, which can look more blob-like than string like, vibrate in an infinite number of ways, and specific vibrations are thought to correspond to certain particles.
(This theory is really much more complex than my explanation above. In fact, there are five different versions of string theory that vary only slightly in their equations. These versions, physicists are now finding, are actually part of a single framework called M-theory.)
So, how does string theory make quantum mechanics and general relativity compatible?
First, it replaces the previously-held notion that particles are point-like with tiny looped filaments. Second, and perhaps most important, it smooths the violence of quantum chaos by softening the “short-distance properties of space.” In other words, things aren’t quite as chaotic at the particle level with oscillating strings.
Much research still needs to be done on string theory (and M-theory), though, to even confirm it. Preliminary experiments have made it more and more likely, but we still don’t have the technology to full on prove it.
While I definitely think the theory is interesting, I am not 100 percent sold on it yet. This book was republished in 2003 after its original printing in 1999. I wonder how many more advances have been made. Does the term string still adequately describe these tiny loops? Are we even closer to confirming whether this really is the theory of everything? If we do show that string theory is the theory of everything, what happens next? What possibilities does this open?
The questions could go on. But no matter how many questions this leaves, it doesn’t diminish the fact that we are closer to truly understanding our universe.
In all, I thought Greene’s book was very interesting. He used many every day examples to help explain difficult concepts, such as a bowling ball sitting on a rubber sheet to show how mass warps space. Yet, I found myself rereading parts of the book to make sure I understood everything. (I still don’t even know if I did.) The writing at times felt a little clunky and academic, and I occasionally got lost in the long illustrations. Even the glossary of terms at the back of the book left me a little confused.
Despite these gripes, I did enjoy learning about quantum mechanics, general relativity and string theory. It made me truly appreciate how complicated and beautiful the universe is. I can’t wait to learn more about it even if I don’t completely understand it.