String Theory in 500 Words or Less

Today we’re going to stray off the beaten path and talk about particle physics and String Theory. What’s in it for you, you ask? Well, for one, since I’m going to take a shot at explaining it in 500 words or less, you can learn quite a lot in a very short time. Also, if this set of ideas that some call "The Unified Theory of Everything" proves out someday, you’ll be able to nod knowingly and say, “Yes, yes, I have always thought so.” If neither of those are enough to keep you, then go away and come back tomorrow when we'll talk about something easier like how screwed up the Supreme Court is these days.

So. We’ve been told that ordinary matter is made of atoms, which are in turn made of electrons whirling around a nucleus composed of neutrons and protons. We call the electron a fundamental particle belonging to a nice little particle family called “leptons," and we believe that its neutrons and protons are made of even smaller fundamental particles called “quarks.” Our current beliefs about the subatomic universe are summed up nicely in what we call the Standard Model of particle physics. This model describes what we say are the twelve basic building blocks: six types of quarks, and six types of leptons. Quarks go by the interesting names of up, down, charm, strange, bottom and top. (For example, a proton is made of two up quarks and one down quark.) The leptons include the electron and its two heavier pals, the muon and the tauon, plus three neutrinos.

The Standard Model also describes the four known fundamental forces in the universe: gravity, electromagnetism, and the weak and strong nuclear forces. It is believed that each of these forces are produced by particles that act as carriers of that force. The most familiar of these is the photon, otherwise known as a light particle, which is the mediator of electromagnetic forces. The graviton is the particle associated with gravity (and is already familiar to Star Trek fans). The strong force is carried by eight different particles known as gluons, and the weak force is transmitted by three particles, the W+, the W- and the Z. (Disappointing little labels after names like “charm” and “strange” – but I digress.)

The Standard Model pretty thoroughly describes all particles and forces, with one exception: gravity. The gravitational force has proven difficult to describe or map. For years this has been one of the most important problems in theoretical physics. We seem unable to come up with a viable quantum theory of gravity. In the last few decades, string theory has emerged as one possible means for developing a microscopic theory of gravity as well as possibly being the possible Holy Grail of quantum physics, the aforementioned Unified Theory of Everything.

The fundamental idea supporting String Theory is that all the different particles of the Standard Model are really just different manifestations of one basic object: something that is too small to be visible on any existing microscope and which looks like a little piece or loop of string. So, whereas we would commonly picture an electron as a point with no dimensions and no internal structure – a point that cannot do anything but stay where it is, or move to another place in space-time – String Theory says that if we had an adequately powerful microscope, we would see that the electron is not really a point and is instead more like a tiny string. And we would see that this string is able to do something besides sit still, or move: it can oscillate and/or vibrate.

So, if one of these strings, of a certain mass, oscillates and/or vibrates a certain way, then from a distance we would be unable to tell it is a string and might see what we call an electron. But if it had a different mass, or oscillated and/or vibrated in some other way, we might call it a photon, or a quark. If String Theory is correct, the entire universe is made of these tiny strings of varying mass that oscillate and/or vibrate at different speeds or “resonances”…and it is our ability to see (and/or hear? and/or sense?) them that will lead to further knowledge and possible theoretical breakthroughs.

Update: I asked my brother to fact-check this post; he emailed with this: "Good summary; you excluded anti-particles, but that's not a big deal. Also, the standard model doesn't contain gravity at all; it doesn't predict gravitons. More importantly, though, is that the key behind string theory is that strings exist in more than 3 spatial dimensions (various theories have different "extra" dimensions, up to 8, I think). This makes it a highly mathematical theory with few testable predictions with current technology."

Update 2: There's now a comment by someone who says I'm wrong in other ways, too. I'm just glad someone besides my brother (and Mom) read the whole thing. But I guess I'd better give up my Dreams of becoming a world renowned String Theory Expert...