The weirdness of physics, part 2

In the first part of this brief series, I posted about relativity and quantum mechanics.

In the second part, I wish to set forth my understanding of what current physicists think about the very substances we are made of.

When I went to school, we were taught that that there were three common sub-atomic particles, namely the electron, the proton, and the neutron. There was mention of some others, such as positrons -- positively charged electrons, or, perhaps, electrons moving backward through space-time. We understood that positrons were uncommon, and that is still true. Positrons are essential for the existence of antimatter -- matter that is, as it were, the exact opposite of regular matter. Antimatter is so much the opposite, that, if it comes in contact with normal matter, the two annihilate each other, in a grand explosion of energy. We don't know why matter predominates in our universe, rather than antimatter. Positrons really do exist. They are used in Positron Emission Tomography, an important detection procedure in medicine and biological experimentation.

Physicists wanted to know if electrons, neutrons, and protons were made of anything even more fundamental. The answer is that electrons are not, as far as we know -- they are fundamental particles, not made of anything else. But protons and neutrons are made of more fundamental particles, called quarks. When I took physics in college, quarks were not even mentioned. By the time I began teaching, they were postulated, but without any experimental evidence. Postulating their existence brought some order, some explanation, to why things are the way they are. By the 1970s, experimental evidence for quarks was forthcoming. There are, it develops, six different types of quarks, although only two of them go to make up neutrons and protons, each of which is made up of three quarks. So, we think quarks are fundamental particles, whereas neutrons and protons are not. Some physicists have called the multiplicity of sub-atomic particles a "zoo," meaning that there are a lot of them, they are diverse, and implying that there are really more than there should be -- there shouldn't be so many "fundamental" particles. Surely there is some even more fundamental type, and not so many of these?

Well, in answer to the last question, perhaps the weirdest proposal of all -- string theory. As it began, string theory proposed that the particles mentioned above, and all the others, were made of a single entity, a string, which vibrated in up to as many as 14 dimensions, the 4 of space-time, and 10 more. If that isn't weird, I don't know what is. The theory, according to the Wikipedia article on it (see link in the first sentence of this paragraph), has moved somewhat beyond the description I just gave it. But it remains, so far, a theory which hasn't been fully vindicated*. There doesn't seem to be any experimental evidence for string theory, so far. Perhaps there never will be.

The Psalmist, in Psalm 139:14, said "I praise you, for I am fearfully and wonderfully made.
Wonderful are your works; my soul knows it very well." (ESV) I don't suppose that the Psalmist had any clue about the existence and description of the cell nucleus, or the atomic nucleus, but, nonetheless, he was right. We, and all matter, are fearfully and wonderfully made, whether quarks and electrons are really fundamental particles or not, and whether or not multi-dimensional strings really exist.

Thanks for reading.

*April 22, 2009. Thanks to a commenter who did read (see below) I changed this sentence, which, wrongly, had said "It remains just a theory." That was a poor choice of words.