Prof. Disbrow takes us through the teenier parts of the universe.
In last month’s column, I discussed distances. Specifically, large distances, as they are used in science generally and astronomy in particular. This month, I thought I’d go the other direction, and discuss distances used in measuring the very (very!) small things that science deals with. Once again, we’ll start things off at a scale humans can deal with and work our way down from there.
Meter (m): The meter is pretty much the standard of distance in science. If you insist on being old-fashioned, that’s roughly three feet (one yard) long.
Centimeter (cm): One meter is made up of 100 centimeters. There really isn’t an easy equivalent to a “foot” in the metric system. But, one inch is about 2.54 centimeters, and that’s easy to remember, right?
Millimeter (mm): There are 10 millimeters in a centimeter, so, that means there are 1,000 millimeters in a meter. This is a very short distance, but, in the world of very small things, this is still a huge distance. For example, a human hair is, on average, around 0.05 mm wide.
Now, you’ll notice that all of these measurements are powers of 10. (In this case, negative powers of 10.) That’s just how the metric system works. You either multiply or divide the last unit by 10, slap on the appropriate Latin prefix, and there’s your new unit. While it’s easy to work with, it’s also pretty boring, and there are a lot of smaller and smaller distances between millimeters and the really small stuff. So, we’re going to skip all that and hop right down to the next interesting point of measurement…
Micrometer (µm): A micrometer (or micron) is one millionth (10-6) of a meter. A typical red blood cell is 6 to 8 microns across.
Nanometer (nm): A nanometer is one billionth (10-9) of a meter. The chips in your computer and smart phone are built using a “nanometer fabrication process.” Basically, this describes how many nanometers apart the components of a computer chip sit from each other. The shorter this distance is, the more components you can squeeze onto a chip and the more “powerful” it is. Remember the Intel Pentium II processor from the late ’90s? That chip was built with a 350nm process and held 7.5 million transistors. Now, compare that with the “Core M” processor that Intel announced in August of this year. That chip uses a 14nm process and will hold billions of transistors!
Picometer (pm): This is 10-12 meters, or one trillionth of a meter. At this point, we’re looking at some really small stuff. Things like the wavelengths of gamma rays and X-rays. In fact, you have to go back up to 25 pm just to get to the radius of a hydrogen atom!
Femtometer (fm): A femtometer is one quadrillionth (10-15) of a meter. This is the size range of atomic nuclei. (It’s also sometimes called a “fermi,” in honor of physicist Enrico Fermi.)
Attometer (am): At 10-18 meters (one quintillionth of a meter), the attometer is pretty small. This is the scale where quarks and electrons live. Electrons, of course, are the particles/waves that exist in a cloud of possibility around the atoms that make up everything in the universe. And quarks are the sub-atomic particles that actually make up protons, neutrons and other, better known, much larger particles.
Believe it or not, the attometer is just a little more than halfway to the absolute smallest distance that there is: the Planck Length.
Named for physicist Max Planck, the Plank Length is actually a hypothetical distance. It’s hypothetical, because, at 10-35 meters, there’s no way to actually “see” it or measure it. At this distance, it’s thought that the universe breaks down into a kind of “foam,” that obeys none of the normal laws of reality.
But even being hypothetical, the Planck Length has a lot of uses in theoretical physics. It’s a big part of String Theory, the study of extra dimensions, and it may even play a role in determining if our universe is just a very poorly tested computer simulation. (If it is, then the Planck Length may well be the “width” of one “pixel” in the simulation.)
So, there you go. The next time the universe makes you feel small, just remember, that small is actually pretty far out, and that there’s always something smaller than you.