Physicist-isms

It is a truth that should be universally acknowledged that scientist and engineer types talk funny. Particle physics is no exception. Not only does this apply to us discussing physics, but it carries into normal conversation as well. My friends and I used to make a game to see who could throw the geekiest physics reference into a discussion; the more advanced the topic referenced the more bragging rights. I mean, anyone can throw a reference to momentum or velocity into a conversation, but it takes creativity to get quantum field theory worked in there.

Anyway, a few of my favorite phrases and buzz-words that have been adapted to other uses.

Critical mass: This isn't exactly a particle physics term, but particle physics once was nuclear physics so it work. In order for a nuclear chain reaction to take place, the decay products of one reaction must be able to set off a second reaction. The decay products of the second set off a third, and the reaction perpetuates itself. For this to happen, however, the decay products need to be able to reach fresh material; if the stuff is too spread out or there isn't enough of it, the reaction will fizzle and die out. The critical mass is the amount of stuff necessary to get a self-sustaining chain reaction started.

We use it to mean the amount of something that must accumulate before something begins. The party is just waiting to reach critical mass before starting the games.



Confidence level/Confidence interval/Anything statistical: So, particle physicists are not necessarily great at statistics, though we try to reteach ourselves regularly because we use it a lot. We also debate and argue about statistics a lot.

We use statistical terms in conversation to express how sure we are of something. I believe he is at a meeting, 95% confidence level.

Non-trivial: When solving equations to find out what a particle would do, often a solution of zero (the particle doing nothing) works out just fine. This is very easy to work with mathematically, but very boring to work with physically. This is the trivial solution, the one that takes no effort but gives nothing interesting. The non-trivial solutions are all the rest, the ones that take effort to find but are interesting to look at. This is also an excellent example of physicists understating, a skill we are all taught as undergrads.

We use it to mean anything hard or that shouldn't be ignored. Getting internet access for my apartment has turned out to be non-trivial.

Rather small: As a sophomore in college, in my first quantum mechanics course, I took a quiz once where the question was to the describe the tunneling probability of a certain particle. The probability numerically was about 1/(2^15), and the answers were a) huge, b) rather small, and c) freaking minuscule. The correct answer was b, because as my professor put it, physicists do not over-state.

So saying something is rather small could mean the exact opposite of common usage. Or not. My patience for remaking these plots again is rather small.

To leading order: Infinite series expansions, or writing a very complicated mathematical solution as the addition of infinitely many simpler parts, come up a lot in particle physics. While it does not seem like it would help to take a complicated problem and write it with infinitely many parts, the parts are often much simpler than the entire mess and some of those parts will be so small that we can't measure them anyway. It's kind of like writing the number 1 as 0.9 + 0.09 + 0.009 + 0.0009 + 0.00009 + . . . The 0.00000000000009 term is necessary to get exactly to 1, but I probably can't measure a change that small so it's safe to ignore that term and just give an error on my measurement. Good series have terms that get smaller and smaller, so you really only need to the first term, the leading order one, to get the rough idea of what the entire answer should be. The other, smaller terms just refine the answer.

Something at leading order or done to leading order is close to, but not exactly, the right or full idea. There are next to leading order, and next to next to leading order, for the second and third largest terms respectively, and even next to next to leading log, but we don't often use those in normal conversations (or as normal as conversation with physicists gets). I know how to start the next project at least to leading order.

Planck scale: As physicists accelerate particles to higher and higher energies, we've found that the different forces by which particles interact start to behave differently. The weak force is just that, extremely weak, at low energies, and is much more significant at higher ones. If you push this far enough, eventually gravity matters to particles as well. Normally, they are too small and light for gravity to matter much, but at a sufficiently high energy we wouldn't be able to ignore it. The energy where this happens is called the Planck scale, and it corresponds to about 100000000000000000 TeV. For comparison's sake, the Large Hadron Collider at CERN, the highest energy accelerator in the world, currently runs at 7 TeV.

So, in energy terms, the Planck scale is large. Sometimes, physicists can be Planck scale insensitive.

Two-body problem: Technically, this refers to trying to determine how two objects interacting according to some force are going to move around each other. The most common examples include the earth and the moon, the earth and the sun, or other planetary motion type situations. The tricky part is that the objects pull on each other, so the motion of one changes the motion of the other. This gets significantly more complicated the more objects are involved; it has been proven that the three-body problem cannot be exactly solved, only approximated.

In my field, solving the two-body problem means getting married to another particle physicist.