Today is a big day for both math and science nerds.  It’s Pi Day, the day we celebrate the magical number 3.141592…, but it also happens to be Albert Einstein’s Birthday.

So for today’s edition of Sciency Words, we have a term that involves both circles (and the number pi) as well as Einstein’s physics.  Today’s Sciency Word is:

Rotating Disk

The rotating disk thought experiment is one of the strangest ideas to come out of Einstein’s general theory of relativity.  Part of relativity is the concept of length contraction.  If I were to somehow accelerate a yardstick to a speed close to the speed of light, the yardstick’s length would contract or shorten noticeably.  The same thing would happen in an extremely powerful gravitational field, such as the gravitational field of a black hole.

But what happens if a rotating disk is accelerated close to the speed of light?  What happens to the circumference of the disk?  Well, according to Einstein’s thought experiment, the circumference would also contract, just like the straight yardstick.  However, the radius of the disk would not change, because the radius is always perpendicular to the disk’s rotation.

The math can get complicated, as it often does in general relativity, because we are no longer dealing with the Euclidean geometry we all suffered through in high school.  Instead, we are now entering the strange world of non-Euclidean geometry, a world in which parallel lines can intersect, the angles of triangles do not necessarily add up to 180 degrees, and the ratio of a circle’s radius and circumference does not always equal pi.

To put that in a simpler way, pi does not always equal pi.  This is not some weird fluke of mathematics but a real phenomenon, one which was predicted by Einstein and later demonstrated through scientific experiments.  Do we live in a strange universe or what?

Happy Pi Day, everyone, and happy birthday to Albert Einstein!

Today’s post is part of a special series here on Planet Pailly called Sciency Words.  Every Friday, we take a look at a new and interesting scientific word to help us all expand our scientific vocabularies together.  Today’s word is:

PARTICLE ZOO

At some point in the last century, scientists thought they had a pretty good grasp on all the subatomic particles.  They knew about protons, neutrons, and electrons, and they thought they understood more or less how these particles interacted.

Then they discovered the photon and the neutrino and the positron and six different kinds of quarks and a few vector bosons and the Higgs boson and the pion and kaon and gluon… this list can go on for awhile.  Particle physics went from being relatively simple to frustratingly complicated very quickly.

Many of these particles cannot be observed directly.  Some have never been observed at all but are predicted to exist by elaborate, mathematical models.  The existence of the Higgs boson, for example, was only recently confirmed by experiment.

There are literally hundreds of different subatomic particles, many of them composite structures made from other subatomic particles.  Some of these particles are truly bizarre, as different from one another as elephants and crocodiles, giraffes and hippopotami.

Some physicists find this embarrassing and derisively refer to the still-growing list of particles as the “particle zoo.”  I prefer to think of this so-called zoo as a beautiful reminder that the universe is far more complicated and interesting than we humans can possibly imagine.

Today’s post is part of a special series here on Planet Pailly called Sciency Words.  Every Friday, we take a look at a new and interesting scientific word to help us all expand our scientific vocabularies together.  Today’s word is:

UNDERDETERMINATION

This word comes to us not from science itself but from the philosophy of science.  According to the philosophy of science, when we have two competing theories to explain some natural phenomenon, we are supposed to choose which theory is correct based on the evidence available to us.  But what happens when we don’t have enough evidence?

For example, let’s say that I theorize that horses are slow moving animals that can only trot, and you theorize that they are capable of running really fast.  If the only experience either of us has ever had with horses is watching one stand still eating its hay, then our two theories are underdetermined by our lack of experience with horses.

In the recent evolution vs. creationism debate between Bill Nye the Science Guy and Ken Ham of Answers in Genesis, Ken Ham never used the word “underdetermined,” but that is exactly what he was trying to argue: that our choice between evolution and creationism is underdetermined by a lack of evidence.  Of course, that’s not the case at all.  There is an overwhelming amount of evidence in support of evolution and plenty of evidence to refute creationism as well.

One example of genuine underdetermination is in the search for life on Mars, where there are some signs of the possibility of life, some evidence that makes life less likely (but still not impossible), and as of yet no discovery of an actual Martian organism, living or dead.  Another example of underdetermination are the various competing versions of string theory, which as I understand it remain untested and untestable due to the limits of technology.

Underdetermination is always a temporary problem.  It would not take long to prove which of our theories concerning horses is correct.  We’d only have to go to a farm or perhaps a rodeo, or we could simply look up horse videos on YouTube.  As NASA rovers continue exploring Mars, the question of Martian life will be resolved.  As for string theory, I’m sure the necessary technology will be invented eventually.  Of course if some people refuse to accept any evidence that disproves their preferred theory, that is another problem entirely, and the sciency word for that is confirmation bias.