diary of infinity

In science we are taught to test the validity of theories by looking for verifiable claims and then testing them. For absolutely no reason at all, I have decided to take the same approach with anime. Some anime takes huge liberties with scientific laws, whereas other anime, for instance Moyashimon, is packed with hard scientific fact which forms the basis of much of the story. Anyway here are two claims made in anime stories which might be tested scientifically, one more easily than the other.

1) Cherry blossom petals fall at 5cm/sec. (source: 5 Centimetres Per Second)

2) If you shorten your skirt by 2cm then you can fly further than yesterday (source: K-On)

Let's look at these claims a bit more closely. In 5 Centimetres Per Second, Akari states that cherry blossom petals always fall at 5cm/sec. Since she gives a constant speed, I think it is safe to assume she is talking about the terminal velocity of petals in still air. In principle this is easy to test, unfortunately cherry blossom season is now over until next year, so a proper experiment will have to wait. However there must be many videos which include the sight of falling cherry blossom so approximate measurements could certainly be made.

From the theoretical standpoint, one might produce a formula for calculating the forces on a cherry blossom petal, however this is not straightforward. In addition to the force of gravity acting on the mass of the petal, and the air resistance acting on the surface area of the petal, we must also consider that the petal flutters, spinning and see-sawing as it falls. This will use up a significant amount of the gravitational force, and the changing orientation of the petal will also alter the air resistance, e.g. when the petal is oriented vertically it will fall much faster. So the motion would be pretty hard to model! To understand the importance of the petals spinning, consider that physicist Richard Feynman once noted that a ball rolling down an inclined plane will only accelerate at 5/7 of the speed that the law of gravity would give you for the angle of slope, since the other 2/7 is used up making the ball rotate. So really unless you are a theoretician of Nobel Prize winning stature like Feynman (who once worked out the equations to explain the rate of wobble of a dinner plate spinning on the end of a stick!) you need to do the experiment first and worry about the theory afterwards (if at all!).

Anyway, next time I will report back on whether I have found any actual footage of cherry blossom falling, also on another question: does the cherry blossom in 5 Centimetres Per Second itself fall at the claimed rate or not? (Preliminary examination says: not!)

Turning now to Claim Number 2 which is made in the OP song of the anime K-On, I will have to defer detailed discussion of that to next time due to lack of time. However it looks to be somewhat tricky, since the obvious way of testing it is to get a girl wearing a skirt to take a flying leap and see if she goes further after trimming her skirt by two centimetres. Needless to say, the repeatability of such an experiment is somewhat problematic. Moreover, note that the specific claim is "further than yesterday" which implies one must compare results of flights that were 24 hours apart, which introduces further variability!

Don’t miss next weeks exciting installment of verifiable anime tales in which I will attempt to recruit a statistically significant number of girls in short skirts to test the K-On claim!