Misc Physics

1. An object’s motion can be described by derivatives and integrals of displacement. The first few derivatives — position, velocity, and acceleration — are familiar, but the succeeding ones have pleasing names: jerk, jounce (also known as snap), crackle, pop, lock, and drop.

The integrals of displacement are absement, absity, abseleration, abserk, and absounce. More here. (Thanks, Colin.)

2. The quarks now known as “bottom” and “top” were sometimes referred to initially as “beauty” and “truth.” Collider experiments designed to produce large numbers of B mesons are sometimes called “beauty factories.” (Thanks, Jackson.)

3. Reader Nick Ortenzio found this unexpectedly poignant quote in the Wikipedia article on false vacuum, from a paper in which Sidney Coleman and Frank De Luccia consider the prospect that our universe exists in an unstable bubble that might wink into a new state and annihilate us:

The possibility that we are living in a false vacuum has never been a cheering one to contemplate. Vacuum decay is the ultimate ecological catastrophe; in the new vacuum there are new constants of nature; after vacuum decay, not only is life as we know it impossible, so is chemistry as we know it. However, one could always draw stoic comfort from the possibility that perhaps in the course of time the new vacuum would sustain, if not life as we know it, at least some structures capable of knowing joy. This possibility has now been eliminated.

Words to Remember

https://en.wikipedia.org/wiki/File:Sans_Forgetica_font_sample.jpg

Designed by a multidisciplinary team at Melbourne’s RMIT University, Sans Forgetica is a typeface that’s intended to reduce legibility, on the theory that the “desirable difficulty” of reading it will result in deeper processing and, ultimately, better retention.

The back-slanted, incomplete letters form a “simple puzzle” for the reader, RMIT lecturer Stephen Banham told the Washington Post last October. “It should be difficult to read but not too difficult. In demanding this additional act, memory is more likely to be triggered.”

The team say they’ve tested the font on university students and found that “Sans Forgetica broke just enough design principles without becoming too illegible and aided memory retention.” You can try it yourself — they’re offering a free download and a Chrome extension.

Erratum

In On the Origin of Species, Darwin wrote that bumblebees are the only pollinators of red clover.

In 1862 he discovered that this is wrong — honeybees do it as well.

He wrote to his friend John Lubbock, “I hate myself, I hate clover, and I hate bees.”

A Wine Slide Rule

https://collection.sciencemuseumgroup.org.uk/objects/co60489/ullage-slide-rule-1759-1776-slide-rules-excise-slide-rules-ullage
Image: Science Museum Group

Revenue agents in 18th-century London faced a curious challenge: how to calculate the excise tax on a barrel that was partially full of liquor. The answer was an “ullage slide rule” — this gauging rod was dipped into the barrel, some brass sliding pieces were adjusted to reflect the height of the surface, and a mathematical calculation would tell how much liquid the barrel contained.

The Science Museum says, “The calculations were very complicated.” A correspondent to the Mathematical Gazette wrote in 1990, “I well remember puzzling, unsuccessfully, over graphs and calculations of measurements until I wrote to the makers whose name was stamped on the rule and who still existed [in 1966] at the same address in London Bridge. At that time they were still making a modern equivalent for the same use by revenue officers.” More at the link below.

(Tom Martin, “Gauging: The Art Behind the Slide Rule,” Brewery History 133 [2009], 69-86.)

Malfatti Circles

https://commons.wikimedia.org/wiki/File:Malfatti_circles_in_equilateral_triangle.svg

What’s the best way to squeeze three circles into a triangle so that the area of the circles is maximized? In 1803 Italian mathematician Gian Francesco Malfatti decided that the best course was to place each circle tangent to the other two and to two sides of the triangle (left) — he thought that some instance of this arrangement would give the best solution.

But that’s not actually so: In an equilateral triangle, Malfatti’s circles occupy less area than the solution on the right, found by Lob and Richmond in 1930 — their suggestion is to inscribe the largest possible circle in the triangle, then fit the second circle into one of the triangle’s three corners, and then fit the third circle into one of the five spaces now available, taking the largest available option in each case.

In the case of an equilateral triangle, Lob and Richmond’s solution is only about 1% larger than Malfatti’s. But in 1946 Howard Eves pointed out that for a long, narrow isosceles triangle (below), simply stacking three circles can cover nearly twice the area of the Malfatti circles.

Subsequent studies have borne this out — it turns out that Malfatti’s plan is never best. We now know that Lob and Richmond’s procedure will always find three area-maximizing circles — but whether their approach will work for more than three circles is an open question.

(Thanks, Larry.)

https://commons.wikimedia.org/wiki/File:Malfatti%27s_circles_in_sharp_isosceles_triangle.svg
Image: Wikimedia Commons

Proteomics

Reader Eliot Morrison, a protein biochemist, has been looking for the longest English word found in the human proteome — the full set of proteins that can be expressed by the human body. Proteins are chains composed of amino acids, and the most common 20 are represented by the letters A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, and Y. “These amino acids have different chemical properties,” Eliot writes, “and the sequence influences how the whole chain folds in three dimensions, which in turn determines the structural and functional properties of the protein.”

The longest English word he’s found is TARGETEER, at nine letters, in the uncharacterized protein C12orf42. The whole sequence of C12orf42 is:

MSTVICMKQR EEEFLLTIRP FANRMQKSPC YIPIVSSATL WDRSTPSAKH IPCYERTSVP 
CSRFINHMKN FSESPKFRSL HFLNFPVFPE RTQNSMACKR LLHTCQYIVP RCSVSTVSFD 
EESYEEFRSS PAPSSETDEA PLIFTARGET EERARGAPKQ AWNSSFLEQL VKKPNWAHSV 
NPVHLEAQGI HISRHTRPKG QPLSSPKKNS GSAARPSTAI GLCRRSQTPG ALQSTGPSNT 
ELEPEERMAV PAGAQAHPDD IQSRLLGASG NPVGKGAVAM APEMLPKHPH TPRDRRPQAD 
TSLHGNLAGA PLPLLAGAST HFPSKRLIKV CSSAPPRPTR RFHTVCSQAL SRPVVNAHLH                                             

And there are more: “There are also a number of eight-letters words found: ASPARKLE (Uniprot code: Q86UW7), DATELESS (Q9ULP0-3), GALAGALA (Q86VD7), GRISETTE (Q969Y0), MISSPEAK (Q8WXH0), REELRALL (Q96FL8), RELASTER (Q8IVB5), REVERSAL (Q5TZA2), and SLAVERER (Q2TAC2).” I wonder if there’s a sentence in us somewhere.

(Thanks, Eliot.)

The Bingo Paradox

https://commons.wikimedia.org/wiki/File:Bingo_cards.jpg
Image: Wikimedia Commons

Surprisingly, when a large number of people play bingo, it’s much more likely that the winning play occupies a row on its card rather than a column.

The standard bingo card is a 5 × 5 square in which the columns are headed B-I-N-G-O. The columns are filled successively with numbers drawn at random from the intervals 1-15, 16-30, 31-45, 46-60, and 61-75. And it turns out that, during play, it’s very likely that at least one number from each column group will be called (enabling a horizontal win) before some five numbers are called that occupy a single column (enabling a vertical win). In fact it’s more than three times as likely.

The math is laid out rigorously in the article below. If a free space appears in the middle of the board, as is common, the effect still obtains — Joseph Kisenwether and Dick Hess found that the chance of a horizontal win is still 73.73 percent.

(Arthur Benjamin, Joseph Kisenwether, and Ben Weiss, “The BINGO Paradox,” Math Horizons 25:1 [2017], 18-21.)

The 36 Officers Problem

https://commons.wikimedia.org/wiki/File:Euler_36.svg
Image: Wikimedia Commons

Suppose we have a group of officers in six regiments, each regiment consisting of the same six ranks (say, a colonel, a lieutenant colonel, a major, a captain, a first lieutenant, and a second lieutenant). Is it possible to arrange these 36 officers into a 6 × 6 square so that no rank or regiment is repeated in any row or column? That is, each row and column must contain an officer of each regiment and of each rank.

In 1782 Leonhard Euler wrote, “After we have put a lot of thought into finding a solution, we have to admit that such an arrangement is impossible, though we can’t give a rigorous demonstration of this.” He saw that the equivalent problem is impossible in a 2 × 2 square and surmised that it’s impossible in every case where the side of the square contains 4k + 2 cells.

It wasn’t until 1901 that French mathematician Gaston Terry proved that the 6 × 6 square has no solution, and it wasn’t until 1960 that Euler’s conjecture about the pattern of impossible squares was proven wrong: In fact, the task is impossible only in these two cases, 2 × 2 and 6 × 6.