S03E02: The Jiminy Conjecture

I fear that this episode may have disappointed over 10 million people—because there was no physics in it.   It has biology: crickets chirping, entomology, and even a discussion of the neurobiology of alcohol’s effect on the brain.  But apparently no physics.

Not so fast.   Physicists work on biological problems all the time.   So much so that at my own university, UCLA, there is a popular undergraduate major in biophysics.   The fundamental equation of the episode,  the rate of chirps of a cricket versus temperature, as Sheldon tells us, was given by A. E. Dolbear in 1890.  Dr. Dolbear was a professor of physics at Tufts College, not biology.   If you look carefully, you will see his equations describing temperature (in Fahrenheit) versus the number of cricket chirps per minute on the whiteboard in the boys’ apartment.

Dolbear's Law: Equation describing how a cricket's chirps per minute (N) is related to the ambient temperature (T).

Of course it must be given separately for the common field cricket (FC) as well as the Snowy Tree Cricket (STC)  and even Katydid (K).  Each chirp is made when the cricket rubs its right forewing against its left forewing that is covered with ridges.  In the process, the creation of this sound is much like running your fingernail over the teeth of a comb.  For insects, the behavior is called stridulation.  For a person strumming a comb, it is probably just called annoying.

The alert viewer no doubt noticed that one digit was different on the whiteboard in the episode than above.  Also, Prof. Dolbear’s first name was Amos, not Emile.  So much for the fact checking by the show’s consultant.

Modern biophysics looks different from Dolbear’s time.  Physicists work on fundamental biological problems, such how a cell works using the special points of view and tools they they have been trained with.   For example,  proteins drive much of the activity of a cell and the subtle folding and unfolding of proteins that occur versus temperature are key to the cellular activity.  Using statistical mechanics, non-linear dynamics, and laboratory techniques borrowed from the physical sciences, physicists are characterizing this key aspect of proteins and thereby understanding the inner workings of a cell.   In another example, a friend of mine tries to understand how our inner ear manages to be such a good amplifier, allowing us to hear both extremely quiet and loud sounds entirely with a small hair that moves only one billionth of a meter and produces very little extraneous noise.

Several years earlier Dolbear had previously done very important work as a physicst.  In 1885 he performed the first wireless telegraphy—several years before Guglielmo Marconi.

New York Times article, Oct 6 1899

So Dolbear was the first to perform wireless telegraphy.  Without wireless telegraphy we’d have no radio.  Without radio we’d have neither the technology for television, nor the first sit-coms written for radio.  And without either, we’d have no show The Big Bang Theory.

S03E01: The Electric Can Opener Fluctuation

Sheldon, Leonard, Raj and Howard have finally returned from their National Science Foundation expedition above the Arctic Circle, having  been away from the apartment (and us) for the past three months.  Even the whiteboards in their apartment have not changed–they are as they were left in the season finale.  Sheldon is ecstatic about their trip, convinced the data he’s collected will win him a Nobel Prize.   Sheldon has finally observed a signal of magnetic monopoles.

Or has he?  Sheldon is a theorist, not an experimentalist.  We saw Sheldon’s experimental skills on display back in the fighting robots episode–he could not even open the toolbox.   An experimentalist is always on the lookout for stray signals, or “noise”.  Every discovery is not initially met with shouting and champagne as one might expect, but close consideration of every recorded signal as a mundane process that could possibly be noise fooling the apparatus.  The process can take years.

A few years ago, I was taking data with some electronics we set up with scientists from the Jet Propulsion Lab in the pedestal of their large (230-foot diameter) radio telescope.   We designed the electronics to look for neutrinos, but by design the apparatus  would record a signal, most likely an uninteresting background, about once every six minutes.   But there was something else going on.  Sometimes we would see a burst of signals recorded at once.   Could it be that neutrinos were arriving in bursts?   Ultimately it turned out to occur whenever someone sat in a particular chair. When its wheels passed over a speck of dirt on the floor,  the weight would compress it slightly and cause a tiny spark, much like how a piezoelectric cigarette lighter works.  That was a source of electrical noise.   With a quick tweak to the electronics, we were on our way with no more chair-trigger  events.

Coming back to Sheldon’s experiment, some time ago an experiment at Stanford saw a beautiful magnetic monopole candidate.  The induced current in a loop of superconducting wire took a sudden jump, as measured by the magnetic flux through the loop.  The event became famous:

Other experiments sometimes noticed that such jumps could be produced by ordinary electrical noise:  interference, perhaps from spark plugs, or,  as Sheldon eventually finds out,  from a nearby small motor.    An electric motor constantly makes and breaks electrical contact with small brushes that carry the current from a spinning wheel.  These interruptions  in the circuit can make a very tiny spark, and thus produce a spurious electrical signal, noise.   You can sometimes hear these on your AM radio as static.   Still, the Stanford event was special because the change in current was exactly the value expected from a magnetic monopole.  The experimenters were absolutely first-rate and took pains to show they were not subject to stray electrical noise.   A monopole was never seen again.  But the world’s one candidate has never been disproved either.

S02E23: The Monopolar Expedition

In this epsiode, the season-two finale, Sheldon wins a National Science Foundation grant to go to the Arctic and look for a magnetic monopole.   He’s excited because if he finds them, he would finally win his Nobel Prize.

What is a magnetic monopole?  “Mono” is Greek for “alone”, but every magnet ever made or found always has at least two poles, called North and South.   As a child I would play with magnets that had two poles and looked like this:

The North pole of a magnet is always attracted to another’s South Pole and like poles (North-North and South-South) always repel.

If anyone ever discovers a magnetic monopole, a Nobel prize is assured.  So it’s worth a try.  What if you tried to be clever and make a monopole by cutting the magnet above in half?  You can try this at home with a hacksaw and a friend’s magnet:

Too bad. You’ve just made two smaller magnets each with their own North and South poles.   Try again. The same thing keeps happening:

Ad infinitem (or more precisely, whatever Latin is for “to the smallest”).   At some point you will cut the magnet so small that you will have cut down to the size of a single  atom.  (Atom being Greek for “do not cut”.)   Even then, a single atom often behaves as a magnet, but always with both a North and South pole, and you can’t cut it any finer.  Well, with a lot of money, you can cut even the atom into to subatomic particles:  protons, neutrons and electrons, but even these little magnets still always have one  North and South magnetic pole.   With a pile more money, you can cut the proton and neutrons into their smallest parts, quarks, you will still have magnets with North and South poles.  Nobody knows if it is possible to cut an electron or quark but particle physicists keep trying.

Magnetic monopoles have been tantalizing physicists for over a century.  In the late 19th century, the Scottish theorist James Clerk Maxwell summarized everything that was known about electricity and magnetism with just four simple equations.  (They weren’t so simple the way he wrote them, but we’ve cleaned them up since then.)   These equations displayed a beautiful symmetry of form between electricity and magnetism.    In fact one point where they lacked symmetry between electricity and magnetism  led Maxwell to add a term and as a result he (correctly) predicted how light is comprised of just oscillating electric and magnetic fields.  This was one of the most amazing moments in all of physics.

But there is one glaring obvious lack of symmetry remaining in Maxwell’s equations.  Electric monopoles are everywhere you look: Electrons are a monopole of one charge and protons are a monopole with the other charge.    Yet not a single magnetic monopole is ever found.  We are forced to put a zero in Maxwell’s equations that breaks their otherwise  symmetrical treatment of electricity and magnetism.  Now, over one hundred years later, modern theories such as string theory predict the existence of magnetic monopoles.  However, since there is little that string theory does not predict, the question remains to be proven by experiment, perhaps Sheldon’s experiment….

Scientists have looked for magnetic monopoles, in particular in the 1980’s when they were predicted by a Grand Unified Theory which was beautiful, theoretically compelling, and wrong.  Sheldon’s idea was to take his motivations from string theory and improve on the old experimental technique by using the Earth’s magnetic field to increase his chances.   Much like you can collect more rain and more accurately measure the rainfall by putting a funnel over a cylinder,  Sheldon’s idea was to use the Earth’s magnetic field as a funnel for magnetic monopoles.  Oddly enough, the Earth’s  “North” magnetic pole is the “South” pole of the Earth’s magnet, and vice-versa.  That means “North” magnetic poles would be directed to the Arctic, and South magnetic poles would be directed to the Antarctic.    (There is a loophole that the monopoles can’t be moving to fast.  Listen carefully to the dialogue and you’ll hear Sheldon say “slow-moving magnetic monopoles”.)  The show’s writers knew that the Antarctic is inaccessible in May (the time the season finale aired) so sent Sheldon and his friends to the Arctic.

The National Science Foundation’s polar programs helps scientists, including me, move themselves and their gear into the polar regions to conduct their science.  They give us the gear, training, and support so we don’t kill ourselves out in the field.  For this episode, the NSF gave the show their official logo to use, which you can see on all the boys’ shipping crates.  The boys’  clothing are exactly the same ones that are issued to the scientists in the real polar program:  Their red parkas are extremely warm and nick-named “Big Red” by polar scientists.  Even their big white (sometimes blue)  insulated boots, which scientists call “bunny boots” are issued to real scientists by the NSF.  Here’s a picture of our science team wearing the gear on the ice:

Physicists on ice.

A fun fact to impress your friends when watching this episode in re-runs:  The diagrams on the whiteboard in Sheldon and Leonard’s apartment show classic equations and diagrams describing magnetic monopoles.

Welcome to The Big Blog Theory

The science of The Big Bang Theory is revealed!  (Of the sit-com that is, not the theory of the origin of the universe.)  Last season, I was discussing possible titles for this blog with the writers of the show, who had lots of  terrific ideas.  After all, that’s what writers do.   One of the lead actors passed by, overheard us,  and  gave us this title over his shoulder,  just as he was walking into a scene.

The title “The Big Bang Theory”  may originally have been coined in derision.   (Of the theory of the origin of universe that is, not the sit-com.)  Starting in the 1940’s, Fred Hoyle and other proponents of a theory they called the “Steady State Theory” of the  universe,  took the observation that  the universe  expanding as discovered by Edwin Hubble in the 1920’s, and proposed that the universe was constantly generating new matter to fill the new space.  They went further to say the new matter was generated at exactly the rate to keep the universe always looking the same at all times.

The Steady-Staters dubbed this idea  “the perfect cosmological principle”.  “Perfect” because their universe was the same at all times, compared to the more prosaic “cosmological principle”,  whose universe is merely the same in all places (homogeneity) and in all directions (isotropy).    Some readers may complain that such a cosmological principle is clearly not true.  Of course standing on Mars your immediate neighborhood would look quite different than to someone standing (briefly) in the central core of Jupiter.  However, the cosmological principle applies only to the universe only on its largest scales, distances crossing many hundreds  of galaxies.  The principle is an empirical observation,  something subject to change if observations ever dictate it.  There are even some tantalizing hints in recent data to that effect.

A view of the Universe on the largest scales ever observed. Every dot is a galaxy. Although features like walls and voids are visible, on the largest scales (hundreds of millions of light years) the universe appears homogenous and isotropic.

Their rival theory originated a couple of decades earlier, in the 1920’s.  A Belgian priest, Georges Lemaître, took  guidance from the (then) recent theory of General Relativity by Einstein and  proposed that all the matter and energy in the universe was created in a single event and the universe became less dense as it expanded.    Perhaps Lemaître, a priest,  was pleased with the creation event implicit in the model.  The Steady-Staters disagreed with the  idea that so much matter and energy could be created in a single event and Hoyle poked fun at Lemaître’s theory by giving it the moniker “The Big Bang” during a radio interview in 1949.

The Steady-State and Big-Bang models each were plausible and provided a good description of the history and evolution of the universe.   But at least one had to be wrong.  Fortunately, like all useful theories,  each made definite and distinct predictions which could be tested by observation.   It took several decades, but by now, the Steady-State idea is in conflict with a wide variety of data.  For example, the two theories predict a different number of distant galaxies, and the numbers found by astronomers agree with the Big Bang Theory and disagree with the Steady State Theory.    Moreover, the relative abundance of  elements such as deuterium, helium and lithium compared to hydrogen can be measured.  The data are explained well by the entire universe having been a nuclear reactor when it was between about 3 and 20 minutes old, a state which the Big Bang Theory implies the universe must have gone through, but never existed in the Steady State model.   The final death knell of the Steady State theory occurred in the 1960’s when a microwave radiation was observed coming from all directions in the sky.  This radiation, now known to be the oldest light in the universe is called the “Cosmic Microwave Background”.  It was produced when the early universe was hot and opaque, a period that never existed in the Steady State model and which it could not explain.

A more advanced summary of problems with the Steady State idea is given by my friend Ned Wright in his terrific cosmology tutorial.

The Steady-Staters were not crack-pots, and they were certainly not dumb. Quite the contrary, Fred Hoyle was the first to describe how heavy elements were synthesized from hydrogen and helium in stars.   Many of the observations which eventually favored the Big Bang Theory took a long time to become convincing.  For example, it took decades to unravel what fraction of lithium observed was primordial and what was generated later in cores of stars.   The initially predicted age of the universe by the Big Bang Theory made it younger than the oldest stars, a situation only fixed when the difficult to measure expansion rate was finally pinned down.

Even after most of the scientific community favored the Big Bang Theory,  Hoyle tried to keep the Steady State theory alive.  While some have ridiculed his stance, there is a healthy place in scientific discorse for a few serious-minded skeptics.  Hoyle continued to mold the Steady-State Theory to explain the data although the theory necessarily became more and more baroque.    Ever the skeptic, later in life Hoyle challenged that biological evolution could be driven by natural selection.   However, one of his basic ideas, panspermia, that the building blocks of life may have come to Earth on comets was for a time  a serious contender.   At least two views of such contrariness can be taken:  Perhaps his skepticism caused a sharpening of the mainstream arguments, overall serving science by making its arguments stronger.   Or perhaps we are left to take comfort in the adage:   Funeral by funeral science marches on.

Perhaps most importantly, had the Steady State Theory been right, the theme song to the show would have been nowhere near as interesting:

The whole universe was in a Steady State.

And nearly 14 billion years ago, nothing special happened, wait…

…