Relativity from a photon's point of view

kw: musings, special relativity, physics

I am between books, catching up on journal reading. Something has arisen in my thoughts from time to time, and this is as good a time as any to solidify it a little. The question: If a photon had consciousness, what would it experience?

I have read in numerous books and articles that Albert Einstein began the mental journey that led to the special theory of relativity by imagining he could ride along with a photon. Reading his own writings, though, we find that he was really thinking of riding a very fast railway carriage, and seeing how this might affect the photon's motion. Based on the Michelson-Morely experiment and on theoretical work by Lorentz, Fitzgerald and others, he concluded that no matter what speed he attained, the photon would zip by at the same speed, the one we define as c, the "speed of light". Then, taking the constancy of c as an axiom, he derived the special theory of relativity.

Supposing the photon could be endowed with the ability to observe on its own, what would it observe? Based on a wealth of experimental data, we can discuss the "career" of a photon in three sections:

1. Emission
2. Propagation
3. Absorption

Although we seldom think about the time it takes for a photon to be emitted, we can consider that the "wavicle" model implies a finite "size" that is similar to the wavelength, according to Feynman's probability-wave diagram (actually, when I saw Feynman draw this during a lecture, he only put in about 1½ or 2 cycles of the wave inside the envelope). Therefore, though we typically think of the emission as occuring "instantly"—if we think of it at all—it is reasonable to posit that it takes about the time required for one cycle to occur. In this discussion we will assume that everything occurs in a vacuum or near-vacuum, so that we don't need to consider refractive index or the reduction in the value of c within a material medium.

For a visible photon of wavelength 546.1 nm (the green Hg line), which has energy of 2.270 eV and a frequency of 549.0 THz, that emission might take 1.822x10^-15 sec, or 1.822 fs (femtoseconds). We may also assume that absorption occurs in a similar amount of time.

This photon-observer needs to have quick reactions indeed to observe anything at all during such brief periods of time! Will it, then, have more leisure for observation during propagation? No! According to the special theory of relativity, no matter the physical length of its journey, the time experienced by the photon will be zero; it will be unable to observe its own propagation.

From the photon's point of view, whether the photon was emitted by an electron transition at one end of the lab, and absorbed by inducing a similar transition at the other end, or the photon was emitted billions of years ago in a galaxy far, far away and today happens to arrive and produce an electron transition in the CCD attached to yon telescope, its experience is the same: less than 2 fs of emission immediately followed by less than 2 fs of absorption, after which it exists no longer. To us, one photon "was there" for a few nanoseconds and the other, for billions of years. The "experience" of the two photons, however, was identical: be emitted/be absorbed.

That is it! A photon of green light can at most experience 3-4 fs of emission and absorption. The rest of the universe is irrelevant to it. For a photon to have a longer "career", from its point of view, it would have to have a longer wavelength, a lot longer! For example, the power grid leaks a lot of 60 Hz (ultra-low-frequency) radio waves, photons with a wavelength of about 50,000 km and photon energies of 4.1x10^-15 eV. Such a photon might "experience" a time period of around 1/30 of a second. Pity the poor X-rays and gamma rays, with energies of thousands to millions, and even billions of eV! Their wavelengths are very short (from about a nanometer to a femtometer or less) and their frequencies are very high (from thousands to billions of THz). A one-billion-eV gamma ray photon is likely emitted in about 4 fs, and would most likely "experience" a total of less than 10^-23 seconds of existence.

Had Einstein actually spent his time thinking like a photon, I doubt much would have come of it. But instead, he thought of a very fast railway carriage observing a photon, which is much more interesting, and led to much more interesting results.

Scoping out lamp spectra

kw: analytical projects, spectroscopy, photographs

Technical photography of biological subjects has its tricky aspects. An important one is the quality of the lights. This picture shows one setup I have used to avoid the use of the compact fluorescent lamps (CFL's) that were brought in to replace the incandescent flood lamps they had been using, but which burn out on a regular basis…and they are hot. CFL's have serious drawbacks for color photography, which we'll see later on.

The little blue lamps, wrapped in tissues, are "work lights" from Harbor Freight, with 18 small LED bulbs each. They have a pretty good spectrum (I'll point out a similar one below).

We have been considering a more quantitative approach, particular for photos of birds. Few mollusks have "interesting" colors, but nearly all birds do. Birds have an extra color sensor in their eyes and can see ultraviolet light, so it is also of interest to be able to photograph birds in UV light.

I decided to explore the various lamps available, not only for these reasons but a few extra ones. In recent years I used pieces cut from a page-size sample of diffraction grating, obtained from Edmund Scientific many years ago, to make two spectroscopes. One, about a foot long, is for handheld use, and another, about twice the size, is for use with a camera.

I originally made them to investigate which yellow lamp would be the best "bug light". Night-flying insects see UV even better than birds do, and many of them cannot see yellow or red light, and have low sensitivity even to green. The ideal bug light would have a cutoff in the yellow-green range, and would be rather orange. In order to keep people on your doorstep from looking too weird, all commercial bug lights include some green and look distinctly yellow.

This shows a test setup with the large spectroscope on my workbench, using a black light as the source. Not only does the camera "see" UV, it is also being overloaded by the bright blue and violet lines of mercury (Hg). That black light bulb is not nearly this bright to my eyes. The camera at the left is set back a little farther than usual; I usually use it with the front of the zoom lens about two inches from the grating, which is at the end of the white bell-shaped "front" of the spectroscope. The "slit" is currently a thin slot sawn into a PVC cap at the end where the lamp is.

Initial tests verified that the camera's sensor can record UV and that the lens passes it, and also that none of the lens elements is fluorescent (a problem with the lens of another camera I have!). I also learned that the "UV filter" I was sold with the camera does not block UV-A (longwave, or near-UV). It does block short-wave UV, that is UV-B and UV-C, pretty well. So I bought a better filter, a UV(0) filter from Hoya. Now to the recent batch of tests, summarized in this image, a screen shot from PowerPoint:

Depending on your monitor, this might be hard to read. To summarize, the top shows the spectrum of a "black light" CFL (a "party light"), at two exposures; the next 11 sets are at three exposures each. From the top, then, we have

• two sets for different hues of fluorescent tube, 
• two sets for incandescent bulbs, 
• two sets for different hues of CFL, 
• a yellow CFL "party light", 
• two commercial "bug light" bulbs, and 
• two sets for LED bulbs from different manufacturers; the spectrum of the work lights from Harbor Freight is a little bluer than the bottommost set.

Only the black light has a spectrum that includes a strong UV line at 365 nm. Most of the lamps have a cutoff near 420 nm, though a couple of the CFL's let through a little deeper blue and the UV line. The spectra of the CFL's show very strong lines with darkness in between, which is why these lamps have poor "color rendering", as it is called. LED's, as shown at the bottom, come the closest to mimicking the spectra of incandescent lamps.

My preliminary conclusions are (1) that for ordinary color photography, LED lamps are the best choice among the "non-incandescent" ones, and (2) to get good UV images we'll need to use black light CFL's, probably with a visible-blocking filter. It may also work to use UV LED flashlights like the ones used by TSA at airports, though they are a bit costly, because they don't produce any visible light.

Riding Mars Mania

kw: book reviews, nonfiction, planet mars, popular treatments

As large as the planet Mars looms in history and in the popular consciousness, a 250-page book can at best skim the surface of the many facets and subjects. This is as I expected when I began to read 4th Rock from the Sun: The Story of Mars, by Nicky Jenner.

The book is well written, and I found it enjoyable. I might have preferred the author to settle down to a smaller number of subjects, and to treat them in more depth. But that's just me. For those who have read little about Mars, this is a good introduction, covering history, science and popular culture. Also, with the chance to sign up (for a fee) to actually go there, albeit on a one-way trip with little chance of actually happening in this generation, some folks with Mars dreams but little knowledge could benefit from this book.

We have sent more spacecraft to Mars than any other "place" except the Moon. A useful Appendix lists them all, all 43 Mars missions by all nations, to date. That includes, of course, the USA and USSR (later Russia's Roscosmos), plus Japan, Europe's space agency, China and India.

The waxy snails

kw: species summaries, natural history, natural science, museums, research, photographs

In the course of time I have come to a cabinet-and-a-half containing a couple of thousand lots of a family of snails (gastropods) named Cerionidae. Though there are four genera in the family, the Delaware Museum of Natural History holds members only of the type genus Cerion. The family was split out from a large family, Urocoptidae, by Henry A. Pilsbry in 1901. "Harry" Pilsbry spent much of his career at the Academy of Natural Sciences in Philadelphia, where he described hundreds (thousands?) of new species.



This first photo is of the type species (of the type genus of the family Urocoptidae), Urocoptis cylindrus (Dillwyn, 1817). Lewis Dillwyn originally named this species Turbo cylindrus, using a genus name created by Carl Linnaeus in 1758, when he single-handedly invented biologic nomenclature. At the time these specimens were collected the species was considered of the genus Cylindrella, then was shifted again to the genus Urocoptis when the family Urocoptidae was set up. The family Urocoptidae contains many genera, and while many of the species are similar to this one, being cigar-shaped with a flaring aperture, they vary a lot around this gestalt.

The genus Cerion, pronounced "kerion" or "Syrian", from the Latin word cerea, meaning "waxy", was named by Peter Röding in 1798, based on his renaming of Turbo uva as Cerion uva (Linnaeus, 1758). The genus has just a handful of fully accepted species, but the DMNH collection contains representatives of more than 200 species, which have varying levels of acceptance among workers carrying on a decades-long reworking of land snail families. This photo shows two characteristics of many Cerion species: the off-white waxy color and the ribbing along the entire shell. The flared aperture is less pronounced than it is in most of the Urocoptidae. The following photos showcase three more Cerion species, chosen to illustrate the range of variation in the genus.



The photo below shows Cerion weinlandi (von Martens, 1860); Edward von Martens originally placed it in the genus Pupa. It does look like a pupa! I chose this species to illustrate the extreme of nearly absent ribbing. Also, while the background color tends to be waxy off-white, this species is one of many with color banding and mottling also.



Though this lot is labeled Ceriod dalli Maynard—publication date is probably 1889—it was renamed and included in the species Cerion rubicundum (Menke, 1829). I don't know what name Karl Menke originally gave it. The species name means "ruddy", and when the shells are fresh and moist, the brown markings are reddish-brown. I chose this species for its narrow ribbing.



Finally, Cerion marielinum Pilsbry, 1927 (the museum curator attributed the species to Carlos de la Torre, who had edited the journal in which Pilsbry published the description) is so named for its occurrence mainly near Mariel, Cuba. This species shows wider, more robust ribbing, and also has a ruddy background with the waxy white being confined to the tops of the ribs.



I chose the scale for these photos so that they would show the shells close to life-size on a 17-inch monitor. On my 22-inch monitor they are about 25% larger than life. Comparing the four Cerion species with Urocoptis cylindrus, there is certainly a resemblance. It is easy to see why the genus was originally put in the same family. However, details of their morphology, including not only the more pronounced ribbing, but also the smaller aperture and the small teeth inside the aperture, distinguish Cerionidae from Urocoptidae…at least for now! Biological naming is always a tug-of-war between "splitters" and "lumpers". In some mollusk families, large numbers of species have in recent years been combined into a relative handful of species, and this may soon result in the few hundred species of Cerion being lumped into a smaller number of species that are recognized as being rather variable.

Genetic studies and breeding studies are going on in parallel, and revealing more and more about the species and inter-species relationships of many animals, not just snails. But, you know, I just like opening a drawer full of shells once in a while to simply admire them.

The mistake collector

kw: book reviews, nonfiction, psychology, neurology, errors, consciousness

Oliver Sack's fifteenth, and last, book is The River of Consciousness. He died just two weeks after completing the design of the book, composed of his essays in various medical and popular publications. I first came across his books three years ago; this is the third of his that I've read and reviewed in that time. He may be best known to the public for The Man Who Mistook His Wife for a Hat, which I have yet to read…but it is on my short list.

As any good clinical "brain worker", he collected mistakes. Freud with his "slips" may be the one we know the best for elucidating the shortcuts our mind and brain use, from certain mistakes that we make. I find Dr. Sacks to be the best at explaining the usefulness of the categories of our errors to us.

Not all the chapters in the book are explicitly about "useful errors". The chapter "Speed", for example, attacks questions such as, "Just how fast can we think?" and "What is it like to think a hundred times faster, or slower?" We all have heard of phenomena such as having one's life flash by in a moment during severe emergencies, or of becoming so absorbed in minutiae that hours can pass with hardly a ripple on our thoughts. Sundry drugs can affect our time sense: I once began to take a prescription drug for systemic fungus, and on the fourth day managed to work up enough ambition to phone my doctor to say, "I just realized that the wallpaper texture in my office is so interesting that I've been looking at it for four hours." He recommended that I stop taking it, and dropping by for a different prescription!

The chapter "The Creative Self" dwells much on the apparently unconscious problem-solving abilities we have (you can call it "right brain" but it is more involved than that). For much of my career as a systems programmer, I relied on it: Near the end of a work day I would often set up a structure in my mind, of the current algorithmic problem I faced, and sort of give it a mental push. I could usually expect to awaken at 3:00 AM with a flowchart "sitting there," ready for me to spool out into working code. From the dancing flames that Kekulé was watching when the structure of Benzene suddenly sprang to mind, to the introduction to Das Rheingold that Wagner had been struggling with, and which erupted into his consciousness while he took a hike to take a break, creative "flashes", while not too common, are well enough known to us all. They do not really denote lightning inspiration, but rather, they culminate a long and laborious fitting and re-fitting of ideas that goes on in the background; it seems almost independent of our conscious problem-solving, and usually quite linear, processes.

I was also quite taken with the chapter "Scotoma: Forgetting and Neglect in Science." The author digs into the lore of "ideas born before their time." It is usually the case that such ideas enter an arena that is already full of competing theories, and in particular, they usually incite the ire of numerous and powerful figures whose work is threatened thereby. My father used to say, "Really good ideas often have to take Moses's way: 40 years in the wilderness for a generation to die off." Sometimes it is more like a century or two! The most extreme example is that Archimedes seems to have invented calculus nearly 19 centuries before Liebnitz and Newton (re)formulated it.

Rather than comment on every chapter, I'll leave it to the reader to enjoy the book.

Biography of a friendship

kw: book reviews, nonfiction, biographies, celebrities, actors, friendships

This was a wildcard selection for me; I seldom read biographies. Hank & Jim, by Scott Eyman, was too alluring to pass up. It chronicles 50 years of friendship between Henry Fonda and James Stewart.

Henry Fonda and James Stewart were opposites in some important ways: politically left vs right; Fonda marrying five times (and finally getting it right) and Stewart taking his time and hitting a home run on the first try; Fonda never giving up his first love of live theater but Steward gravitating almost exclusively to film, where together they dominated for decades.

Their similarities were sufficient to sustain a friendship in which they didn't need to talk about what was different. In fact, they were both introverted and "lived inside" much of the time and could spend tons of time together with little said, if anything. They both got their start in The University Players, though at different times and didn't meet until later. They soon became roomies, along with a few other close friends, during their "starving artist" years. They loved model airplanes (these were not the punch-out-and-glue kits, but the sort that yielded a room full of balsa wood shavings and could make you dizzy with glue fumes). They both enlisted during WWII, Fonda in the Navy and Stewart in the Army Air Corps; both were considered war heroes, they weren't just pretty faces that hung around the base. Stewart, in particular, remained active in the Reserves for years thereafter, retiring as a Brigadier General.

The book is really a triple biography, one for each man, and one for their bond. They spent years apart but always stayed in communication. Stewart was particularly solicitous during Fonda's last days, though he wasn't present for his final moments. Trying to think of a way to encapsulate the impression the book made on me, I find myself tongue-tied (metaphorically; "finger-tangled?"). It is a bittersweet book.

I find a further similarity they shared: they managed to keep at least some of their private lives out of the limelight. I am not sure how possible that would be today, now that the paparazzi are so much more aggressive (and deadly at times!), and are getting drones. But perhaps a couple of expert radio-control airplane aficionados could playfully engage in homemade anti-drone warfare!

The book is far from the fare I typically favor, but was quite enjoyable anyway. Like trying a new and very different restaurant, I got a nice surprise.