More Sense on Senses

It appears that bacteria have over 100 sensing mechanisms. Quoting  [my underlining]

“According to John S. Parkinson, a professor of biology at the University of Utah, “most organisms – even bacteria – can sense sound, light, pressure, gravity and chemicals” (University of Utah, 2002). E. coli bacteria “can sense and respond to changes in temperature, osmolarity, pH, noxious chemicals, DNA-damaging agents, mineral abundance, energy sources, electron acceptors, metabolites, chemical signals from other bacteria, and parasites” (Meyers and Bull, 2002, p. 555). Bacteria are very sensitive to chemicals – for instance, E. coli bacteria have five different kinds of sensors which they use to detect food. As Di Primio, Muller and Lengeler (2000, pp. 4 – 5) explain, common bacteria like E. coli swim in chemical gradients towards attractants (e.g. glucose) or away from repellents (e.g. benzoate) – a phenomenon known as chemotaxis. Other bacteria display phototaxis and magnetotaxis, or movement in response to light and magnetic fields, respectively (Martin and Gordon, 2001, p. 219). Bacteria possess an elaborate chemosensory signaling pathway, which involves the phosphorylation (combination with phosphorus compounds) of a set of proteins in the cytoplasm of a bacterial cell (Blair, 1995, p. 489).

There are several philosophical questions relating to the sensitive capacities of bacteria. Should we call these capacities bona fide senses? For that matter, what are senses, anyway? Is there a distinction between sensing an object, and being sensitive to (or being affected by) it? And is the possession of senses by an organism a sufficient condition for its having perceptions (which, in common parlance, are mental states), or can an organism have senses without the capacity to have perceptions?”

The article continues with an in-depth philosophical discussion that is quite interesting but probably too abstruse for most readers – I didn’t have the patience to read it through. Is it worthwhile to “translate” obsolete ideas by Aristotle into modern terms, as does the author, or is this merely a source of confusion? You can decide by reading the post.

Bottom line, my comment that bacteria don’t have sense organs is incorrect. Whether they have perceptions is up for grabs, an issue that is addressed in the article.

Authenticity – Part One

Monterey, California 1959
Monterey, California 1959

There is strong evidence from cognitive psychology that we are by nature highly attuned to detecting cheaters. This makes evolutionary sense, because one of our distinctions as a species is our cooperativeness, our ability to trust and share with others. Cheaters naturally arise in an environment of trust, and our obsession with cheater detection limits the number of cheaters in a group. We punish cheaters, as well as those who fail to punish cheaters.

We are also obsessed about genealogy. One of the reasons languages tend to develop arbitrary rules that have little to do with transmitting meaning is to sharpen the ability of experienced speakers to detect outsiders. In “My Fair Lady,” ’Enry ‘Iggins claimed to be able to tell what London block someone came from by their accent.  Early humans evolved in small groups, and it was important to know who was “in” and who was “out,” not only to know who was on your side, but to avoid incest. Likewise, we are exquisitely sensitive to nuances of the appearance and behavior of others. We are deeply interested in whether the person across from us is genuinely smiling, or just putting on a smiley face while wishing you would go away. The battle between our drive to reproduce and our need to establish the authenticity of our partner’s professions of love figures in the plot of many a tale (sadly, this obsession with whether we are insiders or outsiders underlies our xenophobia).

Both art and science rely heavily on these two traits working together. Doing science is intensely cooperative and based on trust, so science cheaters make headlines and lose their credibility, and often their jobs. Also, it must be possible in principle to trace the genealogy of evidence back through all the actions taken to arrive at it. Scientists are highly skeptical and openly critical of each other, and as a result, there is a culture of cooperation and trust that makes it unnecessary to check every step in a discovery unless someone smells a rat, In the end, the findings of science are the consensus of experts (I borrow this from a lecture at the Marine Biological Laboratory in Woods Hole by Harvard historian of science Naomi Oreskes). I have more to say on this subject elsewhere.

Genealogy is important in art for similar reasons. Much of the value of a work of art depends on how sure you are that it is genuine. Musicologists research and argue about whether a note in a score was intended to be an A or an A#, how and when improvised decorative figures were originally used in the Baroque and Classical eras, or whether a newly discovered chorale was written by Bach, a contemporary of Bach, or a present-day charlatan. Never mind that the average listener can’t tell the difference – the experts can. Art that can be faked needs a pedigree to maintain its monetary value, and as these are not always easy to document, cheating is more widespread in art than in science.

One much-discussed subject is why an art work with a pedigree is better in some way. Can’t a work be judged simply through your senses? Imagine three Federal style silver cups. They are all exquisite and physically identical, except that the first is by an unknown silversmith, the second is by Paul Revere, and the third, also by Paul Revere, was owned by George Washington. No doubt their monetary value is in the same order, and escalates dramatically from one to the other. Yet without their pedigrees (no fair turning them over to see the silversmith’s marks on the bottom) they are indistinguishable.

You can see that provenance is much more important in science than in art, because the whole enterprise of science is founded on authenticity, whereas a work of art can in principle stand on its own, although its monetary value and part or most of its public appeal lies in its provenance.

When talking about authenticity, I think most of us would equate it with whether something is genuinely what it is advertised to be. But there are other aspects to authenticity that are more subtle and more interesting, and I want to focus on those in subsequent installments.

Odd Man Out

The Author at Age 4
The Author at Age 4

I was, and am, an odd duck. One manifestation of this is that I withdraw from things other people do. I hated sports. I can vividly recall an incident from the sixth grade, probably reconstructed from several such incidents, when despite my being placed in the relatively safe position of right field, some jerk swung late and the ball headed straight for me. The damn thing was big and hard and moving fast, and humans evolved to get out of the way of such things, which I did. Groans, “Tully’s done it again,” that sort of thing. Luckily, the rare hit in my direction usually dropped short and rolled (if I stood far enough out), so that I could, with luck, pick it up and throw it to the wrong base.

Music was important to me in my teens, but not the music everyone else listened to. I went to the library and picked out 78 records that I had not heard, discovering Bartok and Bantock and especially Stravinsky’s Le Sacre du Printemps which I listened to over and over with an equally maladjusted friend, letting my imagination run wild through the mists of prehistoric time. My high school peers were listening to rock and roll, the newest thing in the 1950’s, and to me they were illiterate unwashed hoodlums who spent their time in car shop chopping and channeling old Fords to make hot rods. I was far above such trash. I was an intellectual. I belonged to the model railroad club. It didn’t help that my much older brother, a talented jazz trumpeter, shared my disdain for rock and roll.

Berkeley was a shock. In my third semester, when I lived in an apartment instead of a dorm, my virginity was terminated by an older woman (Tchaikovsky’s First Piano Concerto was on the radio). Later, she persuaded me to leave college and go with her to the Olympic Peninsula to pick ferns (such people were called “Bohemians” in those pre-hippie days). My mother had to take the train up from LA to keep me in school. I withdrew from the relationship when she called me at 2 AM during summer break, waking the whole household because in those days you had one phone in the middle of the house and everyone’s door was open because no one had air conditioning.

My first drunk was sensational. At some point I withdrew from being conscious. The first thing I remember was being led around the block by the girl assigned to bring me back to earth. For the next month I heard one tale after another, told with malicious hilarity, about how I had made passes at every female present. I quenched the terrifying prospect of being successful with women by getting sick thereafter whenever I had too much to drink.

But I digress. Over my life, I have withdrawn from one aspect of cultural life after another. As I describe elsewhere, I stepped outside religion at age 14 (I’m back, sort of). I enjoyed television for many years, until my wife and I decided we just didn’t have the time or the patience to pick the wheat from the mountains of chaff and gave up the habit when I was 60 or so. This makes it hard to converse and can cause embarrassment.

For example, as I write, Prince has just died. I had heard the name, and an extravagant fuss was made over his passing, so I went to You-Tube and watched “Cream,” from 1991. It was the classiest pornography I have ever seen, even better than the cover of Cosmo. The guy was a genius, and I missed him entirely. Oh, well, I did tune into Michael Jackson and Led Zeppelin and The Wall, thanks to the kids. A noted psychoanalyst friend and his wife introduced me to the Sergeant Pepper album and I never looked back. I introduced her to Bartok. How could she not have known about Bartok?

Having bowed out of a belief system shared by most Americans, along with popular culture, I was on a roll. Over the years, I and others have observed that our infrastructure is not being maintained. I was all in favor of a crash program to repair infrastructure until I read an article by a civil engineer pointing out that our infrastructure is a Ponzi scheme. Here’s how it works.

Americans like to live in the country, but they have to work in the city. Americans do not like to pay taxes or mortgage payments. Solution: divide up the cheap farmland into little parcels, connect them with roads and bridges, and add sewer, water, electricity, telephone, cable, gas, street lights and other infrastructure. Build inexpensive houses out of wood, which is OK because they aren’t attached to each other, so you can burn up your home without burning up your your neighbors’ homes.

Now most infrastructure has a life span of 60 to 100 years, so you need to salt away some property taxes in a trust fund to repair the infrastructure and replace it when it wears out. This is an unpopular idea. Bernie Madoff to the rescue! Build more infrastructure so you get more taxes, and use the new taxes to fix the old infrastructure. This works splendidly until the infrastructure needs to be replaced.

So our suburban approach to living doesn’t work. I spent many years designing nice solar houses for people living in suburbs, doing research on building houses, and writing and teaching about houses. Now I had to admit that this was all a mistake and that I must in good conscience withdraw from this wicked practice. I love designing houses and must admit to cheating from time to time. Inconveniently, we live in a suburban house.

This led me to the notion that civilization is a Ponzi scheme. Think about it: we invent a clever way to do things, and then we have to invent another clever thing to deal with the unexpected consequences of the first clever thing. Take mills for instance. We invented machines to do the more work with fewer workers, but mill-owners exploited the workers, so we needed rules and bureaucracy to stop them. More bureaucracy means more taxes, and as I just mentioned Americans don’t like taxes (or rules for that matter). So we skimp on taxes and the infrastructure stops working.

Mill on the Mayenne, 2001
Mill on the Mayenne, 2001

Another example: whale oil is a lot better for making light than wood or wax, so we cut down a lot of trees to build whaling ships. Just as we were running out of whales, we discovered oil. This saved the whales for a while, but oil made shipping cheaper, so now the ships are threatening whales with their noise.

Well, if civilization is a Ponzi scheme, maybe it wasn’t such a great idea. I needed perspective to think about this, but withdrawing from civilization did not appeal to me. The next best thing was pretending to be a visiting alien, which given my history as an outsider wasn’t all that hard. A little observation convinced me that human nature was to blame.

First I had to decide whether human nature exists. This is controversial. John Locke back in the 17th Century decided that there wasn’t much to human nature because we were born with minds that are blank slates (except of course for those pesky instincts like sex) and we learn how to behave through experience.

On the other side of the net were people like Hobbes and Machiavelli, who thought humans have a nature and that it is intractably wicked (I’m not sure what they thought of themselves). The battle lines were drawn: it was nature versus nurture.

Today scientists generally agree that we have a human nature, but that how it gets expressed varies a lot due to our having big heads. We are born prematurely because a fully developed brain won’t fit through the birth canal, so the long trek from conception to maturity leaves ample time for our parents, peers and culture to shape how our human nature is expressed.

Some psychologists and other scientists believe that we can overcome the parts of human nature that we don’t like by using conscious reasoning. Others believe that for all practical purposes, we can’t and don’t. I subscribe to the latter school.

Of course, as my son pointed out, this raises the question of why I am so sure about which school I belong to, because I must have used conscious reasoning to arrive at my decision. That’s why I inserted that little “for all practical purposes” qualifier. I believe we really can reason consciously, it’s just not something one normally does. But I may be wrong about this – I think.

Some people, especially scientists, believe that science is how you find out what’s actually going on in the world because it deals with facts you can demonstrate by experiment. If you use science, you can get to the moon, although we don’t normally do this either. Whereas if you use prayer or magic or certain chemicals, you may THINK you went to the moon, but you didn’t actually go there, according to scientists and probably most of your friends. (Some people believe the moon trips by astronauts were an elaborate hoax perpetrated by the government to force Colgate to use fluoride in their toothpaste – it worked!)

All this inspired me to look further, and I found a scientist who cleared things up for me. He pointed out that we are the kind of animal that doesn’t have an “off” switch for acquiring things. This seems about right, based on how much stuff my wife and I have in our basement and attic. During 50 years of marriage one tends to accumulate stuff.

For example, we have 3 or 4 nifty U-shaped vegetable peelers. You really only need one. We found that they worked as well as the guy who peeled mountains of vegetables at the Boston Flower Show said they did. They get dull after a while, so we bought new ones, but couldn’t part with the old ones. We are thinking of moving, so stuff is on my mind.

I believe that I have to withdraw from the human race to think about all this. This is definitely a challenge, but I am working on it. Luckily, I have a head start.

The Wonderful, and Wonderfully Misleading, Powers of Ten


I was lucky enough to study in my first year of college under the designer/architect Charles Eames, inventor of the molded plywood chair (among many other things). He showed us the first draft of a movie he called “Powers of Ten” which zoomed in and out in a sequence of images depicting what you would see if every ten seconds you multiplied the distance by a factor of ten. The movie moved outward to galactic scales, then inward to atomic particle scales, covering 40 powers of ten. On the trip out, the first version had a neat clock that showed you what percent of the speed of light you were moving. This was dropped from the version referenced.

Eames remade the movie in 1977, advised by a number of scientists including Philip Morrison, a physicist who also narrated the film. You can find it at

Philip Morrison is one of my heroes. He worked on the Manhattan Project and could read a substantial book in a day. He wrote the book reviews during the golden years of Scientific American when Martin Gardner was writing “Mathematical Games” and the magazine featured beautiful pointillist pencil drawings.

The link takes you to the Google Earth blog, unsurprisingly, since Google Earth uses the same technique to zoom you in to your chosen site (except it “only” zooms by 7 powers of ten, i.e. ten million times). Another term for powers of ten is order of magnitude.

Powers of ten is a way of thinking about exponential growth. The concept is a two-edged sword. One edge is an indispensable tool for understanding nature; the other is among the most misleading concepts in modern life. “Powers of Ten” allows us in just a few minutes to visualize the smallest thing we have direct evidence for (quarks) and the largest (super-clusters of galaxies), over 40 powers of ten.

Thinking in terms of powers of ten is routine for mathematicians, scientists and statisticians. But in our daily lives things grow by adding up. We think and act linearly, 1, 2, 3, 4, 5, 6, 7, 8, and so on. Thinking exponentially you get 1, 2, 4, 8, 16, 32, 64, 128 and so on. Already in just eight steps, powers of two has outdistanced our thinking by a factor of eight. Using powers of ten, you get 1, 10, 100, 1,000, 10,000, 100,000, 1,000,000, 10,000,000. Eight steps and you go from an individual to nearly the population of New York City.

This huge disparity in modes of thinking can be seen more clearly using examples.

There is a famous Chinese story about a poor man who was granted a wish from the Emperor. He asked that he be given one grain of rice, but added the stipulation that on each successive day, he would receive twice what he had received on the previous day (powers of 2, or doubling). In a month he owned just over a billion grains (230) and it wasn’t long before he owned all the rice in China.

Another often-cited example is lilies on a pond. Let’s say your pond is 750 feet in diameter, which comes out to 10 acres – nice big pond. Let’s assume a lily takes up 1 square foot, and that the number of lilies doubles every year.

You start with one lily, hardly noticeable. After sixteen years, you have just the lily patch you were looking for, covering about about 3/4 of an acre. The next year, however, the lilies cover one-and a half acres and you begin to worry. The next year they cover 3 acres, the year after that 6 acres, and before the end of the next year the entire pond is covered. So it took 16 years to get where you wanted, then less then 3 years to obliterate the pond. This illustration from the wonderful YouTube channel XKCD illustrates the point humorously.


Some wonderful examples that translate a huge power of ten (67 orders of magnitude) can be found illustrated at on one of my favorite YouTube science channels, “Vsauce” narrated by Michael Stevens. The whole 20 minute episode is worth watching, but the examples illustrating a huge power of ten starts at minute 14.

Finally, to illustrate the futility of manned space flight, consider this. It is hard to get a grasp on the sobering fact that the universe is almost empty of matter as we experience it. Of the three components of the mass of our universe, ordinary matter accounts for maybe 2-3 percent, the rest being mysterious “dark matter” and the even more ubiquitous and mysterious “dark energy.”

Our solar system, which compared with outer space is as crowded as a subway platform, is terrifyingly empty. I made a conceptual model of our solar system at a scale of 1 billion to one, set in a place familiar to many. Here is an illustration showing the model:

Manhattan small


Imagine that the sun is a ball about four and one-half feet in diameter, on a pedestal in the Grand Army Plaza in front of the Plaza Hotel at 59th Street and 5th Avenue in Manhattan.

The orbit of Mercury, the inmost planet, crosses 5th Avenue a block away, at 60th Street, and is about half the diameter of your little fingernail. Venus at 61th Street and Earth near 62nd street are about the size of your middle fingernail. Our moon is half the size of a pencil eraser and is 15” from the earth.

Mars, another block away, is a little bigger than Mercury. Then there is a gap where the asteroid belt occurs, with the largest asteroid being virtually invisible, the size of a fine grain of sand. Outside the gap is the first of the “giant” gaseous planets, Jupiter, which in this model is the breathtaking size of a large grapefruit, with an orbit that crosses 5th Avenue around 70th Street. Another 7 blocks gets us to softball-sized Saturn. At 95th Street we encounter the orbit of Uranus, which like Neptune at 115th Street is 2” in diameter.

In this model, the orbit of Neptune, now the outermost planet, swings out over the Hudson and into Union City, NJ, then back across the river and down Houston Street, across Brooklyn and Queens passing through the Sunnyside Railroad Yards before crossing the East River back into East Harlem. This is plotted on another Google Earth image:

Manhattan large

Now that you have a sense of the sizes of these bodies and their orbits, try to imagine away everything else: the earth below, New York City, the sky above, and replace it with black emptiness. Just a 4-1/2 foot ball of fire surrounded by tiny spheres slowly orbiting in one plane, the outermost of which is almost 3 miles away and the size of a golf ball. And this is a high density of matter by the standards of the universe.

Within this disk of orbiting motes 5 ½ miles in diameter we humans have traveled the distance from your elbow to your fingertips. Mars is 150 feet away, while the nearest star at this scale is the distance of a trip around the earth, 25,000 miles. We talk a good game about fleeing into the galaxy when the going gets too tough here on earth, but the facts are starkly clear: we will forever need to cling to the nurturing surface of our tiny speck in the vast emptiness that surrounds us.

It pays to keep our nest in good shape, as it is all the home we will ever have.

More on Income Inequality

Our friend Anne Orange sent a chart showing relative global income inequality (not wealth inequality), which led me to this site on NY Times:

It contains this chart:


The horizontal axis is how much you make, broken into 20 equal percentage groups at 5% each. The vertical axis is where your income stands relatively to the rest of the globe. What the chart shows is that the poorest 5% of USA population are as rich as the richest 5% of Indians. Income has been adjusted to even out what you can buy with your money.

The steepness of the curve shows relative income inequality. If everyone made the same, it would be a straight horizontal line, at a height on the chart representing how prosperous you are. If the curve arches up, that indicates less income inequality than if is sags in the middle.

The NYT author Catherine Rampell quotes the author of the book “The Haves and the Have-Nots,” by Branko Milanovic from which this was taken:

One’s income thus crucially depends on citizenship, which in turn means (in a world of rather low international migration) place of birth. All people born in rich countries thus receive a location premium or a location rent; all those born in poor countries get a location penalty.

It is easy to see that in such a world, most of one’s lifetime income will be determined at birth.

In the US, 80% of your life’s potential is determined by where you were born and who your parents are. So that leaves a 20% chance to cash in on the Horatio Alger myth. I believe that this stat goes far to explain the difference between Republicans, who believe that ratio is more like 20% and 80%, and Democrats who are more in line with the reality.

If we are so rich, why are so many people unhappy? Why do they feel so poor? Good questions.

Sense about Senses

Cannery Row, 1959
Cannery Row, 1959


A sense is a physiological systems that provides information for perception. It is how a brain-body finds out what’s going on inside and outside itself. Most people think of the usual 5 senses that feed information directly to the brain, but there are an indefinite number of others when you consider other systems in the body, some of which bypass the brain altogether.

The first matter that needs to be cleared up is the difference between sensing and perceiving. Perception is sensory input that has been processed. In normal usage perception takes place in the brain, but again we need to expand the definition to include all processing of sense data, no matter where it occurs or what effects it has.

Although most perception is not conscious, it always involves some kind of transformation of the sensed information. For example, the pattern of photons that strike the eye are transformed and processed even before any nerve signals leave the retina. Furthermore, it is possible (indeed common) to perceive things without involving the senses, in dreaming, hallucinating and imagining. An amputee can for example experience pain in a limb that is no longer there (phantom limb syndrome).

My approach is to sort through the various environmental phenomena that do and do not have an effect on the brain-body, and also to see what those effects are. The hidden agenda is to argue why it is highly unlikely that a brain-body can sense certain things that some of my friends and relatives (and many, many other people) think it can. These fall into the general category of “paranormal phenomena,” where the Greek root “para” in this context means “beyond.”

As a card-carrying materialist, I discount paranormal phenomena on the grounds that such a thing cannot exist (if it did, it wouldn’t be paranormal). In this respect, I differ from most skeptics, who twist themselves in knots supporting the notion that science must always be open-minded about the possibility of something new coming along. A common way to express this idea is that science cannot prove something correct, but only prove something wrong. I respectfully disagree, but the argument is long and I may be mistaken. It’s certainly not something that philosophers agree about.

I will go through my list of environmental phenomena that could possibly have an effect on any living thing, with special emphasis on the living things we most admire: us.

Electromagnetic Radiation

Visible light and radiated heat are forms of electromagnetic radiation. Technically, it means energy that is transmitted by massless photons. We have to accept that electromagnetic radiation can be either waves or particles, because in practice they “really” are mathematical expressions. “Waves” and “particles” are merely convenient ways of turning these expressions into something we can manipulate. It is useful to think of short wave-length radiation as photons, but not very useful to think of radio waves in terms of photons. Here’s why.

Different wavelengths of electromagnetic radiation have different effects on organisms. They range from extremely short wavelength gamma rays to extremely long wavelength radio waves, with visible light in the middle. The frequency (rate of vibration) of an electromagnetic wave is the inverse of its wavelength, so gamma rays are high frequency, and radio waves are low frequency.

The energy carried by a photon goes up dramatically as the wavelength gets shorter, and falls off dramatically as it gets longer. Thus a single visible light photon has enough energy to trigger a retinal cell to fire, whereas a typical radio wave photon has such low energy that there may be a trillion of them in a single wave several feet long.

Of particular interest are the specialized sense organs that are “tuned” to certain wavelengths. This naturally implies a complex organism, unlike the vast majority of organisms in this world (bacteria and “archaea”) neither of which have organs.

The many kinds of eyes that have evolved time and again in nature are receptors for radiation that is named visible light because it is, well, visible. Some animal eyes can detect “near ultraviolet” light, which has wavelengths just too short for us to see, and some animal eyes can detect “near infrared” light, with wavelengths just too long for us to see. Each kind of eye has its own spectrum of sensed radiation. Birds for example have eyes that respond to color very much as ours do, whereas dogs do not.

Luckily, the molecules in our atmosphere block harmful forms of radiation, which is why we are alive. It is transparent to a wide range of radio waves down to the wavelength that might cook us, where it becomes opaque. Just below that, a window opens to let in heat and light, and just enough ultraviolet to give us sunburns or fade fabrics. The degradation of the ozone layer in the upper atmosphere has allowed more ultraviolet to get through, which is not good for us or other living things. The diagram shows the frequencies that are blocked by the atmosphere.

Atmospheric attenuation of electromagnetic radiation (Oregon State lecture notes from web)
Atmospheric attenuation of electromagnetic radiation (Oregon State lecture notes from web)

Around 40- 45 percent of the sun’s radiated energy that reaches the earth is in the infrared, depending on sky conditions. Beyond infrared are microwaves, with just the right wavelengths to cause water molecules to boil, which is how they cook food, so they can cook us as well. Luckily, microwaves of the cooking frequencies are blocked by our atmosphere or the dots on the microwave oven window.

The next-shorter waves than ultraviolet light are X-rays, which pass through different tissues in different amounts, helping us to see inside our bodies They cause cancer if you get too much of them. And gamma rays, the shortest ones, are destructive to living tissue, which is one reason you don’t spend much time around highly radioactive materials.

Summarizing, we have a specialized organ for detecting one bit of the electromagnetic spectrum, visible light. Short, destructive frequencies from outer space are blocked by our atmosphere, but we are vulnerable to man-made radiation in those wavelengths.

We are bathed in long-wavelength radio waves, with too little energy to harm us, even right next to a transmitter. In the worst case, the risk is less than leakage from a microwave oven, which is pretty small. We have a lot of other things to worry about, believe me. Note: electric fields from power lines are something else, discussed below.

Physical Media and Objects

Air, water and solid objects transmit sound and other pressure waves such as wind or the shock waves from supersonic jets and explosions. We sense sound with our ears, and other pressure waves affect various sense organs including the balance sensing machinery in our ears (the vestibular system), pressure (touch) sensors in our skin and sensors that detect motion at joints. We also feel air motion with the touch receptors of our skins. Special receptors register coolness when water evaporates from our skin, when the wind blows on us, or when we are immersed in a cold liquid. Yet others sense heat directly from air or hot objects, and from infrared radiation (from the sun or hot source such as a fire).

Heat and cold also trigger signals from pain receptors. When you touch a hot or cold object, the pain signal shoots quickly to the brain to cause you to let go, and only later do you know whether it was hot or cold. Colliding with or handling objects can trigger a whole battery of touch, pain, joint position and balance machinery. Whether animals can detect earthquakes before they happen is controversial, except immediately before, when they detect the preliminary effects before we do.

Our mouths and noses have taste, odor and pain receptors that help us eat and drink safe and nourishing things and  avoid toxic things. Our sense of smell detects all sorts of chemicals in the air, an ability that other creatures such as dogs and rodents use much more than we do. Just for comparison, we typically have about 6 million odor receptors, while a dog might have 300 million, with a proportional amount of the brain devoted to odor perception.

Odor receptors are interesting because they are direct extensions of neurons from the brain, unlike vision where the retinal cells are many steps removed from the final brain cells that register what we are seeing. Our sense of taste detects only 5 distinct classes chemicals (sweet, sour, bitter, salt, and umami); most of the “taste” of food comes from odor, texture, pain and temperature sensors. Many creatures in water sense various chemicals, and even the gradient of a chemical. We can taste water just as we can taste food.

Our various senses involved in eating and smelling can detect chemicals that were present and important when our senses evolved. Today there are tens of thousands of man-made chemicals in our environment, some of which are toxic to varying degrees, alone or in combination. We can directly sense some of them, but not most of them. This makes us very nervous. Luckily, we can learn certain chemicals to seek or avoid because our brains continue to develop from the moment of conception to maturity. Unluckily, we are built to crave tastes that were in short supply when the senses evolved, but now are very cheap, notably sugar, salt and fat, with predictable results.

Each type of odor or taste sensor is specially designed to glom onto a specific type of molecules. When it does, it changes shape, sends a signal to the brain, lets the molecule go, changes back to its original shape and waits for another one.

The five iconical senses
The five canonical senses (wiki commons)

If you stretch the definition of “sense,” you can argue that our immune system senses invading bacteria, viruses and parasites. The information is not sent directly to the brain, but is used by various other cells to fight off the infection. Sooner or later the brain gets an indirect message about the battle because you feel crappy.

Fast Molecules and Particles

Various kinds of molecules and elementary particles whiz about and either strike us or pass through us. Particles are distinct from the photons that carry the electromagnetic force in that they have mass, while photons don’t (one or two other particles are or may be massless, but they are not relevant to this discussion). They are distinct from the molecules we detect with our noses and mouths because they are moving very fast and are minuscule by comparison.

Radioactive materials emit Beta particles (fast electrons) and Alpha particles (helium nuclei) that can harm living tissues. Powerful cosmic rays (high-energy protons and atomic nuclei, from unknown sources) luckily don’t normally strike us because we are protected by the earth’s magnetic field, but a few get through and collide with molecules in the atmosphere to produce a shower of particles that can damage tissue. Neutrinos, probably the most common particles in the universe, pass through almost all atoms (which are almost entirely  empty space) without interacting with them, which is why it is extremely difficult to detect neutrinos. Trillions of neutrinos pass through your body every second.

If you become part of an electrical circuit, electrons will stream through your body, causing a shock or convulsions. This occurs because our nerves operate with very small electrical currents, and when you overload them, they react violently. Positrons (positively charged electrons) can be created and focused on the brain to illuminate brain processes. Radioactive materials are also used for various medical purposes such a treating cancer, tracing metabolism or tracking blood flow. But no sensations are involved, only direct effects on tissues.


We are immersed in various kinds of fields. Fields can only be understood mathematically, and I don’t have the math and most likely neither do you. You can get a sense of a magnetic field by scattering iron filings on a piece of paper over a permanent magnet, as many do in high school experiments. Fields transmit forces. For example; the magnetic field transmits a force that causes a compass needle to swing, while the gravitational field transmits the force of gravity.

Iron filings on paper over a permanent magnet.
Iron filings on paper over a permanent magnet.

The most important field is earth’s gravitational field. Our bodies are designed for the amount of gravity we experience on the earth’s surface, and without that force acting on us we may get a form of motion sickness, which is why astronauts need a few days to acclimate themselves. On the moon, you can leap very high; on a bigger planet, you would have to crawl because you couldn’t support yourself. We don’t have a true “gravity” sense; instead we have a sense of balance that helps us cope with sideways forces as well as gravity. We also have pressure sensors in our joints and our skin that directly register the effects of gravity, as it presses us against objects.

We cannot detect the earth’s magnetic field, but some birds, insects and other animals can, and use it to navigate – no one is quite sure exactly how, but they are close to finding out. Gravitational waves are so weak by the time they get to us that only recently (2016) have they been detected, triumphantly supporting Einstein’s general theory of relativity. Electrical fields in the brain can be detected, and magnetic fields that make temporary changes in the brain allow us to detect and locate brain activity.

Electrical fields are sensed by certain fish that live in the dark of the deep sea. They can actually “see” prey and mates with these fields. Electrical fields can affect us, even if we can’t sense them directly. Powerful electrical fields can disorient our brains during electro-convulsive shock therapy, and any powerful electrical field can hurt or kill us, as when lightning strikes nearby. It is unlikely that the electrical fields from power lines or cell phones affect us, but they might – it is hard to tell because the effects are so small. Again, we have a lot more important things to worry about.

In any case, we don’t “sense” these because we don’t have special nerves dedicated to receiving information from electrical fields. The molecules in our bodies directly react to electrical fields, just as they do to Gamma rays or X-rays, without their being sensed by a sense organ.

On the cutting edge there is some question about whether we can detect and use quantum fields. If so, it is very likely that the process will be entirely internal.

Closing Remarks

I hope this gives you some sense of what “sense” is all about. It goes without saying that science has found zero evidence for any other senses, and that if any new senses are discovered, they will have to detect one or the other of the outside forces I have described above. For example, it is possible, although unlikely, that we have a weak ability to extract information from certain kinds of electrical or magnetic fields. Extremely sensitive equipment has not yet detected any such thing so far.

There is no last word in science, but the options become more and more restricted the more we know, which means any future senses we discover will be extremely subtle. Those who believe in paranormal senses pounce on this to claim that only special people (usually themselves or someone they know) are able to sense these imaginary things. Thousands of careful tests have failed, over and over, but believers, who operate with faith and hope, are not deterred by scientific evidence.

I discuss elsewhere the relation between those who believe in non-physical phenomena (such as souls) and those who like me believe only in physical phenomena. Conflicts arise when those who believe in non-physical things get anxious about their beliefs and misuse the scientific belief system for support. What’s wrong with just believing in non-physical phenomena? Why pretend to support them with science?

In any case, if there is a subtle sense we have not detected, it is likely many people will have it, or it would not have remained in the gene pool. It is highly unlikely that anything as complex as a sense organ could evolve spontaneously in one person. Such things take time, and thus affect many people.

Once again, there is a huge difference between what we sense (information that hits the sense organs) and what we perceive (information from sense organs or internal processes that has been transformed in some way). Perception transforms raw sense data into forms that trigger actions, memories, emotions, imagery and the like. Perception can result from brain processes that imitate sense data, as in hallucinations, dreams and imagination. It is very easy to perceive something that doesn’t exist outside the brain that invents it.

Bottom line, if you know of any new phenomenon in nature that could be detected by a sense organ, please contact your nearest physicist, who will be anxious to hear about it.

April 20, 2016

Energy Use in USA, China and India

TOPIC  (approx data for 2015) USA CHINA INDIA
Population in millions 320 1,364 1,275
Area in million square miles 3.8 3.7 1.3
People per square mile 84 369 979
Energy consumption (annual gallons of oil equivalent per person) 2,200 570 137

It seems to me that these stats explain a lot about why the future will not look anything like the present.  Our energy consumption stats are similar to those of other western democracies, although they typically have more renewables in the mix.

I once found a stat on income inequality between countries, can’t find it for the moment, noting that the poorest 25% of Americans are richer than the wealthiest 25% of Indians. Can’t recall whether this is income or wealth inequality – they are different.

A New Way to Think about Art

What we consider art has a staggering range and undefined limits. The oldest art form for which we have evidence is body painting; red ocher has been found in ancient sites well before the evolution of Homo sapiens. It is still a popular art, revived in the 1960’s by Veruschka, the tall German model noted for being painted in the nude so that she blended into her surroundings. The newest form I know of is social practice art, in which you do good works and call it art.

Veruschka as a rock
Veruschka as a rock

Art, craft, artifact and decoration blend seamlessly: it is a hopeless task to draw lines between them. Commercial art blends with “fine” art blends with graffiti. Everything we use is designed, and as an architect I would be quite offended if you excluded design from the realm of art. Yet is a cereal box art? How about a Hummer? Is there anything in our lives that hasn’t in some way been “made special,” to use a term invented by Ellen Dissanayake. Is there such a thing as a purely functional human-made artifact?

This raises the issue of quality. I venture to insist that late Mozart or Beethoven plumbed the depths of the human condition in their music, and that the paintings of Thomas Kinkade plumb the depths of kitsch, but Kinkade left an estate of $66 million and both the composers struggled to make a living (as have all but a handful of musicians then and now).

So we move on to popular versus “serious” art. I find much to admire in both genres, and much to criticize. But popular art is well-named if we compare a rock concert that can fill a stadium at $100 a seat with the struggles by the excellent chorale in which I sing to persuade 800 people to spend $30 to listen to Mozart.

Cinema, TV, video and still photography are new and vibrant worlds of art. No one would deny that acting before the camera is a form of art, yet does that apply to the most widely viewed cinematic genre, pornography? Are cat videos on YouTube a form of art? Why not? What about the snapshots you took of the family last weekend? What about TV ads?

Science brings in an entirely different set of issues. The Hubble telescope eXtreme Deep Field (XDF) image, created by combining 10 years of observations of a tiny patch of the sky, shows about 5,500 galaxies, some reaching back over 90% of the age of the universe. It is awe-inspiring. By far the most striking images I have seen in the last few decades are of natural phenomena and of computer-generated mathematical constructs such as the Mandelbrot set shown below.


And so we come to the concept of the sublime, which to the 18th Century philosopher Edmund Burke contrasted with beauty in arousing horror as well as awe. A lot of artists have spent a lot of energy scaring the hell out of people.

It took me a long time to register that beauty was something quite separate from art. A woman can be beautiful without being a work of art. However, she can dress, walk and apply makeup artfully. Beauty is in the eye of the beholder, yet there are cultural norms of beauty, and even (so claim some investigators) cross-cultural norms of beauty. One of these often cited is the widespread preference for landscapes formed by open spaces with clumps of trees and rolling topography. Another is a preference for bodily symmetry. Much in nature is beautiful, and much art is ugly.

Probably the most confounding use of the term art is to describe anything done well. There is no end to this; the concept can be applied to any act from a feat of athletics, crime or warfare, through sex and other bodily functions, to cooking and housekeeping.

Yet another aspect is the treacherous swamp of intentionality. Duchamp famously labeled a commercial urinal as art, and it as ever since been considered one of the greatest works of the 20th Century. Andy Warhol pulled everyone’s leg with his deliberately tacky images of soup cans and Marilyn Monroe, which have become priceless.

The original "Fountaine" by Duchamp. It was lost, likely discarded by the photographer (Stieglitz)
The original “Fountaine” by Duchamp. It was lost, likely discarded by the photographer (Stieglitz)

Art has from the earliest times had political, economic and social functions. It has always been closely associated with religion and power, and been a form of wealth and social status. Marxists make much of this aspect.

So the concepts of art, beauty, sublimity, skill, intention, emotion, spirituality and power are all mixed up. I have thought about this mess for a long time, and have come to believe that we need to step outside the usual lines of thinking. I am not alone: an increasing number of scientists have entered this morass, but with a refreshing new take on the subject. They are asking why we make art.

If humans spend an enormous amount of their resources and energy doing things skillfully, making useless artifacts and embellishing everything they touch, we need to ask why evolution has allowed such a thing to happen. Doesn’t it make sense that skill, beauty, awesomeness and embellishment have a function (or more likely, several functions) in support of our physiological, social and behavioral economy?

I think so, but trying to decipher what these functions might be is not a task for the faint of heart. Not being faint of heart, at least in this arena, I will tackle the issues in other essays. For now, have respect for the complexities, and stop equating art with Rembrandt, Shakespeare, Mozart … or Thomas Kinkade.

Shedding My Homunculus

I used to think that the brain was the most wonderful organ in my body. Then I realized who was telling me this. -Emo Phillips

My religious career must be typical for many of my generation. My parents were unreflective about their Presbyterian/Methodist religious ideas, and shared the prejudice against Catholics, Episcopalians (closet Catholics), and Jews common in the Midwest before the Second World War (and after). My father, from a farm background with no pretensions to gentility, preferred Baptists. Mother, deeply disappointed by her failure to rise higher in the middle class, detested the noisy Baptists, and was probably drawn toward the Episcopalians, although put off by the Catholic overtones. They compromised in the gentile Presbyterian middle ground, along with all their close friends (some were Methodists). I don’t know where the Lutherans stood in their Pantheon.

I went to Sunday School, of which I remember only identifying a gorgeous Brown Thrasher and a Cardinal in the Omaha alley on the way to church, poring over the stuffed bird collection in the Parish Hall, and doing neat craft things like making Easter baskets out of kraft paper and library paste. After the war, my family migrated to the LA area, along with millions of other Midwesterners, including every one of my parents’ close friends. We lived first in beautiful Santa Monica, where I was happy for several years.

Responding to a periodic wanderlust, and to get my father closer to his work, we moved to a dingy garden apartment in a decaying part of Hollywood, near which was the dumpy West Hollywood Presbyterian Church, with an evangelistic pastor named Antisdale who plagued my dreams for many years. A teenager, I was drawn into the youth program, trying to build a social life. It got more and more evangelistic, and I, being too naïve to adopt a saving hypocrisy, was drawn deeper and deeper toward a Commitment. I hated the idea, but there was no way out: Jesus’ existence implied my service. I was doomed to a life of embarrassing prayer sessions.

I took piano with a Miss Mikova, who lived and taught in a wonderful Modernist home in Hollywood, bathed in light through a bank of glazed terrace doors. Driving me to my lesson one day during my 14th year, my jazz musician brother, by this time a card-carrying atheist, continued an ongoing family argument about religion by noting that Jesus may have been an invention, an amalgam of any number of charismatic figures. I grabbed the lifeline and pulled myself to shore without a second thought. Jesus’ existence implied my service, so if Jesus was a myth, I was free. That night I refused to say blessing at dinner. I am sure my mother’s ghastly silence was occupied by the thought that my brother had done the devil’s work yet again, polluting the mind of her precious youngest child, her last hope for social legitimacy. She had after all shrewdly named me after a virtuous school-mate of my brother’s who went on to become a minister.

Atheists are fully preoccupied with conventional religion, often being more devout as an atheist than the average Sunday Christian or Saturday Jew. After all, an atheist accepts the definition of not being something everyone else is assumed to be — a theist or a deist or some other -ist.  I remained an outspoken atheist, refusing once even to play Christmas carols for the office party when I worked for Percy Goodman in New York. He and his more well-known brother Paul Goodman were archetypal Jewish intellectuals for whom Christmas carols were proud symbols of moral independence – he was not amused.

I was intensely uncomfortable on the few occasions in which I found myself in church, and remained so until I met my wife. Her family was and remains solid southern Episcopalian, and if I wanted to marry this wonderful and beautiful woman, religion would have to be part of  the bargain. I survived my re-immersion in church, and grew to like the rector who married us and many of his successors at the lovely 18th Century Virginia country parish church.

Children appeared, my wife took them to Sunday School at Christ Church Cambridge, Episcopal, (Massachusetts, not England) and from time to time I stopped working long enough to join her.  We had many friends who went there, but I remained true to my disdain for the words of the liturgy, adamantly refusing to mouth the Creed or go to the rail at communion, although I certainly sang lustily enough, paying little attention to the words.

The time finally came when the kids learned to do what their father and mother did and not what they said, and it became apparent that if I did not attend church regularly the kids would revolt and stay home with me. Sunday School held no particular joys for them, as they had made few friends there, but they would go if we did. I struggled with myself, finally arguing that, should a dictator try to shut the churches, I would man the barricades; and therefore, it was inconsistent of me to turn my back on an institution for which I, at least in theory, was ready to lay down my life, or at least throw a few rocks. I joined the choir.

This great event was possible for me only because the interim rector, a wonderfully warm woman, assured me that many worse hypocrites than I went to the altar, and that I was unlikely to be struck down by a thunderbolt if I pretended a piety I lacked. I indeed was not struck down, and realized with no little shame that I was disappointed.

Those ten years of involvement at Christ Church were wonderful years in which I made many good friends, headed a committee, learned to sing better, and gradually cleared my mind of the confusion between belief and experience. I could have a religious experience, as good a one as any contemporary Christian ritual allows, and not have to subscribe to an outdated mythology. I ceased being an atheist, and simply became religious. If someone wished to call me an atheist because, in their view, I didn’t believe in what everyone else in church believed in, that was their business. They would be surprised to find out what their co-religionists really believed.

I found I had many companions in my adventure into the experience of religion, and ceased my intolerance for others who found the church important in their lives. The church was filled with people in various stages of confusion about life and its meaning, each searching for something, each dependent to one degree or another upon the lovely rituals, the music, the symbolism, the Bible’s poetry, and each other; and all were grateful for the time to think about ethical matters for an entire morning once a week.

I paint this history as a background for a moment of epiphany. As I read and thought about the paradoxical need almost everyone has for religious beliefs that make no sense to a modern Westerner, I gradually extricated myself from the untenable if almost universal belief that there was a little man – my Homunculus – that must reside in my brain in order for me to be me. Whatever one called it — consciousness, a soul, a mind — I became convinced it can’t exist outside the context of neuronal and hormonal activity.

I was thoroughly convinced rationally, yet I had not taken the crucial next step and internalized this reasoning. I had to face up to my real beliefs, that I and everyone else was made of the same stuff as stars and rocks, the same bosons and hadrons, the same molecules. Stuff is what everything is, and that is all there is — stuff and how it is organized and transformed. The dualistic alternative was simply untenable. That alternative had formed the foundation for my thinking, breathing, living, feeling, for 50 years, and I had to shed it, like a molting crustacean. What kind of vulnerable creature would be exposed if this protective carapace were discarded?

Christ Church is a fine, simple, wooden structure built in the mid-1700’s, with a vaulted nave, two side aisles, generous arched windows, and a semi-circular apse.  On this occasion, like many others, I entered through the door to the right of the Apse to take my place in the Chancel for choir rehearsal. It was a lovely day. As I walked into the sunlit church, I took the final step into a fully materialistic view of the world. I “realized” — made real to myself — my conviction that everything I thought, that my notion of myself, that everything I imagined and said and saw, was a construction of a network of neurons in my brain. That was all I was, there wasn’t anything else. My precious “me” was an electro-chemical artifact, the byproduct of the metabolism of my brain. Only stuff. It was a devastating moment, and I felt emptied and depressed. My skills, my loves, my enthusiasms, my despairs — all were chemical artifacts. How could anything take on any deep meaning, now that it had been reduced to the automatic operation of some chemical machinery? How was I anything but a meaningless computation?

It isn’t possible to reproduce all the confused emotions I felt, but only to note that I felt them, and was in a mild state of despair. Yet it WAS mild, and it lasted a remarkably short time. I never needed to retrace my steps, and never have. I want to recount one of the lines of thought that helped me through this door in my life. The flaw in my despairing argument was the “only” — that I was “only” an artifact of my chemistry.
There are at least 10 billion neurons — nerve cells — in my brain. Each of these cells has an average of 10,000 connections with other cells, called synapses, making a total of 100 trillion connections. Most of these cells have within them the entire book of instructions about how to make me, my entire genome. Each of these 10 billion neurons is comparable to a city in its complexity.

Much of this machinery is dedicated to moving electrical impulses down the axon of the cell, its main trunk line, by pumping chemicals in and out of pores in the cell’s wall. When these impulses reach a terminus, a great cascade of chemical changes occurs, with pores opening and closing, chemicals being carried in and out in little vesicles, until at the other side of the terminus, the signal continues in another nerve cell. Or maybe elsewhere in the same cell. These cascades of activity move down the cell and across the synapses at an average rate of about 45 MPH, but since they usually haven’t far to go, many such cascades can occur in the 10th of a second it takes someone to react to a new stimulus. Chemical processes in cells take place in billionths of a second.

So this “only” turns out to refer to perhaps the most complex assembly of stuff in the universe. Within my brain stuff, I might remember the essence of perhaps 1,000 pieces of music, 500 people, 20,000 English words and who knows how many plants and animals. I can design buildings of indefinite size, write an essay, throw and catch a ball, draw a convincing image of almost anything (given enough time), swim, sing. There are 7,000,000,000 of me, each one unique, each convinced that he or she is in some way special, identifiable, worth saving, worth feeding, worth contributing to the next generation, each with a story, a fascinating story, many fascinating stories.

There is miracle enough in a piece of my brain the size of a rice grain to satisfy the most insatiable craving for the impossible. There is no need to add something ineffable to turn myself into a person or to infuse nature with magic. But this was a long and complicated journey for me, and I have great respect for the different journeys made by others.

And very little patience with proselytizing atheists.

The Infamous Plane of the Ecliptic

The Infamous Plane of the Ecliptic

The Plane of the Ecliptic or simply the ecliptic (as I shall call it) is infamous in our family because I have tried to explain it to various family members with very limited success. So I have thought hard how I can explain something that requires some spatial visualization to the many people who think differently.  But maybe this will help. There is a short quiz at the end of you are of such a mind.

Imagine yourself sitting comfortably all wrapped up on a heated chair, at the north pole. We are starting at the north pole because it greatly simplifies the relationship between the plane of the ecliptic and the plane you are sitting on, in this case an ice flow.

The heavenly bodies are of course very far away, but like the ancients, we can imagine that they are all attached to a celestial sphere. You are at the center of the sphere. The sphere is divided up into 88 constellations. For the ancients, the constellations were collections of stars that they remembered by imagining figures defined by the collection. Everyone is familiar with the big dipper, or great bear, that rotates around the north star. In fact all the constellations rotate around the north star, but we will come to that shortly.

For astronomers, a constellation is one of 88 irregular areas that precisely divide up the heavens. (Factoid from Google: there are 14 persons, 9 birds, 2 insects, 19 land animals, 10 water creatures, 29 inanimate objects, a head of hair, a serpent, a dragon, 2 centaurs, a flying horse and a river – which adds up to more than 88 because some constellations have more than one object in them). You can find a map at Click “Dark on Light” to see it clearly. It is laid out like a Mercator projection, so the little dipper stretches across the entire top like Greenland. The ecliptic is the sine-wave shaped line across the middle of the map (there is another line, the galactic equator, that follows the Milky Way, not relevant to the present discussion).

Twelve of these constellations make up the zodiac that forms the basis for astrology. Click on “show only zodiacal constellations” to see them on the map. Astrology is complete nonsense, but Newton spent a lot more time on astrology than he did on astronomy. These constellations are important because they lie on the ecliptic, by definition. We will see why shortly.

As the earth spins daily, the parade of constellations seems to move around the north star, Polaris, from east to west. We know this is an illusion and that the stars are fixed (at least relative to our solar system, and over a short time period – they all move at fantastic velocities). But we can pretend that the heavens rotate around our fixed location.

OK, just as the earth has an equator, so does the heavenly sphere. It is called the celestial equator and it is located where the plane you are sitting on at the north pole intersects the celestial sphere. If you were sitting at the equator, the celestial equator would be an arc that runs straight overheard from horizon to horizon. Polaris is near the north celestial pole, which by definition aligns with the earth’s axis.

To follow a star with a telescope anywhere on earth, all you have to do is set the telescope up so it is perpendicular to the north celestial pole, then set a clock mechanism to move the telescope so it would make a complete circle once a day.
As you well know, the sun, moon and planets (and all the other objects in our solar system) seem to move against the backdrop of stars. Our goal here is to figure out how they move, and the ecliptic plays a key role.

The ecliptic  is the plane of the earth’s orbit around the sun. The centers of the earth and sun are always in the plane, by definition. All the other large objects in the solar system orbit close to the plane, and sometimes cross the plane. The solar system is a flat disk because that’s the way solar systems form out of gas clouds.

The earth’s axis (and therefore the celestial reference system) is tilted relative to the plane of the earth’s orbit (the ecliptic). It is this tilt that creates the seasons. When the north pole is tilted toward the sun, we have warm weather, while New Zealanders have cold weather.
The earth’s tilt is about 23.4 degrees, making it easy to remember. It is no accident that the Tropics of Cancer and Capricorn are at latitude 23.4 north and south respectively, nor that the Arctic and Antarctic Circles are 23.4 degrees of latitude from the poles. Figure 1 shows why these are important latitudes.
Figure 1

On any given day, all the planets and the sun and the moon will be at a (relatively) fixed point on the celestial sphere. Obviously they are all moving, but for our purposes, we can freeze them in place for a day and see how they move. And that’s easy, because like the stars and galaxies, they move in a circle around the earth’s axis.

So every body in our solar system on a given day are located in one constellation or another (except for comets and very close objects that become meteors).  For instance as I write this in April 2016, the sun is in Aires (the ram) and the moon is in Pisces (the fish).

As mentioned above, the ecliptic runs through the constellations that form the zodiac. 2,500 years ago there were 12 constellations (or signs) in the zodiac, and for astrologers there still are. Astronomers, who being scientists stubbornly rely on evidence-based fact, note that the sun’s path now runs through 13 constellations (it just clips Ophiochus during December). This is because of the precession of the equinoxes. As this does not concern us, look it up in Wikipedia.

Furthermore, the sun will lie somewhere on the ecliptic, by definition. The moon and the 7 planets also lie close to the ecliptic, but only occasionally right on it. When the full moon happens to drift into the plane of the ecliptic, we have a lunar eclipse, and similarly when the new moon is in the plane, we have a solar eclipse. We will assume for simplicity that all bodies in the solar system except comets lie exactly on the ecliptic.

If you could see the ecliptic drawn on the celestial sphere, how would it look during a typical day? Well the four following diagrams show how the plane of the ecliptic (in red) looks as the earth spins through a complete day. Each follows the other at 6 hour intervals. Remember, we are still at the north pole. The blue plane is the ground plane you are sitting on – or rather the ice plane!
Ecliptic Left
Figure 2
Ecliptic Back
Figure 3
Ecliptic Right
Figure 4
Ecliptic Front
Figure 5

I hope you can see that the ecliptic plane will seem to wobble like a coin or a dinner plate or a vinyl record dropped at an angle onto a table, making one wobble per day. But the diagram has some strange notations, and I need to explain their significance.

What is meant by the “daily orbit of the equinoxes”? My wife logically insists that an equinox is a time, not a location. Well, the time of the vernal equinox is set by when the sun reaches a certain point in the heavens known at the vernal equinox or the first point of Aires (because the vernal equinox was in the constellation Aires in ancient times – it is now in Pisces). So it’s scientifically accurate to use the name of the time to designate a point on the celestial sphere.

What happens to the solar system bodies during a year? We can use the sun as an example, but all the bodies do the same thing. If you took a picture of the sun at noon every day for a year, it would appear to bounce up and down like a yo-yo, in a sinusoidal motion, gradually slowing to a stop at the solstices (which means “sun standing still”) and moving up or down fast at the equinoxes.

So each year the sun makes a complete trip along the ecliptic, and each day it, along with the ecliptic and all the heavenly bodies makes a complete circle around earth. It is important to keep these two motions separate in your mind.

All the major bodies in the solar system make a complete trip along the ecliptic, but at different rates. Mars makes the trip in about 2 years, while Neptune takes 165 years.  The moon takes one month. Mercury and Venus, because they are inside our orbit, oscillate back and forth around the sun, and follow the sun on its annual trip. At its furthest distance, Venus is 45 degrees from the sun, while Mercury is 25 degrees.

Aside from the weather, the north pole is a very good place to watch the stars and planets, because the geometry is so simple. Things get interesting as you move south, let’s say to Philadelphia (or Naples or Beijing, which are also at 40 degrees north). What happens is that the celestial equator is no longer the same as your horizon, and the celestial pole (up near Polaris) is no longer straight up. Check out the following diagram:

40 degrees north
Figure 6

At the north pole we had two reference systems, the celestial system and the ecliptic. Now we have a third reference system, which is what makes thinking about the ecliptic hard. The ground plane of the  new system is shown in green (you are looking at the back) and it is tilted 50 degrees relative to the celestial system. Why 50 degrees and not 40 degrees? Well, imagine that you take a fast trip from the North Pole to Philadelphia. You would travel 50 degrees, which brings you to latitude 40 degrees because there are 90 degrees from the pole to the equator. – 90 minus 50 equals 40.

To recover your the simpler orientation you had at the North Pole, all you have to do it lie back at an angle of 50 degrees from straight overhead (or 40 degrees up from the horizon) and voila! you are back at the North Pole!

If you trace the orbit of the summer and winter solstices and the equinoxes on the celestial sphere, you would have drawn something that looks like a globe of the earth, with the path of the equinoxes being the equator, the path of the summer solstice being the Tropic of Cancer, and the path of the winter solstice being the Tropic of Capricorn. So let’s modify the last diagram to just show the portion of these three paths that you can see without looking through the earth:
40 degrees north simple
Figure 7

Now every day the ecliptic will wobble back and forth between these two lines in the sky representing the Tropics, just like it did at the North Pole.

So what happens if you go all the way to the equator? Well, no surprise, the celestial equator and the two “celestial tropics” will be perpendicular to your local horizon and you will have to lie on your back to reconstruct what you saw at the North Pole. Polaris will be at the horizon, and the corresponding south celestial pole will be at the opposite horizon.

40 degrees north simple equator

Figure 8

Back at Philadelphia, we can make a few observations. The equinoxes  meet the local horizon due east and west. If the sun is at an equinox, the day will be 12 hours long, and the sun will set directly west. But since the whole reference system is tilted 50 degrees, it will set at a 50 degree angle to the horizon. This is readily seen if you watch a sunset carefully.

The following diagram shows what the three paths look like at various latitudes:
Figure 9

The dotted lines running across the paths represent hours of the day. The plan projection is there for information – it’s not essential. Here is the celestial sphere for latitude 40 north blown up and rotated for a better view (it is the same as Figure 7).

40 north skydome detail
Figure 10

The angle of sunrise and sunset at the solstices (32 degrees north and south of east-west in this case) is specific to the location. At the equator, it is 23.4 degrees. At Philadelphia it is 32 degrees and sunrise is at 5:40 AM.  In Stockholm the angle is 64 degrees, and sunrise is at 2:40 AM. At the Arctic Circle it is 180 degrees, which means that sunrise and sunset occur at the same moment, when the sun is directly north at the horizon. Every location north of the Arctic Circle has continuous day on Midsummer Night, which is a little confusing.

The hardest part of this picture is that every day the ecliptic does a complete wobble, and during its orbital period each heavenly body does the same wobble – the moon once a month, the sun once a year, Neptune once every 165 years.
Just to complete the picture, I show the ecliptic superimposed on Figure 9. This diagram shows the condition of the ecliptic at a time when the summer solstice occurs at noon. This happens at a different place every year, and sets the time of the solstice.
That is why the dates of the solstices and equinoxes vary. If it happened to occur near the international date line, it might differ by a day depending on which side it occurred. The likelihood of it occurring at your location depends on how precisely you define your position – if it is defined as one degree wide, it will occur on average once every 360 years, since there are 360 degrees of longitude.

40 north skydome detail with ecliptic
Figure 11

As Richard Feynman is credited with saying “If you think you understand quantum mechanics, you don’t understand quantum mechanics.” I hope you don’t feel the same way about the ecliptic!


1.    If the moon is full and the sun is at the winter solstice, where is the moon?
A.    Near the autumnal equinox
B.    Near the summer solstice
C.    Varies year to year

2.    At the north pole, is it possible to see both equinoxes and both solstices at the same time? – yes or no

3.    At the time of an equinox, the sun rises and sets very close to directly east and west at every point on earth except the poles (where it never sets)- true or false

4.    At the time of the summer solstice, the sun sets further north of west in Boston than it does in Philadelphia – true or false

5.    The ecliptic is so named because that is the only place that an eclipse can occur – true or false

6.    The number of degrees between the north pole and straight overhead is the same as your latitude – true or false

7.    How likely is it that the time of the summer solstice will occur at noon (sun time) within 1 degree of longitude from your location?
A.    Extremely unlikely
B.    Every year
C.    One year out of 180
D.    None of the above

8.    When and where is the sun directly overhead? (choose all that apply)
A.    Anywhere between the two Tropics, at solar noon, at certain times of the year
B.    On the equator at solar noon during the equinoxes.
C.    On the Tropic of Capricorn at solar noon during our winter solstice.



Answers: 1.B  2.No  3.True  4.True  5.True  6.False – it is 90 minus your latitude  7.C  8.A, B and C