The Sun Also Rises…

…to the south and to the north of due East. Indeed the sun rises in the East only on two days of the year, March 20 and September 23, the vernal and autumnal equinoxes.

This subject came up yesterday when, discussing the tilted wind-rose on our newly acquired gazebo, I kept insisting that what Brigitte called East was really West. She kept insisting that the sun rose in the East—and never mind which way the wind-rose was pointing. I kept arguing feebly for a while until she said: “If you are right, Arsen, the sun is right now setting in the East—and you can see it for yourself by looking out the window!” Sure enough. Some windstorm had managed to turn our wind-rose helter-skelter.

Another fix-it chore goes on my list, but I rather dread having to climb up there just to correct that problem. I am as challenged by heights as I am by spherical geometry.

Herewith a graphic that shows the rather considerable deviations of sunrise from due East for the North 42nd Latitude where Detroit lies on the map.

I have this diagram from a paper published by the Griffith Observatory in Los Angeles in 1948 and accessible here. One of the reassuring aspects of astronomy is that what was true in 1948 is still true in 2014—and will presumably still hold in 3014. Until the skies go into disarray, all’s well with the world.

We Never See All of Venus

We were returning from an outing the other night (on the 19th) and Venus in the sky had a great brilliance. In the wonder of watching it—on the road and then later from home—my early telescopic days back in Kansas returned to me. A bit of knowledge returned as well, but knowledge, unless well-maintained, has a way of eroding. What I remembered was that Venus has phases. And so I said, “It must be a full Venus up there.” Alas.

It turns out that Venus is at its brightest when it is quite close to the earth and shows an intermediate crescent shape. At that point the planet is about 42 million miles from the earth, and now is such a time. The image shown, from the U.S. Naval Observatory’s web site (link), is an apparent image, not a photograph. It is for November 19th. Visible portion of Venus will continue to grow, and grow brighter, until December 10th of this year.

When Venus is closest to us (25 million miles away), it goes dark; it is directly between us and the sun. It is full only when it is on the other side of the sun from us—and therefore we cannot ever see her full face. At that point Venus is 162 million miles from us—and bright although Venus is, almost full as it approaches the sun from the back, its brightness has decreased by more than one fifth.

The next image, from Wikipedia (link), shows images of the planet in 2004 (the date stamps are month-day-year). After “new” Venus is reached (the last image), the same images appear but in reversed orientation.

Beautiful planet—but you have to be outside to experience it. Watching Venus and reading about the planet is a nice illustration of the difference between knowledge and experience.

Supermoon

Last night was a supermoon, thus the coincidence of a full moon taking place very close to the time when the moon is closest to the earth. In matters of astronomy, someone like me, who tends to be geometrically challenged, can never remember exactly what this sort of things means. Hence I don’t apologize in repeatedly revisiting such subjects: at least for a week or two I can remember the relationships of these mysterious bodies hanging in the sky.

The moon’s orbit around the earth is ever so slightly elliptical. Hence at one point in its travels it is closest to the earth (perigee), at the other farthest (apogee). The image I show comes courtesy of the Physics Department of Utah State University (link). The words are from Greek, peri meaning near, apo meaning away, and the ge is derived from the Greek for earth; we get Gaia from that. The official name for this point in the lunar cycle is called Perigee Moon. “Supermoon” was a very recent coinage by the astrologer Richard Nolle in 1979 (per Wikipedia).

The graphic, as noted, exaggerates the ellipse. The inset, also from Wikipedia, shows the difference in perceived size of the moon at its last perigee before yesterday (on March 19, 2011) and its more or less average size (on December 20, 2010). The difference between perigee and apogee according to NASA is 14 percent, but The Huffington Post shows 13 percent, which pleases this tiny subset of humanity here. Supermoons occur once every 14 full moon cycles, thus  roughly every 378 days—just long enough to be news every time, weather permitting, of course, while the memory of why the moon should now seem so much brighter and larger will, each time, have been once more forgotten. That’s when blogs come in handy to have a private reference… How can those monstrously big jets stay in the air? (one of Brigitte’s favorite questions). How can that moon stay up there rather than falling down into the pit of eternity?
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See the correction a year later here.

Pregnant Young Sun

A story in today’s Wall Street Journal (link) reports on the discovery of what may be a new planet forming in the gaseous disk surrounding a young sun quite near us in the Milky May. Near is 335 light years from here. The sun’s name is HD100546. The “planet” is an asymmetry in the gas disk; the point where the asymmetry is observed also emits strong radiation. I note this here for future reference. Of the two theories of planet formation, one has particles, large and small, colliding and cohering as they circle a sun and then, slowly, aggregating into planets. This would suggests that the asteroid belt in our own system has simply failed to “get with the program.” The other model is that planet formation is a spontaneous process that takes place in the wake of a star's own formation—the planets forming, much as the one reported today, from the same raw materials that gave birth to the sun and soon after—thus while a good deal of dynamism is moving that disk of gases and dust. I’ve long favored this second view—and prefer to imagine that the asteroid belt is the record of some planet that got shattered in some collision. The discoverer here is Sascha Quanz, of the ETH University in Switzerland, working with his team at one of two observatories operated by the European Southern Observatory in the Atacama Desert of Chile. The one used was not reported but was probably Paranal, the location of the Very Large Telescope.

Up Against The Wall

Reading a truly excellent science popularization, Stephen S. Hall’s Mapping the Next Millennium, made me aware of developments in astronomy of which the first, the discovery of The Great Wall, had first alerted me in the early 1990s that major changes were afoot.

Back in the 1950s, theories about the universe as a whole had a pleasingly simple duality. The universe had but one ultimate fate: it would end in total heat death after continuous expansion until all energy had been exhausted—or the universe would begin contracting at some point, the galaxies converging again, until it all ended in the Big Crunch. In this view what mattered was the velocity of the expansion. If the velocity of the expanding universe was less than “escape velocity”—meaning that gravity would prevail over the outward impulse—expansion would halt and then reverse. Observations then (of the universe’s mass, of the velocity) were not precise enough to determine which was more likely—but the ratios of mass to velocity were close enough so that it could go either way. The out-in, out-in sequence appealed to me then. You know: Vishnu breathing.

Both models, to be sure, crucially depended on observations, credited to Edwin Hubble, that the universe, now, was definitely expanding—and had done so ever since the Bang. Indeed the Big Bang theory was the consequence of Hubble’s observations. If the universe is expanding now, that expansion had to have a start, and reading the observations backward—after all galaxies were moving away from every other galaxy in a uniform pattern—then in the beginning there must have been a great explosion from a mere point.

News of the first problem with that theory were published in 1989 by astronomers Margaret Geller and John Huchra, she a theorist, he an observer. A survey (or map) of the Nordic sky produced the first image of The Great Wall, usually and more humbly called Cf2A. That stands for the (Harvard-Smithsonian) Center for Astrophysics; the 2 stands for “second survey.” The great wall is a very massive, thick clustering of galaxies, thus a great structure. It challenges the theory of a uniform distribution of matter in the universe. The formation of such a wall also takes a huge amount of time—far more time than would seem to have elapsed since the Big Bang, thus approximately 14 billion years ago. Then, in succession others, in essence replicating the work of Geller and Huchra, discovered a number of other walls in turn, the largest of all being the Sloan Great Wall, named after the Alfred P. Sloan Foundation. Half a dozen such walls have now been mapped.

At around that same time (1986), but based on work conducted in the 1970s, seven astronomers, known as the Seven Samurai†, discovered that the Milky Way itself, along with all 39 galaxies of our Local Cluster (prominent in that list ourselves, Andromeda, and Triangulum), were themselves in uniform motion toward a distant spot. Other surveys later followed showing other galactic clusters also heading towards an enormously dense region (difficult to see because it is shadowed by our own galaxy’s clouds). That region is itself part of one of these walls. It was named The Great Attractor by one of the Samurai, Alan Dressler. After that arose the prediction that if one attractor has been found, others may exist as well. And the work goes on.

What are we to conclude? One conclusion may be that galactic expansion has already stopped—and what we see out there is in a much more distant past. The cosmos may already be in process of gathering its errant sheep—and that that gathering is very, very ancient. Those wall are very old, and yet still in formation. Pondering such discoveries not only enlarges my understanding of the cosmos but also of the nature of science. Young tendrils of it are exposing new knowledge—while the orthodoxy grimly clings to exciting news a hundred years old.

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†David Burstein, Roger Davies, Alan Dressler, Sandra Faber, Donald Lynden-Bell, Roberto J. Terlevich, and Gary Wegner.

The first image, from Wikipedia (link), shows some of the walls, including the largest, the Sloan Great Wall. In astronomical terminology, these are called filaments. And it turns out that the universe is quite thick with them—as shown in the second image (link), taken from a YouTube film produced by the Sloan Digital Sky Survey in New Mexico.

The Minimalists

The German Gustav Spörer (1822-1885), who had studied mathematics and astronomy, began as a school teacher but then, at age 36, turned to astronomical observation. His interest centered on the sun and using sunspots to discover where the sun’s equator lies. His work led him to discover, searching ever older records, that a period from 1645 to 1715 the sun had virtually no sunspots. Nobody paid much attention. The younger Edward Maunder (1851-1928), an English astronomer, later made the same observations and was a much better publicist—perhaps because his second wife, Annie Russell, helped him. As a consequence, that period of minimum sunspots came to be known as the Maunder Minimum. Spörer, however, managed to get his own minimum—posthumously. John A. Eddy (1931-2009), discovered a yet earlier period of solar inactivity dating from 1460 to 1550, and, having a kindly temperament, presumably, he named it after Spörer to make up for that pioneer’s lack of recognition.

Having mentioned these names, we’re far from exhausting discoveries of solar minima, thus periods of unusually low sunspot activity. We also have the Oort Minimum, dated to 1010-1050 and associated with the Dutch astronomer Jan Oort (1900-1992), the Wolf Minimum, dated to 1280-1350, associated with Swiss astronomer Rudolf Wolf (1816-1893), and the Dalton Minimum, 1790-1820, named after the English chemist, physicist and meteorologist John Dalton, but I cannot discover who actually made the observations and named this minimum after him. The period from 1300 to 1850, thus encompassing the Spörer-Maunder minima and what might be called the Dalton Dip are known as the Little Ice Age.

I show above a graphic from Wikipedia (link) charting carbon-14 measurements from about 850 AD to 1950. These are thought to be meaningful because sunspot activity interferes with cosmic-rays. Therefore fewer rays reach the earth in periods of strong sunspot activity—and therefore produce less carbon-14. The more quiet the sun, the more radiocarbon is formed. This gives us a way of measuring, indirectly, sunspot activity down here on earth. The graphic above does not single out the Dalton Minimum, but it is there to the right of the 1800 peak.

Now we have ample, indeed abundant, evidence that solar maxima are warm periods while solar minima, if they last a while, produce a cooler climate; hence we look back on a Little Ice Age. Currently, what with a very wide trough in the last solar cycle, the 23th, and a “weak” 24th underway now, some NASA-ites have speculated that we may be seeing another Dalton. Interesting. We’ll have to wait. It might be ironical that just as the population finally gets with Global Warming, the New York Harbor might freeze over as it did in 1780. (See also my post today on LaMarotte.)

AC B's P

To spell it out, our closest solar neighbor, Alpha Centauri, has three suns. Of these Alpha Centauri A is the biggest; it is about 10 percent more massive and 52 percent more luminous than our sun. It is about 4.4 light years from our sun. Alpha Centauri B is nearly as big as our sun (90.7%) but significantly less luminous (44.5% of the sun). This post is here because quite recently a Swiss astronomical team, headed by Xavier Dumusque, at the Geneva Observatory, discovered an earth-size planet orbiting a Cen B (to use a naming convention from astronomy). They published their findings in Nature on October 17 of this year. A and B are quite close to each other—the nearest distance between them is 900 million miles. The third sun that forms this system, known as Proxima Centauri, is the smallest (about 12.5% of the sun) and circles the AB twins at a trillion-mile distance. For that reason, periodically, it is the closest to the earth.

Our interest, of course, is in that unnamed planet, the P of my title. The current scientific consensus is that planets must be circling distant suns. One might say obviously. Seen in the frame of science, we are just a random sample, and if our sun has planets, others must have them too. But science is cautious, and rightly so. For decades, though, a search has been underway; in the course of it several gigantic, Jupiter-sized bodies have been discovered. a Cen B’s P, not named thus far, is the first of the right size. Alas, it orbits B at a distance much closer than Mercury circles our sun. For this reason the size is right but nothing else is. If there is life there, it has to take the form of fire demons.

Somewhere, surely, as probabilities dictate, there must be a planet of earth’s size and density, at the right distance from its sun, one neither too hot nor too dim to support life, with the same endowments of gas and water as ours, in existence just the right amount of time—to produce life spontaneously. And then, life once given, inevitably (given time and happy accidents enough), intelligent life will have evolved.

That is why we are interested in P.

Much food for thought. As this most recent addition to our knowledge shows, the improbability of life is a good deal higher than its inevitability. But there are those billions of galaxies filled with billions of stars. So, surely… Here and there, I assume, there are contrarian views. And vive la différence. Something even more improbable may be life’s explanation than all that we can possibly discover by microscopes and telescopes.

I show the same graphic, an artist’s rendition, everybody else does, courtesy of Wikipedia (link); that crescent on the right is P; B looks much bigger than A, but that is due to perspective. And my hat tip, and thanks, go to John Magee of eagle eyes and bottomless energy. He pointed me to this phenomenon and—amusingly—on a day when the Tigers were still struggling and the spin on the debates still raged. The subject of his e-mail? “The actual big news yesterday…”

The Cepheids of Henrietta Leavitt

There is a category of stars, known as the cepheid variables, that grow bright from a relatively dim state within a fixed period of days and then revert to a dim state in the same period—only to do it again. Their name derives from the first of these discovered, the Delta Cephei, in the Constellation of Cepheus in 1784. These suns are big—five to twenty times the size of our sun. They expand as they grow brighter, grow small again as they go dim. The following graphic, from the European Space Agency (link), illustrates the process.

The mechanism of pulsation is explained by doubly- or singly-ionized helium in the stars. Doubly means that two electrons are missing, singly that one is missing. Doubly ionized helium is more opaque. When the cepheid is dim, its outer atmosphere is high in doubly-ionized helium; it holds radiation in. As the sun heats, it expands and cools; as it cools the helium becomes less ionized and more transparent; the expanded star is bigger and brighter; more light escapes. Expansion is countered by the sun’s gravitational pull, and the process reverses.

Henrietta S. Leavitt (1868-1921) discovered an interesting relationship between these stars’ change in luminosity and the period (measured in days) it took them to go from peak-to-peak or trough-to-trough: the brighter the star, the longer the period. This news surfaced in 1912—and Leavitt appeared in my own telescope again yesterday when I was looking back to that year. Ah, yes! An interesting story. The paper in question was by the Harvard astronomer Edward Pickering (1846-1919); Leavitt worked for Pickering at Harvard with other women studying and cataloging photographic images of the sky. She turned sixty-six that year. The paper was called “Periods of 25 Variable Stars in the Small Magellanic Cloud”; it was published in the Harvard College Observatory Circular and cited Leavitt’s work. Leavitt had written an earlier paper, but it was only available in the Annals of Harvard College Observatory. It was dated 1908 and titled “1777 Variables in the Magellanic Cloud.” (Image from Wikipedia here.)

The ladies who worked for Pickering did the mind-numbing “clerical” work so that their male betters could do the “serious thinking.” My own conviction, to the contrary, is that real discoveries are made when creative people study the actual raw data—whatever form they take. And Leavitt was one of these. She began to record the luminosity and periods of the cepheids—and as any awake mind will do, she began to chart them. Soon she discovered the highly predictable relationship between period and luminosity. The longer the period, the brighter the peak. Leavitt had made a very fundamental discovery—used to this day to measure stellar distances.

So how does this work? The apparent magnitude of a star is provided by its luminosity as observed from the earth. If the two variable stars have the same regular periodicity, they can be assumed to be the same size, wherever they are. As for their absolute magnitude, that all depends on how far away they are. Leavitt made the simplifying assumption that the Cepheids in the Small Magellanic Cloud (SMC) were roughly at the same distance from us. Therefore, their absolute magnitudes could be measured as soon as the distance to the SMC became known. Thereafter, the periods of the stars alone, no matter how dim or bright they were at peak, could yield their absolute magnitude. And then, in turn, those two values (M for absolute, m for apparent) could be used to calculate the distance. And, indeed, that turned out to be true. The formula is D = 10^(m-M+5)/5 .

Absolute magnitude needs a little more unpacking. It is the brightness that a stellar object would have if it were observed at a distance of 32.6 light years (10 parsecs) from the surface of the sun. The star nearest to us, Proxima Centauri, is 4.2 light years (1.3 parsecs) from us.

The distance to the SMC was first estimated by Ejnar Hertzsprung in 1913. He used the cepheid variables in his method. His estimate, of 30,000 light years, was way off, but the method was later perfect. Now we know that the distance is 199,000 light years. The current method of calculating the absolute magnitude of a cepheid variable star is to:

• Measure its dimmest and brightest luminosity, calculate an average, and call that apparent magnitude (m).
• Calculate the absolute magnitude (M) from the period (P) using the following formula: M = -2.78 log(P) - 1.35. The constants used are built-in factors and adjustments necessary to indicate distance to the SMC.
• Use the distance equation (D = 10^(m-M+5)/5) to obtain the distance in parsecs.
• Multiply that number by 3.26 to get light years. 

Henrietta Leavitt thus, a hundred years ago, gave us what are called standard candles (they flicker, sort of, after all). Using them we can measure how far away they are. The art has made great advances since. Other categories of cepheids, with much longer periods, have been discovered. Methods of measurement have greatly improved. And the art is still somewhat iffy. But it’s good enough for astronomy work.

Perseus and the Perseids

In a literal sense we live in an age of enlightenment—meaning that the lights of cities are so bright that they make the night-sky almost invisible. The sky was clear last night. We saw faint glimmers—but street lights reflecting off the high branches of trees and the general luminosity of very near Detroit diminished hopes of seeing the Perseids, meteor showers named after the sons of Perseus. Perseus? The Greeks are still with us, even looking up at the sky. He was the son of Zeus and of the mortal lady, Danaë. His name is less generally recognized than that of the monster lady that he slew, the Medusa. To look at her turned you turn to stone, but looking at her in a mirror didn’t have the same effect. Perseus, therefore, holding a bright shield Athena had given him, approached the Medusa and made an end of her. This story greatly pleased the ancient Greeks—so much so that looking at the sky they could see the outlines of his form. Here is one version of the Perseus constellation:

He is holding Medusa’s head in the crook of one arm, his sword in the other. I have this figure from Wikipedia (link).

Now once every year, peaking at around this time, the northern skies are marked by a meteor shower. They are named after Perseus’ sons because the meteors arrive as if from the direction of the constellation. They come from a cloud of rocky debris that coincides with the orbit of a periodic comet, the Swift-Tuttle (130-year period). The cloud is thought to be debris left behind by the comet at least 2000 years ago, but a new filament appears to have been added late in the nineteenth century. So now we’re in the same neighborhood again, and those lucky to live deep in the country—thus about 50+ miles from a city—will see a portion of the wealth of rock bestowed on us by the Swift-Tuttle drawing swift bright lines in the skies above.

Being unable to see much, I thought I’d compensate by learning how to find the constellation next time we are really, really out of town. The following illustration (modified from telescoping.com, link) will do the job.

Find the big dipper and then use its more tilted side to locate Polaris. From there, follow roughly the same angle that brought you, going down again, you will find it pointing at Perseus’ head. For legibility, I’ve turned this image so that north is toward the bottom. A little bonus in staring at these lines comes from the realization that the Big Dipper forms the chest portion of the much greater Big Bear.

One of our happier books is Skywatching, published by The Nature Company and Time Life Books, 1994. It compensates for our excessively enlightened skies. Wonderfully illustrated. And it has yet to fail me in running down meaningful explanations and illustrations in gorgeous colors, artfully fusing myth and astronomy.

Candles in the Sky

The physicist David Bohm used to say that physicist were not physical enough. They relied too much on mathematical equations and had no, as it were, viscerally physical sense of what they were talking about. A variant of this came to mind yesterday as I first heard and then read about the 2011 Nobel Prize for physics awarded to Saul Perlmutter, Adam Riess, and Brian Schmidt. The variant is that we interpret physical observations based on theoretical structures. But the work these gentlemen engaged in was right physical, actually. They used arrays of massively modern telescopes to observe one type of supernova activity, that associated with Ia supernovae.

The terminology here is unfortunate. We have two kinds of supernovae, 1 and 2, but these are rendered in Roman form as i and ii. In the first category, i, interests us here. Type ii are produced by large stars late in their lives. In the first category, we have three subdivisions: 1a, 1b, and 1c; the first is produced by dwarfs, the last two by massive stars. On YouTube videos we hear people talking about “one A,” but in press accounts we see Ia. But never mind. the 1a’s are all white dwarf stars to begin with, and these are always associated with another sun; each dwarf is thus one member of a binary system. Furthermore, each is the collapsed form of the bigger of the two, with immense density. Most white dwarfs are about the size of the earth but have mass equivalent to 0.6 of the sun. The 1a supernova comes into being when the white dwarf sucks the mass of its binary companion to itself. Slowly its mass increases. When it comes very close to having 1.38 solar mass, it produces an enormous nuclear explosion, the supernova of type 1a. That number, 1.38, is called the Chandrasekhar limit, named after Subrahmanyan Chandrasekar who wrote a 1931 paper titled “The Maximum Mass of Ideal White Dwarfs.” The process described above is illustrated by the fabulous graphic authored jointly by NASA, the European Space Agency, and A. Field; I bring it courtesy of Wikipedia Commons (here).

The important point here is that white dwarfs never go into nova unless they reach that mass. And knowing that mass, we can calculate their brightness at peak with great precision. It is always just about the same. For this reason whenever such a supernova appears, we know how bright it must be where it is. Measuring its observed brightness with our by now stupendous instruments, we can therefore calculate how far away it is. 1a supernovae, therefore, act as a pretty reliable standard candles, thus objects of known absolute magnitude (luminosity). Knowing their observed magnitude, we can calculate their distance from us using a simple formula.

Our Nobelists looked for and found many, many supernovae of type 1a and measured their distances from us. In the absence of any kind of theory of the cosmos, this would give us a nice, clean idea how far away the most distant galaxies—those housing the 1a’s—are from us. Instead these men were greatly surprised by their findings. The most distant galaxies turned out to be much dimmer, thus much farther away, than they had expected them to be. I emphasize that word because “the model” now comes into the picture. That model, simply, is that the universe began with a Big Bang and has been expanding for 14 billion years. The expectation was that over time, the expansion would have slowed, decelerated, owing to the gravitational pull of everything on everything. Adam Riess uses the image of throwing your car keys into the air (read Big Bang). You expect the keys eventually to lose their upward energy—and to fall back down again. Instead, these keys just seemingly kept on going up. The following little graphic shows what they expected and what they actually saw.

Not to forget. The Big Bang is behind this expectation, thus a certain energetic, one-time dynamism. The Big Bang itself is based on Edwin Hubble’s observation that the farther galaxies are from us, the more red-shifted their light actually is, thus that the peaks of the light waves are farther apart. This used to be explained by saying that space was expanding and, as it expanded, it stretched the light. Today the explanation is that some kind of energy must be causing the expansion, dark energy, dark because we cannot detect it directly. And the observed red shifts—and now the unexpected dimming out of supernovae at great distances—has been interpreted to mean that the universe is mostly just that, dark energy (as I’ve had occasion to report here).

Alternative models are not even on the back burner these days. One of these might be that light gets tired as it moves, and therefore a red shift simply means tired light; hence there is no expansion. Fritz Zwicky (1898-1974), a physicist associated with supernovae, proposed the tired light hypothesis. Astronomer Halton Arp (1927-) holds “heretical” views on the red shift as well. If the red shift doesn’t always mean what Hubble thought it did, there might never have been a Big Bang. But we like the Big Bang. In the beginning, etc. Let there be Light. And having light, we now complete the picture with energetic Darkness.

The Ecliptic

Today’s the day of the autumnal equinox. I understand it better this year than ever before. In the course of writing a post on the astrolabe for LaMarotte, I came to understand what’s known as the ecliptic. It is one of those maddening words. It reflects simultaneously two different points of view and two theories of the solar system. In one the sun goes around the earth; in the other we go around the sun. Here for instance is Webster’s definition of the ecliptic:

The great circle of the celestial sphere that is the apparent path of the sun among the stars or of the earth as seen from the sun: the plane of the earth’s orbit extended to meet the celestial sphere.

If it is a circle, why call it the ecliptic? It comes from creating eclipses, not the shape, although the earth’s orbit is ever-so-slightly elliptical, but not so much that you would notice. That path of the sun among the stars is the legacy of the geocentric view. It prevailed from the end of the Hellenistic era to the acceptance of Copernicus and Galileo in the West. The earth as seen from the sun is the other, the heliocentric view. Now, confusingly, virtually all pictures of the ecliptic have the earth smack in the center—so that the sun seems to be doing all the moving. That, of course, shows that our real orientation is egocentric. The ecliptic only interests humans because it explains the seasons on earth. An honest picture is the following:

The sun is squarely in the center. We do the traveling. The line we describe is the ecliptic. The sun is “in Aquarius,” as people say, meaning from our perspective; therefore it’s late January or early February. The circle of the zodiac was first determined by people waiting for sunrise. As soon as the first light appeared, they looked above that spot at the still dark sky. The constellation they detected right above the sun was the “house” in which the sun was rising. In July-August, when the earth will be where Aquarius is shown on the sketch, the dawn-watchers will see the constellation of Leo instead. Brigitte was born in Aquarius; I was born in Leo. Astrologically we complement each other. But, of course, neither Aquarius nor Leo ever move. Nor does the sun except around its axis. Anyone who could survive on the sun and live in a fixed spot there could divide his sun-day into twelve sun-hours by looking at the sky and reading off a sign of the zodiac. “See you no later than Sagittarius…”

But let’s now turn to the more usual illustration. An attractive one is show below from Wikipedia’s page on the Equinox (link). As expected, it shows the ecliptic circling the earth, whereas the earth is circling the sun, but never mind. What Wikipedia is doing here is depicting the first part of Webster’s definition above, the sun’s apparent path.

Notice next that the earth, which circles the sun following the ecliptic (the horizontal light-green ellipse), does so at a tilt to the ecliptic. This also means that our equator—and the “celestial equator” that we project from it (tilted dark-green oval)—are also at a tilt. As this diagram clearly shows, the ecliptic is therefore located below the equator through half the year and above it through the other half. And where we see the ecliptic, there we see the sun. Therefore the sun appears below the equator and then above it. The exceptions are two days of the year when the ecliptic makes its two crossings. Those days mark the autumnal and the vernal equinoxes; the sun is precisely over the equator. During those two 24-hour periods, day and night are of equal length. Note that the point of crossing is at the intersection of the vertical line drawn at 90° to our actual orbital plane, thus to the ecliptic.

They Bended the Light

The trials and traumas of being a science-fiction writer? There are plenty, let me tell you. How do you reconcile the following, for instance: Newton believed that light was made of tiny little particles with mass—but that gravity did not affect them. But Einstein believed they had no mass, but gravity pulled them nevertheless!

Fortunately SF-writers have a kind of license, like court jesters used to have. The latter could speak truth to power and still stay out of dungeons. In our more commercial times, SF-writers don’t aspire to publication in peer-reviewed journals. They worry more when Marvel Comics frowns.

My problems have been with gravity bending light. A writer needs light to fly in straight lines to produce decent space tales. If massive things bend light, even if ever so slightly, and if dark matter is as prevalent as science tells me that it is, how do I know that a star I see at night is actually where it is? It might be somewhere quite different, hiding at the tail end of a million-light-year-zigzag course and not be rotating where it seems to. There may in fact be a huge body entirely obscuring the star I see, but the light from it has managed, by Einsteinian assists, to curl around this obstruction. To illustrate this hide and seek, I provide a graphic I made myself, but the inspiration for it was Jeffrey Reynolds’ here.

The way science explains the dilemma is to say that photons “follow the geodesic” and their mass-less nature does not guarantee straight paths. But what does such phraseology mean? By “geodesic” scientists refer to the curvature of space, more correctly of space-time. It isn’t as if gravity affects a mass-less particle. No. It is that great masses cause space-time to curve. And once that space-time has curved, light follows it. Self-evident, isn’t it? Or is it? Well, let me not try to explain that to a science-fiction reader. Space-time exists (in the sense of really being there) largely as a mathematical conception. And if it exists in reality, there is no actual physical description of how this “whatever” tangibly influences things we can actually see (like light) or touch and feel (like matter). It’s a muddle. I can fill whole walks just pondering how space-time knows to straighten itself out again after a big bad ball has caused it to curve. Or is it just displaced? Like water by a sinking ball of lead? But if so, it must be something. Is there a Theory of the Elasticity and Fluidity of Space-Time? I wonder.

The trigger for these thoughts? Well, in today’s paper I came across a front page story on a discovery, by Takahiro Sumi and team, at the Osaka University, that hundreds of billions of gigantic planets, gas giants like Jupiter, clutter-up our galaxy, none of which is associated with a solar system—orphans, in other words. There are supposed to be twice as many of these orphans as there are suns in the Milky Way—thus around 400 billion of them. Okay. But the interesting thing, for me, is that this discovery is based not on actually seeing these giants in their enormous numbers but by a method called microlensing. And what is microlensing based on? Why, the ability of big heavy objects to bend light. Now we have yet another marvel to add to black holes (that relentlessly suck everything in but, no surprise, sometimes let things escape), the curvature of the universe into a self-contained sphere (what is outside that sphere?), the blackness of space (why isn’t space brilliantly lit when light cannot escape the sphere?), the perpetual expansion of the universe (into what? the as yet undiscovered Cosmic Container?), the big bang before which there was, what? nothing? And finally the energy-death of reality when every last hydrogen has been burned up? Lordy. I sometimes think that treating science as if it were immune to the current philosophical and cultural meltdown is actually a mistake. But not a mistake we have to make in fiction. Those 400 billion lonesome giants might one of these days come in quite handy. And soon there might even be a country-song about them…

You’ve Come a Ways, Henrietta

In looking up how distance is measured in astronomy, I came across something that tells about change in our times. The person who discovered that Cepheid variables can be used for measuring distance was Henrietta Swan Leavitt (1868-1921). I could not find an article on her in my (new) 1956 Encyclopedia Britannica but did find an article on her in my 1989 World Book Encyclopedia. I recently got my EB from the Magees as Christmas present. Some Christmases back, John also gave me a very fine biography of Rosalind Franklin (1920-1958). Does the name ring a bell? With James Watson and Francis Crick she was a co-discoverer of DNA; they got the Nobel and she did not. Okay. Nobel Prize rules insist that the award can only be given to living persons, and Rosalind had died by 1962…

Variable stars pulse in luminosity, and Leavitt discovered that those with longer periods between bright and dimmer phases are more luminous than those with shorter pulses. The earliest of these were discovered close enough to us so that we could measure their distance from us using simple geometry—the parallax method. How that’s accomplished is shown here. We could therefore correlate changes in measurable brightness, short and long pulses, and known distances. Then later, by extrapolation, just a reading of luminosity and period enabled us to use Cepheids for distance measurement even when they were too far away to discover their distance by parallax.

Franklin saw the DNA’s structure by taking an X-ray diffraction image of it—and that image then greatly helped Crick and Watson to zero in on the structure. The image, known as Photo 51, is available here.

Equinocturnal Frustrations

Welcome Spring and so forth. I note that the weather, which cooperated magnificently for about the last two weeks of so-called Winter, refuses to smile today. It’s gray out there, cool, and humid. The weather perhaps shares my frustration at six month intervals when it’s time, once again, to celebrate the equinox. I understand this thing perfectly well in conceptual terms. The sun today is directly above the equator, straight up there in the perpendicular. As time now advances, that angle will become more and more acute, the sun appearing north of the equator until the summer solstice on June 21st. After that, back we go again, the angle increasing until the arrival in September—on the 23rd of that month this year—of the autumnal equinox. Thereafter the angle becomes obtuse (from our point of vantage), the sun beaming south of the equator to the delight of all Patagonians until December 21, the blessed winter solstice. Then it marches back again to March of 2011. I do get all this. Yes. But I can’t picture it properly. It’s all due to the earth’s tilted axis, isn’t it, which puts us now closer to the sun and now removes us farther away in wintertime. Every season—it’s amazing, actually, how this sort of thing fades from memory in six months’ time—I end up getting my ice-pick and an apple, and actually doing a kind of dance around a lamp holding the ice-pick at an angle until my geometrically dense brain finally gets it again. With that comes a moment of satisfaction, but the juices of frustration that came before—while trying to find good visuals on the Internet—linger long enough in my body to yield…well, a post “celebrating” the Vernal Equinox.

Keep Looking Up

Valentine’s day is now well, well behind us, but in this household it was a late bloomer. In a reversal of 50 years’ tradition, Brigitte decided to give me a Valentine’s Day present for a change, and she decided to give me the stars. The package took a long time arriving, so we celebrated late.

But let me unwrap this. Decades ago now, in the late 1970s, Jack Horkeimer appeared on Public Television in brief vignettes about the stars—and how to make the most of them by looking up with naked eyes. The program then was called Jack Horkheimer: Star Hustler, but Horkheimer changed the name to Star Gazer thanks to the inadvertent influence of the Internet. Children looking for his videos using a search engine got the wrong kinds of sites when they typed in the phrase “star hustler.” Rolling my eyes. In any case, Brigitte got me Horkheimer’s most recent disk, Space Oddities, which is a collage, with linking commentaries, of his recent and some older brief video “articles”—and it is a delight. The place to go to is here. And here you will find a YouTube broadcast of one of the shortest kinds of items Horkheimer produces for PBS, a one-minute snippet.

Jack Foley Horkheimer is the Executive Director of the Miami Space Transit Planetarium at the Miami Science Museum and has been at his job for more than 35 years. Each of his episodes ends with the phrase “Keep looking up”—very good advice at any time, not least in this day and age.