Monday, November 29, 2010

Three Websites

This is one of three websites containing short essays I have written about astronomy.

The present site describes and explains various astronomical phenomena and events.

The two others are:

Philosophical Astronomy, which takes a more theoretical look at the subject,


SkyMarks, a compilation of stargazing columns that appeared monthly for a couple of years in the New Haven Register.

And here is a list of all of my publications on astronomy.

Enjoy, and clear skies! -- Joel

Wednesday, December 31, 2008

Dueling Designations

Copyright © 2007 by Joel Marks

Look, up in the sky! It's a planet! No, it's a pluton! No, it's a ... kenning!

On August 24, 2006, the International Astronomical Union voted to demote Pluto from a planet to a dwarf planet. This has not sat well with many in and out of the astronomical community. For one thing, the term “dwarf planet” is bizarre since it is intended to remove Pluto from the ranks of the planets. But if something is a dwarf x, isn’t it still an x? For example, a dwarf star is a kind of star; indeed, our own sun is one.

This means that the term “dwarf planet” is a kenning, a term to which I was led by rhetorician extraordinaire Prof. Kip Wheeler and defined in Wikipedia as “a figure of speech, substituted for the usual name of a person or thing. … compris[ing] two terms, one of which (the 'base word') is made to relate to the other to convey a meaning neither has alone.” Allison Griswold, a former student of mine, suggested the apt example of “starfish,” since a starfish is neither a star nor a fish (and, even more aptly, has the technical name in zoology of “asteroid”!).

Meanwhile there are independent reasons for wanting to retain the planetary status of Pluto. As I argue in a recent article in Think (“A Planet by any Other Name,” winter 2007, pp. 103-106), a periodical of the Royal Institute of Philosophy in Great Britain, it is perfectly legitimate to assign a dual designation to an object of both popular and technical interest. I note that even Brian Marsden, who just stepped down after his long tenure as director of the IAU's Minor Planet Center and who seems quite content to have Pluto added to his erstwhile bailiwick, is “prepared at least to consider a … compromise [that] allows that some planets could be both ‘major’ and ‘minor’ – like music” (personal communication, 8/12/06).

Actually I have no objection to retaining the “dwarf” label for Pluto, for I think there is an analogy that suits the case perfectly. Why not categorize Pluto as a Brown dwarf ... after Mike Brown, the astronomer whose team discovered 2003 UB313, thereby precipitating the current controversy? This seems especially fitting, given that brown (lower-case "b") dwarfs have long held an ambiguous status relative to stars that is analogous to the status large Kuiper Belt Objects like 2003 UB313 hold relative to planets. Nonetheless brown dwarfs are still commonly referred to as stars, albeit “cold, dark” ones, so a Brown dwarf Pluto would still be a planet.

This might even resurrect the planetary status of Mike Brown’s baby, now dubbed Eris. But the name “Eris” presumes the object is not a planet. If it were recognized as a Brown dwarf, and so a kind of planet after all, I would like to suggest it be renamed “Planet X.” This seems triply meet since (1) the name evokes the historical idea of a trans-Neptunian planet, (2) “X” is the Roman numeral for ten, this being then the tenth planet, and (3) it retains the consistency of Roman names for all the planets (except ours!).*

-- January 14, 2007

* Mike Brown subsequently commented that “the name Eris definitely does NOT presume that it is not a planet! We specifically chose a Greek name to fit into the Greek & Roman names (well, ok, mostly Roman, but the Roman version of Eris is Discordia, which just doesn't seem as good a name) of all of the planets” (personal communication, 10/13/08).

Monday, June 16, 2008

Going Lightly

The designation "dark energy" for the something that constitutes the bulk of the known universe is clearly a placeholder. A permanent name for this fifth force of nature may await the determination of what exactly it is. All that seems to be known about it thus far is that it has a repulsive effect that is in some sense "the opposite of gravity." Whether this will prove to be its most distinctive feature once its full nature becomes known is anybody's guess (and certainly not mine, since I'm not a physicist). Should it turn out to be so, however, I propose that it be named "levity." Not only would this be suitable in its literal meaning (as the opposite of gravity), but it would also serve to lighten things up a little in a universe which heretofore has been dominated by gravity. So ... let there be levity!

(I've been promoting this idea for many years, as witness a letter to the editor in Natural History magazine, which you can see by clicking here.)

Sunday, April 23, 2006


Copyright © 2006 by Joel Marks
Revision of “Reckoning Might Come from Sky,” New Haven Register, April 13, 2006, page A6

Twenty-three years from today, on April 13, 2029, the residents of this planet will witness an unprecedented harbinger of their doom. An asteroid the size of the Empire State Building will be visible to the naked eye as it hurtles by at a distance of less than the earth’s circumference.

The asteroid's scientific name is 99942 Apophis. Its proper name comes from the Greek rendering of Apep, the ancient Egyptian spirit of destruction. This name fits. If Apophis were to strike the earth, it would wreak untold havoc. And given certain as-yet unknown contingencies of the asteroid's orbit, it might do just that.

It is especially meet to reflect on this today, which commemorates the ancient Passover, when people in Egypt took steps to assure God’s slaughterous spirit would pass over or spare them.

Apophis was discovered on June 19, 2004, when it was given the preliminary name “2004 MN4,” and has been tracked closely ever since. It raised significant alarms as early data suggested a greater chance of Earth-impact than had ever before been predicted by modern science. These estimates were subsequently reduced, but the asteroid is still rated 1 on the 10-point Torino Impact Hazard Scale because there is a small but non-zero probability of its hitting the earth exactly seven years after its 2029 flyby, that is, thirty years from today.

Unbeknownst to most of the population of the world, this kind of threat hangs over us at all times. The good news is that astronomers are keeping an eye out for it. It may come as a surprise to you to see, for example, the level of daily monitoring that is in evidence at the NASA Website devoted to NEOs or Near Earth Objects.

The bad news, however, is twofold. First, the detection program is limited: It targets only the largest objects, like the one that wiped out the dinosaurs, and also does not include comets, which tend to be discovered only haphazardly rather than systematically. But a comet can do as much damage as an asteroid, and a relatively small object can be catastrophic. Apophis itself, whose impact would pack a wallop 65,000 times that of the “Little Boy” atomic bomb dropped on Hiroshima, comes in way under the threshold size of one kilometer that Congress has order NASA to inventory.

The second bit of bad news is that detection is not enough. For one thing, it obviously would not help humanity if an object large enough to disrupt or even destroy all life on earth were discovered but we couldn’t do anything about it.

In fact there are various more-or-less feasible proposals on the drawing board for averting disaster. But the critical factor is lead time. The political, economic, and engineering effort demanded could require decades for its implementation.

Meanwhile, consider some recent “near misses” by NEOs. Asteroid 1996 JA1 came to within almost the distance of the moon to the earth on May 18, 1996. This asteroid is 1/3-mile in diameter and was discovered only four days prior to its closest approach. Then on June 14, 2002, Asteroid 2002 MN came to within 75,000 miles of the Earth -- less than 8 Earth diameters. It is 100 meters long – three times the size of the meteoroid that laid waste the Siberian region of Kunguska in 1908 -- and was only discovered three day after its closest approach!

In a little more than a year we have seen, and many have experienced, the devastation of the Christmas Tsunami and then Hurricane Katrina. More than likely an incoming asteroid or comet would hit water, which constitutes 70 percent of the earth’s surface. Thus we have some sense of the “ripples” such a large “pebble” hitting such a large “pond” would make, albeit the recent events have been minor by comparison to the global reach of a large impactor.

I recommend, therefore, that we all support the B612 Foundation, chaired by former astronaut Rusty Schweickart, which is lobbying hard for increased attention to this ultimate threat. Their Website contains updates and simulations. See also my own more extended treatment of this subject, "Stones and Fish Falling from the Sky."

Tuesday, January 03, 2006

And Then There Were Eight

Copyright © 2005 by Joel Marks
Originally published with the title “Discovery of 10th planet may mean there really are only eight” in the New Haven Register on August 3, 2005 (page A6)

At first I was excited to learn that a tenth planet has just been discovered in our solar system. But a moment's reflection made me realize that this probably means there are only eight planets.

How could that be? The status of the ninth planet, Pluto, has been in question ever since a new category of solar system object was discovered, which are now collectively known as the Kuiper Belt. Analogous to the ring of asteroids that orbit the Sun between Mars and Jupiter, these are tens of thousands of planetoids that orbit the Sun beyond the orbit of Neptune.

That is also where Pluto spends most of its time (although Pluto's eccentric orbit sometimes brings it closer to the Sun than Neptune). So there has been the surmise that Pluto may not be a planet but simply the largest member of the Kuiper Belt of planetoids. I am afraid that the discovery of a new Kuiper Belt object that is even bigger than Pluto may sound the death knell for Pluto's planetary status.

This makes me sad. To lose that planet is to lose a world – the world of ”nine planets,” which is as axiomatic as “The Earth is round” and as dear to this former little boy's heart as the sky shows at the old Hayden Planetarium in New York City. That lonely outer orb in particular has always held a special allure for the imagination.

But for me Pluto has had in addition very personal significance. First and foremost is that my twin goddaughters were born on February 18, 1970, the fortieth anniversary of Pluto’s discovery. It only added to that delightful "conjunction" to have Pluto itself turn out to be the closest there is to twins in our solar system. In 1978 James Christy discovered that "Pluto" really consists of two objects very close together, whose relative sizes make them unique. Prior to that, Earth's Moon had been thought to be the largest satellite relative to its planet, but the newly discovered Plutonian satellite, named Charon, is more than half the size of its planet.

A close second to my excitement about that cosmic coincidence was my having met the man who discovered Pluto itself, Clyde Tombaugh. When I learned that he was going to be speaking in Boston some years ago, I determined to make a pilgrimage to shake his hand. The idea of having physical contact with a human being who had been integral to the history of our solar system, and had even, as it were, "capped" that history, thrilled me no end.

I did meet and speak briefly with him. I eyed the massive hands of this former farm boy, but, when I reached out to shake one of them, alas, he refused! He said that his hand was tired from having autographed so many posters. Of course I bought one and later presented it to my goddaughters.

More recently the big news has been that planets have been discovered circling other stars. In only the last decade scores of new ones have been found! So Pluto had already been getting crowded out before this latest find in our own solar backyard.

Thus I suppose I should not have been surprised or even dismayed that the story about this latest discovery appeared only on page 2 of last Saturday’s New Haven Register. Pluto’s discovery had been front-page news. Indeed the account of Pluto’s discovery is itself a fascinating astronomical detective story and was also connected tangentially to the search for intelligent life on Mars undertaken at Percival Lowell's fabled observatory in Flagstaff, Arizona.

The Register article does have a silver lining, however, for it reports that a local person was involved in this latest planetary discovery: David L. Rabinowitz, a research physicist at Yale. You can be sure that I will look him up and hope that he does not refuse to shake my hand!

Two more essays about Pluto: A Planet by any other Name and Dueling Designations.

Golden Age of Astronomy

Copyright © 2004 by Joel Marks
Originally published in the Evening Division Student Newsletter of the University of New Haven, vol. 1, no. 5, June 2004

We live in the golden age of astronomy. The discoveries that are being made on a daily basis dwarf anything before in human history. Perhaps the only rival would be the prehistoric discovery of the starry sky itself, when our ancestors first looked up at night (or in the daytime too) and took note that what was above them was something wonderful.

Sad to say, the current explosion of human understanding of the cosmos is matched only by the unprecedented indifference to it by contemporary humanity. And that is likely due to the simple fact that what was plainly visible to our distant, and even recent, ancestors, is no longer so to most of us urban and suburban dwellers. The starry sky has been all but eliminated by light pollution. There is ignorance of even the most basic phenomena that were known for thousands of years, such as the phases of the moon, or the fact that the moon is not “up” at night all of the time, but spends half of each month (or “moonth”) in the daytime sky.

It is fitting, therefore, that I have been asked to write something about astronomy for the Evening Division Newsletter. When you folks leave your classes at night, your first response should be to look up! I would like to give you a few pointers about what to look for.

Paradoxically enough, the light pollution we experience might actually be an aid to beginning to learn your way about the night sky (provided you are still motivated to do so even though the light pollution obliterates so much). That is because only the brightest stars (and the planets and moon) will be visible, which form very recognizable patterns. Once you learn these, you can find everything else. I call these constant and readily recognizable denizens of the night sky “skymarks” – analogously to “landmarks.” (Any resemblance to my name is purely intentional.)

For example, the constellation of Orion is very easily identified. When you know where it is, then you can easily find Sirius (the brightest star in the sky), which is in the constellation Canis Major (the Big Dog), and the star Procyon, which is in the Little Dog nearby. I have chosen this as my first example because just the other night I was able to use this simple knowledge to find a comet! A sky chart I had found on the Internet showed that the newly discovered Comet NEAT (whose name is all uppercase because it is an acronym) would be just to the left of Procyon on that night. So I went outside with my binoculars and pointed in that direction. Right through the haze on the horizon I spotted the fuzzy patch that was Comet NEAT. Neat!

This won’t help you if you are a novice skygazer because Orion is not in a good position for viewing at this time of the year. It is highest in the sky during winter. Right now it has pretty much set by the time darkness descends. But my general familiarity with the sky had enabled me to find Procyon anyway. There were clues in abundance to one who knew his way about.

I would like to start you off on this lifetime journey of discovery in the same way that I began it: with a particular book, called simply, The Stars, by H. A. Rey. (Yes, the same H. A. Rey who wrote the Curious George books.) This book is readily available in bookstores and on the Internet. Its hallmark is the stick figures Rey used to illustrate the constellations. These are so much more effective than the fancy mythological drawings of yore. The stick figures really work.

I will never forget the first time I tried out Rey’s method. I was standing on a hill on the UConn campus at Storrs, looking towards the eastern horizon. According to the book, I knew that the constellation Sagittarius was rising before me. Suddenly the stick figure pattern jelled in my vision. Wow! There was this gigantic archer striding over the horizon, bow in hand and arrow ready to be let loose on the Scorpion he was pursuing (and has been since time immemorial).

I was hooked. Thereupon I studiously learned and located every other major constellation in the northern hemisphere. Now I can find anything at all in the sky, because all I need to know is what constellation an object is to be found in, and the rest is easy. Even if you use a telescope, the first thing you have to know is where to point it. The constellations will get you more than half way to your target.

So what do you look for? H. A. Rey’s book will give you sufficient background knowledge about what is up there to keep you busy for quite awhile. Another wonderful book (of which there are many) is 365 Starry Nights, by Chet Raymo, which will take you through every night of the year so that you can learn the whole sky systematically. Contrary to the common conception, there are many things besides stars in the starry sky, such as nebulae and galaxies. Even with the naked eye you can see objects that are millions of light years away (one light year is six trillion miles!) and, even more astonishing to contemplate, millions of years in the past.

But that’s just the “constant” sky – the skymarks. Meanwhile, and again contrary to today’s common (mis)conception, there is always something happening in the night sky: comets, eclipses, planetary conjunctions, even novae. With your knowledge of the constellations, you will be able to find them all.

Finally, one of the main things “happening” up there is the aforementioned knowledge explosion about what we are looking at. To keep up with this I can recommend no better source than Sky and Telescope magazine. My jaw drops (and stays there) when I read each monthly issue’s “News Notes” section. And by reading the regular articles and features over the course of the years you will become an expert amateur.

Then what you will crave to do is share the knowledge and wonder with everybody else. In other words, you’ll become just like me!

Clear skies! – Joel Marks, philosopher to the stars

Friday, November 01, 2002

The Ultimate Sky

by Joel Marks
Published in Sky and Telescope 104:5 (10), November 2002

Every fall semester when I am teaching my philosophy classes, which are mostly sections of introductory ethics, I am reminded of Immanuel Kant's exclamation, "Two things fill the mind with ever-increasing wonder and awe … the starry heavens above me and the moral law within me." For this is the season when M31 rises to the top of the sky for all to see on a clear dark night, and I cannot resist telling my students all about it and, conditions permitting, taking them outside to see it.

The reception I receive is both gratifying and discouraging. There is no question that most of the students enjoy the break in routine from arguing about right and wrong. They are in fact genuinely curious about the stars. And the story I have to tell them has got to be at least tied for first place as the greatest ever told: How the very same Immanuel Kant whom we study in the philosophy course was one of the first to postulate the correct identity of the Andromeda Nebula, perhaps by analogy to Galileo's discovery of the stellar nature of the Milky Way (which is a story in itself, of course); how this informed inference was spectacularly confirmed in the Twentieth Century, thereby opening up the floodgate of galaxies; how immense these objects are (I do a Carl Sagan with the numbers) and hence the universe in toto; and so on.

To cap it off I roll open my giant Palomar poster of the Andromeda Galaxy and its companion galaxies. I point out that this is "an actual unretouched photograph"; that the stars filling the frame are in our galaxy; that to somebody residing on a planet in M31, we would look just like this picture (pointing to our location two-thirds out from the central bulge); that when we see the bulge as a tiny smudge in the sky, we are seeing something utterly unique in our (naked-eye) visual experience (from the Northern Hemisphere, anyway), namely, an object that lies outside the Milky Way galaxy; that our unaided eyes therefore have the capacity to see 2.3 million light-years into the distance; hence also, that we can literally look into the prehistoric past; etc., etc. M31 is the ultimate wonder that has been revealed to us by science, as far as this amateur astronomer is concerned.

But while I am getting carried away, I also recognize the tragedy that underlies my ability to "wow" my university students in this way: Hardly any of them has ever heard about any of this stuff. They have never taken an astronomy course, and probably never will. Astronomy is simply not considered to be a part of their basic education. Their location in the physical scheme of things has been known only up to a point, say, Earth, Solar System, without the rest of it: Milky Way, Local Group, Universe. It's like forever being a child who learns that she lives on Joralemon Street in Brooklyn Heights, but not that Brooklyn Heights is in New York, the United States, North America.

I feel so sad for the vast majority of people, who are never exposed to this particular reason to wonder. But it is also a drag on the continued uncovering of these revelations, since they depend upon funded research, hence, public support, hence, public understanding. I do my bit in my courses, but something much more wide-reaching and direct is called for.

I know one thing that would do it. I would like to see some enterprising geek invent goggles that would do for Andromeda what Galileo's spyglass did for the Milky Way -- just point it up at the sky and look through it to see the glory of Creation! For perhaps the most marvelous fact of all about M31 is that it is BIG -- that is, not only physically, but also phenomenally. Its angular dimension in our sky is huge – at least eight full moons across. Imagine seeing that whenever you looked up! If people could view such spectacles simply by donning a pair of spectacles (especially if it were cheap), then I think we would see the dawn of a new age.

I also think this points to a general fact about astronomy that is often lost on people who fail to reflect on the obvious, or, more precisely, on the implications of things already known. (This is my forte as a philosopher, you see.) It is commonly assumed that what telescopes do is to magnify. So when we see these gorgeous images of galaxies and nebulae and whatnot deep-sky objects, we think it is the enlarging power of the observing instrument that has done the trick.

But equally important in astronomical observation is light-gathering power. It struck me one day (many years ago), probably when reading an issue of this very magazine, that the angular sizes of many of the discoveries discussed were quite large. M31 is not at all unique in this regard, and is even dwarfed by other objects (just one of countless examples: The September Sky and Telescope, on page 17, announced the discovery of a 10-degree-long tail for the globular cluster, Palomar 5).

Imagine, then, if some inexpensive, enhanced-CCD goggles would instantly show us all of these marvels. I wonder what that sky would look like! I have no doubt it would blow everybody's mind -- permanently.

One more thing: I would insist that at least part of the proceeds from the sale of these goggles go to the International Dark-Sky Association. This would help ensure that future generations would be able to view the starry sky sans goggles and thus be every bit as awed and inspired as we and our predecessors have been.
P.S. I would like to see somebody like Bradley Schaefer do a comprehensive inventory of large-angular objects in our sky and illustrate the results on a Sky and Telescope all-sky gatefold map. Compare also this "modest proposal" in Planetarian v31 n4 p4 December 2002.

Wednesday, May 04, 1994

John Dobson: A Personal Reminiscence

by Joel Marks
Published as "Astronomer Spreads Pearls of Wisdom," New Haven Register, May 4, 1994.
It is not what one expects in middle‑age: To meet a godlike man. Yet there he was, in our living room, this small, white‑haired, almost‑octogenarian, physically beautiful man, holding forth on the cosmos. John Dobson had come to visit. 
You may have heard of him: He was featured a number of years ago in the first episode of the PBS television series, The Astronomers. He's even been on Johnny Carson. Among amateur astronomers he is known for two major contributions. He beat swords into plowshares by adapting an old cannon mount for use as a telescope mount. The mount, as well as telescopes that use it, have come to be known as "Dobsonians," although Dobson claims he has invented nothing. Dobsonians are noted for their ease of construction and ease of use; thus they have proliferated. 
In concert with this technological innovation, Dobson had a moral idea: Let us amateur astronomers bring our telescopes to the people! And so began the Sidewalk Astronomers. Simply by setting up a telescope on a street in San Francisco, and inviting anyone to peer through it, Dobson sparked a revolution that has since spread round the globe. Dobson's goal is to have a million telescopes in the hands of amateurs, each of whom will let several thousand laypersons use one to see the Moon or a planet. In this way, every person on Earth will be given the opportunity to view a neighboring world first‑hand, their first step on an infinite journey. 
Dobson himself continues to bring the universe to wherever people congregate. He spends nine months of the year away from his San Francisco home (where he rents a room), speaking to astronomy clubs, college classes, and school children, and teaching courses in telescope‑building. When funding permits, he also travels by van into the national parks, carrying large Dobsonians to lucky campers at "dark sites." On the other trips he will stay with whoever will put him up. That is how he ended up in our home for a few days. My wife, who was vice president of the Astronomical Society of New Haven at the time, invited him to speak to the Society during one of his visits to the Northeast and to accept our hospitality. 
My first response was to look forward to having an interesting houseguest. But as I took the opportunity to spend many hours with him, I came to feel we had been blessed by a visitation. It was a combination of little things; for instance, Dobson is socially attentive in a way I do not often experience. He is also a master teacher, speaking quickly but calmly, ever articulately, and with vivid images to convey abstruse points. 
Admittedly, Dobson’s method of argument can be very rhetorical. Is this good teaching, or suspect science? Dobson is noted for out‑of‑the‑mainstream cosmological views. (Of course, all cosmological views tend to be outlandish.) For example, he insists that the Big Bang theory must be wrong because "Nothing doesn't exist," so something cannot have come out of nothing. This way of arguing physics by means of verbal flourish has long gone out of favor. But Dobson welcomes skepticism. As far as he is concerned, the only assurance that someone is really listening is that they express doubts. I heard him address many questions, and I could not help but be impressed by his technical assurance and ingenuity as well as his occasional acknowledgments that he did not have an answer. 
A former Vedantic monk, Dobson sees the universe as "apparitional." Just as a coil of rope may be mistaken for a snake, our perception of the whole world as consisting of a multiplicity of changing things in a spatially and temporally bounded cosmos is "based on a boo‑boo." Science has the power to reveal this truth. For example, according to Einstein's special theory of relativity, spatial distance is negated by temporal recession; hence, all things are, despite appearances, "adjacent," not separated. But, even aside from science, the individual who becomes like a child, indifferent to the "two prime genetic directives" to fend for oneself and the species, will be able to see the underlying One. 

As John Dobson boiled his free range hen's eggs on our kitchen stove, he strove for the infinite.