19 July 2009

You're Not the Center of the Universe, You Know

My Op-Ed published in the Washington Post, July 19, 2009

Walk into an open field on a clear, moonless night. Overhead, sparkling stars sprinkle the sky. All of them seem equidistant from you―and no one else―and you are lulled into imagining yourself at the center of the universe.

For nearly 500 years, astronomers have struggled to break that illusion. Our petty standing in the cosmos is a scientific fact, if not a visceral experience. Earth zips at nearly 67,000 miles an hour around the sun, which in turn completes one lap around the Milky Way every 220 million years, meaning that the last time we were in this neck of the galaxy, dinosaurs were getting ready to rule the planet. Still, as you look skyward in that pitch-black field, Earth seems to be at the heart of all creation.

We could blame Aristotle. So authoritative was his pronouncement of an Earth-centered universe in the 4th century B.C. that few challenged the idea for nearly two millennia. Over time, the urge to better explain the universe's behavior gave rise to new models. In 1543, Nicolaus Copernicus boldly placed the sun at the center of the universe, shoving the Earth into motion. The radiant sun was at last in its proper perch, "as if resting on a kingly throne," he wrote.

Copernicus was not disturbed at all by a moving Earth but was troubled by a rotating sky. The Polish mathematician and astronomer, though, knew quite well the consequences of challenging conventional notions. In the preface to his great work, "On the Revolutions of the Heavenly Spheres," he predicted that "as soon as certain people learn that in these books of mine . . . I attribute certain motions to the terrestrial globe, they will immediately shout to have me and my opinion hooted off the stage."

That fate fell upon Galileo, who starting in 1609 gathered the crucial evidence supporting Copernicus's heliocentric vision. In 1633 he was brought before the Inquisition and eventually put under house arrest for daring to oppose an Earth relaxing at the universe's center.

By the time of Newton, decades later, such hostility had faded. For one, Sir Isaac's physics could at last explain why we aren't thrown off the planet as the Earth rotates and orbits the sun. But even though Copernicus moved Earth from the hub of the solar system, its inhabitants remained confident that they retained a privileged place at the center of the Milky Way, the sole galaxy. Homo sapiens is an egotistical species; we resist being kicked out of a prime spot in the cosmic scheme of things.

That confidence, though, withered as astronomy underwent a spectacular transformation starting in the 19th century, an era teeming with technological innovation. Prominent industrialists, enriched by the Gilded Age, provided the money that allowed dreamers to construct the powerful telescopes they had long desired.

With one of those new instruments atop California's Mount Wilson, Harlow Shapley resized the Milky Way. He discovered in 1918 that it was 10 times larger than previously thought and, along the way, he relocated the sun and its planets into the galaxy's suburbs. The sun resides roughly 30,000 light-years from the galactic center, more than halfway to the Milky Way's edge. "The solar system is off center, and consequently, man is too," Shapley liked to say.

But Shapley did not take the next step; he, too, fell victim to cosmic pride. Despite the growing evidence that the Milky Way was not alone in the universe, he held fast to his beloved Big Galaxy model: Our galaxy remained at center stage. We lived in a solitary, star-filled oasis suspended in a darkness of unknown depth.

Shapley's vision was demolished in 1924, when Edwin Hubble proved that the cosmos is populated with myriad galaxies as far as the telescopic eye can see. The Milky Way suddenly became a bit player in a much larger drama.

The history of astronomy is a continuing extension of the Copernican principle, moving us farther and farther from the front row. It's a principle of irrelevance that involves not only our position in space and time but also the contents of the universe. In recent decades, astronomers have learned that a hidden ocean of cosmic matter―comprising about 85 percent of the universe's mass―surrounds us, possibly elementary particles yet to be discovered. The stuff of stars, planets and us is but the flotsam in this enveloping sea.

More startling―and taking the Copernican principle to its finale―our universe may not be the only one. As physicists attempt to construct a theory that unifies all the forces of nature, one theme repeatedly arises: that additional cosmic realms may be lurking in other dimensions. We could be part of the multiverse; the Big Bang might have occurred when universes outside our dimensional borders bumped into one another.

The main response to this astounding theory has been to bury our heads in terra firma. Yet such a wider perspective offers some succor, allowing our earthly concerns to shed away. Hubble knew this. During a visit to the astronomer's home, the English poet Edith Sitwell was shown slides depicting the many galaxies that cannot be seen with the naked eye. "How terrifying!" she exclaimed. To which Hubble replied: "Only at first―when you are not used to them. Afterwards, they give one comfort. For then you know that there is nothing to worry about―nothing at all."

Granted, the hugeness of the cosmos is difficult to perceive and, as Sitwell expressed, horrifying to ponder. A character in Thomas Hardy's 19th century novel "Two on a Tower" gives splendid voice to this apprehension: "There is a size at which dignity begins; further on there is a size at which grandeur begins; . . . further on, a size at which ghastliness begins," says astronomer Swithin St. Cleeve. "That size faintly approaches the size of the stellar universe."

Indeed, our cosmic address is getting excruciatingly long: Planet No. 3, Solar System, Orion Spur on the Sagittarius Spiral Arm, Milky Way, Local Cluster, Virgo Supercluster, Universe, Multiverse.

It's time for earthlings to acknowledge our minor-league status and collectively grasp the magnificent vastness that engulfs us all. While a widespread recognition of Earth's humble station is unlikely to end conflict here, fully comprehending our planet's infinitesimal place in the universe might be a modest step toward diminishing our hubris. Earth is but a speck, the cosmic equivalent of a subatomic particle hovering within an immensity spanning billions of light-years.

And we can still savor our cleverness in figuring this out.

Image Credits: (top) Sagittarius Star Cloud (Hubble Heritage); (lower) Imagined Multiverse (Nature)


  1. Wandeing through websites and using up my free fruitless hours, I stopped by your blog and read this piece. I hail you for such a crafty and profound articulation. It helped me feel less pain. It was like a poem of science.

  2. Professor Bartusiak,

    Man's perception of the universe, and his place within it, is a topic that I commend you for bringing to the Vancouver Sun recently. Amongst all our daily 'news', it's certainly important for us to think about our culture's cosmology and its history once in a while.

    Your narrative about Earth's progressive displacement from a universal center, and its ever 'shrinking' size relative to the entire cosmos, is the traditional one. It's so traditional, in fact, that it just seems natural. That should probably worry us.

    There are very different narratives that one could tell, narratives that would would actually engage with Aristotle, and pre-Copernican astronomy generally (as well as Copernicus himself). You have shortchanged this huge expanse of time.

    Medieval and Renaissance cosmologies that placed Earth in the 'center' were far from hubristic, as your article claims - and as our current (post-Englightenment) world view would suggest. On the contrary, the 'center' of the medieval universe was the lowest, heaviest part of it, where the grossest materials had 'fallen' and accreted together. The planets and heavenly spheres, on the contrary, were considered to be lighter and more perfect (In Aristotle, we remember, everything below the moon was imperfect and changing, while everything above was solid, perfect and eternal).

    In the rich and influential cosmology of Dante's Divine Comedy, Satan is frozen in a pit of ice in the physical center of the Earth - because he is the most imperfect, most sinful, most unlucky of the universe's creatures. Dante's Comedy as a whole shows readers that the physical center of the Earth - coincidentally the physical center of the universe - is actually (morally, truly) the periphery of the universe. The Earth-'center' is farthest away from God, and becomes 'tiny' (a dot, in fact), when it is seen from the larger, ultimately 'real' perspective of Paradise/God/eternity. There is a difference between 'center' and 'central'.

    This (supposedly "earth-centered") cosmology was a profoundly humble one. Dante didn't invent it in the 14th century - it had been current for centuries, building on Aristotle - and his epic poem's popularity ensured that it would remain central to Western consciousness.

    So we haven't simply been 'getting smaller' in universal terms. "Our cleverness in figuring out" - to quote your article - the fact of our own universal smallness seems, rather, to belie a great deal of hubris and self-aggrandizement.

    For a succinct paper outlining the argument I am making here, I suggest "Copernicus and the tale of the pale blue dot" by Dennis Danielson (whose work I have really just been re-atriculating in this comment). But beyond his particular thesis, and my own support of it, all one really has to do to complicate this linear story you outline in your article is get familiar with (and get respectful of) some classical, medieval, or renaissance literature and cosmology. You will find all sorts of surprises and complications - from Giordano Bruno's hypothesis of infinite worlds (before Copernicus and the telescope) to Nicolas of Cusa's (since scientifically 'proven') insights about the universe, all made without physical evidence.

    Understanding - to as great a degree as possible - the world views of centuries ago will show us that we haven't just been getting progressively 'smaller' - or smarter - with the passing of time.

  3. Copernicus' cosmology, as Professor Danielson shows in the article I mentioned above, doesn't involve a dethroning of the Earth at all, but rather a promotion of the Earth into the planetary realm. No longer fixed in the 'centre', Earth becomes for Copernicus an active participant in "the dance of the stars". The Sun, taking over the 'central' position in Copernicus' universe, actually appeared to have been 'demoted' by heleocentrism. And so the position of universal centrality had to be "renovated" by Copernicus and his followers, in order for contemporaries to be convinced that the noble planet of light could really occupy that once-humble station. Once this renovation project became successful, it proved 'difficult' for us to look back and imagine how the universal centre was once no more than a "cosmic basement".

    Or maybe we just didn't want to look back ...

    In any case, if it's true that "The history of astronomy is a continuing extension of the Copernican principle", as you say, then we're basing this history (and thereby also building the future of astronomical thought) on a cliche and a misreading of Copernicus.

    Rather than just patting ourselves on the back for our scientific discoveries and apparent humility, we might start asking some challenging questions about our current cosmologies and the value systems, and actual human initiatives, they reflect and create.

    What does the now-traditional, linear 'dethroning' narrative you propose, for example, say about us? How does it reflect and influence our behavior on our one and only home, planet Earth?

  4. Dear Jennifer,

    You are absolutely right. Given the restricted word count I had in my Washington Post essay, I could barely scratch the surface of this engaging topic and left out many of the nuances that you so thoughtfully summarized. However, I do mention some of the points you make in my book "Archives of the Universe."

    I would argue though that it is later astronomers and historians who have labeled this principle of diminishment of Earth's position in the universe the "Copernican principle," despite what Copernicus himself may have thought how his model affected Earth's status. In hindsight we can interpret it as the first step in Earth's moving away from the center of cosmic attention.

  5. In this piece you write the sun circles the universe once every 220 millions years. And 220 mya the dinosaurs were just getting ready to rule the planet (paraphrase). I thought the dinosaur extinction occurred c. (225) mya? The Permian-Triassic c 225mya? The (?) marks placed as I am not confident of the dates.

    Are you are of any suggested correlation of Permian extinction and this period of time?

  6. The dinosaur extinction occurred around 65 million years ago, at the end of the Cretaceous period and the beginning of the Tertiary period.

  7. Of course, excuse me, ☹ , and thanks for the (any) time, and the correction ☺. I was a bit addled at the time I wrote the previous note. I was referring **not** to the K-T transition, but to Permian-Triassic, ie The Permian extinction.

    The Permian extinction c. 225 mya. (Gould, "The granddaddy of all extinctions' from essay entitled, Chance Riches, in Hen's Teeth and Horse's Toes, p. 338; also Gould, "The Great Dying" Essay 16, in Ever Since Darwin).

    I am aware from these essays that the formation of the supercontinent, Pangea, is considered as possibly contributory to the Permian extinction (and the breakup, 60 mya, possibly po)ssibly contributory to the K-T related extinction of the dinosaurs.

    But maybe there is something in this neck of the galactic woods? Have there been any suggested correlation(s) to the 220 million year revolution about the center of the galaxy, and this "granddaddy of extinctions."?

    Also, can you explain how these Cepheids work. Is it just by chance that their period of blinking (blink rate) relates to their intrinsic luminosity? Could you be kind enough to throw in a few more sentences on these stars to render more clearly how they work(ed) to enable astronomers to figure out distances. I have always been unclear on this.



  8. I'm not aware of any firm connection between extinctions on Earth and the solar system's position within the galaxy. But there has been speculation. Some wonder whether the solar system's oscillating motion (like the horse going up and down on a carousel) through the galactic plane might be linked to extinctions. Check out http://www.americanscientist.org/issues/pub/perturbing-the-oort-cloud for more on this hypothesis.

    As for how a Cepheid works, here's a description from my book "The Day We Found the Universe":

    "It was long believed that a Cepheid was an eclipsing binary star—one star regularly circling another like the Earth going around the Sun. But by 1914 it was recognized that this type of variable was actually a single, pulsating star, its atmosphere regularly ballooning out and then shrinking back in, over and over again. When the origin of a star’s power was at last understood, astronomers came to see that a Cepheid is a star far more massive than our Sun, anywhere from five to twenty solar masses, that has reached a particular stage in its evolution. Having used up its main supply of hydrogen, the Cepheid becomes unstable for a while (about a million years) as it adjusts to burning new sources of nuclear fuel. When the star is compact, pressures build up, causing the star’s outer atmosphere to expand and thus become more luminous. But once stellar pressures are reduced, gravity takes over and causes the star to contract back and become dimmer—that is, until stellar pressures build up once again. In this way, the Cepheid comes to pulsate in a regular fashion. More importantly, the brighter and more massive Cepheids oscillate more slowly than the fainter and smaller ones."

    So, you see that it is more than chance; there's a true physical reason that the luminosity is linked to the period of the blinking. Leavitt found the pattern for this.