Your Place in the Universe

by Paul M. Sutter

  The Drake equation won't ever give us solid numbers to go on, so we have nothing specific to predict, and of course I can't say anything more than the guesswork offered above. With our searches for planets outside the solar system, with enough sleuthing, we're bound to find a planet with an oxygen-rich atmosphere, a smoking gun that photosynthesis got its game on there, meaning life has found another home. While I'm sure we will celebrate the day that we find life outside the Earth (whatever form it takes), there won't be much to do after that. Back to business as usual.

  This line of thinking leads to even more unsettling questions that, if we're going to take our cosmological jobs seriously, we're going to have to confront. It's one thing to talk about the chances of life appearing in our universe at or near the present epoch, with its particular blend of elements and stellar activity. Thoughts along that road lead to some puzzling and partly contradictory answers. But at the next level of existential brainteasers sits something even more critical: why is life even possible in our universe? Like, at all?

  Look at it this way. Depending on how you arrange them, there are about one or two dozen raw numbers that govern and control all the fundamental physics and cosmology that we know about. The speed of light. The charge of the electron. The strength of gravity. The amount of dark energy. These numbers are like the director of a classic movie. In the finished product, watching the actors emote and dialogue on the screen, we the audience don't get to hear the director shaping and guiding their performance. But take away the influence of that director—or change their attitude or personality—and you get a completely different movie. Sometimes an unwatchably bad one.

  Let's say that tomorrow the universe grew tired of having the electron be of a certain charge and decided to double it. Do you think atoms would behave the same way? Molecules? Chemistry? Do you think you would still be alive? Would stars still shine with nuclear fires in their hearts? Would we even recognize the cosmos?

  What if there were four spatial dimensions instead of three? Who decided that? Would light and gravity propagate in the same way, or would it diminish in intensity so quickly that nothing would ever feel the radiant heat of another object?

  What if gravity were stronger or weaker? It wouldn't just affect our ability to get out of bed. Would large structures still form in the cosmos, with reservoirs of gas and dust driven to forge new stars, creating the heavy elements necessary for life?

  Dark energy is especially suspicious. We live in a very special time, when dark energy is strong but not too strong, when accelerated cosmic expansion is just beginning to tear the universe apart, but not disastrously so. Currently, regular matter makes up 5 percent of the energy budget of the universe, 25 percent goes to dark matter, and 70 percent is in the form of dark energy. Aren't those numbers suspiciously similar? In the distant past, when everything was crammed together, it was more than 99 percent matter. In the future, as our cosmic butter gets spread too far out, it will be more than 99 percent dark energy.

  Why are we in the middle point? That seems too rare and unique. When physical processes compete, especially over the time and energy scales that we're talking about here, it rarely ends up even steven. When one process dominates, it dominates. Dark energy's current density value is very, very close to zero but not exactly zero. What's going on? Did something suppress it but then give up? What process brings a competitor to its knees, to the floor even, but doesn't deliver the coup de grâce? If you had to pick a random number for the value of dark energy, you'd expect it to be pretty much anything but its current value. In other words, survey says that dark energy should have long ago ripped apart the universe before planets, let alone life, had even formed.

  In short, our leaps of understanding of the cosmology over the past few centuries have led us to examine in a new light an old and familiar question: why do we exist, rather than not exist?

  We are not special in a cosmic sense, but the universe seems a little too fine-tuned for comfort. Change a fundamental constant or the nature of the some of the big players on the cosmological stage, and life is simply snuffed out. If we're going to take the bold move of shrugging off articles of faith to explain our existence (a surely unintended consequence of the revolutions of Copernicus, Kepler, and Newton), then, well, how are we going to explain our existence?

  The short version is that there may be no (scientific) answer and we're just going to have to deal with that on a personal level. Also, that's a deeply philosophical question. I have absolutely no problem with philosophy as a discipline, and I think there are some valuable routes to understanding our world through that lens (and, if we're going to be fair, the entire endeavor of “science” is really just a particular branch of philosophy that highly prizes empirical, in-your-face evidence and lots of math). But this is not a book on philosophy, and I'm certainly no expert at it, so there's not much for me to offer you there.

  I will say, however, that when it comes to questions like this, that we have to be very, very careful. Like, holding a baby chick in your hands careful.

  It's very tempting to shrug our scientific shoulders and say, “Oh, we're here because we're here.” If the universe were any different, there would be no life, no consciousness, and no contemplation and examination of matters cosmological. Statements like this are part of a broader category called the anthropic principle. Usually these arguments are cast in the mold of eternal inflation or more exotic string theories: if there are a bunch of possible universes, all existing and all offering one particular combination of particles, forces, constants, and all the other junk that we call “the physical cosmos,” then most of them would necessarily be lifeless—they don't have the right combo. But we see this particular universe with this particular set of physics because it's the right combination that could make us us.

  This feels a little bit empty, like eating a bag of potato chips for dinner. It kind of explains the problems we have with fine-tuning, but it doesn't really offer any testable predictions or deeper explanations of how the universe ought to work, which is kind of the point of the whole scientific endeavor, so it leaves a lot to be desired. I hesitate to even elevate it to the level of principle more than, say, utterance. But, like I said, this is getting a bit philosophical, and whether you're comfortable with this concept or not is a decision you're going to have to make on your own. No help from me there, kid.

  The part that we have to be especially careful about is in counting our probabilities. Let's say you're at the casino playing a game involving dice, laying down the really big bucks. Feeling the excitement—and maybe a little tipsy—you decide to go all in on a single game. The dice are tossed: snake eyes. Bummer. But being mathematically inquisitive, you start to ponder a way to get yourself out of the doldrums. Given that single throw, that one result, what were the chances of getting that bum result?

  Well, if the dice were fair, it's pretty easy to calculate. But what if they weren't? What if the game was rigged?

  With just a single throw, it's impossible to tell. Testing for riggedness requires a full statistical study with lots of trials and probably a spreadsheet. With only one result to go on, you'll never know if all the outcomes were equally fair or if the casino slipped in some funny dice to tilt the odds in their favor.

  We only have access to our one universe, folks. That's it. If the physics that surround us are the result of some random chance, we'll never be able to calculate how “fair” each kind of universe is. It could very well be that our kind of cosmos really is rare. Or maybe it's super common. Just how shifty is the grand cosmological casino? It's definitely not something we can observe, since other universes are by definition not a part of our universe and hence not observable. No data = no progress. You can make all the high-powered vocabulary-stretching arguments you want, but without evidence, they're going to be just that: arguments.

  Finally, there's a lot (and I wish I could make something double-italic to show I really mean it) that we don't know about the univers
e. The story of the past few hundred years has been one of continually pushing against the sky, laying mysteries on top of answers on top of more mysteries. Questions that puzzled our ancestors now seem laughably quaint and outdated to us, but at the time, they were deep conundrums that challenged our core notions of how reality operated at a fundamental level.

  When the tensions grew too thick, like when the old Earth-centered cosmology just wouldn't agree with the wealth of data pouring out of European observatories, or when the debate over the true nature of the spiral “nebulae” spiraled (sorry) out of control, the resolutions came in the form of new physics or new models of the universe—and usually both.

  We seem to be at a similar crossroads in our modern era. We've just begun to map out the nature of dark matter and are only beginning to pierce the veil that is dark energy. We've explored with our telescopes and our brains the very cusp of the big bang itself, but earlier moments are shrouded in mystery. We know that our physical models of quantum mechanics and general relativity are incompatible with each other, but we don't have a clear path forward (that snake pit is another book).

  We've come almost unimaginably far since the days of Kepler and company. Their search for meaning out of the chaos of our world took an unexpected, and unexpectedly fruitful, turn, uncovering a bounty of mysteries—and beauty—within the cosmos that we call our home. The sky that wheels above us every day and every night is only the first layer of a grand and complex structure, almost alive itself in its energetic dances that have lasted for billions of years.

  Countless sleepless nights poring over cold data and wrestling with arcane mathematics have teased out a few of nature's jealously guarded secrets. Observation by observation and theoretical insight by theoretical insight, a path forged by generations of scientists ever eager to look upward and inward, we've revealed the full complexity of the universe as it really is to a level that would frighten Kepler and sicken Galileo, while simultaneously discovering deep symmetries and fundamental forces that operate throughout the vastness of space and through cosmic time—a fact that would delight them.

  Ultimately, what is our place in the universe? To Kepler's horror, we are at the center—of our observable bubble, but that's only a trick of our vantage point. To his, well, equal horror, we're but a tiny, insignificant speck in a cosmos far vaster than he could have possibly imagined. We're simultaneously—and paradoxically—in the middle of nowhere and at the center of it all.

  It's so easy to feel disconnected and separate from this universe of ours, but there is something deeper going on. Just as Kepler assumed for all the wrong reasons, we are connected to the cosmos. But the stars don't govern our births. Instead, the physics that rule our lives down here on Earth are the same throughout the vastness of the universe.

  A hydrogen atom in the laboratory behaves exactly the same as one on the opposite side of the Milky Way. The same force that pulls an apple from a tree shapes and sculpts the largest of structures. The blood in our veins runs with the ash of long-lost generations of stars.

  We've come so far in the past few hundred years. What more mysteries await us? What is the nature of the dark part of our cosmos? What is the true mechanism of inflation? How will our universe evolve, and possibly end? As always, scientists are building new engines to enhance our senses. Giant telescopes, gravitational wave observatories, atom smashers, neutrino detectors buried in the ice sheets of Antarctica, satellites operating at all wavelengths of the electromagnetic spectrum, and the stalwart chalkboards, all at the ready. Prepared to wrestle with nature one more time, to fight for one more ounce of understanding, to push our knowledge just one level deeper.

  Our assumptions about how the universe works at large scales, using Copernicus and Kepler as a guiding light, have led us well for centuries. We assume that physics is the same throughout space and time. We assume that the universe is, once you look wide enough, homogeneous and isotropic—the same from place to place. And indeed, like all good scientists, we've put our assumptions to the test time and again. Maybe future work will show that those assumptions are wrong, or that our theories are inadequate to the task. I can only hope that our decedents will wistfully say, “They were so close, if only they knew…” while at the same time pursuing their own, even more profound, questions. Which is fine: the joy of science isn't in the destination but in the path. Curiosity is its own reward.

  All the while, deep questions motivate and drive us ever onward. What is our place? Are we special? Does the universe care about us? Well, we can think we're special, and we can care about each other. And since we—Earth, life, humanity—are a part of the universe anyway, maybe that's enough.

  A peek of what's to come in the universe, even though we're just getting started. The scale is chosen to give each major transformational epoch its rightful due. Image courtesy of NASA / JPL / Planck Collaboration

  In the 1800s, Sir Norman Lockyer sketches a bunch of fuzzy things in the sky, some quaintly called "nebulae."

  We used to think that the Andromeda Galaxy was just a "nebula." Whoops. Image courtesy of NASA / JPL-Caltech.

  It turns out that there are hundreds of billions of these "nebulae." Oh, boy. Images courtesy of NASA / ESA.

  The baby picture of the universe as revealed by the Planck satellite mission. These are incredibly tiny differences in microwave temperature—less than one part in 10,000 variations away from the average, which are directly related to density differences way back then. The small blips are the seeds that will one day grow up to become galaxies; the large blotches are caused by sound waves crashing around the infant cosmos. The image is distorted at the top and bottom because it's representing the entire sky (a sphere) as a rectangle, just like how on a map Greenland and Antarctica look way bigger than they actually are. Image courtesy of ESA / Planck Collaboration.

  When two galaxies collide: a hot mess. Image courtesy of NASA.

  The (in)famous Bullet Cluster viewed in the many ways necessary to reveal the lurking dark matter. In this image, the relatively tiny galaxies are embedded in the much larger clusters, which are caught in the act of a titanic collision. The hot gas of the clusters is tangled near the center, while most of the mass—including dark matter—has sailed through itself. Image courtesy of NASA / CXC / CfA / STScI / ESO WFI / Magellan / University of Arizona.

  While immense for us humans, this is but a small slice of the vast cosmic web. It is taken from a computer simulation of the universe soon after it began coalescing into the large-scale structure that we know and love today. We can see in this 50-million-light-year section the dense and tangled system of clusters and filaments embedded among the open maws of the voids. Image courtesy of Wikimedia Creative Commons; author: Andrew Pontzen and Fabio Governato; licensed under CC BY 2.0.

  We've learned a lot in the past few centuries, I swear it. The top image is an illustration of the old-school geocentric model of the universe, drawn by Bartolomeu Velho in 1568, just on the eve of the coming cosmological revolution. The bottom is a creative interpretation of our modern view, where, due to the finite speed of light, different observers see themselves at the “center” of “their” universe, with greater distances revealing a younger cosmos. As in the timeline shown earlier, the scale is chosen to highlight various scales…. I'm guessing old Bartolomeu had a similar plan. Image courtesy of Wikimedia Creative Commons; author: Pablo Carlos Budassi; licensed under CC BY-SA 3.0.

  A type Ia supernova expends more energy than its entire host galaxy. Briefly, but it counts. Image courtesy of NASA / ESA.

  An example of a so-called H-R Diagram, which neatly sorts stars according to their temperature and their luminosity. How wonderful: a pattern emerges in nature, unlocking a clue to stellar lives. Image courtesy of Wikimedia Creative Commons; author: Jessica Repp; licensed under CC BY-SA 4.0.

  It turns out that galaxies have all sorts of weird and wonderful shapes, and they can even violently collide. What is nature trying to tell us? Image courtesy of NA
SA, ESA, the Hubble Heritage [STScI / AURA]-ESA / Hubble Collaboration, and A. Evans [University of Virginia, Charlottesville / NRAO / Stony Brook University].

  CHAPTER 1. SACRED GEOMETRY

  1. There's a chance they may have also been totally wasted. S. M. Russell, “Some Astronomical Records from Ancient Chinese Books (Continued),” Observatory 18 (1985): 355.

  2. A good starting point for reading summaries and translated texts from this era is Anniina Jokinen, “Medieval Cosmology,” Luminarium, January 31, 2012, http://www.luminarium.org/encyclopedia/medievalcosmology.htm.

  3. For a fun recounting of the spread of Copernicus's viral idea, see Owen Gingerich, The Book Nobody Read: Chasing the Revolutions of Nicolaus Copernicus (New York: Walker, 2004).

  4. I'm serious. Ann Blair, “Tycho Brahe's Critique of Copernicus and the Copernican System,” Journal of the History of Ideas 51, no. 3 (1990): 355.

  5. Kitty Ferguson, Tycho and Kepler: The Unlikely Partnership That Forever Changed Our Understanding of the Heavens (London: Transworld Digital, 2013), Kindle.

  6. Ibid.

  7. Indeed, Kepler seems like an eager fanboy writing to a reluctant Galileo. Anton Postl, “Correspondence between Kepler and Galileo,” Vistas in Astronomy 21, no. 4 (1977): 325.

  8. Of course I'm paraphrasing, because Kepler goes on and on about this stuff. For example, see a translation of a letter in Edwin Arthur Burtt, The Metaphysical Foundations of Modern Physical Science (Garden City, NY: Doubleday, 1954), p. 48.