is Laniakea, measureless heaven in Hawaiian: the 500-million-light-year-wide fibrous structure which contains the Milky Way and 100,000 other galaxies in clusters like knots in a spilled skein of yarn.
It’s a structure so vast that no one thought to look for it—to look past the Virgo supercluster which contains the Milky Way for any sort of larger shape or order governing the movement of our galaxy—until 2014, when astronomers in Hawaii and Lyon announced their discovery. Its name, chosen to honor the Polynesian navigators whose astronomical knowledge guided them across the Pacific, was suggested by Nawa’a Napoleon, a community college professor of the Hawaiian language.
(Speaking of Hawaii and astronomy: a word about the struggle of indigenous Hawaiian people against the construction of a giant telescope atop Mauna Kea, the most sacred mountain to indigenous practitioners of pre-conquest Hawaiian religion. Arrests, public actions, court conflicts, and the experience of years of repression of indigenous spirituality are at work here. For now, a judge has ruled that construction can go ahead, with “mandatory cultural and natural resources training” for the telescope’s employees. This is small comfort for communities who have seen their sacred lands despoiled and occupied for centuries, and certainly not the challenge activists were hoping for to the colonialist presumptions of many American scientific institutions.)
One of my favorite categories of discovery is the one which changes our sense of cosmic scale. Edwin Hubble discovering that the Milky Way wasn’t alone in the dark but was one of at-the-time-uncountable galaxies; the 1964 hypothesis and then discovery of quarks; the 1998 discovery that the universe’s expansion is accelerating over time. We feel a change like this in our body, a tug at the fibers that constitute our sense of self and place. The feeling is awe. One of my favorite Jesuits, astronomer (and former chair of the Pontifical Sciences Council) George Coyne, was asked, “When you pray, does it make any difference that the universe has 10,000 billion billion stars?” Coyne replied:
Absolutely. When I pray to God, it’s a totally different God than I prayed to as a kid. The God that I pray to now is a God who not only made me but brought me to be in a universe that is dynamic and creative. The universe is not itself a living being, but it is a universe that has thus far given birth to human beings who can pray to God.
I pray to a God that, from my scientific knowledge, has made a universe in which people have come to be and are still coming to be, even from a scientific perspective. The universe is continuing to expand. Just in the past 50 years, look at what the human being has come to be.
The awe of these sorts of discoveries is sublime, but it’s not exactly comforting, especially considering the mounting scientific evidence that worlds like Earth, congenial to life, are not common as once thought, but are probably very rare in the Milky Way, in Laniakea, and in the universe as a whole.
Why are Earth-like planets rare? (I sponged up much of this information is from two popular-science books I adore, Peter Ward and Don Brownlee’s beautiful downer Rare Earth and John Hand’s breathtaking summary-of-everything Cosmosapiens. Hurry up and read them both.)
First, our sun is in perfect galactic real estate—far from the crowded, explosive environment of the galactic core and the sterilizing lashes of radiation that emanate from the black hole at the Milky Way’s center; far too from the obscuring clouds of unaggregated cosmic dust at the Milky Way’s edge—and it’s stayed in this sweet spot for its full lifespan. The Sun is a G2 star, not too big or small, and stable (few flares, no surprise expansion) over its multi-billion-year life. Both of these factors mean that life has has 4 billion relatively undisturbed years to flourish on Earth.
Earth also had a lucky collision early in its existence: fewer than a billion years after it was formed from loose rock and dust, our young hot planet was struck by a meteor the size of Mars.
This meteor’s iron core sank and was absorbed into Earth’s, enlarging and strengthening our magnetic field, which protects our planet’s surface from the scouring, cancerous effects of solar radiation. The rubble blown off from this collision also collected into one satellite: the Moon. The Moon’s mass considerably slowed Earth’s rotation (its day), so our nightside surface can shed heat that could otherwise collect into a planet-wide greenhouse effect. The Moon also stabilized Earth’s axial tilt: this means our planet is spared what would otherwise be a violently wobbling axis periodically turning the Arctic tropical and vice versa. Tilted now at 23.4 degrees, our planet instead enjoys steady, regular seasonal change: great for life.
Earth is also blessed with a helpful big brother, Jupiter. The immense mass of Jupiter draws in most meteors and comets that come charging through our solar system. Instead of crashing into Earth, these meteors and comets collide with Jupiter. It’d be much harder for life to flourish on Earth if our planet was struck every few million years by a dinosaur-killing-sized meteor.
Our earliest ancestors likewise got lucky with where and how life first appeared. (First learned about this from, of all places, the appendix of a wonderful Natural Geographic book my dad got for Finn.) As simple proto-algae creatures spread throughout the ocean, they absorbed CO2 (which further limited the greenhouse effect), and breathed out oxygen. This oxygen rose from the ocean and was fused into ozone, creating an additional buffer against the Sun’s radiation for the life that did eventually creep onto land. If life had appeared on land first, solar radiation through Earth’s early ozone-less atmosphere would have introduced mutations so severe that evolution over time may never have taken off.
No one knows exactly how life itself first appeared, but it now seems likely that there are billions of near-miss planets in the universe: nice, temperate worlds with liquid water that never got a chance for life (or where life could never spread) because of galactic or solar radiation, a too-short or too-long day, a veering axis, or meteor bombardment. We now have strong enough telescopes that we can find evidence of planets around other stars. We can detect their mass and movement by how their gravity causes stars to wobble, and by how their transits slightly dim the stars they circle. The vast majority of the planets we’ve found are not even near-misses: they’re just no good for life. They’re “hot Jupiters,” gas giants squeezed up closer to their stars than Mercury is to the Sun, or they’re rocky but tidally locked, with the same side facing their star (and cooking into lava).
As a kid who read a lot of science fiction, I drew comfort from the idea of a universe as busy and amicable as a beehive with intelligent life. This dream now seems unlikely. Some scientists argue that any civilization that develops sufficiently may not choose to explore and populate the planets of other stars; but, in any case, our galaxy seems quieter than my kid self had hoped, and less congenial to life than we’d thought.
So, is Laniakea still beautiful in a universe full of stone and fire, radiation and rainbow dust, but largely empty of life? Yes, but it’s a beauty more like a thundering waterfall than like a garden: a beauty that doesn’t comfort us, but one that, for now, “serenely disdains to annihilate us.”
How does it change your perspective and life to find yourself at home in Laniakea? Or, put in terms closer to me, what prayer is appropriate to this scientific knowledge? The king-and-parent language of my own tradition feels impoverished before these discoveries, but I feel myself drawn toward the simple root prayer of the Orthodox: kyrie eleison, Lord have mercy! Or the open-palmed confession of human smallness and contingency in Islam: allahu akbar, God is greater. Or the recognition, central to Hinduism, that our being and will themselves are grounded in God: “What cannot be thought with the mind, but that whereby the mind can think: Know that alone to be Brahman, the Spirit; and not what people here adore… What cannot be indrawn with breath, but that whereby breath is indrawn: Know that alone to be Brahman, the Spirit; and not what people here adore” (Kena Upanishad). This prayer says that God–whatever that bare, wonderful word means to you–is the condition, the ground, for our questioning, smallness, curiosity, and fear. Our planet’s cosmic improbability and fragility might provoke the same questions as we face when we think about our own mortality: If it’s so delicate, so brief, what was ever the point? Did it matter that we ever lived if our planet will be boiled by its dying Sun and our universe stretches the fabric of itself into a fizzle of loose, dead particles? Questions like this resist an answer, but demand a response. How do you live, having absorbed knowledge like this into your body?