Yesterday I received an email from a reader. He noticed I occasionally write about astronomy and wondered what I thought would happen to the human race when the Sun died, an event he expected in another thousand or so years. Would we have colonized other planets, other solar systems by then? Could enough of humanity survive the loss of its home to continue on as a species?
Questions like these have been on my mind a lot lately. Over the last few months I had the privilege of volunteering with a local library, guiding tours through a traveling exhibit titled Visions of the Universe. I led hundreds of people of all ages, in groups large and small, through this wonderful exhibit that first began to make its rounds from library to library in 2009, the International Year of Astronomy. Most of my tour groups consisted of second graders from Title One schools. Talking to them about the Moon and the Sun, the dry river deltas on Mars and the billions of tiny particles that comprise the rings of Saturn, and showing them the inconceivable scale of the universe through photographs like the Hubble Ultra Deep Field, was one of the great joys of my life.
Most of the kids really seemed to take to the subject. The tours often ran long because they had so many questions. Some were unnervingly astute — one girl noticed a parallel between how the particles form rings around Saturn, and how the stars gather in rings or discs around the centers of galaxies. Some were heartbreakingly innocent — several of the children asked whether wishes wished on shooting stars actually came true. One question that came up over and over was “What happens to the Earth when the Sun explodes?”
The kids weren’t morbid enough to bring that up all by themselves. (Most of them, anyway.) They were just putting two and two together. An early panel of the exhibit is devoted to the Sun, which, I explained to them, is a star just like those tiny points of light we see in the night sky. We see the Sun as big and bright because we are so close by it, whereas the other stars are all very far away. Later in the tour, I took them through a trio of panels showing different stages in the life cycle of a star — first the relatively young blue stars of the Pleiades, then back a step to the stellar nursery of the Orion Nebula, then back another step to the supernova remnant Crab Nebula, which could be viewed as both the end and the beginning of the stellar cycle.
Talk of exploding stars would invariably compel someone in the group to ask about the death of the Sun, and what it means for us. The Sun isn’t big enough to explode, I would tell them, though it will swell up into a red giant, swallowing the inner planets, including the Earth, before shedding its outer layers and collapsing into a dense, slowly cooling white dwarf. “But,” I was careful to add, “that all takes a very, very long time, and none of it even starts to happen for another five billion years, so we’re good.” The kids seemed okay with that.
My reader got the Sun’s projected death date wrong by a few orders of magnitude. Whether it’s a thousand years or a few billion years makes no practical difference to anyone reading this — we’re long dead either way — but it does make a difference as far as humanity is concerned. It’s entirely possible — barring a natural extinction event or some far more likely form of self-annihilation — that there will still be humans living on Earth in a thousand years. But in five billion years? By then we’ll be long gone — so long, in fact, that if there happens to be anyone else living on Earth at the time, they probably won’t even know we were ever here.
That’s the most sobering thing about studying astronomy. You realize that permanence is an illusion. The stars in the sky look fixed to us, but ten thousand years ago those stars were in an entirely different configuration. The earliest humans saw most of the same stars we see, but not in the same places in the sky. The Sun is growing gradually brighter. The Moon is slowly slipping further away from the Earth. The elements of the Crab Nebula are diffusing bit by bit into the interstellar medium. Nothing lasts forever — not us, not our species, not our planet, not our star, not any star.
In his email my reader writes, “Global warming aside, humanity on earth is dead when our sun dies. How will we as a race survive that catastrophe?” The simple answer is, we won’t survive it because we won’t be around to see it. Five billion years is a long time, longer than the Earth has existed. Whether we have been driven to extinction by some natural catastrophe, killed ourselves, or gone the way of the Australopithecines, having been out-competed by better adapted descendants, one thing seems certain: if there are eyes on Earth to witness the death of the Sun, they will not be human eyes.
This is inevitable, and completely natural, and for that reason I don’t find it so depressing. That eventually every trace of human existence will be obliterated isn’t the most cheerful thought, sure, but there are ways of looking at it that make it oddly reassuring. I like to think of it as a reminder that we are more than mere tenants here. We are not in the universe — we are of the universe. We’re made of the same stuff as the stars, and we’re headed in the same direction. The atoms in our bodies were once inside of stars, and perhaps will be again someday. Not so bad, as fates go.
The impending death of our species, planet, star, galaxy, and eventually universe doesn’t depress me nearly as much as the answer to the second question in my reader’s email. After “how will we survive?” he asks, “Can we develop space travel, and colonization before it’s too late?”
Thinking about it yesterday morning, I realized that to fully explore the question I had to split it into two questions. The first is easily answered. Can we develop space travel and colonization before our species goes extinct? Yes.
Now that’s a kick in the ribs.
The Visions of the Universe exhibit is mostly silent on the topic of manned spaceflight. The only astronauts pictured on any of the twelve full-color panels are Dave Scott and James Irwin of Apollo 15, shown standing close by their Lunar Module Falcon and the Lunar Rover. Telling the second-graders about the Apollo program stirred conflicting emotions in me — pride at the accomplishment of landing on the Moon, and embarrassment at having to tell the kids that we left the Moon in 1972 and have never gone back. A few times, kids asked about the prospect of a manned mission to Mars. I explained that it would be a three-year round trip, and perhaps that was one reason why no humans had yet landed on Mars. But I always felt like I was making excuses.
Considering the question yesterday I had a depressing thought — way more depressing than the coming heat death of the universe. What if humanity somehow does cheat evolution and survive the next five billion years? What if there are men and women living on Earth when the Sun swells to a red giant? And what if, even after all that time, they still have not left this planet? The oceans boil away, the atmosphere burns off into space, the swollen Sun swallows the Earth and humanity dies, with no colonies on distant extrasolar planets to carry on.
Having improbably survived to this point, humanity dies with the Sun because it was too lazy and cowardly to ever truly reach for the stars. There was the technology. There was the suggestion by some — the demand, even — that we look beyond the Earth, beyond the Moon, beyond even our own solar system — that we follow our adventuresome spirit (not to mention our ever-increasing needs for resources and living space) out into the galaxy. But we never made use of that technology. We never listened to those voices. There was always an excuse — too expensive, too dangerous, too many more important things to worry about. There were always a million reasons not to do it. So we never did.
That’s depressing. To die as a species isn’t depressing, since that’s going to happen eventually, one way or another, no matter what we do. But to die as a species having willfully chosen not to make the most of our existence, having chosen to stay home and argue about taxes and arbitrarily drawn national boundaries rather than put our differences aside and explore the universe — I don’t think I can summon a more depressing thought.
That’s the road we’re on. No human being has traveled beyond low Earth orbit since 1972. The current space policy of the United States has the vague goal of a manned Mars flight by the mid-2030s. Barack Obama’s speech announcing the policy last year was not one of his best, a far cry from John Kennedy’s “We choose to go to the Moon” address at Rice University in 1962. In the meantime, NASA is a few months away from retiring the space shuttle fleet, with no vehicle ready to replace it.
Forty years ago astronauts landed on the Moon in spacecraft not too far up the technological ladder from tin cans. Today, when advanced technology and international cooperation have made manned spaceflight as safe and inexpensive as it has ever been, the best we can do is “Mars in about twenty years, maybe.”
Our vision narrows and our nerve diminishes, and those points of light in the night sky grow more distant by the day. It has been this way for forty years. It will be this way as long as we continue to choose the least imaginative and the least courageous members of our species to lead us. We are not just bureaucrats and lawyers and priests. We are scientists and explorers and poets. We’re all going to die someday. Nothing lasts forever. We can continue trudging along behind the bureaucrats, lawyers and priests as they lead us nowhere, bleeding our spirit dry along the way. Or we can finally allow the scientists, explorers and poets to set our course, and strive to make the most of this epoch we have been given, however long it may endure.