© M. Kornmesser/European Southern Observatory via The New York Times
There were many forces dividing us in 2016, nation from nation, faction from faction, person from person. But there is a countervailing force that can draw us together: the quest to answer fundamental questions that have captivated humans since ancient times.
At the forefront of this quest are scientists — the true explorers of our era. Every year, they map a little more of the unknown, claim a little more of what seemed impenetrable. In 2016, they made three significant breakthroughs in understanding the universe and our place in it.
In the past few years, NASA's Kepler space observatory and other missions have sparked a revolution in astronomy, arguably as fundamental as the Copernican revolution that spun us from our imagined perch at the center of everything. So far they have identified nearly 5,000 potential planets beyond the solar system, 21 of which are rocky planets that might be habitable. These numbers imply that there could be billions of such planets in our galaxy alone. "Home" no longer necessarily means Earth alone.
In August 2016, the European Southern Observatory announced that astronomers taking part in the Pale Red Dot campaign had confirmed the existence of an Earth-like planet in the nearest star system to us.
The Alpha Centauri system contains three stars: Two sun-like stars, orbiting each other, and a red dwarf called Proxima Centauri. The planet, probably somewhat larger than our own, was found orbiting this smaller, third sun. Its orbit lies within the star's "habitable zone," neither too hot nor too cold, where water may be found in liquid form.
Finding this planet, Proxima b, was a game-changer. It's our next-door neighbor, in cosmic terms. Astronomers plan to study its composition and features to determine whether it has water or an atmosphere. While we know that Proxima b is in the habitable zone, we don't yet know if it's truly habitable — or even inhabited.
This discovery came at a serendipitous moment for me, just four months after the physicist Stephen Hawking and I, with the support of Facebook's Mark Zuckerberg, launched a new space initiative called Breakthrough Starshot. It's a research and engineering program attempting to design, build and launch multiple "nanocraft" — tiny, laser-powered probes — that could reach the Alpha Centauri system within a generation. Rather than building one huge vessel, which would take tens of thousands of years to get there, we're hoping to launch many tiny probes, each no bigger than a computer chip, and with a sail attached. Powerful lasers acting on those sails will, in principle, push the nanocraft to speeds reaching 20% of the speed of light — more than 100 million miles an hour.
Now, with the discovery of Proxima b, Starshot has its first target. What might we find there?
This year's second breakthrough may give us a hint. In July a team of evolutionary biologists led by Bill Martin at Heinrich Heine University in Düsseldorf, Germany, reconstructed the genetic makeup of "Luca" — the Last Universal Common Ancestor. This was the single-celled organism that became the mother of all life on Earth today.
During the reconstruction, the biologists pored over millions of genes from thousands of species of microbes, isolating the 355 most ancient ones — those which were probably present in Luca. But these genes did more than pinpoint ancestry; they sketched a portrait of the organism itself, showing us a creature that lived an extreme life. It metabolized hydrogen, not oxygen, and clung to the walls of deep-sea volcanic vents.
Microbes sharing a high proportion of those 355 genes are still found in such vents today. And that's exactly the environment where some theorists have placed the origin of life itself. The discovery hints that life may have begun in nonliving "cells" that were naturally formed in the volcanic rock; and that the basic processes of energy conversion — which continue today in every one of our cells — were underway there before the first organic cell ever evolved.
The Luca analysis provides evolutionary biologists with hard data about life at a specific point in its early progress. They can use it to look forward in time, asking when and how this organism branched into multicellular microbes and eventually complex organisms. And they can look backward, asking how life might have slowly dawned in the watery rock that became our vital Earth.
We do not yet know the conditions on Proxima b. It may have a relatively gentle climate, like Earth's today. Or it may be "tidally locked," with one hemisphere permanently roasting in the glare of its sun, the other frozen, facing empty space. But if life can emerge in the conditions of hydrothermal vents, it cannot be ruled out even on a world of such extremes.
Starshot's nanocraft could have instruments that measure potential signatures of life. If the technology works, it will take them about 20 years to cross the 25 trillion miles to Proxima b, and more than four years for the photos and measurements they take to be beamed back to Earth.
Beyond Proxima b, our broader goal with Starshot is to foster a unifying, planetary quest for exploration and knowledge: to take our first steps — as a species and a planet — into the galaxy.
Meanwhile, scientists here at home continue to probe the universal questions. What are those miles of blackness the nanocraft will cruise through? What are those years we will wait through? This year's third breakthrough shed light on the fundamental nature of space and time.
A few months before the announcement of Breakthrough Starshot, physicists from the Laser Interferometer Gravitational-Wave Observatory in the U.S. told the world that after years of waiting, they'd heard a "chirp" — a brief signal indicating the detection of gravitational waves in space. The waves were churned up by the collision of two black holes over a billion years ago.
That chirp confirmed the predictions of Albert Einstein's general theory of relativity, which tells us that space and time are not separate dimensions, but are bound together as a four-dimensional "space-time." This space-time is not a static background, but dynamic: It is warped by the presence of massive bodies. And Einstein's theory predicted that it can also flow.
This means that the gravitational waves LIGO detected were not waves of fluid, energy or any known substance. They were waves in space-time. If everything we see in the universe were the brush strokes of a painting, a gravitational wave would be a quiver in the canvas itself.
That chirp also inaugurated the field of gravitational wave astronomy: the use of these waves as an observational tool, advancing our power to explore further. It has been said that the discovery opens a new window on the universe, but a new window would reveal only a different view. This is more like the evolution of an entirely new sense organ. It will enable astronomers to discern immensely violent events that were previously invisible to us, such as collisions between the supermassive black holes that lurk at the center of most galaxies. And it may offer a glimpse of the universe as it was just after the big bang.
Our curiosity about all that we've discovered this year will fuel more breakthroughs, and that curiosity is felt not only by the scientists at the vanguard of exploration, but by all of humanity. Confronting the fundamental questions is the greatest adventure there is, and all of us — no matter where we live or what we do — can be invested in it.