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Are We the First Civilization in the Universe? — Transcript

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0:00On the 6th of December, 1974, a short
0:03paper arrived at the offices of the
0:04Royal Astronomical Society in London.
0:07Its author was Michael Hart, an
0:09astrophysicist working at the National
0:11Center for Atmospheric Research in
0:13Boulder, Colorado, and it ran to eight
0:15pages.
0:17Hart began with one plain observation,
0:19and he gave it a plain name. He called
0:22it fact A.
0:24There are no intelligent beings from
0:26outer space on Earth now.
0:29Then he went through the ways [music] of
0:30explaining that fact away, that nobody
0:32out there wanted to travel, that nobody
0:34could, that somebody came long ago and
0:37left, and he found each of them wanting.
0:40His last sentence was the kind that
0:42astronomers almost never put in print.
0:45Fact A, he wrote, provides strong
0:47evidence that we are the first
0:49civilization in our galaxy.
0:52Half a century later, the question has
0:54grown from our galaxy to the whole
0:57universe, and the measurements have
0:59split it in two.
1:00One body of evidence says we arrived
1:02billions of years late. Another says we
1:05are among the very first.
1:07Both are built on real data, and only
1:10one of them can be describing the
1:12universe you are living in.
1:14Let us begin.
1:17Start with the clock, because every
1:19answer in this story is really an
1:21argument about time.
1:23The universe is about 13.8 billion years
1:26[music] old. Our sun and its planets
1:28formed about 4.6 billion years ago,
1:31which means that by the time the cloud
1:33of gas that became our solar system
1:35began to collapse, the universe had
1:37already been running for more than 9
1:38billion years.
1:40Two-thirds of cosmic history had come
1:42and gone before there was an Earth to
1:44stand on.
1:46Life appeared here quickly by the
1:47standards of a planet, and there is
1:49clear evidence of living things at least
1:513 and 1/2 billion years ago.
1:53But the species that builds telescopes
1:55and asks Hart's question, is new by any
1:58standard.
2:00We have been sending radio signals out
2:01into space for a little more than a
2:03century.
2:04Set that century against the age of the
2:06universe, and it comes to less than 100
2:09millionth of the whole.
2:11Whatever else is true, we did not turn
2:13up at the beginning of the story.
2:15The only question is whether anyone else
2:17turned up before us.
2:19And the universe did not wait for us to
2:21start making planets.
2:23In 2003, a team led by the astronomer
2:26Steinn Sigurðsson used the Hubble Space
2:28Telescope to pin down a planet in the
2:30globular cluster Messier 4,
2:32a dense ball of ancient stars about
2:357,000 light-years away.
2:37The planet is a gas giant about two and
2:39a half times the mass of Jupiter,
2:41circling a dead star and its stellar
2:43companion, and the cluster it lives in
2:46was dated at about 12.7 billion years
2:48old.
2:50Its stars carry only about 1/20 of the
2:52heavy elements found in our sun.
2:55The newspapers nicknamed the planet
2:57Methuselah. [music]
2:58It was already ancient when the Earth
3:00was still a cloud of dust,
3:02and it proved that a universe only a
3:04little more than a billion years old had
3:06already learned how to build worlds.
3:08A giant is not where anyone would look
3:10for life, so consider a quieter star
3:13called Kepler 444,
3:15about 117 light-years from us.
3:18In 2015, a team led by Tiago Campante
3:22measured its age by listening to the
3:23star itself, [music] reading the faint
3:25flickers in its brightness the way
3:27seismologists read earthquakes to learn
3:29what lies inside our planet.
3:31The answer was about 11.2 billion years.
3:35Around that star circle five small
3:37planets, the smallest about the size of
3:39Mercury, and the largest about the size
3:41of Venus.
3:43They sit far too close to their star to
3:45be anything but scorched, and nobody
3:47imagines life on them.
3:49What matters is what they prove.
3:51Rocky worlds were being assembled when
3:53the universe was less than a fifth of
3:55its present age, more than 6 billion
3:57years before the Earth existed.
4:00Closer still to the kind of world we
4:01care about is a planet called TOI 561b.
4:06It is about 1 and 1/2 times wider than
4:08the Earth. It whips around its star once
4:10every 10 and 1/2 hours, and its star is
4:13roughly 10 billion years old, more than
4:15twice the age of our sun.
4:18In December 2025,
4:20a team using the James Webb Space
4:22Telescope reported that this ancient
4:24rocky planet still holds a thick
4:26atmosphere, one that keeps its day side
4:28roughly 900° cooler than bare rock would
4:31be.
4:32It is a furnace, not a home.
4:35But it is a rocky planet with air
4:37>> [music]
4:37>> around a star that had already been
4:38shining for 5 billion years when our own
4:41sun switched on.
4:43Individual planets are anecdotes,
4:44though, and the real question is about
4:46the whole population.
4:48In 2001, the astronomer Charles
4:51Lineweaver tried to answer it.
4:53He started from a simple chain of
4:54reasoning.
4:55Rocky planets need heavy elements, the
4:58iron and silicon and oxygen that stars
5:00forge and scatter when they die. And the
5:03universe has been building up its stock
5:04of those elements star by star since the
5:07beginning.
5:07>> [music]
5:08>> Too little, and there is nothing to
5:09build an Earth from. Too much, and giant
5:12planets form early, spiral inward, and
5:15wreck the small worlds in their path.
5:18Lineweaver ran that window through the
5:20whole history of star formation, and he
5:22[music] reached two numbers.
5:24Three quarters of the Earth-like planets
5:25in the universe are older than the
5:27Earth, and on average, they are about
5:301.8 billion years older, give or take
5:32[music] 900 million years.
5:351.8 billion years.
5:37Run our own planet backward by that
5:39much, and you arrive at an Earth without
5:41a single animal, and without a single
5:43plant on land.
5:45The whole history of animals here, every
5:47trilobite, every dinosaur, every
5:49creature that has ever walked or swam or
5:51flown fits into that head start roughly
5:54three times over.
5:56If life on those older worlds took no
5:58longer than it took here,
5:59>> [music]
5:59>> then the typical one was finished with
6:01everything we have been through long
6:03before the Earth had a moon to look at.
6:05And their planets are not hidden away
6:07somewhere strange. They circle the same
6:10kinds of stars we see every night
6:12>> [music]
6:12>> in the same galaxies under the same
6:14physics.
6:16Three years later, working with Yeshe
6:18Fenner and Brad Gibson, Lineweaver drew
6:20the same kind of map for our own galaxy.
6:23They traced a ring between about 23,000
6:26and 29,000 light-years from the galactic
6:28center, where stars are rich enough in
6:30heavy elements to build rocky worlds and
6:33far enough from the crowded violent core
6:36to keep them.
6:37That ring began to emerge about 8
6:39billion years ago,
6:40>> [music]
6:41>> and it has been widening ever since.
6:43If complex life needs about 4 billion
6:45years to appear,
6:46>> [music]
6:46>> as it did here, then roughly three
6:48quarters of the stars in that ring that
6:50could carry it are older than our sun by
6:53about a billion years on average.
6:56The authors [music] called that
6:57evolutionary assumption highly
6:59speculative, and they were right to.
7:01But the direction of the answer matches
7:03everything else so far.
7:05We did not arrive early. We came in
7:07after most of the house had been built.
7:10All of that was the background to a
7:12calculation made by two astronomers in
7:14the autumn of 2015.
7:16Adam Frank of the University of
7:18Rochester and Woodruff Sullivan of the
7:20University of Washington were tired of
7:22the oldest dead end in the field.
7:25Every attempt [music] to estimate how
7:27many civilizations exist runs into one
7:29number nobody can measure, which is how
7:32long a civilization lasts.
7:35The species that survives for a million
7:37years would leave the galaxy crowded,
7:40and a species that survives for a few
7:42centuries would leave it nearly empty.
7:45And we have no idea which kind we are.
7:49So, Frank and Sullivan changed the
7:50question.
7:52Instead of asking how many civilizations
7:54are out there now,
7:55they asked whether anyone, anywhere, at
7:58any time in the whole of cosmic history
8:01had ever done what we have done.
8:04That question does not care how long
8:06anyone lasts.
8:08It only needs [music] to know how many
8:09places there have been to try.
8:12And that number, unlike the others, can
8:14now be counted.
8:17Using the planet surveys of the previous
8:18decade, they started from about 20
8:21billion trillion stars in the observable
8:23universe,
8:24nearly all of them with planets, [music]
8:26and about one in five with a planet at
8:28the distance where water can stay
8:30liquid.
8:31That came to [music] roughly 4 billion
8:33trillion chances.
8:36Then they asked how small the odds per
8:37planet would have to be for us to be the
8:40only success among all of them.
8:42They called the answer the pessimism
8:44line.
8:46Below it, we are the only technological
8:48species the universe has ever produced.
8:50[music]
8:51Above it, someone came before us.
8:55In June 2016,
8:57Frank put the result in the New York
8:59Times under a headline that said, "Yes,
9:02there have been aliens."
9:04Unless the odds of a technological
9:06species arising on a habitable planet
9:09are less than about one in 10 billion
9:11trillion,
9:12we are not the first.
9:14For our own galaxy,
9:16>> [music]
9:16>> the same line sits at about one in 60
9:18billion.
9:19That is roughly the number of habitable
9:21zone planets they counted in the Milky
9:23Way alone,
9:24which means that if nature succeeds even
9:27twice in all of those tries,
9:29someone in our own galaxy has already
9:32done what we have done.
9:34Think about what that line demands.
9:3710 billion trillion is roughly a
9:39thousand times more than every grain of
9:41sand on every beach on Earth by one
9:43common estimate.
9:45To believe we are the first civilization
9:47the universe has ever produced, [music]
9:49you have to believe that nature, given a
9:52planet like ours with water and time and
9:54sunlight,
9:55almost never takes the path it took
9:57here.
9:58So rarely [music]
9:59that one success in all of those beaches
10:02is the best it has ever done.
10:05Frank's argument was that the pessimism
10:08needed for that is extraordinary.
10:10Life on Earth did not take its time
10:12getting started. [music]
10:14It appeared early, almost as soon as the
10:16young Earth had cooled enough to hold
10:18water.
10:20It is worth being precise about what the
10:21pessimism line does not say.
10:24It says nothing about whether anyone is
10:26alive out there now.
10:28The ones who came before might have
10:30lasted a few centuries, as we have so
10:32far,
10:33and vanished [music] billions of years
10:35ago.
10:35Their planets cooled, and their signals
10:38long since spread too thin to hear.
10:41It does not say they ever left home,
10:43or that they would recognize us,
10:45or that they would care.
10:47It says only one thing,
10:49and it says it with numbers.
10:52The experiment that produced us has
10:54almost certainly been run before,
10:56somewhere,
10:57and it came out the same way at least
10:59once.
11:01So here is the default, the answer most
11:03astronomers would give you if you
11:05stopped them in a corridor.
11:07The universe is old.
11:09Rocky planets were being made when it
11:11was young.
11:12Most worlds like ours are older than
11:14ours,
11:15>> [music]
11:15>> and the number of chances is so vast
11:17that being first would take a
11:19coincidence beyond anything else in
11:21science.
11:23We are late.
11:24Somebody, somewhere, long ago, got there
11:27before [music] us.
11:29But every one of those arguments rests
11:31on a quieter assumption.
11:33And it is the assumption [music] Hart
11:34himself never had to face.
11:37They assume that the universe in the
11:38past was as kind to life as the universe
11:41is now.
11:43Frank and Sullivan posted their
11:44calculation on the 19th of October,
11:472015.
11:49The very next day, the 20th, a paper
11:52went online from the Space [music]
11:53Telescope Science Institute in Baltimore
11:55that pointed in exactly the opposite
11:57direction.
11:59Its lead author put it in one sentence.
12:02"Compared to all the planets that will
12:04ever form in the universe," he said,
12:06"the Earth is actually quite early."
12:09Before we go further, if you are kind
12:11enough, a gentle like and tap on
12:13subscribe would mean the world to me.
12:17It is a small gesture, but I hold it
12:19with deep gratitude because every bit of
12:21your support keeps [music] this tiny
12:23universe alive.
12:25The lead author was Peter Behroozi, then
12:27a young researcher at the Space
12:29Telescope Science Institute, and his
12:31co-author was Molly Peeple.
12:34They had not set out to write about
12:35aliens at all.
12:36>> [music]
12:36>> They wanted to know how the universe had
12:38built its planets over time, and they
12:40had two great surveys to work from.
12:43The Hubble Space Telescope had measured
12:44how fast galaxies of every size, at
12:47every distance, and therefore at every
12:49age, had been turning gas into stars.
12:52The Kepler Space Telescope had measured
12:54how many planets those kinds of stars
12:56tend to [music] carry.
12:58Put the two together, and you can do
12:59something that had never quite been done
13:01before,
13:02which is to take a census of every
13:04planet in the observable universe,
13:06sorted by when it was born.
13:08Their estimate was about 100 billion
13:11billion Earth-like planets in the
13:12observable universe as it stands [music]
13:14today,
13:15and around a billion in our own galaxy.
13:18The first thing that census said was not
13:20surprising, and it agrees with
13:22everything we have heard so far.
13:24When When solar system formed, about 80%
13:27of the Earth-like planets that exist
13:29today had already been born.
13:31By that measure, we are late, just as
13:34Lineweaver said.
13:35But Behroozi and People's kept going
13:38>> [music]
13:38>> past today, because the universe has not
13:40finished.
13:42Around every large galaxy, there is
13:44still an enormous reservoir of gas
13:46hanging in space, cooling slowly.
13:49And gas that cools falls inward and
13:51becomes [music] new stars.
13:53And new stars come with new planets.
13:56When the Earth [music] formed, only
13:57about 8% of the gas now available around
14:00galaxies had been turned into stars.
14:03If that gas keeps cooling and forming
14:05stars the way it is expected to, then
14:07the universe will make more than 10
14:09times as many planets as exist right
14:11now.
14:12And the Earth formed before at least 92%
14:15of all the planets like it that will
14:17ever exist.
14:18Both sentences are in the same paper.
14:21Late compared with everything that has
14:23happened.
14:24Early compared with everything that
14:25will.
14:27It sounds like a contradiction, but it
14:29is the whole shape of the problem in one
14:31place.
14:32Because whether we are first depends
14:33entirely on which half of history you
14:35are counting.
14:37Most of the planets still to come will
14:39form in the very far future, between 100
14:42billion and a trillion years from now,
14:44long after the sun has died.
14:47Behroozi drew one conclusion of his own
14:49about civilizations, and it is worth
14:51hearing exactly.
14:53If the future goes the way the gas
14:54suggests, [music] there is at least a
14:5692% chance that we are not the only
14:59civilization the universe will ever
15:00have.
15:02Notice the [music] tense.
15:03He was not talking about who came before
15:05us. He was talking about who comes
15:07after.
15:09And the verdict changes with the size of
15:10the neighborhood.
15:12For our own group of galaxies, the Milky
15:14Way and Andromeda and their small
15:16companions, the same paper found that
15:18the Earth formed earlier than only about
15:2061% of the planets that will ever form
15:23there.
15:24Locally, we are a little early.
15:27Across the whole universe, we are very
15:29early.
15:30The further out you look, and the
15:32further ahead, the earlier we become.
15:35That leaves the question of the past,
15:37where the first half of this story left
15:38it, resting on one assumption.
15:41The late answer assumes that the old
15:43universe was as friendly to life as the
15:45universe we see now.
15:47So, the honest thing to do
15:49>> [music]
15:49>> is to test that assumption. And the easy
15:51answers fail first.
15:54The first easy answer is that the early
15:56universe simply lacked the ingredients.
15:59The very first stars were made of almost
16:01nothing but hydrogen and helium, the two
16:03elements that came out of the Big Bang.
16:06And you cannot build a rocky planet out
16:08of those.
16:09Every atom of iron in your blood, and
16:11every atom of silicon in the ground
16:13beneath you, was forged inside a star
16:15that lived and died before the sun was
16:17born.
16:19It is tempting to say that the universe
16:21needed most of its history
16:22>> [music]
16:22>> just to stock the shelves.
16:24But the evidence does not cooperate.
16:27In March 2025,
16:29astronomers using the Alma radio
16:31telescopes in Chile reported oxygen in
16:34one [music] of the most distant galaxies
16:36ever seen.
16:37A galaxy whose light left it less than
16:39300 million years after the Big Bang.
16:42It held around 10 times more heavy
16:44elements than anyone had expected.
16:47One of the researchers, Sander Shows,
16:50>> [music]
16:50>> compared it to finding an adolescent
16:52where you would only expect babies.
16:54And the planet [music] hunters have
16:56found that small planets form around
16:57stars with a wide range of metal
16:59content,
17:00>> [music]
17:00>> not only around stars rich in heavy
17:02elements as the giants seem to need.
17:05Kepler-444
17:07was building rocky worlds 11 billion
17:10years ago.
17:11The ingredients came early.
17:13That easy answer fails.
17:16The second easy answer runs the other
17:17way, and it is just as tempting.
17:20In 2014, the Harvard astrophysicist Avi
17:23Loeb pointed out that the whole universe
17:25was once warm.
17:27About 10 to 17 million years after the
17:29Big Bang, the afterglow of creation that
17:31now fills space at a few degrees above
17:33absolute zero, was somewhere between the
17:35freezing and boiling points of water,
17:38everywhere at once.
17:40Any rocky planet anywhere would have had
17:42liquid water on its surface without
17:44needing a sun.
17:45It is a startling idea, and Loeb himself
17:48added the qualification that kills it as
17:49an answer.
17:51Those planets could only exist if
17:52[music] any existed, and at 10 million
17:55years, there had barely been time for
17:56the first stars to make the heavy
17:58elements that rock needs.
18:00A warm universe with nowhere to stand
18:02>> [music]
18:02>> is not a home.
18:04That one fails, too.
18:06The third answer is the one that does
18:08not fail, and it comes from the most
18:10violent events in nature.
18:13Gamma-ray bursts are flashes released
18:15when certain massive stars collapse, or
18:17when dead stars collide, and for a few
18:19seconds, a [music] single one can
18:21outshine everything else in the
18:22universe.
18:24Their energy is squeezed into narrow
18:26beams, and a planet caught in one of
18:28those beams, even thousands of
18:30light-years away, could lose most of its
18:32ozone layer, leaving its surface exposed
18:34to the full ultraviolet light of its own
18:36star.
18:37In December 2014, two physicists, Tsvi
18:41Piran of the Hebrew University of
18:43Jerusalem and Raul Jimenez of the
18:45University of Barcelona, asked what
18:47those beams mean for the history of
18:49life.
18:50Their answer, published in Physical
18:51Review Letters, was severe.
18:54Near the center of a galaxy like ours,
18:56they found, the chance of a planet being
18:58hit by a lethal burst is about 95%.
19:02Only beyond about 33,000 light-years
19:04from the center does that chance fall
19:06below 1/2.
19:08The Earth sits about 26,000 light-years
19:10out, inside that danger zone, and they
19:13estimated a good chance that at least
19:15one lethal burst has struck near us in
19:17the past 5 billion [music] years and
19:19about an even chance of one in the last
19:21500 million.
19:23Other researchers have argued that a
19:24burst may have helped cause the
19:26Ordovician mass extinction about 445
19:29million years ago when most of the
19:31species in the oceans disappeared.
19:34That remains a hypothesis but it shows
19:36what the danger looks like on a living
19:38planet.
19:39Across the universe, they concluded,
19:42life of the kind we know could exist in
19:44only about one galaxy in 10, mostly in
19:47the quiet outskirts of large galaxies.
19:50And earlier in cosmic history it was
19:51worse because stars formed faster,
19:54galaxies were denser, and bursts were
19:56far more common.
19:58By their reckoning, life like ours could
20:00not have taken hold in the universe at
20:02any time before a red shift of about one
20:04half.
20:05In plain terms, that corresponds to
20:08roughly the last 5 billion years.
20:10Put that beside the other dates in this
20:12story.
20:13The universe is 13.8 billion years old.
20:17If Piran and Jimenez are right, the
20:19window for life like ours opened about 5
20:22billion years ago.
20:24Our sun formed about 4.6 billion years
20:26ago.
20:27On their model, the solar system was
20:29born in the first few hundred million
20:31years after the door opened.
20:33All those ancient planets Lineaweaver
20:35counted, older than the Earth by nearly
20:372 billion years, would have spent their
20:40early history in a universe still bathed
20:42in killing light.
20:44They existed. [music]
20:45They may simply never have been safe.
20:48This is a model and it rests [music] on
20:50how often bursts happened in the past
20:52and how much damage each one does and
20:54neither is known as well as anyone would
20:56like.
20:57But it is the first piece of evidence
20:59that can turn late into early
21:02because [music] it says the clock that
21:03matters did not start at the Big Bang.
21:06It started much later.
21:08The fourth piece looks forward instead
21:10of back.
21:11In 2016, Avi Loeb returned to the
21:14question with two colleagues, Rafael
21:16Batista and David Sloan,
21:18>> [music]
21:18>> and asked when life should most likely
21:20exist across the entire lifetime of the
21:22universe.
21:24The answer depends on stars.
21:26Our sun will last about 10 billion years
21:28in all.
21:29The smallest stars, red dwarfs with
21:31about a tenth of its mass, burn so
21:33slowly that they will shine for around
21:3510 trillion years.
21:38They are already the most common stars
21:39in the sky, and they will still be
21:41shining long after every star like the
21:43sun has died.
21:45Count every planet around every star
21:47across all of time, and Loeb's team
21:49found that life is most likely to exist
21:51near those small stars about 10 trillion
21:54years from now, with a probability a
21:56thousand times larger than for a star
21:58like ours today.
22:00If that is right, then life on Earth is
22:02not just early, it is premature. A
22:05flicker at the very start of a story
22:08that will mostly happen after us.
22:10There is one way out,
22:12>> [music]
22:12>> and the authors named it themselves.
22:15If life around small stars is typical,
22:17>> [music]
22:17>> then we are strangely early.
22:20If we are typical, then something must
22:22make small stars hostile,
22:24and there is a good candidate.
22:27Young red dwarfs flare violently again
22:29and again,
22:30and those flares may strip the air from
22:32the planets that circle them.
22:34Their paper ends with a test that is
22:36already being run.
22:38Look for signs of life in the
22:39atmospheres of planets around small
22:41stars,
22:42and you will learn whether we are early
22:44or whether those planets are dead.
22:46The last piece of evidence for earliness
22:48comes from an economist, Robin Hanson of
22:50George Mason University,
22:53the same man who gave the world the
22:54phrase great filter [music]
22:56in 1998.
22:58In 2021, with three co-authors, he
23:01published a model in the Astrophysical
23:03Journal that tried to explain why we
23:05appear so early.
23:07Start from the idea that intelligent
23:09life requires several unlikely steps,
23:11and you find that more than 99% of
23:13advanced life should appear after today
23:16under most of the assumptions they
23:18tested.
23:19So, why are we here now?
23:21Their answer was a deadline.
23:24Imagine civilizations that do not stay
23:26quiet.
23:27They expand outward through space at a
23:29large fraction of the speed of light.
23:32They change everything they reach, and
23:34they leave no room for new species like
23:36us to arise inside their territory.
23:39Hanson called them grabby.
23:42If such civilizations exist, then every
23:44newcomer anywhere has to appear before
23:46the grabby ones arrive,
23:48which is exactly why we would find
23:50ourselves early.
23:52The model fitted itself to the one
23:53observation we have, our own timing,
23:56and it returned numbers that sound like
23:58science fiction.
24:00Such civilizations would already control
24:0240 to 50% of the volume of the universe.
24:05We would not see them yet because they
24:07expand so fast that their light barely
24:10arrives ahead of them,
24:12and we could meet them in anywhere from
24:13200 million to 2 billion years.
24:17Hold that model at arm's length.
24:19It rests on the idea that the steps to
24:20intelligence are rare and hard,
24:23and in February 2025,
24:25a team that included Adam Frank, the
24:28same Frank who drew the pessimism line,
24:30argued in Science Advances that there
24:33may be no hard steps at all,
24:35only windows that the changing Earth
24:37opened one after another.
24:39If they are right, a large part of
24:41Hanson's reason for thinking we are
24:43early goes with it.
24:45So, the case for being early has a shape
24:47now.
24:48Most of the planets that will ever exist
24:50have not formed yet.
24:51The smallest, longest-lived stars have
24:54barely begun their lives,
24:55and if they can host life,
24:57nearly all life is still to come.
25:00And the past may have been far more
25:01dangerous than the present, with bursts
25:04of radiation sterilizing galaxy after
25:06galaxy until a few billion years ago,
25:09which would mean the ancient worlds were
25:11old, but never safe.
25:13Against that, there are the old planets,
25:16the head start,
25:18and the overwhelming arithmetic of the
25:19pessimism line.
25:21Neither side is proven.
25:23Each side has numbers that the other
25:25cannot explain away.
25:27What is certain is that the question is
25:29no longer philosophy.
25:31It has become a measurement problem,
25:33and some of the measurements are already
25:35scheduled,
25:36which means it is worth asking before
25:38the answer arrives,
25:40what it would actually mean to be first.
25:43Imagine walking out at first light after
25:46a night of heavy snow.
25:48In front of you is a wide field, white
25:50from edge to edge, and there is not a
25:52single footprint in it.
25:55There are two ways to read that field.
25:57The first is that nobody has crossed it.
25:59You were the first one out, and every
26:01mark that will ever be made in that snow
26:03is still to come.
26:05The second is that people crossed it all
26:08through the night, one after another,
26:10and the snow kept falling and filled in
26:13every track they left.
26:15Standing at the edge at dawn, the two
26:18fields look exactly the same.
26:20Nothing in the snow itself can tell you
26:22which one you are looking at.
26:24To know, you would have to dig, or wait
26:26for someone else to come out of the
26:28trees, or find something buried that the
26:30snow could not quite cover.
26:33That is where the question of being
26:34first actually stands.
26:36The universe in front of us is unmarked.
26:40Michael Hart's fact A has now held for
26:43more than 50 years.
26:44Nobody has arrived. Nothing has been
26:47found on the moon, at the quiet
26:49balancing points around the Earth, or
26:51anywhere else our instruments can reach.
26:54Breakthrough Listen, the largest search
26:56for alien signals ever funded, has been
26:58running since July 2015,
27:01and has heard nothing that survived a
27:02second look.
27:04And if Robin Hanson's grabby
27:06civilizations exist, we see no sign of
27:08them either. No great bubbles of altered
27:11galaxies, no regions of the sky where
27:14the stars have been rearranged.
27:16The field is clean.
27:18The only argument left is about what the
27:20cleanness means.
27:22Start with the snow, because it is
27:24heavier than people think.
27:26A civilization like ours leaves
27:28surprisingly little behind that could be
27:30seen from far away.
27:32We have been loud in radio for about a
27:34century, and most of what we have sent
27:36spreads out and fades with distance
27:39until it sinks into the hiss of the
27:41galaxy.
27:42Our cities glow at night, but only for
27:45as long as someone keeps the lights on.
27:47If a species like ours rose and fell on
27:50a planet 3 billion years ago, its
27:52signals would have passed through our
27:54region of space long before the first
27:56animal crawled out of the sea.
27:59Its cities would be dust.
28:01Its planet might have moved on to a
28:03different climate, a different
28:04chemistry, an entirely different set of
28:07living things.
28:09This is the part of Adam Frank's
28:10argument that people tend to skip.
28:13His pessimism line says someone almost
28:15certainly came before us.
28:17It says nothing about whether they left
28:19a mark we could still find.
28:21And it is perfectly possible that the
28:23field has been crossed a thousand times,
28:25and the snow has covered every track.
28:28But there is something about the snow
28:30that is easy to miss.
28:32It does not fall evenly across all of
28:34time.
28:35If Piran and Jimenez are right about the
28:37bursts, then for most of cosmic history,
28:40the snow was not snow at all.
28:42It was fire, sweeping through galaxy
28:45after galaxy, wiping away anything that
28:48tried to begin.
28:50The field only became walkable a few
28:52billion years ago.
28:53On that reading, the snow is not hiding
28:56a crowd.
28:57It is hiding nothing because nothing
28:59could walk here until very recently, and
29:01we happen to be among the first who
29:03could.
29:05The same empty field, the same silence,
29:08and two completely different histories
29:10underneath it.
29:12There is one more thing the snow tells
29:13us, and it is about where we stand.
29:17Peter Behroozi's census found that the
29:19Earth formed before at least 92% of the
29:21planets like it that the universe will
29:23ever make.
29:25Set aside for a moment the question of
29:27who came before us, and look at the
29:29other direction.
29:31Whether or not we are the first, we are
29:33certainly near the beginning.
29:35Almost every planet that will ever be
29:37warm enough and wet enough and old
29:39enough to try what happened here has not
29:41been born yet.
29:43Almost every red dwarf that will ever
29:45shine is still young.
29:48If minds arise at all, then nearly every
29:51mind the universe will ever hold lies in
29:53the future.
29:55We are not looking back over a finished
29:57story.
29:58We are standing somewhere close to its
30:00opening pages.
30:02That changes what being first would
30:03mean.
30:04It would not mean that we are special or
30:06chosen or better than anything that
30:08comes after us.
30:10It would mean that we are the earliest
30:12test of whether this can work at all.
30:15Every choice our species makes about
30:17what to do with the power we have
30:18gathered in the last century, about our
30:20planet and about each other, would be
30:23the first time that choice had ever been
30:25made anywhere.
30:27There would be no one ahead of us on the
30:29path, no ruins to study, no signal from
30:32an older world warning us about the
30:34mistakes it made.
30:36If we fail, it would not be one
30:38civilization among many failing. It
30:40would be the only experiment so far
30:42coming to an end in a universe that
30:44would go on making planets for a
30:46trillion years with no memory that
30:49anyone had tried.
30:51And even the first experiment does not
30:52have forever.
30:54The sun is slowly brightening as it
30:56ages, and that slow brightening will
30:58eventually undo the conditions that let
31:00us breathe.
31:01In 2021, Kazumi Ozaki of Toho University
31:06and Christopher Reinhard of the Georgia
31:07Institute of Technology ran their model
31:10of the Earth's climate and chemistry
31:12hundreds of thousands of times and found
31:15that the oxygen-rich air we depend on
31:17will probably last for around another
31:19billion years before it collapses.
31:21That sounds like an eternity, and by the
31:23measure of a human life, it is.
31:26By the measure of the questions in this
31:28story, it is short.
31:30A billion years is less than the head
31:32start Lineweaver gave the average
31:34Earth-like planet.
31:35If we are the first, we are not only
31:37alone at the start.
31:39We are working against a clock of our
31:41own.
31:42And if we are not first, the meaning
31:44flips completely.
31:46Then somewhere in the field under the
31:48snow, there are older tracks.
31:50Someone faced [music] the same choices
31:52billions of years ago on another world
31:55around another star.
31:57Perhaps they made it through.
31:59Perhaps they did not.
32:01Either way, the history of minds in the
32:03universe did not start here, and
32:05whatever we do next is a later page, not
32:08the first one.
32:09Neither answer is comfortable, and
32:11neither is small.
32:13Every person watching this is alive at
32:15the moment when that question stopped
32:17being philosophy
32:18>> [music]
32:18>> and started being something we can
32:19measure.
32:21Because for the first time, people are
32:23going out to dig.
32:25On the 30th of August, 2026,
32:27the Nancy Grace Roman Space Telescope
32:30lifted off from Florida on a Falcon
32:32Heavy rocket bound for a quiet point in
32:34space about 1 and 1/2 million kilometers
32:36beyond the Earth.
32:38Among its tasks [music] is a census of
32:40planets across the inner galaxy found by
32:43watching for the moments when one star
32:45briefly magnifies the light of another
32:47behind it.
32:48Its first images are expected early next
32:50year.
32:51And the listening has quietly grown,
32:53too.
32:54Since 2022,
32:56Breakthrough Listen has been riding
32:58along on the MeerKAT radio telescope in
33:00South Africa, recording whatever part of
33:02the sky the array happens to be pointed
33:04at for its own work. And by the middle
33:07of 2026,
33:09that survey had passed more than 1
33:10million 200,000 separate [music]
33:12pointings.
33:14Every one of them is a small patch of
33:16snow that someone has now looked at
33:18closely.
33:19>> [music]
33:19>> The European Space Agency's Plato
33:21mission, built to find Earth-sized
33:24planets around stars like the Sun at the
33:26distance where water can stay liquid, is
33:28planned for launch in March 2027.
33:32And in Chile,
33:33>> [music]
33:33>> the Extremely Large Telescope, with a
33:35mirror 39 m across, is scheduled to
33:38begin its science at the end of 2030
33:41with the power to study the light
33:43passing through the atmospheres of
33:44nearby rocky worlds.
33:47Closer to home, there is a test [music]
33:49that could change the odds all on its
33:51own.
33:52NASA's Europa Clipper, launched in
33:54October 2024, [music] is on its way to
33:57the ice-covered moon of Jupiter, whose
34:00ocean holds more water than all the seas
34:02of Earth combined.
34:04It [music] swings past the Earth one
34:06last time on the 3rd of December, 2026,
34:10>> [music]
34:10>> borrowing speed for the long fall
34:12outward.
34:13And it arrives at Jupiter in April
34:15[music] 2030.
34:17Clipper cannot detect life.
34:19It was built to find out whether that
34:21ocean could support it,
34:22>> [music]
34:23>> and to show where a later mission should
34:24look.
34:25But if life is ever found to have begun
34:27independently in that dark ocean,
34:30then life began [music] at least twice
34:32around one ordinary star.
34:34And the idea that life is a
34:36once-in-a-universe accident would be
34:38very hard to hold.
34:40>> [music]
34:40>> The pessimism line would stop being an
34:42argument and start being a measurement.
34:45Further out, there is the telescope that
34:46may matter most of all. NASA's Habitable
34:49Worlds Observatory is designed [music]
34:51to block the glare of nearby stars like
34:53the sun and photograph the faint planets
34:55beside them directly,
34:56>> [music]
34:56>> then spread their light into its colors
34:58and read the gases in their air.
35:00It is planned for the 2040s if it is
35:03funded, and its funding has been
35:05anything but certain.
35:07If it flies, it will be the first
35:08instrument ever built to look at another
35:10Earth and ask whether anything is
35:12breathing there.
35:13And Avi Loeb's test is already underway
35:15with the James Webb Space Telescope
35:17reading the atmospheres of rocky planets
35:19around small red stars.
35:21If those planets turn out to keep their
35:23air and show signs of life, then we are
35:25early in a universe that will one day be
35:27crowded.
35:28If they are bare and dead, then the long
35:31lives of red dwarfs count for far less,
35:33and the moment we live in may be close
35:35to the best that the universe ever
35:36offers.
35:38There is an asymmetry in all of this
35:40that is worth keeping in mind.
35:42A single discovery can settle one side
35:44of the question for good.
35:46One signal from an older world, one
35:48technological artifact that cannot be
35:50explained any other way. One ruin on a
35:52distant planet,
35:53>> [music]
35:53>> and we would know that we are not the
35:55first.
35:56The case would close in an afternoon.
35:59We have already had a taste of how that
36:00afternoon might go and of how carefully
36:02it has to be handled.
36:04In the spring of 2019, the Parks radio
36:07telescope in Australia pointed [music]
36:09at Proxima Centauri for Breakthrough
36:11Listen, recorded a narrow, steady tone
36:14that looked for a while like nothing
36:16nature makes.
36:17It was given a catalog name, BLC1, and 2
36:20years of checking followed.
36:23In October 2021, the team published
36:26their verdict. The signal was
36:27interference from our own technology
36:29here on Earth.
36:31The search had found us.
36:33But silence can never settle the other
36:35side.
36:36No amount of empty sky proves that we
36:38are first [music] because the snow is
36:40always deep enough to hide one more set
36:42of tracks.
36:43The best that silence [music] can ever
36:45do is make the first answer slowly more
36:47likely, survey after survey, decade
36:50after decade, until one day the weight
36:53of it becomes hard to ignore.
36:55That Michael Hart was doing when he
36:57wrote his last sentence in 1974.
37:00He was not claiming [music] to have
37:01proved anything.
37:02He was reading the empty field and
37:04saying out loud what it looked like.
37:07He had only our galaxy to think about
37:09and he had no gamma-ray bursts, no
37:11census of planets, no surveys of the gas
37:14still waiting around the galaxies.
37:1750 years on, we have all of those and
37:19the strange thing is that they have not
37:21closed the question.
37:23They have made both answers stronger at
37:24the same time.
37:26The arithmetic of the pessimism line has
37:28never been more overwhelming.
37:30And the evidence that the universe only
37:32recently became a safe place to live has
37:34never been more serious.
37:36So, we are left standing at the edge of
37:38the field at first light with the snow
37:40still unbroken in front of us.
37:43Behind us is the line of tracks we have
37:45already made, short and uneven, a
37:48century of radio and a few decades of
37:50spacecraft and a handful of footprints
37:52on the moon.
37:54Ahead of us, as far as any telescope can
37:56see, there is nothing at all.
37:59Perhaps the snow is hiding the tracks of
38:01everyone who came before.
38:03Perhaps it is hiding nothing and this is
38:05what the very beginning looks like from
38:07the inside.
38:09We will not know tonight and we may not
38:11know in our lifetimes.
38:12But for the first time, someone is
38:14digging.
38:15The field is still white
38:17and the only tracks we can be sure of
38:19are our own.

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