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(SCRIPT, IN PRODUCTION) The Most Dangerous Thing In The Universe

Episode Working Title: The Most Dangerous Thing In The Universe
Topic/Idea: Emeka Ekwuribe
: Trenton McNulty

The universe is vast. As old as time, far older than the stars themselves. 13.8 Billion years.

If we reduced that time scale down to a single year, the entirety of recorded human history would take up a minute at best. Your life, the long decades of joy and sorrow and pride and regret, every dreary morning and sunny afternoon, will take up, at best, 1/5th of a second of cosmic time.

This cosmic calendar, first popularized by Carl Sagan in the 1970s, is meant to show us just how... precarious our position in the universe truly is.

We have not been here long, and if the few months of life on our planet are any indication, we will not be here much longer.

Over the past four weeks, the universe has wiped our planet clean of life nearly six times over. Of all the billions of species to ever live, more than 99% have gone extinct.

It would probably be a little arrogant to assume that we, who came along only a few minutes ago, are somehow different from all those who came before us. That our species could and should be the first to endure past our time.

However, the fact that we’re talking about this at all suggests that maybe we are different. We built telescopes, searched the stars and pieced together the story of our universe. We built tools, dug pits and unearthed the stories of our ancestors.

And in all that searching, we’ve found no sign that there’s ever been anyone like us.

The fact is: humans are adaptable. Most animals are uniquely suited to the environments they evolved in. If their habitat changes, they don’t change with it. They die. Icecaps melt and within a few generations, polar bears are endangered.

Humans are different. When it gets cold, we don’t freeze. We knit ourselves a sweater and light a fire. When it rains, we aren’t swept away by the floodwaters. Instead, we build barriers and divert rivers.

The list goes on. Forests burn and we douse the flames with water. Earthquakes topple cities and we build them back stronger.

Knowledge is our power, our saving grace, and with it we’ve conquered challenge after challenge.

At this point, natural disasters don’t pose much threat to our species as a whole. But what couldn’t we withstand? What, if it happened tomorrow, could end the human story for all time? If we want to survive our present, we need to know what dangers our future might hold.

These are the biggest threats our species faces. The threats which stand to put us back into the soil, like the 99% who came before us. These are the most dangerous things in the universe.

The Death of the Universe

There are many theories as to how the universe might end, and we will not live to see any of them come to pass.

The most likely theory suggests that the universe, which once began by expanding ever outward from a single point, will continue to do so for all time.

The evidence for this is clear: every day, our own Milky Way grows more and more distant from neighboring galaxies as the space between them expands. Eventually they’ll disappear from view altogether, leaving us alone in the dark.

We can live like this, for billions and billions of years. The galaxies, though spread apart, will hold together. But eventually the stellar nurseries which add new stars to our galaxy will run dry. The remaining stars will age and burn into nothingness, leaving only black holes to suck up everything that remains.

A hyper-advanced civilization could cobble together distant stellar remnants to create new stars, but in time these too will run out. There will be no material left for us to use, no energy to sustain us. And eventually the black holes will decay, too.

This is the Big Freeze, and it is the one threat we cannot escape.

The Death of the Milky Way

While the galaxies are, on the whole, growing apart, there are a few exceptions.

2.5 Million kilometers from here lies the Andromeda galaxy, and it’s on a collision course with the Milky Way. In 4.5 billion years, this collision will tear both galaxies apart.

Surprisingly, this in itself won’t hurt us. On a cosmic scale, the stars and planets of our two galaxies are actually so distant from one another that no star will directly collide with another.

Black holes, however, are a different story. They can grow far, far larger than any star, and almost every spiral galaxy (including Andromeda and the Milky Way) holds one at their core.

If our sun comes too close to either one of these supermassive black holes, we’ll be consumed, or (in the best case scenario) ejected into interstellar space.

If any trace of humanity remains on Earth at this time, the best solution to this threat would be to simply... push our sun out of the way.

While that may seem like a godlike feat, if there’s any trace of humanity still living in our solar system at this time, they’ll be advanced enough to have already survived the expansion of our sun into a red giant.

If that’s the case, it would be easy work to, say, construct a Dyson sphere: a colossal array of solar panels encircling the sun.

These solar panels would collect energy and beam it directly into a spaceship fitted with two nuclear fusion reactors.

The first reactor would scoop up helium emitted by the sun and fire it outwards to create thrust, while the other reactor would collect hydrogen from solar flares and funnel it back towards the sun’s surface, anchoring the sun in place and pushing it forward.

This would, over 5 million years, bring our star and the planets which orbit it up to a comfortable cruising speed of 200 kilometers per second.

While it would take another few millions years to get ourselves out of harm's way, we’d have at least a billion years advance notice.

The Death of Our Solar System

While we already know about the eventual death and rebirth of our galaxy, there’s one smaller, more local danger that could threaten our solar system in the same way: the appearance of a rogue black hole.

Black holes form when a massive star runs out of fuel at the end of its life cycle. Unable to burn as hot as it once could, the star can no longer support its own weight. It collapses inward until the gravity is so great it warps the fabric of spacetime itself.

While black holes normally stay in the same place as their original star, violent stellar events like the merging of two separate black holes can send them hurtling out into interstellar space at incredible speeds.

It’s not easy to spot objects drifting in the lightless voids between the stars, and an object that absorbs light itself is even more impossible to spot.

If one wandered close enough to our Sun, its massive gravity would disrupt the orbits of every object in the solar system, slowly but surely throwing the planets into disarray.

As it consumes the planets and asteroids in the outer solar system, it only will grow larger, until finally Earth gets caught in the path of the singularity.

After stripping the planet of its atmosphere (and us along with it) the black hole’s gravity would create tidal waves as high as Mount Everest, stretching the Earth’s crust like a ball of dough until finally the tectonic plates rip apart, exposing our planet’s molten core.

As we pass the event horizon, everything that was once our home is crushed into rubble, then dust, then atoms.

While we’d probably be able to detect this black hole long before it became any kind of threat, the more immediate danger leaves moving our sun more or less off the table.

In this scenario, the best strategy would be to move ourselves.

There are millions of potentially habitable worlds in our galaxy alone, and by establishing settlements there, we give humanity a backup plan, saving us from being done in by any one galactic calamity.

This is the same strategy we’d use to avoid extinction through the expansion, contraction, and eventual death of our own sun, which will inevitably cook and consume the Earth just as readily as a black hole would.

The Death of Our Planet

The hardest threats for us to avoid are those that could happen at any time, without any warning: gamma-ray bursts and asteroid impacts.

While neither of them would destroy life on Earth forever, they may very well destroy us. We know this because they’ve done it before, causing two of the past five mass extinction events in our planet’s history.

Gamma-ray bursts are massive blasts of electromagnetic radiation emitted by collapsing stars. They emit so much energy that, for the brief moment of their existence, they’re brighter than every other star in the universe.

If Earth happened to be squarely in the path of one of these narrow bursts, the effects would be immediate: the destruction of up to 75% of the upper atmosphere, specifically the ozone layer.

Without ozone, all life on Earth would be exposed to the violent, ultraviolet radiation of the sun, causing DNA damage and cancers.

The long-term effects are even more devastating.

For several years, acid rain would fall and photochemical smog would darken the skies, reflecting more of the sun’s rays. If this were to happen today, given how unstable our climate currently is, the darkness might even trigger a runaway cooling effect causing a decade-long winter.

These conditions are eerily similar to those observed 450 million years ago, during the Late Ordovician mass extinction: Earth’s first mass extinction event.

Fossil evidence shows that the dominant photosynthetic animals almost all suddenly died out, while isolated populations deep within the ocean, far from UV light, largely survived: the opposite of what would happen in a traditional extinction event.

These same effects were seen during the far more famous Cretaceous–Paleogene extinction: the death of the dinosaurs.

66 million years ago, a 10-kilometer long asteroid struck the surface of our planet, carving a near 180-kilometer long crater in present-day Mexico.

The impact instantly vaporized the water beneath it and scattered hot debris across the planet, setting the world aflame. Soot from the blast turned to aerosol and blackened the skies, causing a decades-long winter that slowly killed off all life on the surface.

While humans today might survive such an impact by hiding away in remote, underground bunkers, the vast majority would be left to die.

If an even larger asteroid struck--say, 30 to 60 kilometers--it would completely eradicate all life on Earth, no matter the hiding place.

Essentially, if an asteroid or gamma-ray burst aimed itself at Earth, there would be very little we could do about it.

As gamma-ray bursts are impossible to predict, our only immediate solution would be to deal with the effects as best we can, just as we’re trying now to deal with the effects of climate change.

We’ve already worked together to restore the holes we’ve made in the ozone layer, and it's conceivable that future technologies could allow us to take more active efforts in the event of an ozone-stripping event.

Unlike gamma-ray bursts, which occur in our local group of galaxies only once or twice every 5000 million years, rogue asteroids are a real and present threat, and the only one that humans have so far taken steps to counter.

Since the 1990s, NASA has identified over 25,000 near-Earth asteroids. While many smaller ones may be out there, they’ve located more than 90% of the asteroids large enough to devastate the Earth.

While no large asteroids are currently on a collision course with our planet, NASA scientists have proposed and even tested a solution to counter them.

In September 2022, NASA deliberately flew the ‘Double Asteroid Redirection Test’ satellite (or D.A.R.T.) into the asteroid Dimorphos, measurably changing its orbit.

Should a world-ending asteroid come barrelling towards the Earth, we’ll simply nudge it out of the way long before it ever reaches us.

The Death of Ourselves

While the dangers we’ve discussed so far are possible, inevitable, and devastating, they only come along every hundred million years or so, if that. The odds that one will happen in the foreseeable future are slim to none.

In that sense, the most dangerous thing in the universe isn’t simply that which could cause the most destruction, but the thing that’s most likely to.

For that reason, we are the most dangerous thing in the universe, at least to ourselves.

If we die, the odds are overwhelmingly clear that it will be at our own hands. There will be no death from above, no gamma-ray burst or rogue black hole. It will be because we chose to die, either through the negligence of human-caused climate change or the short-sighted malice of nuclear war.

We invented the machines that warmed our planet, causing droughts and floods and massive storms. We invented the bombs that can annihilate millions in an instant, and each day we choose to keep them armed and aimed squarely at our own heads.

At this moment there are over 12,000 active nuclear warheads on our planet.

A full nuclear exchange will instantly kill millions, and in the aftermath, radioactive fallout will kill billions more.

The skies will darken and plunge our planet into a decade-long nuclear winter, slowly starving everyone else unfortunate enough to survive, just as it happened 66 million years ago and 400 million years before that.

The Bulletin of the Atomic Scientists keeps a symbolic clock that measures humanity’s proximity to doomsday.

In 1947, when the clock was first unveiled, an expert panel of scientists and academics judged that we were seven minutes to midnight, to our own extinction.

When the Soviet Union fell, ending the cold war, they turned the clock back to 17 minutes.

But now, as we fail to deal with climate change, as nuclear arms treaties fall apart, and as Russia once again threatens war with the West, we’re 100 seconds from midnight.

This is "the most dangerous situation that humanity has ever faced." (Bulletin of the Atomic Scientists)

At this moment, we have two paths forward.

We can listen to the better angels of our nature and survive our present together. Or we can join all those who went before us, hastening the end of our universe just as the universe itself might end—with cold and silence.