- Astronomers are certain that, billions of years in the future, the sun will incinerate Earth's oceans, effectively killing all life.
- The best solution to that imminent demise, according to a recent Scientific American blog post by Harvard astronomer Avi Loeb, is to relocate humanity to other parts of the universe.
- Rather than just settle existing planets, Loeb suggests our species build a mobile "major upgrade to the International Space Station" capable of moving through space and seeding other worlds with our genetic material.
- But, Loeb warns that humanity will likely bring about its own demise "as a result of self-inflicted wounds long before the sun will pose its predictable threat."
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One day, billions of years in the future, the sun will destroy our planet.
As the star runs out of hydrogen and helium atoms to burn in its core, it glows brighter and brighter. Eventually, the sun will bombard Earth with enough high-energy light to incinerate the world's oceans, melt the polar ice caps, and strip our atmosphere of all moisture - effectively killing all life.
But don't fret. We'll likely all be dead by then anyway.
A BBC reporter recently asked Harvard astronomer Avi Loeb what a possible solution to humanity's imminent demise might be.
Loeb outlined his response in a recent Scientific American blog post, where he stated how imperative it is for our species to relocate to other parts of the universe that are less close to our sun's vacillating brightness.
The astronomer doesn't want us to remain shackled to existing planets and moons, either - he said it'd be best if humanity could "manufacture a gigantic structure that will be able [to maneuver] the optimal orbital distance at any given time" from the sun's deadly energy.
Once we successfully colonise both nearby and interstellar space, Loeb added, we can make genetically identical copies of ourselves and "the flora and fauna we hold dear" to seed other planets with life.
That being said, Loeb ended his blog post on a depressing note. In his opinion, humanity will wipe itself out long before the sun might.
How to ensure the (semi)-longevity of our species
Loeb, who is the chair of Harvard University's astronomy department, wrote that humanity needs to "contemplate space travel out of the solar system."
In order to do so, he added, we need to build "an artificial world" capable of bouncing between stars and their neighboring, potentially habitable planets. This industrial spacecraft and human habitat would "represent a very major upgrade to the International Space Station (ISS)," he said.
Once our means of traveling to other planets and moons in the universe is secured, humanity needs to focus on duplicating itself, and other existing species, before we all get annihilated.
"The longer-term solution to our existential threats is not to keep all of our eggs in one basket," Loeb wrote. To him, that means making genetically identical copies of ourselves, plants, and animals, and spreading those copies to other stars.
Obviously, the astronomer pointed out, that future solution won't do much for preserving people alive on Earth today. But to Loeb, its more important to ensure the longevity of our species as a whole rather than protecting "our own skin."
Planning for a future that might not happen
All of his ideas aside, Loeb isn't that sure that humanity will be around to experience its demise at the hands of a brightening, expanding sun.
"I am inclined to believe that our civilisation will disappear as a result of self-inflicted wounds long before the sun will pose its predictable threat," he wrote. "Why do I believe that? Because the dead silence we hear so far from the numerous habitable exoplanets we've discovered may indicate that advanced civilisations have much shorter lives than their host stars."
Loeb is confident that extra-terrestrial life exists, or existed, in the universe. He is in part famous for the idea that the first interstellar object to pass through our solar system - a rock named "Oumuamua" - was an advanced alien spaceship scouting Earth and nearby planets for life. That hypothesis has since been dismissed by multiple astronomers.
In September, scientists announced they'd detected water vapour on a potentially habitable planet for the first time. The planet, named K2-18b, is a super-Earth that orbits a star 110 light-years away.
K2-18b is the only known planet outside our solar system with water, an atmosphere, and a temperature range that could support liquid water on its surface, which makes it our best bet for finding alien life.
But, as Loeb mentioned in his blog post, so far researchers have yet to discover anyone else out there.
One day, the Earth will die - immolated by its own sun
Loeb's ideas offer a solution to a very real problem that will one day plague our planet and its species. His future version of the ISS could ensure that humanity would remain mobile in the face of a changing sun.
Our sun survives by burning hydrogen atoms and converting them into helium at its core. In fact, it burns through 600 million tons of hydrogen every second.
And as the sun's core becomes saturated with this helium, it shrinks, causing nuclear fusion reactions inside it to speed up - which means that the sun spits out more energy.
For every billion years the sun spends burning hydrogen, it gets about 10% brighter. One day in the far future - about 1 billion years, according to Loeb - that brightness will become too much for Earth to handle.
A 10% increase in brightness every billion years means that 3.5 billion years from today, the sun will shine almost 40% brighter, which will boil Earth's oceans, melt its ice caps, and strip all of the moisture from its atmosphere.
Our planet, once bursting with life, will become unbearably hot, dry, and barren - like Venus.
And if that didn't kill us, what comes next would.
One day, about 4 billion or 5 billion years from now, the sun will burn through its last gasp of hydrogen and start burning helium instead.
"Once hydrogen has stopped burning in the core of the sun, the star has formally left the main sequence and can be considered a red giant," Scudder said. "It will then spend about a billion years expanding."
Its atmosphere will stretch out to Mars' current orbit, swallowing Mercury and Venus.
Earth, Scudder said, might either escape the expanding sun's orbit or be consumed by it. But even if our planet slips out of the sun's reach, the intense temperatures will burn it to a sad, dead crisp.
"In either case, our planet will be pretty close to the surface of the red giant, which is not good for life," Scudder said.
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