Could we save Earth when the Sun dies? A scientist says there could be a way

In about a billion years, the solar system as we know it will become unrecognizable: as the Sun starts to run out of fuel, it will expand to become a massive red giant before eventually shrinking to a dim white dwarf. However, long before darkness engulfs the solar system, Earth will be long gone, with its oceans and atmosphere vaporized and the planet itself engulfed by our once life-giving host star. Given the extreme timescales involved, it is natural to accept our cosmic fate, but not everyone's having it: in a bold attempt to defy fate, a scientist named Gabriel Harry has proposed ways in which humans can conceivably prevent the end of all life in the solar system.

Currently available on the preprint arXiv server, Harry's study proposes a multi-stage plan to prevent catastrophe, of which the first stage involves blocking out the Sun. Yes, you read that right. Before the Sun even becomes a red giant, it will continuously brighten, hitting Earth with increasing amounts of energy that can trigger a runaway greenhouse effect and turn our planet into something akin to Venus. To prevent this, Harry proposes constructing a colossal orbital sunshade that would cover a 70-degree arc of the sky. To put that into perspective, this sunshade would have to measure a mind-boggling 700,000 kilometers in diameter, and would need to be parked near the Earth-Sun Lagrange Point (L1) and anchored by high-tensile carbon tethering cables. This structure would essentially act like a massive umbrella for Earth, blocking out excess solar radiation and helping the planet sustain conditions for life.

While blocking out the Sun can help Earth survive our host star's waning years, it would plunge our planet into darkness, stopping photosynthesis and creating freezing, sub-zero conditions that would essentially be a death sentence for most life. This problem, Harry proposes, can be solved by Jupiter. While technically not a star, Jupiter is rich in hydrogen and helium, and Harry proposes constructing fusion reactors deep inside Jupiter. While current technology cannot hold a fusion reactor together, Harry says the immense pressure inside Jupiter would suffice, and fusion reactors 4,000 miles inside the gas giant's atmosphere could generate the energy required by Earth. This energy could then be beamed up to Jupiter's Lagrange point 1, transmitted via a laser to a Lagrange point relay near Earth, and shone on our planet's surface.

While the aforementioned solutions suffice for the billions of years leading up to the Sun's transformation into a red giant, they would be unable to stop Earth from getting engulfed when the Sun eventually takes its penultimate form. So, how can humans tackle this? Harry proposes an outrageous but simple solution: just move Earth. One way this could be done is by making a massive asteroid fly past Earth a million times, but this would be inherently risky for us: even a slight miscalculation could wipe out all life. Instead, Harry proposes extracting oxygen from Jupiter and firing a particle beam past Earth. This beam, which would be "equivalent in mass to half of the Amazon River's outflow," would act as a gravitational whip, slowly but steadily propelling Earth away. Over long enough timescales, this small push would be enough to push our planet away from the expanding Sun.

Harry's proposal not only accounts for the death of the Sun, but also offers solutions against our planet's eventual decay. As Earth's interiors cool over the next two to three billion years, it will halt Earth's plate tectonics, thereby bringing an end to mountain building and "life-giving recycling." This, Harry says, can be averted by producing sizeable quantities of antimatter and pouring it into Earth. Harry's solution goes like this: create antimatter, put it in a container, blast a hole in Earth's surface, and pour molten iron into it along with the antimatter-carrying container. This would, according to Harry, help reheat Earth's interior: when the container with antimatter eventually runs out of energy to keep it from contact with other matter, the resulting annihilation would provide heat to the cooling interior of our planet. "Producing and sinking 2 kg of antimatter per day would maintain Earth's tectonics—at 10% energy efficiency, we could use the equivalent of the total solar-panel area of India to produce this amount," Harry writes for Phys.org.

If all of the steps highlighted by Harry succeed, Earth would still have one remaining problem: over long enough timescales, our planet could get caught up in galactic collisions, such as the one between Andromeda and the Milky Way expected to happen in about 4.5 billion years. This, too, can be solved using the particle beam from Jupiter. Instead of using oxygen, Harry proposes firing a beam of hydrogen just above or below the north or south pole of the Sun. The slingshot effect from this particle beam, Harry says, would also help gradually move the solar system away from impending collisions.

But why do all this if we can just move to another habitable planet? Harry argues that interstellar space travel, and keeping humans alive for such distances, are extremely difficult, and his proposed solutions do not require us to figure this out. He also argues that the safeguards proposed would require a "thousand to a million" times less energy than interstellar mass migration. Moving humanity across the stars would also conceivably require us to send terraforming technology in advance, which would not yield any economic benefits for centuries, perhaps even millennia. Finally, Harry argues that colonizing the galaxy would also create a "security risk", wherein the colonies over long timescales would become their own civilizations independent of humanity. "They would be akin to aliens," argues Harry, saying that their knowledge of Earth's location and its paradise-like conditions could eventually become a threat. Staying as one society within the solar system prevents these issues, and Harry argues that his safeguards would grant life on Earth 9.1 quadrillion years to thrive.