I’d wager a guess that we’re, as a species, somewhat keen on our dwelling planet (our wanton carbon emissions however). However the ugly reality is that the Earth is doomed. Sometime, the Solar will enter a stage that can make life unattainable on the Earth’s floor and ultimately scale back the planet to nothing greater than a tragic, lonely chunk of iron and nickel.
The excellent news is that if we actually put our minds to it—and don’t fear, we’ll have a whole bunch of hundreds of thousands of years to plan—we are able to preserve our dwelling world hospitable, even lengthy after our Solar goes haywire.
A waking nightmare
The Solar is slowly however inexorably getting brighter, hotter, and bigger with time. Billions of years in the past, when collections of molecules first started to bop collectively and name themselves alive, the Solar was roughly 20 % dimmer than it’s right this moment. Even the dinosaurs knew a weaker, smaller star. And whereas the Solar is barely midway by means of the primary hydrogen-burning section of its life, with 4-billion-and-change years earlier than it begins its dying throes, the peculiar mixture of temperature and brightness that make life doable on this little world of ours will erode in only some hundred million years. A blink of an eye fixed, astronomically talking.
The Solar sows the seeds of its personal demise by means of the essential physics of its existence. At this very second, our star is chewing by means of one thing like 600 million metric tons of hydrogen each single second, slamming these atoms collectively in a nuclear inferno that reaches a temperature of over 27 million levels Fahrenheit. Of that 600 million metric tons, 4 million are transformed into power— sufficient to light up the complete Photo voltaic System.
That fusion response is just not completely clear, nevertheless. There’s a leftover byproduct, an ash created by the nuclear fires: helium. That helium has nowhere to go, because the deep convection cycles that consistently churn materials inside the Solar don’t attain into the core the place the helium is fashioned. So the helium sits there, inert, lifeless, ineffective—clogging up the machine.
At its current age, the Solar doesn’t have excessive sufficient temperatures and pressures at its core to fuse helium. So, the helium will get in the best way, rising the general mass of the core with out giving it anything to fuse. Fortunately, the Solar is well in a position to compensate for this, and that compensation comes about by means of a little bit of physics often known as hydrostatic equilibrium.
The Solar exists in fixed steadiness, residing on the sting of a nuclear knife. On one aspect are the energies launched by the fusion course of, which, if left uncontrolled, may threaten to blow up—or on the very least, increase—the Solar. Countering that’s the immense gravitational weight of the star itself, urgent inward with all of the may that 1,027 tons of hydrogen and helium can muster. If that drive have been to go unchecked, the Solar’s personal gravity would crush our star right into a black gap no larger than a mid-sized metropolis.
So what occurs when an unstoppable drive meets an irresistible strain? Swish steadiness—and a star that may reside for billions of years. If, for some purpose, the nuclear inferno randomly ratchets up in temperature, that can warmth up the remainder of the star and inflate its outer layers, easing the gravitational strain and slowing down the nuclear reactions. And if the Solar have been to randomly contract, extra materials would drive itself into the core, the place it could take part within the heady nuclear dance, and the discharge of power that outcomes would conspire to reinflate the star to regular proportions.
However the presence of helium ash, that nuclear trash, upsets that steadiness by displacing hydrogen that might in any other case fuse. The Solar can’t assist however pull inward on itself—gravity is uncompromising and uncaring. And when it does, it forces the nuclear reactions of the core to extend in ferocity, elevating its temperature, which in flip forces the floor of the Solar to swell and brighten.
Slowly, slowly, slowly, as helium continues to construct up within the core of the Solar (or some other star of comparable mass), it expands and brightens in response. It’s tough to foretell precisely when this brightening will end in calamity for our planet—that is determined by a posh interaction of radiation, ambiance, and ocean. However the basic estimate is that we now have roughly 500 million years left earlier than life will grow to be all however unattainable.