Dinosaurs knew a smaller and darker sun than ours today. And we are in the last legs of the viability of life on Earth. In about 500 million years, our sun will become so bright that it will cause a greenhouse effect on Earth. The oceans will evaporate, trapping more heat in the atmosphere, which will cause even more evaporation, which will warm the planet more, causing an out-of-control feedback loop.
Whereas today we know our parent star as the source of light and heat throughout the solar system, allowing life to arise and flourish on our planet. But it’s not guaranteed that things will always be so peachy. Indeed, there are various ways in which the sun can destroy all life on Earth.
UV rays and magnetic fields
Let’s start with the simplest: ultraviolet (UV) radiation. UV radiation is an energetic form of light with wavelengths shorter than visible light but longer than X-rays. The ozone layer absorbs most of the ultraviolet radiation pumped out by our sun every second, but it lets through some significant wavelength ranges.
Left unprotected, exposure to UV radiation can, in mild cases, lead to blackening or an unpleasant sunburn. Prolonged exposure leads to melanoma, a potentially deadly form of skin cancer. Without our ozone layer, the sun would blast us with even higher-energy ultraviolet rays that could destroy life on Earth (and may be responsible for at least one extinction event).
Read more: A view of the solar system from a solar view
Our atmosphere and magnetic field also protect us from another aspect of the sun: its occasional angry outbursts. The sun’s powerful magnetic fields can sometimes become tangled in on themselves, building up energy until they finally snap like overstretched rubber bands. When they do, they release this trapped energy in a burst of X-rays. After this eruption, the sun sometimes ejects a patch of its own atmosphere into space, a furious storm of charged particles and crushing electromagnetic forces.
Our magnetic field deflects most of these forces, but at high enough energies the burst known as a coronal mass ejection, just roughing his way through. The most violent explosion ever which happened in 1859, just confused with telegraph wires. But this is only a small part of what the sun is really capable of.
The sun and the weather
Besides the constant shower of ultraviolet radiation and the occasional burst of even more deadly radiation, the other weapon the sun can use is weather. Slow, relentless time. The problem is that the sun slowly gets hotter and brighter as we age. To live, the sun must fuse hydrogen at its core, each reaction emitting only a tiny bit of energy. But this fusion reaction leaves behind helium.
Over hundreds of millions of years, this helium builds up in the core, getting in the way of the efficient hydrogen synthesis reactions. To compensate for this pollution and maintain a steady state, the sun must burn hydrogen at a furious rate. As the fusion rate increases, core temperatures rise. Hotter temperatures at the core mean hotter temperatures everywhere, and over time the sun slowly bloats and brightens.
When it lights up and our oceans dry up, the out-of-control feedback loop begins. The oceans will not be able to lubricate the mechanisms of plate tectonics and our crust will be fixed in place. Without plate tectonics, carbon would not be pulled from the atmosphere. It will just pile on and pile on itself, building up thick layers of atmosphere.
We will essentially become a copy of Venus. Life may cling to some miserable existence in some shadowy region, but the prospects are dim.
The red giant
But even if life can survive the bright sun, it certainly won’t survive what lies ahead. At the end of our sun’s life, too much helium will accumulate in the core. It will push hydrogen fusion into an envelope that surrounds it. As fusion shifts from the core, the sun’s entire atmosphere will swell to unprecedented proportions.
He will become our star red giant. Scientists aren’t quite sure how big the red sun will get. It’s sure to swallow Mercury and Venus whole. If the outer edges of its atmosphere reach Earth’s orbit, it will engulf our planet as well, the solid part of our home – and everything on it – dissolving into the solar plasma in a matter of minutes.
If we’re lucky, our atmosphere will blow away and our crust and mantle will melt from the intense heat. All that will be left of our planet will be be our core of iron and nickel, a ruined shell orbiting a dying star.
While that future may seem bleak, our advances in space exploration may provide us with the right resources to escape the red giant and continue life in the outer solar system.