Hello, SFIA audio listeners. In this month's Nebula exclusive, big alien theory,

we're asking the reason alien civilizations might be rare is because most aliens are huge.

To hear it and every episode early and ad-free, plus hours of bonus content,

check out go.nebola.tv slash Isaac Arthur and use my code, Isaac Arthur.

The sun gives us life, but one bad day it could take it all away.

So what could we do to defend ourselves?

We owe everything to the sun, every green leaf, every gust of wind, every watt of power, and every breath we take is, in one way or another,

a gift from that glowing sphere, almost a hundred million miles away.

But our star isn't always benevolent.

Sometimes it lashes out, and when it does, both can find itself in the crosshairs, not of a laser

or a death ray, but something more chaotic, massive bursts of radiation, magnetic storms,

and roiling waves of superheated plasma. Today we are exploring solar flares and coronal

mass ejections, how they work, how dangerous

they really are, and what kinds of planetary skilled defenses we might one day build to shield

ourselves, because when your greatest source of life is also a potential existential threat,

it pays to be prepared.

What are solar flares and CMEs?

All life on Earth depends on the Sun, but we only receive a trickle of its power, less than a billionth,

which is why we spend a lot of time on this show talking about Dyson swarms and massive solar power arrays.

You probably only know that it generates all that power by fusion reactions in its core,

burning through around 600 million tons of hydrogen every second, converting into helium,

neutrinos, and radiation that gets absorbed as heat. That heat bubbles up and keeps the upper layers of the sun so hot, they glow in the near-infrared and visible range, and even a little ultraviolet, and this is not a smooth process.

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