The Sun’s impact on the Earth is undoubtedly important. Not only do we depend on the Sun for heat, but this heat can also be our destruction. And, even though the creation of the Sun also meant the creation of the planets, the death of the Sun may also mean the death of the planets, as well.
We can think of the Sun as middle-aged. It is a main sequence star, which means that it is still burning hydrogen (or converting hydrogen into helium) for “fuel.” This is how the Sun is still quite luminous. We never really think about how big the Sun is on a daily basis, but it is massive. And, once it passes the main sequence stage of its life, it will grow up to 100 times its current size. Right now, the Sun may get no bigger than a half dollar. But, in the next several billion years, it can expand so much that it will grace the whole sky.
Currently, we receive about 1300 Watts of useable light from the Sun per square meter. This is just enough (not too hot, not too cold) for most plants to thrive. Much of the Earth’s surface away from the equator will get less than 1300 Watts, but the equator will get that approximate amount. However much sunlight we get, though, we must think that right now we are getting a sufficient amount that sustains life as we know it.
Once the Sun ends its main sequence stage of life, this amount of light will dramatically increase. We look to Mars to the way the Earth may look in 7 billion years (or even less). The Earth right now has air, a protective atmosphere, and water. All of these will disappear once the Sun gets to its massive, red giant stage.
The fates of Mercury and Venus are sealed. They will be “eaten up” as the Sun gets larger. The Earth and Mars may also follow. The larger planets’ (so-called Jovian or outer planets) gas exteriors will be blown away only to reveal their rocky cores. The Solar System in 7 billion years will appear only to include a large red Sun and a few asteroid-looking objects.
Whoever or whatever occupies the Earth in those last moments will have to face making some grave choices. But, as we live today, we can only look at the Sun and wonder why it must destroy what it has created. In essence, it is easy to understand why ancient peoples chose to worship the Sun. It is both a source of comfort and life, but also a symbol of fire and destruction. At any rate, we should enjoy our planet and our Solar System now.