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13.7: Cosmos And Culture
Wed March 21, 2012
Creatures Of The Sun
Originally published on Wed March 21, 2012 11:24 am
Maybe it's the amazingly warm week we are having here in northern New England, but it's hard not to think about the sun these days. Even as we soak up its warmth, we also hear of fearsome solar storms flinging billions of tons of plasma into space, some of it toward us.
These coronal mass ejections tend to peak around the so-called solar maximum, a time of increased solar activity with a period of approximately 11 years. We are entering one.
Our typically naïve picture of the sun as a placid ball of fire in the sky has nothing to do with the real thing.
Close-up images reveal an inferno of intense heat (some 11,000 degrees Fahrenheit at the surface), bubbling with incessant activity and intense magnetic fields.
Solar storms are a reminder that we shouldn't take the sun for granted, assuming it will always be doing its job quietly, even if this has been the case for billions of years.
The sun radiates 4 X 1026 watts, that is, 4 followed by 26 zeros watts, equivalent to 100 billion 1-megaton nuclear bombs. Compare this to your living room light bulb, at 60 Watts. All this power comes from nuclear reactions happening at the solar core, fusing hydrogen into helium at a furious rate. The sun, now in its middle age, is in its main sequence phase, which, fortunately for us, is fairly stable. No one should start having nightmares that we will be fried tomorrow.
At its present age, the sun has converted only about 5 percent of its total mass into helium. As this amount increases, so will the Sun's luminosity, that is, its total power output. In 1.1 billion years, the luminosity will be 10 percent larger than today, and in 3.4 billion years, 40 percent larger. This extra power will have serious consequences for Earth's climate. First it will create a "moist greenhouse" effect, then a true "runaway greenhouse" effect. In the end, we won't be able to take the heat.
Given that life was impossible for the first billion or so years of Earth's 4.5 billion-year existence — due to a steady bombardment from comets and asteroids — it follows that life can only exist within a window of the sun's lifetime, roughly 5 billion of its 10 billion years.
That's a humbling thought. Every species that ever lived, and ever will live, is a passing phenomenon.
Being an optimist, I am confident that, after having halted the most devastating effects of anthropogenic global warming (those still reversible, that is), we will, lessons learned, find a new home for our species, together with the others we manage to preserve until then. Sci-fi style, we may embark in a space version of Noah's Ark, sailing through interstellar space in search of better shores.