Green Comet

Credit Steinhöfel-ESO – CC-BY – Depicting the evolution of a main sequence star – tap for large image

Evolution: A gradual process in which something changes into a different and usually more complex or better form. The Free Dictionary, definition 1(a).

Some years ago I published a series of articles about evolution in my local newspaper. It generated some interest and a spate of letters to the editor, and my publisher liked it. There was even a creationist who challenged me to a debate over it. I decided to reproduce it here. This is part one, which I called Evolving in Spite of Us. See also Part Two and Part Three.

When we think of evolution we usually think of life. It seems natural to think of Darwin’s “origin of species” as being what evolution is all about. After all, that’s what people are usually talking about when they talk about evolution. It’s good to remember, though, that not only life evolves. Pretty well anything you can think of is changing over time. Everything is in the process of transforming from one state to another. Since that’s practically the definition of evolution, it’s safe to say that everything is evolving.

For example, the interior of our planet Earth is gradually cooling over the eons. That means that there is less heat energy to drive the movement of the crustal plates, and therefore continental drift will gradually slow down. Eventually, if given enough time, Earth would cool enough to set and the continents would never move again. Fewer earthquakes. Fewer volcanoes. Less mixing of the various parts of the biosphere. The Earth is evolving.

Our Sun is also evolving. It’s much hotter now than it was when it was young. It’s been slowly heating up in the four-and-a-half billion years since it was born. If it follows the course of other stars of similar mass and composition, and there’s no reason why it shouldn’t, in another four or five billion years it will be a red giant. This will likely happen before the Earth can cool down enough to set. By that time it will have burned Earth to a crisp, possibly even growing large enough to engulf it. Life on Earth has been adapting to the Sun’s increasing output, even to the point of actively adjusting the atmosphere to keep it in the right temperature range. Nothing is likely to compensate for being engulfed, though.

Even the universe as a whole is evolving. We can tell that it’s expanding, which implies that it used to be smaller. We know that the universe was different in the past, to the point where there were no galaxies or stars at all. In the past it was very small and very hot. After about 14 billion years of expansion it exists in a state which supports life. Unfortunately, the rate of expansion is increasing. If nothing happens to change things, the universe is going to grow increasingly cold and dark. Eventually it will no longer support life.

We may continually come back to life when we think of evolution, but evolution goes on regardless of life.

rjb

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