Daisyworld

Posted on May 4, 2011 | 3 minute read

I’ve been reading about the Gaia Hypothesis, developed by James Lovelock. I’m sure I don’t understand it all yet as I’ve only been skimming the surface, but what I’m finding especially interesting right now is Daisyworld.

Daisyworld is a computer simulation of a planet orbiting around a star much like our Sun. The planet hosts two life forms, both being a type of daisy. It has white daisies, which reflect light and black daisies, which absorb light. But wait, there’s more!

We start off with a cold Daisyworld, too cold to support either type of daisy. As the sun starts to give off more and more heat, the temperature on Daisyworld becomes sufficient enough for black daisies to grow. Black daisies are able to absorb more light than white daisies and keep themselves warmer in colder temperatuers than white daisies. so the black daisies spread over the entire planet, each one absorbing the sun’s energy and as a result the large number of black daisies increase the surface temperature of Daisyworld.

However as it gets warmer on Daisyworld the black daisies are feeling a bit too hot for comfort and the temperature now becomes ideal for white daisies. White daisies reflect light so can tolerate hotter temperatures better than black daisies can. As a result the white daisies start to thrive and eventually the black daisies and the white daisies reach a point balance and equilibrium. There are enough black daisies to warm the planet and enough white daisies to keep it from getting too hot. Together the two types of daisies regulate Daisyworld’s surface temperature, making it perfectly habitable for both.

However, the sun’s rays continue to increase in power. As white daisies better reflect light they are able to survive in the hotter weather as the black daisies begin to wilt. As the black daisies die out white daisies spread across Daisyworld, helping to keep the planet’s temperature cooler and live comfortably.

But the sun doesn’t just stop there, either and now even the white daisies can’t cope with the sun’s rays. The lone white daisies begin to die out and eventually you’re left with a daisy-less world, completely barren of life. The simulation then has the sun’s temperature decline until white daisies grow again and help to cool the hot planet further, which presumably allows the black daisies to start growing at some point as well.

This is what happened in Lovelock’s original Daisyworld simulation. But Lovelock went further. In a podcast I listened to a while back, he said that he started putting rabbits into Daisyworld, and eventually (from memory) other animals as well. And the model worked with them as well! It was shown that biodiversity is a good thing that helps to regulate the planet’s climate to make it habitable to all species.

Of course Earth is much more complex than Daisyworld, but it’s a very interesting model on a simpler scale. Perhaps it can be scaled up to our own planet’s complexity?




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