Daisyworld

Daisyworld is a computer simulation of a hypothetical planet, which orbits a Sun-like star, the radiation power and thus temperature as the sun in the course of billions rises slowly, yet the average global temperature of the planet over a long period of time because of self-organizing biological feedback processes remains approximately constant. James Lovelock and Andrew Watson published this model in 1983 to underpin the plausibility of the Gaia hypothesis, which postulates a self-regulation of various environmental parameters of a bustling planet through life itself.

The Daisyworld model

In the computer simulation Daisyworld there on a simulated terrestrial planets only two types of creatures: black Daisys ( daisies ) and white daisys. White Daisy have white flowers, reflect light, and black Daisys have black flowers which absorb light. Both types have the same growth curve ( has their reproduction rate is the same depending on the temperature), but are black Daisys, due to their black flowers warmer than white daisys and bare earth. A planet with a preponderance of white Daisy is cooler than one with more black.

At the beginning of the simulation the planet Daisyworld is so cold that only a few black Daisys and almost no white daisys can survive. Every time the temperature falls, the black flowers begin to dominate. These absorb the heat of the sun, which in turn leads to that the temperature of the planetary increases. This in turn leads to a better growth of the black and Daisy this to further increase in temperature. With the warming of the planet is now better able to multiply and white daisys, which have a better growth rate due to their lower temperature than the now already lying about their optimum black Daisys and hotter. The planet reached temperature equilibrium. Each heating leads to a larger number of white daisys, each cooling to more black Daisys. Such a system is remarkably stable to changing radiation power of the sun. The entire planet regulates itself at a certain point, however, exceeds the external radiation power regulation forces by the competing Daisy and the planet is overwhelmed by heat.

If the simulation is run without the Daisys, the temperature profile rises in synchronism with the radiation power of the sun. Daisy with there at the beginning of the simulation, increased heating and forced air cooling to the end, resulting in an almost constant equilibrium temperature during the greater part of the simulation. In this way, the Daisy's change the climate so that the conditions for it to be more livable. However, the Daisyworld model for certain solar constant also shows hysteresis, so that the planet has two different stable states for these solar constant: Typically, each of the inhabited an abiotic and the other almost 100 %.

Later extensions of the Daisyworld model included so-called rabbits, foxes and other species with one, which have absorption rates between white and black Daisys. One of the more surprising results of these simulations was that the greater was the number of species, the greater the self-regulating forces of the entire planet. This supported the view that biodiversity is valuable, and sparked the modern biodiversity debate from.

Daisyworld also attracted a number of criticism. It has little resemblance to the earth; The system requires an ad - hoc death rate ( γ ) in order to remain in balance and the model, the differences between blurs phenomena at the level of species and that of the individuals. However, Daisyworld is undeniable that biologically regulated balance requires no teleological explanation.

Curiosities

A version of the Daisyworld simulation was implemented in the computer game SimEarth by Maxis.