Gaia hypothesis: the planet interacts with life itself, to keep the planet fit for life.
Albedo: how well something reflects light. Albedo 1 (100%) is a perfect reflector, pure white. Albedo 0 is a perfect absorber, pure black.
Luminosity: amount of light striking a unit area.
DaisyWorld was invented by James Lovelock and Andrew Watson, to explain how the Gaia Hypothesis did not require a sentient Earth, but only feedback loops. Life itself could maintain the planet fit for life - within limits. Which is a cool result. But it means little without a simulator.
Click here to run the simulator.
Like all environmental models, DaisyWorld is a cartoon of the world. In this cartoon, we have daisies and barren land. The sun shines on the world, and some light turns into heat, the rest reflected into space. How much light is absorbed – and how warm the planet is – depends on the color of the planet.
Daisies need certain temperatures to live. And they come in a variety of colors. Basic DaisyWorld has white and black. White reflects most light, and black absorbs it. Barren land falls in between. This ability of a color to reflect light is called albedo.
Sunlight reflects off different color daisies.
Black daisies absorb most light,
turning it into heat.
White daisies reflect most light, and stay cooler.
Ghost-like daisies
represent barren ground.
Daisies aren't perfect. White daisy albedo is 75%, black 25%, and barren ground 50%.
Like all life, daisies die. At least 30% of the land is barren as daisies die, giving up their space that more daisies – of whatever color – may be born.
The minimum temperature for daisies is 5°C. The maximum is 40°C. Above or below that range, the daisy birthrate is zero, and the world is barren. The daisy birthrate is highest at their ideal temperature of 22.5°C. (Fahrenheit 41°F to 104°F livable, ideal 73°F.)
By the mix of white and black daisies and barren ground, DaisyWorld strives to keep its temperature in the livable range.
Over billions of years, the sun changes, and grows brighter. We call this solar input luminosity. The luminosity of "now" is assigned a value of 1.0.
DaisyWorld runs over time - theoretically billions of years - showing how the mix of daisies changes as luminosity grows. At first, the weak incoming light can't warm the planet enough for daisies. Then black daisies begin to survive, and the planet warms. In fact, it warms to the ideal temperature for daisies to thrive. And with nothing but mix of daisies, it keeps the temperature close to ideal over a wide range of luminosity.
This ability of DaisyWorld to maintain the daisy-preferred temperature, is shown on the plots:
DaisyWorld with black and white daisies.
Notice how the daisy mix keeps the planet temperature near the daisy ideal temperature.
The planet cools as luminosity increases. Without daisies, the temperature
rises with luminosity (brown line, bottom plot).
The DaisyBall simulator gives a choice of logic – DaisyWorld classic, and my own custom variant DaisyBall. In DaisyWorld, there is no sense of location. The "neighborhood" of a daisy is simply same-colored flowers.
DaisyWorld display.
In DaisyBall mode, each daisy plot has latitude and longitude. The DaisyWorld game plays out at each location. Each drawn daisy represents the multicolor daisy population at that location. Like Earth, the world is tilted. The poles get less light than the tropics or temperate zone.
DaisyBall display near luminosity 1. The world is pretty equally divided, 30% barren and
35% each black and white. Barren isn't drawn unless a spot is low on living daisies.
Notice how the tropics are white, polar region black, and the
temperate zone mixed. The north pole
daisy has 5 petals.
In both models, you can play with different daisy color scenarios. Even a single daisy color (black or white) can control the planet temperature for a while.
More help files, if you want to delve deeper:
