The Science behind the Simulation
by Anthony Francis Cernosek 11/12/2003
This simulation is based on science, plus some careful and
very conservative extrapolation. Since so much is still unknown, we've avoided
stating specific numbers (of potentially suitable worlds), but instead quoted odds
or percentages. You can work out the math as you wish.....
Biologists are convinced that all life - Earthly and alien -
will be based on complex carbon molecules and will require liquid water. Both are
abundant across our galaxy (and others), especially in the giant gas clouds that spawn stars
and planets. So the basic ingredients of life are abundant. If life is a natural process
of chemistry driven by physics, then it can begin wherever conditions are suitable,
so life might also be widespread. But this depends on many unknown factors,
especially on how many planets are suitable for life.
10% of the nearby, Sun-like stars have a planetary system.
Some astronomers believe the true percentage is 20%,
and that it applies to ALL star types in our vicinity (the "thin disk").
(The simulation assumes 10%, and all star types.) The percentage may
be lower for distant regions of our galaxy (the "thick disk" and the "halo"),
but remember that our galaxy contains
200 to 600 billion stars. ( The current trend is toward the higher end of this range.)
So it's easy to imagine billions of planetary systems.
Carl Sagan was right! He just couldn't prove it.
No one knows how many individual planets (or large moons) inhabit a typical
planetary system. It's impossible (with today's equipment) to detect
bodies much smaller than Saturn ( 95 times the mass of Earth), and the bodies
that astromomers can detect can't be seen. In this simulation, we've guessed that a typical
system has 4 sizable bodies, although our own Solar System holds 9 planets and 7 large moons. (We're being very conservative, but you can override this in the simulation).
Regardless of your choice, it easy to visualize tens of billions of individual
planets, orbiting a variety of stars.
This simulation randomly (but realistically, based on science)
assigns the following values to the "parent star" that your selected
planet orbits:
* star type and luminosity
* star lifetime
* star (and planet) age
* distance in light years
10 of the 16 largest bodies in our Solar System may have liquid water,
but there's no conclusive proof. Candidates include the planet Mars ( possible sub-surface water), the gas giants Jupiter, Saturn, Uranus, and Neptune (likely abundant atmospheric water), and some of their icy moons - Europa, Gannymede, Callisto, Titan ( water under an icy crust), and of
course Earth ( water on the surface). In theory, all 10 bodies might somehow support
life, but in the simulation we focus only on the "roughly Earth-sized" worlds.
How many distant worlds may have liquid water?
We believe the answer is "about 1%". To find out why, see.....
"The Earthlike planetary zones"
Start simulation now !
© 2003 by Anthony Francis Cernosek