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ThePsion5
2008-Sep-30, 02:19 PM
Hi guys!

I'm working on a major project for my Senior year of Computer Science that attempts to (as realistically as can be done) simulate the evolution of life on a stellar scale. I'll be simulating this at a very high level, however, so I have to make some compromises on how detailed this simulation can be, specifically in how much information I can use to represent individual star systems.

This leads me to my questions - I can only use a single number between 0 and 1 to represent the chance of life evolving in a particular star system (far less detailed than I'd prefer), so I would like to know:

1. Which types of stars (Based on standard stellar classification) are most likely to yield solid planets between 0.1 and 10 Gs?

2. Which types of stars are likely to create planets whose chemical composition is similar to that of the primordial Earth?

I'd be happy to discuss my simulation in a bit more detail if anyone is interested as well. Thanks in advance!

PraedSt
2008-Sep-30, 02:54 PM
My advice:

Treat (the probability of life evolving in a star system) as a variable, rather than a parameter. Play around with it.

At the moment, we have a sample size of one. So we know its not 0; but quite frankly it could be anything, up to and including 1. Nobody knows, and anyone who says otherwise is selling something.

As a corollary, using this approach, you don't need to know the answers to your two questions. Interesting questions in their own right, but unnecessary for your model.

Good luck!

ThePsion5
2008-Sep-30, 03:26 PM
Treat (the probability of life evolving in a star system) as a variable, rather than a parameter. Play around with it.
Right - this number will just start out as a range depending on the star type and will change over time as the star ages.


At the moment, we have a sample size of one. So we know its not 0; but quite frankly it could be anything, up to and including 1. Nobody knows, and anyone who says otherwise is selling something.
Yeah, this is where I'm using the largest number of assumptions. As much as I'd like to avoid doing it, if I included all the variables I wanted to I would be doing a physics simulation of the entire universe!
I'm assuming, for the purposes of this simulation:
-Life is carbon-based
-The planet is a solid one between 0.1 and 10Gs
-The elements on the planet approximate those of primordial Earth

So what I'm looking for is what star types are most likely to form planets/planetary disks that would lead to the formation of solid planets between 0.1 and 10Gs and whose composition contains all of the elements present on primordial earth.

I'd also like to look at the presence of liquid water, but one step at a time (and liquid water could be present on a planet due to factors other than the distance to its star).

PraedSt
2008-Sep-30, 06:01 PM
Lol. You seem determined to do this the hard way :)

You've done the standard wiki research I take it?
http://en.wikipedia.org/wiki/Drake_equation
http://en.wikipedia.org/wiki/Extrasolar_planets

And an up-to-date (I think) assessment of the Drake equation from SETI: http://radio.seti.org/

From what I can gather, the rate of planet discovery has been growing exponentially since the turn of the century, i.e. the probabilities you need for your model are changing rapidly. That's either fortunate, or unfortunate, depending on your point of view :)

John Mendenhall
2008-Oct-01, 03:03 PM
Number of planets known as of Sep 2008: 322

Number known to support life: 1.

Probability of life based on this sample: 1/322.

Value of this argument, after a moment of reflection: about zero.

Check here:

http://en.wikipedia.org/wiki/Planet

The Drake equation reminds me of Beyesian statistics; too much guessing.

PraedSt
2008-Oct-01, 03:09 PM
Yeah, too much guessing.

BUT..using your numbers, it could be anything between 1/322 and 322/322, right?

I mean we don't know there ISN'T life on those 322 planets :)

John Mendenhall
2008-Oct-01, 04:56 PM
Yeah, too much guessing.

BUT..using your numbers, it could be anything between 1/322 and 322/322, right?

I mean we don't know there ISN'T life on those 322 planets :)

Right, the argument is terrible. We just don't know enough.

tdvance
2008-Oct-01, 05:04 PM
may be terrible, but still valuable in this way:

get the best (necessarily lousy) estimate you can and put that in the galactic model. Then, find out how likely it is we've been contacted by aliens based on this. Higher probabilities (given that we know of no such contacts) suggest the original probability estimate is too high. You can't actually estimate the probability this way, but can tell how likely it is to be anywhere close to reality.

Assuming the model is valid (Which it might not be--e.g. we don't know if they have a "prime directive" or not, for example, which would affect likelihood of contact).

PraedSt
2008-Oct-01, 05:15 PM
Mmm. Establish an upper bound you mean. Good point.