h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Good job here. All your stuff is first rate. Where do you find the time? Thanks!

Cheers...
I don't really have the time! As I was telling Festival earlier, I have stopped believing in time as a series of events and I now prefer to see it as a string of network connections!

Yes but none of the bits of string I've found go all the way around.

Sounds like your 'looking for string in all the wrong places!'

Yep, well done (du from Community forum?).

I make it 2000! All defaults except fl (100%, of course )

Cheers
2000 intelligent civillizations sounds good to me....

Damn you. Back soon with (drum roll) "The Hudson equation" ( ) - How many should we have reached? / How long 'till we reach one?

Sounds Good!

Can Javascript do cube roots?

Here you go...

http://www.h2g2.com/P200223

The first (probability) calc. assumes that we've been transmitting radio waves for 100 years.

The second, transposes the equation to find what radius our radio event horizon would have to be to make the probability = 1.

I've also got a hacked version of your Drake page which includes this at the bottom. It doesn't let you change the stellar density, but picks up N* and N from the existing form.

Tell you what, I'll include it here...




function Calc(obj)
{
var N_star = obj.N_star.options[obj.N_star.options.selectedIndex].value;
var fp = obj.fp.options[obj.fp.options.selectedIndex].value;
var ne = obj.ne.options[obj.ne.options.selectedIndex].value;
var fl = obj.fl.options[obj.fl.options.selectedIndex].value;
var fi = obj.fi.options[obj.fi.options.selectedIndex].value;
var fc = obj.fc.options[obj.fc.options.selectedIndex].value;
var fLife = obj.fLife.options[obj.fLife.options.selectedIndex].value;
var N;

var Density = 0.120; // Galactic star density (stars / cubic parsec)
var ERly = 100; // Radio event horizon in light years
// (This should be = no. years since major
// radio broadcasting began)
var ERp = ERly/ 3.26; // Radio event horizon in parsecs

var P; // Prob. that we've already been heard
var Tfc; // Est. years to first contact

N = N_star * fp * ne * fl * fi * fc * fLife;
obj.N.value = N;

P = (4 * Density * Math.PI * Math.pow(ERp, 3) * N) / (3 * N_star);

Tfc = 3.26 * Math.pow(((3 * N_star) / (4 * Density * Math.PI * N)),0.333333333);

obj.P.value = P;
obj.Tfc.value = Tfc;
}




N* = the number of stars in the Milky Way galaxy:
1 billion
10 billion
100 billion
200 billion
300 billion
400 billion
500 billion
600 billion
fp = fraction of stars with planets around them:

.0001%
(1 of 1,000,000) .001% (1 of 100,000) .01%
(1 of 10,000) .05% (1 of 2,000) .1%
(1 of 1,000) .5% 1% 2% 5% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
ne = number of planets per star ecologically able
to sustain life: .33 .5 .67 1 1.5 2 3 4
fl = fraction of those planets where life actually
evolves: .0001% (1 of 1,000,000) .001%
(1 of 100,000) .01% (1 of 10,000) .05%
(1 of 2,000) .1% (1 of 1,000) .5% 1% 2% 5% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
fi = the fraction of fl that evolves intelligent
life: .0001% (1 of 1,000,000) .001%
(1 of 100,000) .01% (1 of 10,000) .05%
(1 of 2,000) .1% (1 of 1,000) .5% 1% 2% 5% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
fc = the fraction of fi that communicates: .0001%
(1 of 1,000,000) .001% (1 of 100,000) .01%
(1 of 10,000) .05% (1 of 2,000) .1%
(1 of 1,000) .5% 1% 2% 5% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
fL = the fraction of the planet's life during which
the communicating civilizations survives: 1
/ 1,000,000,000th (10 years) 1 / 100,000,000th
(100 years) 1 / 10,000,000th (1,000 years) 1
/ 1,000,000th (10,000 years) 1 / 100,000th
(100,000 years) 1 / 10,000th (1,000,000 years) 1
/ 1,000th (10,000,000 years) 1% (100 million years) 10%
(1 billion years) 20% (2 billion years) 30%
(3 billion years) 40% (4 billion years) 50%
(5 billion years) 100%



N = the number of communicating civilizations in the galaxy


Hudson's Equation

Probablility that we have been heard
Estimated time until first contact (years)

I'll just call.

What did you think?

Very Good!
I will make a link to it!

Thanks I've tweeked the text a bit.

How'd you decide on the defaults? What are they based on?

Hello Si, long time no hear!

> How'd you decide on the defaults? What are they based on?

They're educated (or as near as I could muster) guesses on my part. I you dig around, though, you can find best estimates for most if not all of the variables. Onre interesting thing I found was that, if you mess around with different values, they don't have as dramatic an effect as you might think.

> Hello Si, long time no hear!

For that past few weeks Oi bin mainly unemployed and very busy. Odd that, but H2G2 has had to take a back seat for a while.

Interesting new news: Looking good for a new job in the new year (software dept. of http://www.cadar.co.uk ) and my mate Jonny.vb asked me to co-author a book! Very cool. This time next year, Rodders, I'll be a millionaire.