who here loves math?

[Stevil]

Okay, I have a problem for you lot to solve.

I want you to take the standard Drake Equation and have it produce additional outputs, rather than just the one it does at the moment. The existing output remains untouched. The additional output(s) are as follows, the average distance between the civilizations. The probability of one of those civilisations being within 10, 20, 40, 80 and 160 light years of Earth.

Please state your model of the Milkey Way i.e. diameter, thickness, star density variation etc.

sure, that's simple enough
N = star dencity* distance^3 /number that have planets /number of planets that support life / number of life planets that support intellegent life

there are roughly 400,000,000,000 stars, and the milky way is roughly 100,000 light years across, and 1,000 light years thick.
so 400 stars per light year, aproximately, is our star dencity. the rest is up for grabs.

400 stars per light year, surely not. apart from our sun, how close is the closest star to us?

[Stevil]

Oh, by the way, anyone going to have a go at my one.
he^2=she
each letter represents a single digit of a number so he is one number, not h X e  but more like h X 10 + e and she is s * 100 + h * 10 + e

This problem is not too hard and is solvable for anyone interested.

[phillip1882]

it was just a rough estimate. if you use the volume of an ellipsoid, 4/3 *pi*a*b*c, star density is closer to 95 stars per light year.
to answer your question, there are 5 stars within 5 light years of us; but there are parts of our galaxy where star density is much more.

he^2 = she.

he = 25.

[Stevil]

it was just a rough estimate. if you use the volume of an ellipsoid, 4/3 *pi*a*b*c, star density is closer to 95 stars per light year.
to answer your question, there are 5 stars within 5 light years of us; but there are parts of our galaxy where star density is much more.

he^2 = she.

he = 25.

Is it more likely that life is on the outer edge of a galaxy rather than the inner?
Other than the sun our closest star is over 4 light years away, it would be pretty bright to have 100 stars only 1 light year away. Maybe the dense parts of the galaxy cannot support life?

You got the answer to mine. Too easy huh? s = 6 btw, but you already know that.

[phillip1882]

you know now that i look at it, my calculation may be entirely wrong.
i was thinking length times depth = volume for some reason, but there's also breadth, of course!
so, my now official estimate of star density; 400,000,000,000/(4/3*pi*50000*50000*500) = .07 stars per light year^3. this seems much more reasonable. at a distance of 5 light years, this gives 125*.07 = 8.75 stars.

[Stevil]

you know now that i look at it, my calculation may be entirely wrong.
i was thinking length times depth = volume for some reason, but there's also breadth, of course!
so, my now official estimate of star density; 400,000,000,000/(4/3*pi*50000*50000*500) = .07 stars per light year^3. this seems much more reasonable. at a distance of 5 light years, this gives 125*.07 = 8.75 stars.

It's always good to validate against some real known measurements otherwise it is too easy to make mistakes or go off into wild tangents. Religious theories don't have this luxury though.

[Tank]

you know now that i look at it, my calculation may be entirely wrong.
i was thinking length times depth = volume for some reason, but there's also breadth, of course!
so, my now official estimate of star density; 400,000,000,000/(4/3*pi*50000*50000*500) = .07 stars per light year^3. this seems much more reasonable. at a distance of 5 light years, this gives 125*.07 = 8.75 stars.

Is that 8.75 stars per cubic light year?

[phillip1882]

no, that's 8.75 for every 5 cubic light years, 0.7 for every cubic light year.

[Tank]

no, that's 8.75 for every 5 cubic light years, 0.7 for every cubic light year.

??? 8.75/5=1.75 & 5/8.75=0.57 I am confused.

[phillip1882]

CUBIC light years. 8.75/5^3 = .07
that is: if you go 5 light years in any direction, you'll run into 8.75 stars.
if you go 1 light year, .07 stars.

[phillip1882]

wait, now i'm confused, should i have stated 8.75 stars for 125 cubic light years??

i think so.

[Stevil]

wait, now i'm confused, should i have stated 8.75 stars for 125 cubic light years??

i think so.

But then earth, being at the edge of the galaxy is in an unusually dense part of the galaxy?

[Tank]

wait, now i'm confused, should i have stated 8.75 stars for 125 cubic light years??

i think so.

But then earth, being at the edge of the galaxy is in an unusually dense part of the galaxy?

Dense? I would have said rarified.

[Tank]

I am falling out of love with maths 

[Stevil]

wait, now i'm confused, should i have stated 8.75 stars for 125 cubic light years??

i think so.

But then earth, being at the edge of the galaxy is in an unusually dense part of the galaxy?

Dense? I would have said rarified.

Well yes, that's the point. We have about 42 stars within about 15 light years or earth, this represents a sphere with radius 15 light years which is smaller that 30 cubic light years., this is much more dense thn 8.75 stars per 125 cubic light years. Phillip was right to suggest that 5x5x5 = 5 light years cubed rather than 125.