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Playing with the Drake Equation


JohnF
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I've been playing with the Drake equation by applying it to each individual star and only progressing the equation to the next stage if the previous stage allowed for it. My reason for doing this is to see what difference it makes when each star is treated as an individual that doesn't know that the intelligent communicating life quota has allready been met.

 

I ran the program a number of times for each set of values and each number of years to get a minimum, maximum and average. In fact the first values at 10000 years quite often produced a result of no civilisations but I restricted the minimum to one since we know there is at least that many.

 

I used the following values from Wikipedia as supposedly being the current best estimates

http://en.wikipedia.org/wiki/Drake_equation#Current_estimates_of_the_parameters

 

R = 6 (New stars per year)

Fp = 50% (Stars with planets)

Ne = 2 (Planets that can sustain life)

Fl = 33% (Planets where life evolves)

Fi = 0.1% (Planets where evolved life is intelligent)

Fc = 0.1% (Planets where intelligent life can communicate)

L = 10000 (Longevity of communcating civilisations)

 

Over 100000 years: 4 to 7 civilisations (Average 5.5 - 64%)

Over 50000 years: 2 to 6 civilistaions (Average 4 - 50%)

Over 10000 years: 1 to 5 civilisations (Average 3 - 33%)

Drake Equation: 2 civilisations

 

 

Also, using the default values I found at http://www.activemind.com/Mysterious/Topics/SETI/drake_equation.html who are clearly more optimistic

 

R = 6 (New stars per year)

Fp = 50% (Stars with planets)

Ne = 1 (Planets that can sustain life)

Fl = 50% (Planets where life evolves)

Fi = 20% (Planets where evolved life is intelligent)

Fc = 20% (Planets where intelligent life can communicate)

L = 10000 (Longevity of communcating civilisations)

 

Over 100000 years: 646 to 675 civilisations (Average 660.5 - 9%)

Over 50000 years: 631 to 675 civilisations (Average 653 - 8%)

Over 10000 years: 559 to 643 civilisations (Average 601 - 0%)

Drake Equation: 600 civilisations

 

What is interesting is that the more optimistic values are more consistent regardless of how they are used.

And if the Wikipedia values are more accurate then according to Drake there is only one other civilisation since we must be the other.

 

If you know of any other values that are considered to be more accurate please post a link to them.

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I read in a couple of places that practically half of all stars that pop in and out of existence are halves of binary systems, pretty much ruling them out. Then you have to figure in the percentage of stars that live long enough to produce life, ie. anything over such a size will not live long enough.

 

Until we get a bigger grasp on the actual mechanics of the evolution of abiogenesis, my numbers on that value are also much more skeptical. From my perspective, some really chancy things have to happen to make the jump from nucleic acid to functioning protocell. It seems pretty hard to just assign some arbitrary number, and that's after you have already filtered out the numerous toxic combinations that a planet could wind up with, not to mention other things, such as distance from the star, etc.

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I read in a couple of places that practically half of all stars that pop in and out of existence are halves of binary systems, pretty much ruling them out.

 

Until we get a bigger grasp on the actual mechanics of the evolution of abiogenesis, my numbers on that value are much more skeptical.

 

I'll quote my stars lecturer from this morning.

 

"Our sun is an exception in being a single start and not part of a binary."

 

It's really rather unusual...

 

I always think that L = 10000 is far too high!

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I always think that L = 10000 is far too high!

 

I thought L was too high as well. I wonder though if a civilisation were to collapse then perhaps the knowledge it had acquired would, in the most part, be retained and allow a communicating civilisation to develop quicker. There may be down times in the 10000 years but they may be quite short.

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I thought L was too high as well. I wonder though if a civilisation were to collapse then perhaps the knowledge it had acquired would, in the most part, be retained and allow a communicating civilisation to develop quicker. There may be down times in the 10000 years but they may be quite short.

 

The thing you must also remember is that we've been sending our lots of EM radiation for about 100 years now, how long before we switch to far more directional stuff, fibre optics are already taking over alot of satalitte traffic...

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The thing you must also remember is that we've been sending our lots of EM radiation for about 100 years now, how long before we switch to far more directional stuff, fibre optics are already taking over alot of satalitte traffic...

 

I agree with you there. I would think there's a relatively short period during which general radio noise is being emitted by a civilisation. I see the Drake equation as just an attempt to determine how many technology based civilisations there may be out there.

 

Regarding the Drake equation though, I wonder if an additional parameter may be required.

 

The value L = 10000 being the longevity of a civilisation seems to imply a dead end for a civilisation.

 

It occurred to me that since the preceding requirements had been met, star has planets, planets can support life, intelligent life evolves and civilisation develops technology, then just having the civilisation removed from the count after 10000 years is not good.

 

I would assume that if a civilisation does fall after 10000 years then the planet can still support life and intelligent life is probably still present.

 

I have then assumed, for this exercise, that it would take 1000 years for the intelligent life to have technology again and put it back in the count.

 

Doing this I've found that where the Wiki values provide for 2 civilisations, if I add this new parameter I get the following results...

 

For 500000 years = 4 to 7 Average 4.5 others (with new parameter 90 to 107)

For 200000 years = 4 to 7 Average 4.5 others (with new parameter 40 to 53)

For 100000 years = 4 to 7 Average 4.5 others (with new parameter 12 to 31)

For 50000 years = 2 to 6 Average 3 others (with new parameter 5 to 13)

 

As you can see from the above the older the galaxy, and so the more stars there are, you also find a continued increase in the number of communicating civilisations when using the new parameter. Without it though the numbers remain relatively constant.

 

What do you think? Is the new parameter a valid addition? What would you suggest as a good value for it?

 

Perhaps I need to re-use the Fi and Fc values to determine if intelligent life re-emerges again and then goes on to develop technology rather than assuming it would after a set time period has elapsed.

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I think that the length of time an intelligent species remains technologically advanced would be indefinitely high. Even if there were a cataclysmic event that destroyed their civilisation, bits of knowledge would remain and would provide a tremendous advantage to those who possessed them. Intelligent, technologically advanced species are far likelier to avoid extinction due to natural disasters, as they would be able to work as a whole to avoid, prevent, mitigate, adapt such disasters. Though it is conceivable that they destroy themselves, I don't think that would be likely.

 

As to the Drake equation itself, it is an obvious equation but the constants are at best educated guesses.

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  • 2 weeks later...

As to the Drake equation itself, it is an obvious equation but the constants are at best educated guesses.

 

Right, I mean, for some of constants, there's just no way of knowing.

What I don't get about it, is that shouldn't there be more constants to it, how do we know that those are all of the factors, maybe there are more that we don't know about

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