Help us calculate the likelihood an intelligent alien species exists!

[TomVassos]

TL;DR Summary

Hello everyone, I need some statistics help. Making various assumptions about how many intelligent alien species have existed and how long they last, we are trying to calculate the likelihood that any of them exist right now, or possibly existed at the same time as homo sapiens.

Hello everyone, I need some statistics help relating to one aspect of the Fermi Paradox.

The Universe is a very big place and even if there are millions of other alien civilizations out there, they are likely so far away from us that we will never ever meet them.

But another factor that will make it unlikely to meet any aliens is that different alien species might spring up and die off, anytime across the entire span of our Universe... 13.8 billion years.

The questions in this paradox focus on "intelligent" aliens that can either communicate at the speed of light (e.g., radio communications, etc.) or can build spaceships to visit other worlds. We have arbitrarily defined "intelligent" in this way because unless they have done one of these two things, it's unlikely that we would ever meet the aliens.

In the case of humans, light-speed communications has only been around for 130 years. If we shrink the entire 13.8 billion year history of the universe down to one Earth-year, that means we have been "intelligent" for only 1/4 of a second. And if intelligent aliens have been popping in and out of existence throughout that 13.8 billion years, it appears to be unlikely that other aliens civilizations are around at the exact same time that we are here.

Let's make some assumptions: one million intelligent alien species have existed (either in the entire Universe or just the Milky Way Galaxy). We also need to guess how long alien species last. Maybe they will be wiped out by nuclear wars, global warming, meteorite strikes, solar flares, pandemics, etc. Let's assume they each last one million years at an “intelligent” level. This works out to only 0.0000725 percent of the 13.8 billion year life of the Universe. And let’s assume that these species randomly popped up and died off at any time.

(As well, the unlikelihood of them being in existence at the same time as us, multiplied by them needing to be in our neighbourhood of a Universe that is 92 billion light-years across, pretty much has to add up to close to zero no matter what assumptions we make.)

But let’s just focus on the “timing” aspect of this paradox. Statistically, how many advanced aliens exist right now, if there was a million of them, a billion of them?

PART B

Next, let's consider the likelihood that they existed any time in the last 300,000 years since homo sapiens/humans have been around. (Maybe they really did visit and help us build the pyramids... :) :) )

300,000 years is .0000217 percent the age of the entire Universe. How many advanced aliens existed at any time during that 300,000 years, if there was a million of them? a billion of them? (Let's keep the same assumption that each intelligent species lasts one million years, or 0.0000725 percent of the 13.8 billion year life of the Universe.)

Thanks in advance for you help… :)

Tom Vassos
Founder, CosmologistsWithoutBorders.org

 

[sbrothy]

A probabilistic analysis of the Fermi paradox in terms of the Drake formula: the role of the L factor

Also, this thread.

 

[sbrothy]

[...] (As well, the unlikelihood of them being in existence at the same time as us, [...]

I think this was what Arthur C. Clarke addressed as the "Apes or Angels" problem. Try visiting this page.

 

[TomVassos]

Thanks so much for the pointers... I love the Apes or Angels quote... :)

Tom

 

[jedishrfu]

This is an unanswerable question. Your guesses are as good as anyone.

Since folks have pointed you to the Drake equation, you are following the same path. The wiki article covers a lot of variants and reasons why the equation is problematic.

https://en.wikipedia.org/wiki/Drake_equation

Criticism​

[edit]
Criticism of the Drake equation is varied. Firstly, many of the terms in the equation are largely or entirely based on conjecture.[81][82] Star formation rates are well-known, and the incidence of planets has a sound theoretical and observational basis, but the other terms in the equation become very speculative. The uncertainties revolve around the present day understanding of the evolution of life, intelligence, and civilization, not physics. No statistical estimates are possible for some of the parameters, where only one example is known. The net result is that the equation cannot be used to draw firm conclusions of any kind, and the resulting margin of error is huge, far beyond what some consider acceptable or meaningful.[83][84]

Others point out that the equation was formulated before our understanding of the universe had matured. Astrophysicist Ethan Siegel, said:

The Drake equation, when it was put forth, made an assumption about the Universe that we now know is untrue: It assumed that the Universe was eternal and static in time. As we learned only a few years after Frank Drake first proposed his equation, the Universe doesn’t exist in a steady state, where it’s unchanging in time, but rather has evolved from a hot, dense, energetic, and rapidly expanding state: a hot Big Bang that occurred over a finite duration in our cosmic past.[85]

One reply to such criticisms[86] is that even though the Drake equation currently involves speculation about unmeasured parameters, it was intended as a way to stimulate dialogue on these topics. Then the focus becomes how to proceed experimentally. Indeed, Drake originally formulated the equation merely as an agenda for discussion at the Green Bank conference.[87]

It's an excellent time to close this thread and thank everyone for contributing here.

Jedi