In the video, she says "even if 0.1% of habitable planets have life, you would expect over a million planets with some form of life."
Where do we get this 0.1%? why it is not 10^-20% and probability of life in the galaxy is impossibly small?
Where do we get this 0.1%? why it is not 10^-20% and probability of life in the galaxy is impossibly small?
Maybe they take the earth as an example, the life existing under very harsh conditions and deduce that it should be a good probability given enough time. But I am skeptical of this.
Try a calculator [1] and puch in your pessimistic and see what chances you actually get. It is really hard to get 10^20 without just getting 0, and we know the chances are higher than 0.
1 - http://www.bbc.com/future/story/20120821-how-many-alien-worl...
Anyway, Here is a simple description I snagged from google search [1]:
> The Drake Equation is: > N = R * fp * ne * fl * fi * fc * L > > where: > N = The number of broadcasting civilizations. > R = Average rate of formation of suitable stars (stars/year) in the Milky Way galaxy > fp = Fraction of stars that form planets > ne = Average number of habitable planets per star > fl = Fraction of habitable planets (ne) where life emerges > fi = Fraction of habitable planets with life where intelligent evolves > fc = Fraction of planets with intelligent life capable of interstellar communication > L = Years a civilization remains detectable
Now grab a pen and cocktail and make the math do whatever you want. I think that is you stick to realistic numbers you will get reasonably high values. But we might just disagree there.
[1] http://www.astrodigital.org/astronomy/drake_equation.html
> One reply to such criticisms 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.
This is the same problem that has the Drake equation: we don't have a good estimation of most of the factors. https://en.wikipedia.org/wiki/Drake_equation#Criticism
Remember too, an earth-like planet can have lots of organic chemicals floating around, and you only have to hit the right combination once over millions of years to end up with life.
it might still be possible "given enough time".
You have to keep in mind that, on earth, today, life cannot just exist. It must compete successfully with other very complex lifeforms. This effectively imposes a minimum complexity level that any lifeform must attain to survive in the current environment. But, conceptually, there are many things that would count as life even though they have zero hope to exist on earth (outside of labs). Such simple lifeforms today can only exist in places like the clouds of Venus.
It took 4 billion years after that and several mass extinction events for a species to evolve that can send radio signals (and so far only briefly ), so even on an astronomical scale we might be rare.
Thus one could posit that technological civilizations, requiring both a planet in the habitable zone of a star and also an appropriately large satellite companion, could be even less probable. It would be interesting to know how probable similar earth/moon systems are in the universe.