Solutions to the Fermi Paradox

[GoSlash27]

I'm inclined to agree. The trouble with the Drake equation is that it is only as good as the estimates that feed it. I think people often vastly overestimate the number of technologically advanced species. When you consider all of the lucky breaks that we've had that have allowed us to develop to our present level of technology, it isn't unreasonable to consider ourselves to be exceedingly rare. Consider, for example, the effect that a close encounter with another star or massive extra-solar planet would have on the orbits of planets around our Sun? Yet our planet's orbit has been stable for billions of years. Then there are cosmic killers like gamma ray bursts, asteroid/comet impacts, etc. Add super volcanoes and other climate shocks to that mix and it is a wonder we've made it this far.

It stands to reason that life is fairly common given the vastness of the universe, but I don't believe that intelligent life is equally so. Maybe there's only one civilization per galaxy on average? And what are the chances that such rare civilizations exist at the same time? The scale of the universe and the time horizons over which a civilization may exist (relative to the age of the universe) would effectively bar those civilizations from ever encountering each other.

I wouldn't go quite that far. I wouldn't be surprised if there were thousands of civilizations in our galaxy right now. All in the thinner regions between spiral arms (high stellar density is unhealthy) and roughly our distance from galactic center (corotation radius).

The requirement for long term stability means there won't be many stars in the neighborhood of any civilized planet to poke at it's Oort cloud or go all supernova. And probability says that the odds are highly stacked against there being another "goldilocks" planet within radio range.

Best,

-Slashy

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Whose to say G class are the only ones with life? In fact, G type stars are pretty unstable, especially compared to K type stars, which can last dozens of billions of years.

Bill Phil,

No particular reason for picking G class stars if merely looking for "life". You could probably expand the search to Ts and still find it.

But looking for intelligent life (as we know it) would assume a goldilocks region that's far enough from the parent star to not have the candidate planet tidally locked.

Even setting aside that consideration and including red and orange dwarves, we have what... 2 potential Earth analogues within 50 LY? And both of them over 3 times Earth's mass?

There's probably life there, but complex organisms would be doubtful.

I just went with G class stars on the assumption that intelligent life is most likely to appear within a very narrow set of constraints, and since we have it here it probably requires circumstances almost identical to our own.

There's still a whole heck of a lot of candidates, but none of them are close to us.

Best,

-Slashy

[*Aqua*]

My statement is an answer, pointing out that the likelihood of is being the first is low, and the same for the last. Billions of years, is a looooooong time, anything can happen in one billion years, and there's been ~14 billion years for that to happen.

You are arguing with numbers of which nobody knows much they affect the result. We know how long the development of life took on Earth but we don't know if that's a short, normal or long time compared to other life developments on other planets.

[Bill Phil]

So? If life started a million years earlier, we could be a million years ahead. And a million is less than 1% of a billion.

[*Aqua*]

That's a spurious argument. There can't be a discussion if you answer like that.

[Newt]

The big problem here is the vast number of unknown quantities. In science we are used to looking at ourselves and our world as fairly mundane; a place that simply happened by accident and probably happened heaps of other times elsewhere. This has held true for many things, the discovery of other worlds orbiting the Sun, the understanding that the Sun is one of many stars, in one of many galaxies, the realization that other stars do also have planets, and all manner of other new ideas have furthered the mindset that Earth is not unique, and that if Earth is not unique life, and therefore intelligent life, civilization, is not unique.

That then leads us to suppose that likely there are many other people out there, wandering about the Universe.

Competing with this idea, is of course the possibility that we are more unique than we think. After all, the only reason that we have discovered life is quite possibly that we are life ourselves, and it happens to, well, be where we are. The only reason that this appears mundane is because other things look mundane, too, and that previous concepts of geo- and anthro-centrism have been by and large shot down. Thus civilization should be mundane, as everything else seems to be. But should we really decide that something is so, just because it is associated so loosely to something that was wrong?

All of these boil down to speculation, to thinking about what the Universe may be like, granted with some background, and logic, but still just speculation about very complex things. We know life arose once. At least. And the same goes for civilization. But in order to surmise whether it arose elsewhere, and in order to understand where, why, and how it can arise, we need to find whether it has arisen elsewhere. Therefore, finding more life is one of the major goals that has been cited by NASA and others pursuing space exploration today.

As for why we have not encountered it yet, if it exists elsewhere, there are myriad possible reasons, as this thread attests. We cannot answer the questions of the Universe by sitting in our armchairs, chatting and hypothesizing. We answer these questions by going out, and finding evidence. That is science.

[Nikolai]

Just to add some fuel to the fire: http://www.news.iastate.edu/news/2015/01/26/kepler444

Five planets, all small and rocky, orbiting an ancient star -- 11.2 billion years old, give or take a billion. While none of them would be comfortable for Life As We Know It, this would seem to indicate that, at least conceptually, Earthlike planets could have formed quite early in the Universe's history (as compared to Earth).

As you were, then.

[KerikBalm]

Earth-like is very vague....

How much heavy elements do they have? and by heavy, I'm not talking Carbon, I'm talking Uranium.

Earth had these:

http://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor

I very much doubt those planets did.

Without heavy elements, the core will go cold much much faster, techtonics stops, and everything will go to pot...