NASA 'alien life' announcement leaked

It's a proof-of-concept for radical new ideas of where/how life can form.

For instance, Titan has a thick atmosphere and lakes of liquid ethane/methane. If Arsenic-based life exists, could there be Methane-based life in those depths?

... and likely accurate assumptions, if the last 100 years is anything to go on.

That's the Great Filter, right there. Something which goes around killing off technological species, or something inherent to their development which prevents them from causing lasting change in the universe.

Of course. As there are in any other speculation about finding live ETs. We don't have a good model.

By analogy, if you could drop a modern human explorer on Earth at a uniformly selected random time in its history up 'till now, at a random spot it would almost always be uninhabitable.

http://www.antipope.org/charlie/blog-static/2009/10/how-habi...

Time is really, really long, and we're biased not to recognize that, especially when it opposes our "space is big" arguments.

I might be underestimating the sensitivity of our instruments, but if we're just now being able to detect planets based on their gravitional signatures on stars, how can we be sure we haven't peered through a telescope at intelligent life already? Our species was pretty damn interesting 300 years ago, but if the aliens were looking for was radio signals we didn't "exist" to them until about 1920. And our radio waves haven't even gone that far yet, 100 light years is nowhere. Maybe in a 1,000 years when they get somewhere and aliens notice, they'll dispatch their ship and another 1,000 years later land here.

I wouldn't expect to get found in the woods a millisecond after I lit the signal fire, and thats where we are today in universe terms.

Look at a few numbers that we will assume to at least be in the ballpark, and roughly correspond with scientific consensus:

1. The Universe is assumed to be 13.7 billion years old.

2. Nothing can move faster than c, so light years are an effective measure of the maximum distance anything can travel since its inception.

3. Our Sun is about 4.6 billion years old.

4. The universe is 13.7 billion light-years across.

Now, from these, I'm going to make a few propositions, given the lack of obvious extraterrestrial intelligence:

1. Stars stable enough to create life didn't appear until fairly late in the game, around the 9 billion year mark.

2. 5 billion years is a better-than-average time for a star system to stabilize and evolve life.

3. Stars stable enough to create life are still fairly sparse, as life in this universe is still fairly young.

4. Assuming 7 billion years as a bare minimum for the starting point for this process, and assuming the Earth is fairly quick, a reasonable upper bound for the distance that a civilization must be from us to have contacted us is 2 billion light-years.

Of course, there are a lot of variables here, and it's highly probable that maximum reasonable speed for a life-form to travel is as low as .1c, which means that even a civilization that sprung into existence at 6 billion years (assuming a star system stabilized very early in the game and then also evolved life in the better-than-average time of 5 billion years) would only be able to travel 1 billion light years, cutting off a fair amount of the universe from contact.

While the numbers involved in the time since the big bang are large, the distances a hypothetical civilization would have to travel are probably larger, especially given that evolving life, in our solar system's case, took well over a third of the time since the big bang, and that's not counting the circumstances that brought about the formation of our solar system, which took the remaining 2/3rds.

that's a lonely way of looking at things; there's probably nothing quite like us. i've said before but should reiterate, we perceive and experience a tiny portion of what makes the universe alive.