[heroic]

Question is to people who say if universe is teeming with life, then why is it not visible close by: We don't know how large the universe is. If say life is "teeming" means it's found every 1M Parsec on the size of 10^100M Parsec, wouldn't it be teeming, and yet nothing in our vicinity?

I'm being genuinely curious, not dissing on anyone.

[hnlmorg]

There’s a few problems when hunting for life:

Distances are immense:

1. Our view of the galaxy is very limited. We know almost nothing about our closest neighbouring solar system, let alone anything further afield

2. And because the distances are so far, we are effectively seeing those distant events hundreds or thousands of years in the past.

3. Where to look? We cannot search everywhere. We can only hope to get lucky that we are searching the right corner of the sky at the right time.

Alien life is completely alien:

4. We can only make assumptions of what to look for. Any sufficiently encrypted signal might genuinely appear like white noise to us.

They might be so advanced that we simply cannot detect them

5. Early communication systems on Earth were noisy in that they were broadcast 365 degrees. Later systems could be targeted, focused in a specific direction. As technology advances, noisy classical methods of broadcasting become less common. This in turn reduces the amount of noisy any extraterrestrial eavesdropper could spot.

And that’s assuming they’re not intentionally “cloaking” themselves. Putting aside Star Trek style fantasy for a moment, there is an advantage to remaining hidden. Whether you’re a predator like a burrowing spider or stealth bomber, or prey like bugs that camouflage themselves as plants; being hidden gives you a massive tactical advantage.

[smegger001]

Cloaking probably isnt possible without discovering someway to violate the laws of conservation of energy. Any work done by a system will produce heat hiding the heat signature of an advanced technological society is probably impossible.

[ryandrake]

And it's not just the size of the distance we can see, it's the size of the slice of time when we are looking. We've had the tools to sorta-kinda detect life signatures for what, 10-20 years? Maybe we can keep that up for another (at best) 100-1000 years until we destroy ourselves? The universe is on the order of 10^10 years old. Star formation will end ~10^14 years from now The last black holes will evaporate ~10^100 years from now. So our temporal search window is astronomically small, too.

[smegger001]

Why do you assume we distroy ourselves? If we can make spacecolonies at somepoint between now and your 1000 year figure why kill ourselves when we can leave for another star. It doesn't even have to be a popular strategy just one that a nonzero number choose to take rather that self distruction.

[yungporko]

it's also not only a question of distance but also a question of time. there could be/have been several alien species that would be our next door neighbours but just not at the same time as us.

[somenameforme]

I'm fairly sure you know this already, but you just described the Fermi Paradox. [1] And the answer to this paradox is that there is no answer, though there are a million hypotheses.

[1] - https://en.wikipedia.org/wiki/Fermi_paradox

[seanhunter]

The first exoplanet was only detected in 1988 and confirmed in 2002. These are things we were really really sure were there and are absolutely huge relative to a vital sign. It would be surprising indeed were we to already have found a biosignature given it's got to be a lot harder than finding a gigantic chunk of rock.

Astronomy is hard.

[ineedaj0b]

We could just be early. We’re one of the first civilizations to ‘wake up’ perhaps.

So it’s teeming, but not much to see with our eyes yet

[xeromal]

I don't know anything about anything but I can imagine a society of bacteria saying the world is teeming with life but they're sadly sitting at the bottom of the ocean in a lava tube and they can't manage to find any life.

[dsq]

Life every million parsecs means less than one life form per galaxy, so hardly teeming.

[zaphirplane]

FWIW there are 2 trillion galaxies in the universe

So says Wikipedia

[echelon]

If the next "hard step" is aliens going from biological to artificial, how can we be sure what sorts of signals they might leak? We're not even there yet ourselves.

[seventytwo]

The real answer is that we don’t know.

We know with 100% certainty that life exists on the universe, we just don’t know where else besides earth it exists.

[contravariant]

I think you can ignore that second number, best we know the universe is infinite. Though the visible universe is limited.

[username135]

Our definition of life is based on 1 single element.

[dylan604]

But why do we think that life would be based on a different single element anywhere else?