The objects observed by the telescopes are supermassive and super luminous. Space craft and other objects are too dim and small to be seen. Look at pictures of earth from space the only thing you can see that shows humans is light pollution on the night side. There are no pictures of planets outside our solar system so basically any planet with a chance at life cant even be viewed by us directly.

Almost all efforts to search for signs of life are limited to our galaxy alone which is only ~53,000 light years across. So at most, the light we're seeing from our galaxy is only ~ 40,000 light years away and thus reflects what was happening 40,000 years ago. Since the universe is roughly 13.7 Billion years old, 0-40,000 years ago all should be roughly "now" on an evolutionary time scale. You're right that when we look at the furthest objects we can see we're looking back billions of years in time, but those objects are so far away we won't have any hope of getting information about planets and their atmospheres or hearing radio signals they might transmit so that's not where we have the ability to look now.

Earth has had life for over 3-4 billion years. The galaxy is only around ~100,000 light years across or so, and the furthest light we can see is no older than that. Additionally, the nearest galaxies are millions of light years away, and what we're seeing is those galaxies from that long ago. Any life on those worlds on planets about as old as Earth would be nearly as evolved as life here, so it would be about as visible.

However, what we can see with telescopes are macro scale things, stars, galaxies, nebula, etc. Smaller scale objects like planets are much more difficult to spot, and signs of life are even harder. For all we know, Proxima b (a mere 4.2 light years away) does in fact have life, but we don't have any way of confirming it because our instruments aren't sensitive enough. Now apply that to stars dozens of light years away, or even in other galaxies. We're only barely able to find planets within our own galaxy, though our techniques are getting steadily better, but we have no way of doing the same for potential planets outside the galaxy.

One caveat to that though is that the reason we can't spot life on Proxima b is because it doesn't transit, and we can't use our only available method for searching exoplanet atmospheres without one, whereas with the TRAPPIST 1 planets, they do transit, so studying their atmospheres is possible, though still tricky. It will likely be a further generation or two of telescopes, and the ability to directly image Earth sized planets (circumventing the need for transits) before we can really detect and confirm signs of life in all but the most specific cases.

We're an "intelligent" life form. If you look at our planet from a relatively close distance, all you see is the pale blue dot. There's no indication from that distance that we are here really.

You're correct though, that light we're looking at, even with a powerful telescope is what that looked like thousands+ of years ago.

Sounds like the "light cone" idea - that information hasn't reached a place yet.

I suspect the objection is that with the age of the Universe and potentially life-supporting star systems there should be advanced civs from well before us whose "light cone" of evidence has reached us.

The objection to THAT being, given possible differences in perceptions of time or lifespans between us and 'them', it could be we are all "ships in the night" missing each other by wide margins. Overwhelming radio evidence may have bathed our planet for a century...while the Roman Empire pushed north toward the British Isles.

Another civ may transmit loud and clear very frequently - by that they mean, once every 400 of our years.

Or they are aquatic or live under haze and don't actually know about space or other stars. Or their own star.

This really doesn't solve anything. While there would be alien civilizations that didn't exist yet for you to see evidence of in the light you're receiving, there would also be alien civilizations that are now extinct that you would ONLY be able to see because you're receiving old light. Even if life is more abundant at this stage in the age of the universe, it still doesn't explain the total lack of clear evidence of aliens when we look at the universe.

Interesting theory.

The theory that I'm into lately is the Young Universe theory; the reason that we haven't seen other life out there yet is that we are one of the first to reach this evolutionary stage, so there aren't any others to see yet, as they aren't as advanced as we are.

That makes us the grandfathers of the universe, which is kind of scary.

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No. Our own solar system is very young in universal terms. There has been billions of years for older civilizations to exist.

Furthermore, only the farthest galaxies are that old, and we can’t see beyond the CMB (300,000 years after the BB). Note that the first stars did not form for hundreds of millions of years after the BB.

Plus your comment only applies to the furthest away galaxies. The closest star to us (other than our sun) is a scant 4 light years away.

Size of our galaxy is about 100,000 light years, means we are looking at most 100,000 years in the past if we are only interested in 100+ billion stars in our galaxy. 100,000 years is short time relative to age of stars or planets.

Read https://en.m.wikipedia.org/wiki/Drake_equation for some estimations on how many civilization we should see.

Also relevant: https://en.m.wikipedia.org/wiki/Fermi_paradox

That’s right. Not only is the light that arrives here from a star 1 million light years away 1 million years old, you should also realise that the star that light originated from is not even in the same place it appears from our perspective. It could be further away, or in a completely different part of the night sky, or both, or may no longer even exist.

Put simply, the sun is eight light minutes away. If it exploded, we wouldn’t know about it for eight minutes.

Despite most of the responses you’re getting here, you’re not wrong. This alone doesn’t explain the emptiness of the Universe but it’s certainly a factor. Detecting alien life isn’t just a matter of looking in the right direction, it also requires looking at the right time.

It's possible, but the universe is really old, so even though we are seeing stuff that happened 10,000 years ago or 50,000 years ago, the universe is around 14 billion years old, so theoretically there should still have been alien life 50,000 years ago somewhere that we can see it. Unless alien life is just extremely, extremely rare. Or stealthy.

The thing is, based upon our best guesses about where humans will be in 10,000 years or 20,000 years (which are obviously just speculation), it only takes one alien civilization to expand throughout the stars. And within the context of the time frame of the universe, it doesn't really take that long to colonize a galaxy. And you'd think that a galactic civilization would have left some observable marks on the galaxy it conquered.

So the fact that it hasn't happened forces us to re-examine our assumptions. Like maybe we're stuck on this stupid rock for good. Or maybe civilizations inevitably collapse prior to becoming interstellar. Maybe class M planets are the only ones that can sustain life, and they are incredibly rare and highly valued and aliens fight wars of extinction over them. Maybe there is some hard to limit to how far technology can develop. Or maybe after a while species' lose their will to power and begin to decay. Or maybe a lot of alien civilizations value homeostasis over expansion. Or maybe it is possible to expand throughout the stars, but it takes a really, really, really long time. Or maybe alien life is extremely rare. There were a few civilizations in our galaxy, but they died out for whatever reason, are we are essentially alone at least for our galaxy our even maybe our local group.

who knows.

Universe is young, human existence is insignificantly short in the cosmic timescale and universe is huge.

Even if advanced life was common, it's too easy to miss. There may be none in this galaxy, but many in trillions of others. We may be a million years too late or a billion years too early.

You are looking for a specific water molecule in the sea.

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All the scientists looking for life already know this. But we also know how far away the things we're looking at are, and therefore how far in the past we're seeing them. All the planets we look at are within our own galaxy, and we only see them a few tens, hundreds or at most thousands of years in the past, definitely not at the beginning of the universe. Even looking at the opposite side of our galaxy would only be 100,000 years in the past. And even other galaxies are millions or tens of millions of light years way, which isn't anywhere close to the beginning of the universe.

It's only observations of ultra distant galaxies that are billions of light years away that are seeing significantly nearer to the beginning of the universe, and we're not looking for life in those observations.

Hello u/Ggoods123, your submission "Why we don’t see aliens" has been removed from r/space because:

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Maybe we don't see aliens is because there are no aliens