CO2 and Methane?
If the planets have an atmosphere of CO2 and Methane then they used to have life.
Life that said "Global warming? Ha, that's just a myth!"
Boffins have made a breakthrough in the search for alien life with a new technique for determining the colours, chemical composition and even physical characteristics of exoplanets that are light years away. Chemical analysis progression of HR8799 planets Chemical analysis progression of HR8799 planets Credit: American …
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(on average) half the aliens can do better. It's reasonable to assume that humanity is nothing special so far as speed of development goes. So it's a reasonable guess, based on zero evidence, that half the aliens out there are more advanced than we are.
So if we can detect alien light, there must be lots of sentient races that can do the same, and have developed the tech. to tell them more about all the other alien races their SETI programmes have marked out.
On that basis, where the hell are they? Sure some will have a prime-directive sort of philosophy and not want to "pollute" us. Some will have seen our TV and decided we're (a) doomed, (b) best left well alone (c) in fear of their sanity. Yet some must have some inking of curiosity and at least started to say "Hi There!" - or "Don't you know there are laws against squirting radio waves everywhere".
However, if humanity really is the most advanced, or only, technological race in this part of the galaxy, then it doesn't say much for evolution.
"where the hell are they?"
A few thousand light years away, on average (give or take a few thousand orders of magnitude). The man-made light that we have really only been generating for a couple of hundred years, or the radio waves which we've been doing for much less than that, are only a fraction of the way to the aliens looking for them.
Unless they happen to have invented a way to bend space-time to detect us, in which case I'm sure they're gradually working through the gazillions of potentially life-supporting planets and will reach us eventually (if they even deem us to be worthy!)
"A few thousand light years away, on average (give or take a few thousand orders of magnitude). The man-made light that we have really only been generating for a couple of hundred years, or the radio waves which we've been doing for much less than that, are only a fraction of the way to the aliens looking for them."
Don't need man-made light. Our planet has been beaming a "THERE IS LIFE HERE" signal into space for hundreds of millions of years. If life is incredibly rare then this alone will have attracted attention.
I mean that's what we are doing, we are looking for life supporting planets. We don't require them to be emitting radio-signals.
Even if they happen to be within a few tens of light-years, even if they are currently watching Lucille Ball on Earth-TV and trying to work out what those strange techno-primitives are up to, they may still be thwarted by real-world physics. In other words, they've come to the same conclusion that our scientists have, that interstellar travel isn't ever going to happen outside of the movies. No wormholes, warp drives, ZPE drives, reactionless drives, or any of the other devices that SF authors use to get an interstellar plot going. Just rocketry and relativity and radiobiology, saying "can't be done".
My riposte to the (strong) Anthropic principle is that the universe is NOT optimised for Homo Sapiens. It's optimised for our silicon successors, who'll be able to slow their clock rates down so that a thousand light-years becomes a few years subjective. They'll prefer just about anywhere in the universe to those hot balls with moist oxidizing atmospheres, where some (mostly ridiculed) few amongst them think their ancestors must have developed, back before the Archives and the Memories.
In the worst-case scenario, they're here in our Oort clouds already, we're making far too much noise, and they're getting ready to drop a comet on us. (It worked last time, 65 Myears ago).
"(on average) half the aliens can do better. It's reasonable to assume that humanity is nothing special so far as speed of development goes. So it's a reasonable guess, based on zero evidence, that half the aliens out there are more advanced than we are."
Considering how young our civilization is I think it actually means 99.9%+ aliens out there are more advanced than us (but some may be dead).
"Considering how young our civilization is I think it actually means 99.9%+ aliens out there are more advanced than us (but some may be dead)."
Only if you consider *intelligent* aliens. It's much more likely that the vast majority of alien lifeforms are more akin to bacteria or pond sludge, and considering the hundreds of millions of years of vertebrate life on Earth vs approx 1million of basic intelligence and a few thousand of civilisation, I think it's a reasonable call that the vast majority of planets out there that DO harbour life have no intelligent life
@Neil B - Fermi paradox fail
The other points in the Fermi paradox seem reasonable enough, but this is a bit too matter-of-fact: "Presumably some of these civilizations will develop interstellar travel".
We are just getting to grips with how incredibly difficult and resource-intensive it is to even get to the next planet up. There are sound reasons to believe that, pace sci-fi enthusiasm, FTL travel is really impossible, and that interstellar journeys will take thousands of years, which in turn has severe implications on complex life (as we know it, at least)
Also the 'Earth is typical' assumption might not hold. No matter how many gazillions of planets there are, there are also so many factors that make up a planet ( size, distance from the sun, size and type of sun, temperature, surface gravity and, especially, chemical composition) that it might still be possible for every one of the gazillion planets in the universe to be quite distinct from each other.
@Pete 2 - Time and distance
We have had 'civilisation' for maybe 7000 years, we have been in a radio tech era for less than 200 years, and judging by our current stewardship of the planet and our limited resources, I would count it as a roaring success if we managed, say, another 10,000. That's a tiny span compared to the age of the Earth, or indeed, the Universe.
No-one will have seen our TV unless they were closer than 70-odd light years.
In other words, the universe is a big place. You might think etc etc
Fantastic as this is (and it genuinely is), it's pretty much worthless information if you have no means to get there - or even just communicate - in a feasible timeframe.
Until we get FTL (for travel and/or comms), the stars (and now their planets) will still just be decoration in the night sky.
You don't need FTL to travel the galaxy if your life expectancy is 10,000 years. You live in space anyway. No-one lives on the planet surface anymore. Dirty, filthy dangerous planet surfaces. Just continue your life while drifting towards a nearby star, it'll only take the equivalent of a "year" of your life. On the other-hand all the stars in the galaxy have already been visited and are in the database, you might prefer to just visit them in simulation.
Visiting other galaxies...exploration becomes old when your computers can simulate all possible variants of chemistry and life that can exist in the universe. If you can't figure out how to buffer overrun the universe and escape you might as well turn inwards, create your own universe in a computer and live within that.
Also FTL would be more of a bad thing if it were possible. It would enable some seriously screwed up weapons.
I thought the long-accepted approach was galactic exploration by self-replicating robots - with added DNA (or local equivalent) payload if you want to spread your kind of life around. This doesn't need any kind of FTL capability, nor a world-busting economic commitment. I think it works out at around a million years to visit every star in this galaxy using this method (depends on the effectiveness of the replication process), hence the "so why hasn't someone already done it ?" "maybe they have..." debate.
I'm getting really tired of all these offhand dismissals of any possibility of real-time interstellar travel. If we listened to every naysayer who said "that can't be done" we'd still be living in caves hunting wild pigs and being eaten by leopards.
I know that the difficulties imposed by relativity and physics seem insuperable now, but so did going to the moon 100 years ago, and so did flying for thousands of years before that. If we give up now, if we toss in the towel and say "relativity means there will NEVER be FTL travel and that's that, end of discussion", then our civilisation deserves to die. Because we will have turned our backs on every principle that has brought us to where we are.
Consider this: there IS a concept of absolute time, regardless of the relativity of time and space. The one absolute clock, applicable everywhere in the Universe, is seconds elapsed since the Big Bang. At some point in time, on the planets orbiting Alpha Centauri, it is the same number of seconds since the Big Bang as it is here right now. We might not see that moment for another 4.5 years, but it's happening now, or has happened, or will happen. So if FTL is possible, say with an Alcubierre drive or some other functional equivalent, and if the ship does go back in time as a result, then it could be put in stasis (brought as close to 0 Kelvin as possible) and released when the number of seconds since the Big Bang reaches the same as when it left Earth. Thus, zero effective time has passed, both for Earth and for the ship. Repeat again on the return journey, and what you have is essentially instantaneous interstellar travel, for both Earth and ship.
Look, I'm no boffin, and there's likely countless flaws with my ideas that could be brought up. But if we give up, if we just throw our hands in the air and say "that can't be done, because Einstein...", then we have abrogated our right to be called intelligent, and we may as well start heading back for the caves right now.
I will leave you with the words of the great poet Tennyson:
We are not now that strength which in old days
Moved earth and heaven; that which we are, we are;
One equal temper of heroic hearts,
Made weak by time and fate, but strong in will
To strive, to seek, to find, and not to yield.
It is not the same number of seconds since the Big Bang everywhere. Time slows down as speed increases. There have been fewer seconds on Mercury and more on Mars in our own system, and AC and Sol are moving around the galaxy at different speeds, and some galaxies are moving hundreds of times faster than ours.
And the things at the beginning of 2001 were tapirs, not pigs, if that was your reference.
You're right, of course, I do know about the differential passage of time in different locations, due to gravity.
That's why I specified at some point in time. At some point in time, everywhere in the universe will pass through a moment of t seconds since the Big Bang where t is the number of seconds that has elapsed since the Big Bang here on Earth right now. For us that time t in a different planet in a different galaxy may be a million years ago, or a million years in the future, but at some point in time that planet will pass through t seconds since the Big Bang. Sooner or later, everywhere in the universe will. That is your benchmark for interstellar travel.
Follow my reasoning now?
To find 'civilization' in the stars, they should be scanning for massive pollution levels, radioactivity, and television airwaves choked with 'reality' shows.
If any alien species with a modicum of intellect saw those things on our world, they would turn around shaking their heads while they did so.
"If any alien species with a modicum of intellect saw those things on our world, they would turn around shaking their heads while they did so."
There always seems to be an assumption that advanced alien life would see as as peurile or stupid or whatever because of the television we watch, the wars we fight, the damage we do to our surroundings, or similar.
I would think it highly unlikely they would assume any such thing - I imagine they would be well used to it:
I think it's a pretty safe bet that even the most advanced civilizations would have their fair share of numpties both watching and appearing on their Jeremy Kyle equivalents.
"If any alien species with a modicum of intellect saw those things on our world, they would turn around shaking their heads while they did so."
How many heads are they shaking?
But seriously, they wouldn't shake their heads. If they were intelligent beings their wisdom would enable them to fully understand the psychology that leads low-intelligence beings like humans to watch Jeremy Kyle and fight each other. They would expect such behavior before they even laid eyes on us. Whether or not they engaged in similar behavior.
We can't even work out how to communicate with cetaceans. What chance have we got with something with which we share no common ancestry at all?
(They sometimes save our lives by swimming us back to dry land. That shows a remarkable capacity for abstract reasoning by dolphins and orcas, and inter-species empathy in advance of our own. )
Sounds a bit sinister in a non-descript way. Like Projects Paperclip, Grudge and Blue Book. I know the names don't describe the projects' purpose (because that would give the game away to anyone attempting to spy on said projects) but "Project 1640" sounds like they know more than they are telling.
Or am I just being paranoid? :-)
Colin
Where's my tinfoil hat? In that coat there, thanks!
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Imagine that, now SETI will have the ability to choose planets with the most likely signal for life to start recording it for electronic signatures and possibly will be able to tune in on "Alien" television stations. Hope they don't send us a bill. Like "Pay per View".
Seeing the colors and composition of life on a planet, from a great distance...if this technique works, it will be the next best thing to actually hearing aliens with the SETI program. What could be more inspirational to would-be space explorers?
We're opening up a whole new chapter of science, one that astronomers and planetary scientists have been dying to read for as long as those sciences existed.