Alien life could be found within 40 years - really?

Wibbs wrote: »

Not quite. It had cooled down for many millions of years before we see any evidence of life.

I'd agree on that one. Of all the novel adaptations evolution came up with, there's only one example of intelligence as an adaptation and even then the kind we exhibit today only happened to the degree it did with our Homo Sapiens species.

Yet there is a lot of varied intelligence on Earth, something human beings forget, higher level intelligence has been around some 100 million years or so. It did take a long-time to reach space faring capability but 100 million years has shown relatively quick progress once intelligence got started, if you put it against the backdrop of billions of years of lower intelligent or non intelligent life. A take home lesson, intelligence is robust, and once intelligence comes out of the magic lantern it would be very difficult to put back in. It survives and it prospers.

If you rolled the dice again it could have turned out very differently and you could have ended up with Neandertals and not us. Given apex predators like us tend to be small in number in the landscape*, chances are good we might have died out. We very nearly did. Modern humans at one point got down to only a few thousand individuals because of natural disaster(Volcano 60,000Yrs ago IIRC?).

Yes it seems we have lived a rather charmed existence. There are now proven to have been at least two more modern species of humans in existence, Flores man and the Denisovans. It may have been that we outcompeted the others, or that homo sapiens finally unlocked a few key gene changes that gave us the leg up over the competition, evolution working the keys through the lock so to speak under the pressure of natural selection and intelligent competition.

Until we find an example of life outside earth we simply can't know if it's out there, nor can we begin to guess at the likely numbers out there. Yes the universe is vast, but in a near infinite universe of near infinite possibilities within the laws of nature "one offs" occur. Unique single events unrepeated elsewhere. Life, certainly intelligent life could well be one of those, or could be ridiculously rare, like one per galaxy. Plus given the huge time factor, you could well live at a point where there's only one every ten galaxies.

If we think of intelligence of occupying a normal distribution curve, then it is more likely to be very common than rare. It goes back to a good ole scientific principle..you usually ain't so special as you think you are! That's been a good maxim through the years if we look at how our view of our place in the universe has progressed. How many things in nature are truly unique? How many exist as a set of one? If we saw a given rock or a given plant or animal would we think that this is probably the only one in existence? Thinking we are somehow special intelligence wise is probably just the next step of hubris to knock down.

Actually if we can find an example of different life here on Earth that would up the odds. So far we haven't. All life today and so far discovered is related and is of the same "type". You, me, a fungus, an amoeba and a giant redwood are all the same type of life. So this suggests either that's the only kind of life possible on a planet of our kind and/or that it's an incredibly rare event.

Yes this is absolutely true, we are all close relatives, even to plants. This can be argued in terms of existing life stopping new life popping up, that life is hard to get started, that life was seeded from elsewhere from a rare event early on, that our type of life is the common type of life in the universe, or that we have not fully examined the diversity of microbial life yet. The vast majority of microbes cannot be grown in a lab, they are only identifiable from their ribosomal RNA. The question then is, if we cannot grow them and there are microbes that do not use DNA/RNA such as all the life we know of so far, how are we going to know if they are there? I'd say the jury is still somewhat out on this one.

Then look at the history of our planet and how we ended up here. It was a long list of ingredients required. Right distance from star(unlike Venus), right size to hang onto an atmosphere(unlike Mars), presence of the right sized moon(a biggie), right collection of elements. Big cosmic Hoover in the shape of Jupiter to mop up flying rocks that would otherwise hit us. Even so for the vast majority of the history of life on earth it was unicellular slime and such. It seems we then needed the whole planet to freeze(snowball earth) to really kick off complex life. If that hadn't happened... Then we had various mass extinctions to reset the mechanism and force new adaptations. That's just scratching the surface. You could have a near identical "earth" where the big freeze never happened and complex life remained very rare.

This is more of a looking backward 'just-so' argument. Of course all the events that occurred in history were suitable for development of life as we know it, otherwise we wouldn't be here. That doesn't mean if things went differently that other types of life wouldn't have existed. Who is to say that if history was different our type of life could have developed billions of years earlier and we are already distributed throughout the galaxy?
The multiverse theory is a good way to examine these concepts also.

YFlyer wrote: »

What does the 2nd decimal point do to the percentage?

So adding to what I worked out above; finding the earth in the milky way is similar to finding an individual glucose molecule in a disk-shaped cloud with a diameter stretching from about dundalk to dublin airport as the crow flies, and with an average thickness of about 660 metres high. And for aliens to find this in one particular century of the last 4.54 billion years, is equivalent to finding the above glucose molecule at a particular 2 milliseconds in a 24-hour day. Obviously this is all "back-of the envelope" type calculations but I find it fairly bewildering!

And this is just one galaxy. I'd say there's some mad stuff going on in other galaxies. My guess is that the big bang is the result of something an advanced civilisation did, before this universe, and I think that before this universe, and probably regressing forever into the past, there was always "something", and questions about what was before that etc. just don't make sense. To me, the universe seems a bit too "young" in the grand scheme of things, seeing as it is expected to go on for trillions of years and we just *happen* to be living at the birth of it, relatively speaking... and I'm not falling for the anthropic principle here, I know humans aren't the centre of the universe, but it still strikes me as noteworthy that the big bang didn't happen that long ago.

Any foreign organism probably isn't optimised for life on earth. Our oxygen atmosphere would be toxic to any life forms that existed on our planet over a billion years ago, nevermind somewhere else. The levels of Oxygen are lower than the were during the carboniferous so the giant insects of long ago wouldn't survive here because there is too little oxygen.

Temperature , pH , redox levels, UV levels due to composition of atmosphere - there is a chance ET evolved to break down molecules formed by lightening in an organic rich reducing atmosphere - , length of day/night etc. etc.

The thing is though that based on what we know about earth's position in our galaxy there seems to be a habitable zone in galaxy's.

The centre is too dense and a planet like earth couldn't form, the outer edge of the galaxy isn't habitable either, so maybe up to 50% of a galaxy just isn't likely to support life. Then they could further whittle the numbers down by ignoring stars that aren't suitable for supporting an earth like planet, or solar systems at the wrong stage of their life span.

It's still a stupendous number of planets but with our computers likely to be able to calculate those kind of numbers in practically no time within the next 50 years, their computers are probably well able to crunch that kind of data and more.