given what we know of the universe (how many stars, planets etc., there are), and what we know of how life was first created (the primordial soup - DNA, proteins and what have you) is it probable within the likely life of the universe (15 billion years or whatever)that life should exist? From an atheist point of view, can we say statistically that it is likely that there is a single universe, or that an infinite number of universes exist?
I think it is highly probable. Indeed, life probably exists on some other planets.
I would imagine that it isn’t that improbable. My recollection from college is that in the 1950s, in an experiment (the “Miller-Urey experiment”), simple compounds of common biological elements (water, carbon dioxide, ammonia, etc…) were mixed in a reaction chamber and subject to “lightning” (electrical discharges). After about a week, amino acids had been formed “spontaneously”.
Also, organiz molecules have been found in interstellar bodies. A few years ago (1996?) some scientists claimed to have found evidence for fossilized life forms in a meteorite that came from Mars and landed in Antarctica.
As far as other universes, isn’t that just speculation on the part of science fiction writers?
I’m just a total layman here but I do recall a Carl Sagan piece a read somewhere which quoted a mathematical formulae for estimating the current number of other worlds on which life currently exists.
For me the beauty of it was that you could fill in values for the symbols dependent on your own views and the state of current research and thus take into account views coloured by religion etc. (although admittedly if a value got a “0” then zero other worlds with life would be computed).
I can probably go away and find the cite and give you the formulae (in fact I will, unless somebody else beats me to it) but the really interesting thing for me was the key influence was whether advanced civilisations (if they develop) blew themselves into extintion (nuclears) shortly after securing the means.
If the did virtually automatically then we are probably the only ones here right now irrespective of the other variables. On the obverse, if even a small proportion learn and survive then there may be millions of other advanced civilisations out there let alone life forms.
One way of minimising our chances of wiping ourselves out would be to colonise other worlds so they can survive independently - for sure a very long term plan but supporting Sagan’s views on the justification for intensive space exploration/research etc. But maybe a better chance of success than achieving total nuclear disarmament…
I think it is highly probable. Indeed, life probably exists on some other planets.
The equation notquitekarpov refers to is known as the Drake Equation. A search on the term will get you lots of stuff on it. As I recall the SETI site has some interesting info.
I’ve been reading a book that gives, IMHO, a new, interesting, and thought-provoking view on the subject. It’s At Home in the Universe by Stuart Kauffman. His basic idea is that if you have a sufficiently complex system of molecules interacting with one another, not only is it possible for life to emerge, but it is inevitable. Life becomes as expected as the sun rising in the morning. I can’t do it justice, but if you are really interested in the sunject, I highly recommend this book.
Basically, the equation goes something like this:
Take the number of stars in the Universe
Multiply this by the percentage of stars of appropriate type for life
Multiply by the percentage of these that have planets
etc.
Now, many of these terms are controvertial, and estimates range from one civilization per galaxy, to one every dozen light-years or so. However, look at the first term there: The number of stars in the Universe. At a rough estimate, that’s, oh, let’s say infinity. Know what you get when you multiply infinity by anything other than zero? If the Universe is, in fact, infinite, as seems likely, then not only is life inevitable, but an infinite number of species is inevitable. The real question is, is there anyone else close enough that we might ever reasonably expect to make contact with them?
I don’t think enough is known about natural abiogenesis that would allow for calculating the odds. I don’t think enough is even known about the early conditions of the Earth that would allow for a decent computer model to be run.
As far as other universes go…we have no way of obtaining info from outside this universe…so anything “outside” would be speculation. Although I wonder if a theory of quantum gravity would shed some light on the origin of the Big Bang.
The Drake equation is a nice way to make an educated guess at the number of civilizations in the universe based on current observations.
As Chronos mentioned Drakes Formula adopted the viewpoint that unless we can actually detect the existence of advanced civilisations, then all this is just speculation. I think that was why Drake defined an advanced civilisation as one having radio astronomy technology. Unless they did they would not be able to send messages for us to detect or visa versa and it is obviously totally impractical to attempt a search by any other means. Also as the distances between galaxies are so vast it was also assumed that the search should be concentrated on other civilisation in our own Milky Way. This also avoids having to consider the implications of an infinite number of stars and worlds that obviously would make the equation rather meaningless as a means of estimation.
I cannot resist making my own stab at a possible estimate! I would welcome any constructive comment on my estimates that do not involve creationist theory. As a geologist I am a bit of a sceptic about how easy evolution is as a process to account for all life on earth - I don’t think it is wrong but suspect there may be something extra big out there we have been missing so far. Thus I suspect my estimates for the ease of life arising and evolving may therefore be very much lower than the norm but whatever.
The estimate for the number of stars (N*) in the Milky Way I saw was around 4 x 10 power 11. The fraction (fp) of those with planetary systems is a very rough estimate of course but I recall that the first planets outside our solar system had been detected a little while ago. That was done by picking up the wobble of their star under gravitation attraction of an orbiting body and the news story I read suggested astronomers now believe most stars may have them - but lets say 1/3. The next requirement is an estimate for the number of planets in such systems that may be ecologically suitable for life (Ne). We do not know if liquid water is a likely requirement to support life, if so that would presumably narrow the suitable orbital zone greatly, but being super cautious can I suggest again a 1/3 of only one planet?
We are now down to 44 billion suitable planets within our galaxy but from here on is where the estimates that are really wild and woolly.
On what fraction (f2) of the above has life evolved at least once? If you are a literal biblical creationist then your estimate might be 0 (zero) whereas I guess if the book that Smeghead recommends is correct then it is 1 (100%)! Again being cautious let us assume a figure of 1 x 10 power -4 and as the proportion of those life forms that evolve into technological civilisations (ft) maybe 1 x 10 power -4 again - although equally it could be near to 1.
Even with very conservative assumptions we are still at around 500 worlds within the Milky Way on which technological civilisations have existed - still an impressive number! However if earth blows itself up within the next 50 years for a total of approximately 100 years of sufficiently advanced technological existence and that experience is typical then the fraction of the planetary lifetime during which the civilisation survives (fs) then the chances of just one other technological civilisation currently being in existence is only 1 in 200,000. Depresssing.
However if most civilisations get over that learning hump and fs is nearer even 0.5 rather than 1 x 10 power -8 then there are 250 other civilisations relatively nearby let alone starting to count other galaxies.
Apologies for my not figuring out how to write sub and superscripts here in the formulae - I cut and pasted from Word and it seems it did not transcribe…
IIRC from my high school biology text, there is a theory that maybe life is pretty common, but land based (therefore tool and/or metal using) life may be much less common. The idea being that the dynamic tides caused by the Earth having a very large (with respect to the primary) satellite allowed land based life to evolve, or at least made it easier.
I am 100% with Phobos here. Not only do we not know which reactions occurred to create life (we do know some ways of synthesizing the necessary organic chemicals, but it is not clear which ones, if any that we are aware of, occurred naturally), we don’t really know what the prevailing conditions at the time were (heck, we can only narrow the time it occurred down to within about 500 million years). Speculation on the odds of producing life rests on an extremely poor foundation. Obviously, creationists want the numbers to be low and atheists want the numbers to be higher, and they’ll get the numbers they want.
I have no idea about other universes. I know that some notions in physics support the idea of alternate universes, but are those notions testable?
Actually I’m totally with Phobos too - we simply do not know enough and maybe never will.
But surely the elegance of the Drake Formula is that for virtually ANY value of f2 which is not zero (literial biblical creationist theory) then the universe (if not the galaxy) is (or has been) literally teeming with life.
I am certainly neither an atheist nor a creationist so it is not just playing with numbers. Well, if it is then at least it is rewarding play if it gives an insight into the overwhelming statistical importance our removing the main threat to our total extinction.
Of course if the creationist are correct, and we ARE alone as a technological civilisation, then it is even more important we don’t screw it all up.
So, it’s a one way bet…
Wouldn’t it be helpful, at this point, to differentiate between “life” and “sentience”? By “life” do we mean organic life (i.e. a bunch of amino-acids bumping together, etc), or is there some larger context where we can define “being alive”? It’s been suggested (whether or not it’s actually possible is debatable) that we can eventually make machines that, at least, simulate real conciousness. If we could do that, would that make them living things? If so, is it possible that life can arise from any variety of system (biological, electrical, nuclear, etc) and possibly exist everywhere?
Wouldn’t it be helpful, at this point, to differentiate between “life” and “sentience”? By “life” do we mean organic life (i.e. a bunch of amino-acids bumping together, etc), or is there some larger context where we can define “being alive”? It’s been suggested (whether or not it’s actually possible is debatable) that we can eventually make machines that, at least, simulate real conciousness. If we could do that, would that make them living things? If so, is it possible that life can arise from any variety of system (biological, electrical, nuclear, etc) and possibly exist everywhere?
Well, this question is certainly large enough for Great Debates, but being that it is here, I’ll tell you all the answer - yes.