Are We Really Alone in the Universe?

[Gil Fuller]

The amount of Real Evidence for space aliens existing on this planet is zero. The amount of imaginary/specultative evidence is massive-enough to be certain. Take your choice: Which one is more plausible?

 

[Nereid]

The amount of Real Evidence for space aliens existing on this planet is zero. The amount of imaginary/specultative evidence is massive-enough to be certain. Take your choice: Which one is more plausible?

To continue in the same vein ... the amount of good observational data showing life elsewhere in the universe is (almost*) zero. The amount of speculation and fact-free imagination is humongous. Choose.

*it's not quite zero, e.g. the Mars meteorites, Europa spectra, methane in Mars' atmosphere, ... some would even say the "Wow" signal

 

[plum]

Look at it this way: recent observed data shows

a) our solar system is not special at all; it is a typical one amongst what are likely billions.

b) water and carbon are in no way confined to Earth.

c) complex organisms appear to flourish in regions on planets with temperatures in the 70-120 degree temperature zone (of which ours is the only one currently known to us and our tiny sphere of collective perception).

d) There are feasibly almost as many such temperature zones as there are stars in the universe; for life to form there need only be a planet to form within this zone- an event which, though unlikely on a per star basis, would be very likely on a per 100,000 or 100 billion star basis.

Given these stats, I'd say there is a 99.9999% chance that we are not alone.

 

[Nereid]

Look at it this way: recent observed data shows

a) our solar system is not special at all; it is a typical one amongst what are likely billions.

b) water and carbon are in no way confined to Earth.

c) complex organisms appear to flourish in regions on planets with temperatures in the 70-120 degree temperature zone (of which ours is the only one currently known to us and our tiny sphere of collective perception).

d) There are feasibly almost as many such temperature zones as there are stars in the universe; for life to form there need only be a planet to form within this zone- an event which, though unlikely on a per star basis, would be very likely on a per 100,000 or 100 billion star basis.

Given these stats, I'd say there is a 99.9999% chance that we are not alone.

This is a simplified version of the famous Drake equation; AFAIK, the most uncertain parts are the probability of complex life developing from simple life (even on Earth, we are still in the Age of Bacteria) - over realistic timeframes - and the probability of 'our kind' of intelligence developing from complex life.

Interestingly, astrobiologists would really have to go back to their drawing boards if, in ~<50 years, no evidence for former life on Mars is found!

 

[Andre]

I seem to remember this discussion before. My two cents say (have said before) that the possibility of earth-like life on a Earth like terrestrial planet with -similar abundances of elements- is severly reduced by the usefull life time of that planet.

Without a big moon, to stabilize fluctuatons of the spinning, it may be tough for a liquid cored planet to last more than a billion years or so.

 

[Andre]

I came across quite a http://cfa-www.harvard.edu/~scranmer/SPD/crichton.html about SETI and Drake's equation.

In 1960, Drake organizes the first SETI conference, and came up with the now-famous Drake equation:

N = N* fp ne fl fi fc fL

(...)

This serious-looking equation gave SETI an serious footing as a legitimate intellectual inquiry. The problem, of course, is that none of the terms can be known, and most cannot even be estimated. The only way to work the equation is to fill in with guesses. And guesses-just so we're clear-are merely expressions of prejudice. Nor can there be "informed guesses." If you need to state how many planets with life choose to communicate, there is simply no way to make an informed guess. It's simply prejudice.

As a result, the Drake equation can have any value from "billions and billions" to zero. An expression that can mean anything means nothing. Speaking precisely, the Drake equation is literally meaningless, and has nothing to do with science. I take the hard view that science involves the creation of testable hypotheses. The Drake equation cannot be tested and therefore SETI is not science. SETI is unquestionably a religion.

Faith is defined as the firm belief in something for which there is no proof. The belief that the Koran is the word of God is a matter of faith. The belief that God created the universe in seven days is a matter of faith. The belief that there are other life forms in the universe is a matter of faith. There is not a single shred of evidence for any other life forms, and in forty years of searching, none has been discovered. There is absolutely no evidentiary reason to maintain this belief. SETI is a religion.
(...)

But scientists in general have been indulgent toward SETI, viewing it either with bemused tolerance, or with indifference. After all, what's the big deal? It's kind of fun. If people want to look, let them. Only a curmudgeon would speak harshly of SETI. It wasn't worth the bother.

And of course it is true that untestable theories may have heuristic value. Of course extraterrestrials are a good way to teach science to kids. But that does not relieve us of the obligation to see the Drake equation clearly for what it is-pure speculation in quasi-scientific trappings.

The fact that the Drake equation was not greeted with screams of outrage-similar to the screams of outrage that greet each Creationist new claim, for example-meant that now there was a crack in the door, a loosening of the definition of what constituted legitimate scientific procedure. And soon enough, pernicious garbage began to squeeze through the cracks.

This ought to give a whole new dimension to the discussion.

 

[Chronos]

I don't like falling back upon the 'Principle of Mediocrity', but, the question remains. It is no more logical to argue we are at the physical center of the universe than it is to argue we are the only sentient consequence of it. Any cosmologist worth a grain of Einstein-Bose condensate would not forbid that possibility. Even a one per million galaxy chance gives a huge probability that life not unlike ours exists. We even have the science to explain why we can't chat.

 

[ШЇSЭЯ]

the science:

"Current Estimates put this time at 14 billion years, but the exact number is not important. Together thetwo things mean that we cannot see the whole universe, We can see only the contentsof a region that extends around us to about 14 billion light years-the distance light could travel in this time.This Means that science cannot, in principle, provide the answer to any question we might ask. There is no way to find out, for example, how many cats there are in the universe, or even how many galaxies there are. The problem is very simple, no observer inside the universe can see all of what is in the universe. We on Earth cannot receive any light from any galaxy, or any cat, more than 14 billion or so light years from us."

"Since it takes only four billion years for cats to evolve on a planet no observer inside the universe could know whether cats have evolved in some region of space so far away that the light reflected from their mysterious eyes could not yet have reached here."

"Furthur more, an observer who lives on Earth a billion years from now will be able to see much more of the universe, for they will be able to see 15 billion light years into the universe rather than the 14 billion light years we can see"-Lee Smolin

 

[mee]

Such as the idea of the existence of light based entities?

You mean entities like jellyfish in the deep ocean that use light or wholly light based entities. If the luxon theory is right, and I'm not saying it is, we are composed of light. (not trying to start a thread on luxon theory.) ;)

 

[Gerinski]

Surely chances are that conscious life has not only developed / will not only develop uniquely on Earth at our time epoch.

But from this to concluding that they must be around us ...

The time span of humanity is much too small in astronomical scale. In order for 2 civilizations to get in touch they must overlap in a very limited combination area of time and space in universal scale terms (at least as far as we can tell so far, time and space separation being physical limitations).
Despite whatever claims, we have no reasonable evidence that they are among us in disguise.

So... Occam's razor, take the bet that they are not.

Believe me, I simpathise with the value of speculation and free imagination, but always staying aware that it's that: speculation