Why don't we ever encounter aliens?
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04-06-2012, 08:55 PM
RE: Why don't we ever encounter aliens?
I always take the Drake equation with a grain of salt. Neither then nor now do we really know enough about the commonality of Earth-like planets in the universe to begin to put any sort of equation like that together.

There are huge sources of gamma rays we don't even understand, stars that are much larger than we ever thought was possible, and an incredible variety of volatile processes out there churning away. It may just turn out that the universe is a much more hostile environment than we thought, and we are orders upon orders of magnitude more lucky than first realized to have survived it so far.
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05-06-2012, 12:41 PM
RE: Why don't we ever encounter aliens?
(04-06-2012 08:55 PM)Superluminal Wrote:  I always take the Drake equation with a grain of salt. Neither then nor now do we really know enough about the commonality of Earth-like planets in the universe to begin to put any sort of equation like that together.

There are huge sources of gamma rays we don't even understand, stars that are much larger than we ever thought was possible, and an incredible variety of volatile processes out there churning away. It may just turn out that the universe is a much more hostile environment than we thought, and we are orders upon orders of magnitude more lucky than first realized to have survived it so far.
The latest science is indicating that extra-terrestrial life may be a lot more common than we once thought - and life may exist in several locations within our own solar system!

It's a 2 hour NOVA documentary, but well worth it.




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02-08-2012, 11:53 PM
RE: Why don't we ever encounter aliens?
(30-05-2012 02:44 PM)Carlo_The_Bugsmasher_Driver Wrote:  As the universe is just so huge, with billions and billions of galaxies, each containing billions and billions of stars, planets, asteroids, comets, planetoids, moons, and nebulae, it's reasonable to believe somewhere in the universe life exists, possible intelligent and or very advanced intelligent life with advanced space colonization and space faring capabilities, the question arises as to why these forms of life have not been seen crossing the realms of interstellar and intergalactic space. And given the egocentricity of Homo Sapiens, why have they not noticed us?

It's not like humanity has tried to conceal itself from its possible interstellar neighbors. Earth is an extremely bright source of radio waves in the night sky. And to our knowledge, Earth is the only source of artificial radio wave activity in the cosmos. We have hurled massive radio transmissions deep into the cosmos as a calling card with the SETI program, and have sent various mechanical probes to our neighboring planets and beyond the realm of the Kuiper Belt for their departure into interstellar space.

It seems we signal but there's no answer. Where is everybody?
The reasons for not running into aliens very often, quite possible, can be determined by five factors.

1) MATERIALS AND LOCATION: In this we assume that lifeforms will be carbon or silicon based as we are and require liquid water to survive. First, we are going to need locations where water is abundant. Fortunately Hydrogen is the most abundant element in the universe and Oxygen is a very common byproduct of stars in their Red Supergiant death throes. So water is very common throughout both our own solar system and the universe. Next we need locations where liquid water is very common. This can be achieved either on a planet or moon which is at a correct distance from the star it orbits to facilitate liquid water on the surface of the planet or has subterranean liquid water kept in that state by geothermal means (e.g. Jupiter's moon Callisto). So out of the billions and billions of solar systems out there, we need planets with liquid water, not too far or not too close to the star they orbit or with a source of strong geothermal energy that can last a great deal of time.

2) ENERGY: Life needs a constant supply of energy to sustain itself. On Earth, life is almost entirely solar powered, relying on the energy of the sun to power the biospehere through a complex of solar food factories, food chains and vital gas exchange. Stars are excellent energy sources. The hydrogen they have amassed from local dust clouds provides enough fuel for several billion years of thermonuclear fusion, if not more. The energy output for most mid range stars is uniform and constant - relatively, which provides a steady, unwavering supply to sustain budding life and ecosystems for the eons until they become sufficiently advanced enough to fend for themselves. But stars do present hazards to a thing as fragile as life. The stellar furnaces pump out gargantuan amounts of X-rays, radioactive particles, plasma solar flares, and energetic emissions. Also large stars run the risk of going supernova. And blue supergiants and hypergiants near the planet or in neighboring star systems have so much mass, they may form a quantum singularity (black hole) in its core, consuming and destroying itself in a few seconds in a gargantuan hypernova thermonuclear explosion. Clearly life needs an energy source which will not do this and must not be nearby solar systems with such stars. Only mid-range stars will suffice for this role. So we need only planets in the right spots with liquid water and stars in the mid range with no large solar threats looming in nearby star systems. So this narrows the field a bit as well.

3) TIME: Provided all the necessary materials exist on the planet in question, it takes a great deal of time for original abiogenesis and evolution to ply their trades and produce living organisms. On earth, life is believed to have existed for approx 3 billion years prior to our arrival. If we could shrink all of life's history down to 1 year in length, where 12:00:00.00am, January 1 represents the point at which living things emerged and 11:59:59.99pm, December 31 is present date, we enter the picture very, very, very late. Bacteria appear somewhere at March 1, single celled Eukaryotes appear sometime around June 25. Autumn is spent largely with the development of basic multicellular eukaryotic organisms like slime molds, sponges, hydra, and cnidaria. The Cambrian Explosion takes place on November 18. The dinosaurs were wiped out on December 24. Mammals begin their rise to prominence on December 27. Homo Sapiens comes into being on 11:42:48pm, December 31. Our ancestors settled in the fertile crescent of Mesopotamia and developed agriculture on 11:58:45.88pm, December 31. Christ was crucified on 11:59:39.99, December 31. The Renaissance happened on 11:59:54.75, December 31. Humans walked on the moon on 11:59:59.55pm, December 31.

If we say that this is a typical length of time for lifeforms to have traveled from proto-organisms to very advanced, sapient multi-cellular creatures on the precipice of major space faring capabilities, then we could say that this is that any planet capable of life must have a stable environment with a mid range star capable of supplying constant energy and liquid water for this length of time. A planet has only a few billion years for all this to come together before the star it orbits burns out in a red giant finale, taking the planet and everything on it with it. If there are delays in the evolutionary process, it may leave too little time remaining before the end for evolution to produce a sentient species capable of space travel. All this effort would be for naught.

4) INTERNAL HURDLES TO PROGRESS: OK, so lets assume an alien species reaches this point where its ready to begin space travel. It still may face a series of internal social hurdles e.g. dogmatic beliefs, social taboos, and a lack of motiviation to explore. There may be internal strife (e.g. a global nuclear or anti-matter weapon exchange) that ruins the ecosystems and decimates the species or utterly destroys it altogether. Biological threats, like a global pandemic, might kill off the species. Cosmic events such as an impact by very large asteroids or comets may end advanced life here as well.

5) THE LIMITATIONS IMPOSED BY PHYSICS:
Even if our aliens are now sufficiently advanced technologically, they must now develop a means of space travel that allow them to travel the vast distances to other planets and stars. In the space time continuum, we have an imposed maximum speed limit of 186,000 miles/second. The problem is, even if you can get to that speed, it still takes several months to several years to reach nearby stars. Galaxies can be hundreds of thousands of light years in diameter. And galaxies can be separated by millions - or billions - of light years. Clearly some kind of propulsion system must be developed which can do this successfully, in a short period of time, and is not affected by the penalties of time dialation (as you go faster, time, at least for you, slows down.). Another problem is that any kind of light or radiation which would allow us to detect an alien race on another star system thousands of light years away will take thousands of years to reach us. There may be many alien cultures like us, sending messages into space. But like a message in a bottle bobbing in a vast ocean it will not arrive at its destination for many, many years to come. Even if it is possible to build some kind of machine for travel (e.g a tesseract machine, hyper-drive, etc.), the energy penalties imposed by such devices may be so large that they are impractical to use. So space travel past our own solar system may never be possible in short periods.

So we need a planet in the right place from a stable medium sized star, with liquid water, and enough time undisturbed so it can produce advanced lifeforms which can send messages or ships into space, before they die from a plague or blow themselves to hell with nukes or their suns burn out and their lives end before they make contact with us. This may be very rare, indeed. If this is true, then we will be, quite possibly, forever alone in the universe and truly unique creatures. It should give us great pause, when pondering this, to consider how we treat our world and ourselves.

Could also be they have met smarter pond scum out there in deep space. If I were on a starship somewhere out there observing the actions on earth, the last thing I would do is land to say hello. I might set up shop and take bets on how and when humans would wipe themselves out, but then that is just the way I am. Maybe if we learn to get along and become less agressive (not just assume a landing spacecraft has to be hostile), they might stop by. I doubt that my grandkids will even see that day, and I don't even have kids yet.
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03-08-2012, 03:59 AM
RE: Why don't we ever encounter aliens?
(30-05-2012 07:04 PM)aurora Wrote:  Nice post, Carlo.

It's sorta like a super-extended version of the Drake Equation Smile (which I think in recent times has been updated)

I think if life is extremely rare that's it's an awful waste of space Unsure

Intelligent life may be extremely rare, but let us not forget that we have visited, what? Four planets? Holy shit, must be extremely rare.

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09-08-2012, 11:58 AM
RE: Why don't we ever encounter aliens?
This is a favorite subject of mine. But I do tend to think that intelligent life is just much more exceedingly rare than expected. I think there is probably a couple other instances out there, but they are so far away it will remain meaningless to us. Space is hostile, it is only by extreme luck our species has survived this long. If Jupiter and Saturn weren't around in our solar system we would almost certainly have been wiped out by an asteroid by now.
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09-08-2012, 12:27 PM
RE: Why don't we ever encounter aliens?
Alien Civilisations might be millions of years ahead of us biologically and technologically..... we may be of very little interest to them.

We could be so primitive to them..... that to make lasting contact may be damaging not only to us but to themselves (think capitalism in space)

If they exist and they visit us.... if they have the ability to travel faster than light then I guess they would of clocked bending light (invisibility), hence why we dont see them.

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09-08-2012, 12:30 PM
RE: Why don't we ever encounter aliens?
(09-08-2012 11:58 AM)Superluminal Wrote:  This is a favorite subject of mine. But I do tend to think that intelligent life is just much more exceedingly rare than expected. I think there is probably a couple other instances out there, but they are so far away it will remain meaningless to us. Space is hostile, it is only by extreme luck our species has survived this long. If Jupiter and Saturn weren't around in our solar system we would almost certainly have been wiped out by an asteroid by now.

Consider that there could be thousands or millions of planets with intelligent life and technological civilizations in our galaxy alone right now, but there just hasn't been enough time for any signal to get here from any of them. Not enough time for a signal from any of them to get to any other one. The distances are huge.

What's less unlikely is that there may have been thousands or millions of technological societies that did themselves in, or that electromagnetic technology is less common.

There are many other possibilities.

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09-08-2012, 01:01 PM
RE: Why don't we ever encounter aliens?
maybe they
Existed a
long time ago
in a galaxy
far far away

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11-08-2012, 08:32 PM (This post was last modified: 11-08-2012 08:40 PM by Superluminal.)
RE: Why don't we ever encounter aliens?
(05-06-2012 12:41 PM)Carlo_The_Bugsmasher_Driver Wrote:  
(04-06-2012 08:55 PM)Superluminal Wrote:  I always take the Drake equation with a grain of salt. Neither then nor now do we really know enough about the commonality of Earth-like planets in the universe to begin to put any sort of equation like that together.

There are huge sources of gamma rays we don't even understand, stars that are much larger than we ever thought was possible, and an incredible variety of volatile processes out there churning away. It may just turn out that the universe is a much more hostile environment than we thought, and we are orders upon orders of magnitude more lucky than first realized to have survived it so far.
The latest science is indicating that extra-terrestrial life may be a lot more common than we once thought - and life may exist in several locations within our own solar system!

It's a 2 hour NOVA documentary, but well worth it.




Oh I agree, I think there is life all over, just not intelligent. It took life 3 billion years to produce intelligent life on Earth. That is roughly 21% of the age of the entire universe. It is a very tall order to have a biosphere be safe and stable for that amount of time. Most planets are probably lucky to get up to some sort of sexually differentiated multicellular creatures before the biosphere is cooked, frozen, irradiated, the star blows up, hit by an asteroid, the atmosphere blows away, or the planet's core cools off and they loose their stable rotation.

If someone put a gun to my head right now and said, you have to decide, is there cellular life on Mars? I'd say yes, but it isn't going anywhere complex. Same thing with Europa.
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11-08-2012, 08:38 PM
RE: Why don't we ever encounter aliens?
(09-08-2012 12:30 PM)Chas Wrote:  
(09-08-2012 11:58 AM)Superluminal Wrote:  This is a favorite subject of mine. But I do tend to think that intelligent life is just much more exceedingly rare than expected. I think there is probably a couple other instances out there, but they are so far away it will remain meaningless to us. Space is hostile, it is only by extreme luck our species has survived this long. If Jupiter and Saturn weren't around in our solar system we would almost certainly have been wiped out by an asteroid by now.

Consider that there could be thousands or millions of planets with intelligent life and technological civilizations in our galaxy alone right now, but there just hasn't been enough time for any signal to get here from any of them. Not enough time for a signal from any of them to get to any other one. The distances are huge.

What's less unlikely is that there may have been thousands or millions of technological societies that did themselves in, or that electromagnetic technology is less common.

There are many other possibilities.

Maybe. But the whole Milky Way is only 100,000 light years across, and 13.2 billion years old. So in 13.2 billion years another technological civilization would only need to be about 100,000 or so years ahead of us in development to have completely permeated the entire galaxy with electromagnetic signal by now. That civilization would only be ahead of us by .00075% of the galaxy's lifespan. If that hasn't happened by now, it means it is incredibly rare to have intelligent life.
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