Why We Haven't Met Aliens Yet

I doubt if we're alone. Our signals may not have reached an advanced civilization or our signals are misinterpreted or the civilization may be too primitive to have radio. There may even be a civilization that knows we're here but isn't interested in us at all.
 
Cainkane1 said:
I doubt if we're alone. Our signals may not have reached an advanced civilization or our signals are misinterpreted or the civilization may be too primitive to have radio. There may even be a civilization that knows we're here but isn't interested in us at all.
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Alternatively, the civilization could have outgrown radio a few thousand years earlier.
 
I have had this discussion a number of times before and there are always a number of elements and possibilities that often get ignored.

1. Communications.

We have been looking for radio waves mostly as a sign of civilization. However, even our own civilization is starting to use other means of communication rather than sending powerful radio waves into space. Efficient communication means that only the intended recipient receives the message and only enough energy to get that message to the recipient is used. For example, early tv shows were broadcast by radio waves that went into space but now most are transmitted via cable. For us, there will be a period of about 60 years or so that you could detect us via radio waves. After that, you could not.

2. Spreading through the galaxy.

The assumption is that a civilization would spread throughout the galaxy. Again, efficiency would tend to dictate that such a process would be done with an eye to minimizing the cost. Planets would be observed first, likely remotely as we do now, and then scouted. The biggest argument I see on that subject concerns the use of Von Neumann probes. In my opinion, there is not enough discussion on the vast technological problems involved in creating Von Neumann probes. Even if it were possible to do so, Von Neumann probes would not be more efficient than living organisms since they would have to find materials to reproduce, which would be difficult, time consuming and energy intensive. I think the time scale involved in settling the galaxy is likely enormous, even if faster than light drives were possible.

Lastly, I don't think arguments such as "It is the nature of intelligent life to destroy itself", "It is the nature of intelligent life to destroy others" or "Life is periodically destroyed by naturally occurring events" are likely solutions. A galaxy is a huge place. To make the assumption that every potential civilization is going to follow a similar path seems unlikely.

The biggest problem in this is that we don't know exactly what is required for life to arise. Once we solve that, we can make an better estimate of the chances of life in the universe.
 
An amusing hypothesis in the url referenced in the OP. In the "Old Days" someone would have written a short story and had it published in Amazing Stories.

There have been many many SF stories written to explain the lack of Contact. Just as valid.

Ask the Galactic Federation. ;)
 
On the timescales involved, I still have a hunch that the "first past the post" on expanding beyond one's solar system gets the whole galaxy, unless two separate intelligent-life bearing planets happen to reach that point close to the same time--and the odds of that seem very slim to me. The reason it's just a hunch for me is that it is sensitive to variables we don't truly know the values of.
 
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One of the problems with detection, being detected is creating an energy signal of some sort that is not expected. Any attempt we make has to be able to over power the energy signal of our own sun.

With current technology the only way we have to do this is by nuclear detonations in space. Effectively make mini Gamma Ray Bursts. If aliens are anywhere near our technology they would already have detectors watching for these events.

We would need to explode these bombs at regular intervals over a reasonable period of time and hope someone is looking.

In the future there is potential to either use petta watt lasers rigged up to the larger telescopes around the world to flash the universe, by simply sending a signal that outshines the sun for a few fractions of seconds.

The other idea is neutrino pulses, these unfortunately are very directional so we could miss a target altogether. Currently we need a collider with about 10 x the current maximum power output to create a beam of any value
 
Who says we haven't? The assumption is that if there are aliens visiting the planet that they'd make themselves known more visibly but is that realistic?

We certainly have a lot of UFO reports. Maybe that's aliens. Maybe not? But considering diseases that could stem from more personal contact, causing panic by just their appearing and possibly getting shot at, if there are aliens, they may think a more personal, visible encounter where they basically sit down with people and try to communicate is unwise both for them and us.
 
"Maybe that's aliens" is a fairly thin statement, considering how many other things it can be, and how often it turns out to be those other things.
 
gnome said:
"Maybe that's aliens" is a fairly thin statement, considering how many other things it can be, and how often it turns out to be those other things.
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LOL I am not sure of your age, but I recall the flap created when the first pulsar stars were detected in the late 60's. Some astronomers really thought we might have got one.
 
I find it funny that those theories about aliens speak about them as if they were merely a different race of humans or something. We have absolutely no idea how an alien life form would be and whether they would reproduce like earth life forms or whether their evolution would have anything to do with our evolution.
 
Without reproduction, aren't we left with spontaneous generation? Evolution is at least something of a strange attractor towards more highly ordered forms that could be recognized as life.

It seems like anything else would practically have to poof into existence already ordered, by sheer cosmic luck.

Now, this is something of an argument from personal incredulity, I admit. Seriously it would be neat to imagine a way for something recognizable as "life" to form outside the two options I described.
 
gnome said:
Without reproduction, aren't we left with spontaneous generation?
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I have no idea, but why for example couldn't alien life be -at this moment- something like software which self-corrects and expands and needs no "children" ?
 
Software running on what, exactly?

Whatever aliens are, they're real. And reality comes with the unfortunate limitation of being a bugger to get anything done in. What we call "evolution" is nothing more than a descriptive term for what happens when everyone tries to get their stuff done at the same time. Evolution, Intelligent Design (turtlesturtlesturtles), and Spontaneous Generation are the only ways we've thought up for complicated things to now be where they were not.

But don't worry, evolution doesn't come with any inbuilt notion of what creatures should evolve into, so said aliens can still be plenty strange.
 
The universe is very big and very old. If there are, or were, aliens elsewhere we might never know, or only find out long after they've died out, or they could only find out about us long after we've died out.

I think the assumption that intelligent aliens would inevitably colonize the entirety of the galaxy they were in is unjustified. They might have no urge to colonize outside their solar system; they might find it cost-prohibitive; they might die out before they develop the technology to do so.
 
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