In article .com,
Ian Parker wrote:

No, I think it will be nornal. Probably if we are the first
civilzation the gap will be of the order of a million years, or at
least 100,000. However you can't be absolutely sure.

You can be very extremely darn close to sure. In a normal distribution,
the spacing between the outliers is quite large (as compared to those
near the mean, which of course is rather small). What "large" means
depends on the standard deviation, but in the case of
time-to-civilization, any reasonable model will result in a standard
deviation of hundreds of millions of years, if not billions.

In that case, the spacing between the two most extreme outliers at one
end of the distribution being a mere 100 KY is quite unlikely. Millions
or billions is more likely.

The model I was
thinking about at the back of my mind was the radioactive atom. It is
not impossible that there could be another civilization close to ours.
Unlikely perhaps, but just possible.

Right. Not sure what radioactive atoms have to do with it, but of
course we can only speak of probabilities. The probability you bring up
here is very, very small.

In my discussions on ET I have sought to eliminate the impossible. NOT
the improbable.

Well, great, but that doesn't help much. It's not impossible that we're
all just figments of the God computer's imagination, which will be shut
off next week. It's not impossible that the our solar system is inside
a vast shell 1 LY across, built by aliens, which serves as a giant 3D
display, and eventually the Pioneer and Voyager probes are going to go
splat against it. It's not impossible that there is some way we can't
yet fathom for advanced races to leave the universe of their birth and
get an entire universe to themselves, thus explaining the apparent
emptiness we see.

But, most of those we can't even assign probabilities too. This one we
can, and it works out to a very small number. (No, I don't have a
number handy; it's been a while since I actually did the math.) Why
focus on such an unlikely situation, when there are far more likely ones
that fit the observations just as well? (Namely, that we're the first,
and our closest competitors are millions of years ahead or behind us.)

I am saying that with a large number competition is more intense and
there might be one near us. We of course don't know. For all we know
Earth could be rare.

It really doesn't matter how many there are; competition won't be more
intense in any case, since all that matters is the first couple of
outliers. If there are many participants, then the outliers will be
more extreme, and thus more spread out. If there are few (i.e. life is
rare), then the outliers won't be as extreme, but they'll still be
spread out.

I feel I'm explaining this poorly... where's a statistician when you
need one?

It is possible that there are civilizations (allowing for speed
of light) that are 20-300 years ahead of us or 100+ yars behind.

Yes, and SETI proponents seem to implicitly assume this, but it's a
ridiculous position that I think comes from watching too much Star Trek.

It could be too much Startrek. It could also be that SETI knows that
it can only look for civilizations within these limits. If a
civilization is a million years ahead of us we sure would have heard
from it by now. If it is behind us, does not have radio of any type it
will be impossible to detect.

Good point. Yet, if you've invested years of your life into SETI, you
get emotionally attached to it and can't let logic or negative results
sway your position. So you end up imagining a galaxy full of
civilizations that have evolved at exactly the same moment as us
(geologically speaking), illogical though that is.

And because of the exponential progress of technology, even a few
hundred years makes a big difference at this point. At thousands or
millions of years, you're looking at the difference between no
civilization at all, and some post-biological star-spanning civilization
that would make us seem like mildly clever monkeys.

Indeed. I believe that well within 50 years we will have a full space
capable Von Neumann machine. An interstellar probe may well be closer
than we imagine. Unmanned of course.

Perhaps. I believe that within 50 years, we'll have mind uploading.
(Ray Kurzweil puts it at more like 20 years, but I am a pessimist.) If
you and I are both right, then those "unmanned" probes may well have
people on board, albeit in digital form.

A civilization a million years in advance of us, I repeat, is an
impossiblility. We would know about it.

Unless they are intentionally hiding from us. In that case, I have no
doubt that they could do so successfully, and our crude efforts to
detect them would be futile.

But I tend to feel that this is unlikely. More likely, there's simply
nobody out there, and won't be anyone else for millions of years. When
those late-comers finally arise, they'll awaken to a galaxy long since
settled by us and our descendants.

What I have in mind for the medium future is in fact the large
fragmented telescope. Justification - Finding out for sure. I think
Einar is right. If we do not advance it we do not have curiosity we
are indeed doomed. This is not to say that manned space flight is the
best strategy, or that we need to think of colonies in the solar
system in the medium term. In the medium term, and possibly even the
short term, we need to think about improving automation techniques
with an eventual VN aspiration.

I don't agree. VN machines are certainly possible, but I hope they're a
long way off, and carefully regulated. If ever there was a technology
ripe for disaster, that's it. I see very little benefit to justify the
risk.

Best,
- Joe

--
"Polywell" fusion -- an approach to nuclear fusion that might actually work.
Learn more and discuss via: http://www.strout.net/info/science/polywell/