Eric,

Your comments below are such a mix of lucidity
and obfuscation that I am not sure I can disentangle
the two. Here's my attempt with previous apologies:

Eric Hawthorne wrote:

> On the likelihood of detecting alien intelligences:
> (single-world case)
>
> 1. It is an enormously stupid conceit of us to assume that
> aliens would be broadcasting, or tightbeaming something like
> analog radio signals, for communication.
> We ourselves have only being doing that for 100 years,
> and will be ceasing to do it before the next 100 are up,
> having switched to a combination of closed fibre-optic and
> massively spread-spectrum (i.e. noise-like) digital radio.

There is a group of people in the institution I work for who
spend their time and some taxpayer's money doing just that.
I would not call them stupid but this is what I can anticipate
of their answer: they do not look at radio signals and they
only did that because that was the only spectrum accessible
for a long while. Today the radio universe is pretty well
charted so they are looking at MW,Visible, UV,Xray data
etc... as satellite missions make each part of the spectrum
available. The correlation techniques developed beforehand
are now sharp enough to use with broad spectrum data...

> 2. We have not built dyson spheres, nor are we likely
> to. There were a number of crazy megaproject engineering
> fantasies that we had for the first few short years after
> we discovered how to build with reinforced concrete, and
> Dyson spheres were one of them. (As were those incredibly
> ugly but functional 60s and 70s concrete skyscrapers. The
> first crude phalluses erected using a new but not completely
> mastered building technique.
>
> I'd like to think that we have a slightly more refined
> sense of megaproject risk analysis now that will prevent
> us doing quixotic projects like Dyson spheres.

How are analog radio waves somehow "passe'" in your
opinion but Dyson sphere and Rings or skyscrapers any
kind of standard for observing alien life? Or our own,
by that matter?

>
> 3. We can barely detect planets the the size of Jupiter around
> nearby stars today. Why would we be able to detect non-radiating
> dyson spheres? Wouldn't we mistake them for black holes at the
> least?

Try to see it this way: in a mere 4 years and employing a single
technique (maybe a couple) we have been able to detect a good
150 Jupiters (give or take)! I'd say it is not a bad working rate
specially for a race that had not found one for a few million years.
Now when you consider that, for two or three jupiters we may
anticipate a dozen or so habitable zones in our close experience
I'd say you would not have to be a Sagan to find this encouraging...

>
> 4. The life span of a higher mammal species (clad, actually i.e.
> tree of derived species i.e. branch of evolution)
> like ours is estimated in biology to be 5 to 10 million years,
> and we're a significant way through our tenure, so we'd
> better hurry up sending out those self-replicating V-ger
> robot probes all over the place for them to be detected a
> million years hence. We'll probably be gone (as a species
> and clad) by the time the reply arrives.

I'd say that by your count we are already gone!


In any case nothing you say above appears relevant to the
gist of Fermi's argument which is taken perhaps too seriously
by many of ET's friends! The best answer I have heard is in
the way of your first point above: how arrogant of us,
backward eartlings, to assume that any advance civilizations
would care to meet us!

Cordially,

-Joao Leao

--

Joao Pedro Leao  :::  [EMAIL PROTECTED]
Harvard-Smithsonian Center for Astrophysics
1815 Massachussetts Av. , Cambridge MA 02140
Work Phone: (617)-496-7990 extension 124
VoIP Phone: (617)=384-6679
Cell-Phone: (617)-817-1800
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"All generalizations are abusive (specially this one!)"
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