Space Forum / SETI / September 2006

To recap rather than quote Matt's post, he mentions space-telescopes
capable of discerning actual detail on terrestrial-type exoplanets - and
suggests that if such a telescope is possible, radio SETI is a waste of
time because direct observation will be far more efficient.

I have a few thoughts / comments:

It's probably fair to assume such scopes are possible - though the
proposal for the TPF (Terrestrial Planet Finder) would only have
resolved an Earth-sized exoplanet to ten pixels, IIRC. Presumably
larger-scale technology could improve on this, in time. (There may be
fundamental limits imposed by quantum 'fuzziness' or
wavelength-vs-resolution issues, I wouldn't know.) However...

1. First, you've got to find the planets. And radio searches might still
useful here, because they target whole star systems.

2. If we detected an exo-civ, we'd quite possibly send a radio message
to it rather than waiting to develop near-light-speed probes. Even if
governments decided not to, SOMEONE would. So, if that's what we'd do,
others might, too. Sure, these would be focussed signals, not beacons -
but it still means radio SETI's worth a shot.

3. At one time or another (mostly while making TV documentaries), I've
tackled members of the radio / optical SETI community about the limits
of electromagnetic searches. Even without this telescope idea, it's
perfectly believable that radio / laser technology might be a passing
phase: electromagnetic SETI could be looking for civilisations that are
passing through a very narrow time-window - a few hundred to a few
thousand years. The answer I have received has always been the same: "We
search this way because it's the way we CAN search, not because we
believe it's the best way possible. When new communications technologies
emerge, we'll use them, too." Now, I think this deserves further
examination...

You could argue that O-SETI is an example of this actually happening.
Laser technology plus advances in optical detection have made a new SETI
sub-model available - and we're using it. Fair enough. BUT...

Look how long it took, and how much of a struggle it was, for O-SETI
proponents to get projects up and running. There is an inherent
resistance to change in any scientific community - and SETI is no
exception. All sorts of issues provoke an almost-instinctive resistance
in those who adhere to the existing standard model: Will this new
proposal dilute my own funding? Will it invalidate my existing approach?
Will I get as many papers published? Will it discredit SETI in general -
because, let's face it, SETI has to try harder than many other
disciplines to 'prove' it's a hard science; both the public and the
powers that be have a tendency to think it's based more in science
fiction than in logical fact-based conjecture. From a lot of these
standpoints, SETI is a fragile endeavour - and competition is rarely
welcome when you're already struggling to get by.

So, *would* new SETI models get a look-in? I think the answer is that
they will spend much of their time marginalised. They will be staffed by
amateurs and part-timers rather than fully paid-up members of the core
SETI community. It will be significantly harder to get even excellent
science published. Funding will remain scarce or non-existent. This is
already happening with almost every SETI proposal based around searching
for artefacts rather than signals. Stuff *does* get done, but slowly,
and in the twilight.

No one (today, at least) would propose the telescope Matt describes
purely with SETI in mind. SETI would be a piggy-back project on the back
of a far wider research remit that would involve meteorology, geology,
exobiology, oceanography, astrophysics, etc. SETI scientists would be
lucky to get a look-in. They might, after many years be able to fight
for a little time, Arecibo-style.

And some projects are likely to remain off-limits to SETI for ever.
Anything that involves searching for ETI technology in our own solar
system (active probes, long-crumbled artefacts on the moon, pieces of
billion-year-old junk, you name it) - all these are generally ignored by
mainstream SETI. I'm bored with articles claiming it's ridiculous to
look closer to home; they never actually tackle the real arguments
head-on, they just ascribe false premises to the idea (such as, 'they'
are flying here all the time, which no one into real SETI is actually
claiming) - and then 'disprove' the false premise, as though that proves
the whole idea is garbage. If they can't apply this approach, then they
ignore the proposals completely, and hope they will go away.

It's understandable, and it comes down to two things:

a) SETI's fragile status: it needs to constantly 'prove' it's scientific
- and that means putting clear blue water in between itself and anything
that might *sound* like UFOlogy. If, in the process, genuine rational
SETI proposals fall into that clear blue water and sink, then so be it.
It's the price of survival.

b) The tendency of any committed group or community to reinforce a set
of core values, and exclude members who might prove to be a threat to
them. It's natural, and all of us do it. But this is the part of science
that has more to do with us being apes than it has to do with being
rational.

So, in summary - regardless of telescope possibilities, I think the
primary paradigm for SETI will remain as it is, or change only very
slowly. Electromagnetic SETI is one perfectly valid approach to SETI.
It's not the only one. But it has a natural tendency to crowd out its
competitors. This is the cultural equivalent of natural selection. It's
hard for new species to evolve into a niche that's already filled.

But who knows what will come? SETI is a science where we can't really
predict what we're looking for. Could be a radio signal - could be that
the Pluto Express will discover that Charon's artificial... However
things pan out, the one thing that is certain is that we're all doing
our best.

Just some thoughts,

Richard

____
Richard Burke
<www.richardburke.co.uk>

You SETI folks simply need to FOCUS, FOCUS, FOCUS your best talents and
resources upon whatever's a whole lot closer to home.

For example;  placing a 10 meter KECK into LL-1 might become worth
doing, a whole lot better off than any terrestrial 60 meter fiasco that
simply can't avoid our global warming pollution nor the signal
distorting affects of our failing magnetosphere, as it simply would not
demand all that much station-keeping energy and, it would certainly
remain as being handy and cost effective as for getting whatever
instrument updates robotically to that sufficiently nearby location.

Manned expeditions to/from that LL-1 location (parked roughly 60,000 km
from the moon), means that we could use the likes of our terrestrial
KECK in order to keep an eye on such robotic operations, while if
accomplished within earthshine or that of a brief Earth shadow might
also be safely doable in person.

This would also become a terrific radio/radar telescope platform that
could represent the best pixel resolution and/or ET signal detection
capability in town, not to mention laser cannon packet transmitting
potential.

There shouldn't be any technical reasons as to why a 50t SETI/OSETI
platform couldn't be established within the moon's L1(LL-1) interactive
zone.
-
Brad Guth

Telescopes are theoretically limited in resolution by the diffraction limit
(quantum fussyness if you like).
http://en.wikipedia.org/wiki/Diffraction

The resolution r is as small as the wavelength w times the distance R
divided by the diameter of the telescope d. Or in other words, the diameter
of a telescope is equal to the wavelength times the distance divided by the
resolution. Something like r/R = w/d.

To get 60 meter resolution at 10 lightyears, at 200nm or so, you need a
telescope with a diameter of something like 10^9 meters (sorry I dont have a
calculator handy, but it should be in that range). That is larger than the
Earth-Moon system. If we only have a radio-telescope of that size;  SETI
would be easy...

There are two possible breaks (that we know of) in this theoretical
limitation :

(1) Use interferrometry. You don't need a full circular telescope of
diameter d to obtain the resolution.Simply linking some smaller telescopes
separated by that distance d will get you the resolution. Unfortunately, you
will not be able to determine the actual location of what you are looking as
better than the refraction limit of the real diameter of these telescopes.
So you might be able to see that there are details of a certain size, but
you cannot determine where they are w.r.t. each other. You cannot take a
normal picture with such a interferrometer.
So it will be almost impossible to determine if there is something
'artificial' about the details that you are looking at.

(2) Scientists have found that materials with negative magnetic and/or
electrical permeability might allow for lenses that are not restricted to
the diffraction limit. Materials with such properties do not exist in
nature, but certain 'meta-materials' have been constructed that show such
properties for at least microwave regions. This meta-material development is
truely facinating. For example, 'cloaking' devices can be built (a microwave
cloak is currently under development) that can totally hide objects from any
observers at certain frequencies. The microwaves just go around it. When
used as lenses, meta-materials can observe details below the refraction
limit. However, I understand that the distance to the object should be very
small (smaller than the size of the lens).
So it is still unlikely that any ET can make a 'small' telescope with
smaller-than-refraction-limit resolution. At least we have still not yet
found a theoretical trick around that limit.

There can be MANY reasons why we have not detected a beacon signal yet, so
to postulate that yet unproven (even in theory) telescope technology
eliminates the objective for ET to send out any radio signals seems rather
arbitrary.

What am I saying ? Here you go :
We have scanned only a minute fraction of the radio spectrum for ETI beacon
signals.
We have scanned only a minute fraction of the stars of the Galaxy for ETI
beacon signals.
We have scanned these radio spectrums and each star only for a minute
fraction of time.
We have a scanned with a sensitivity that is astonishing for terrestrial
communication, but rather poor when talking about interstellar radio
transmissions.
We have scanned an even smaller fraction of stars of optical beacon signals
(OSETI).
Frankly, we barely started listening...

I think so far the only thing that we have shown is that there does not seem
to be an extremely powerfull semi-omnidirectional beacon in the Galaxy that
is transmitting in the 'water-hole'.
Not that that means anything, because if you would calculate the power
requirements for such a beacon (in the water hole) then you would find that
only a Kardashev type III  civilization could be able to sustain such a
beacon. And we know that there is no Kardashev type III civilization in the
Galaxy, or else there would be no stars visible at night.
Also, there are much better (cheaper) ways to build ETI beacons if someone
would want to do so. They would likely be in the 50Ghz and above area. And
we have not looked there at all yet.

And all this is assuming that anyone would ever want to send out beacon
signals. We (humans) certainly do NOT do that. Why would anyone else ?

I think it is more likely that a beacon will be directed at us after some
(radio/radar leakage) signals from us have been detected by an ETI.

The size/sensitivity requirements for such a system (than can detect our
early TV CW cariers) are much less than the requirements for a telescope
with 60 meter resolution that can distinguish a building or a city from a
mountain...

By now (50 years after first powerfull transmissions), a few hundred or
maybe a thousand star systems have had the ability to receive and respond to
our early transmissions. A few hundred out of 300 billion stars in the
Galaxy....
There can be many reasons why we have not received any signals yet, and I
think it is unlikely that the development of super-telescopes is one of
them... It's a nice idea though...

My 2 cts.