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From: Ernest Major <{$to$}@meden.demon.co.uk>
Newsgroups: talk.origins
Subject: Re: New SETI search
Date: Wed, 4 Sep 2024 14:03:32 +0100
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On 03/09/2024 02:22, Mark Isaak wrote:
> On 8/26/24 10:24 PM, El Kabong wrote:
>> RonO wrote:
>>
>>> A group is using the Murchison wide field array to monitor for super
>>> civilizations in other galaxies.  The civilizations would have to be
>>> super advanced in order to generate the 100 MHz signal that they are
>>> scanning for.  Huge amounts of energy would have to be channeled into
>>> transmission of such signals.  Would we ever expend such an effort to
>>> tell someone in another galaxy that we exist?  100 MHz is in the middle
>>> of the FM radio band, but in our expanding universe what would have been
>>> the frequency transmitted by any one of the 2,800 galaxies scanned in
>>> the survey?
>>>
>>> https://www.sciencedaily.com/releases/2024/08/240826131354.htm
>>>
>>> Ron Okimoto
>>
>> Previous searches at Aricebo and other sites looked for
>> alien signals at 1420 Mhz.  They picked that frequency
>> because it is a hydrogen line.  The thinking is that
>> aliens would more likely broadcast there than an
>> arbitrary frequency.  It never made sense to me because
>> the signal will be attenuated by any hydrogen lying in
>> the path, and because if you tune in to the hydrogen
>> line, you'll find... hydrogen noise!
>>
>> Maybe space aliens will broadcast on 100 Mhz because it's
>> a nice round number?  Then again they might have 3 digits
>> per hand and use a base-6 system and think 60.466176 Mhz
>> is a nice round number where other hexadigits would
>> listen.  In any case you have to pick a frequency
>> somewhere.
>>
>> The article you cited does link to an article on a
>> previous survey done in 2020, but it doesn't mention the
>> frequency.
>>
>> If the aliens transmit from a large phased array like MWA, they could 
>> transmit a large effective power within
>> the beamwidth, without actually transmitting huge power.
>> But the beam has to be aimed in our direction.  Maybe
>> they send signals periodically in every direction.
>> Similarly the MWA has to have its array pointed in the
>> right direction at the right time.
>>
>> The chances are slim, but worth trying.
> 
> If I had vast technological resources and wanted to send an "I'm here" 
> signal to unknown aliens over potentially vast distances, I wouldn't 
> generate light. That would take way too much energy, especially if it 
> was broadcast widely. Instead, I would rig up some opaque sheets and set 
> them orbiting around a star, with gaps in places so that anyone watching 
> from the plane of orbit would see a dit-dah message spelled out 
> repeating every 6 (of our) months or so.  It would work only on a fairly 
> narrow plane, but at least it's better than a laser pointed at a single 
> target.
> 
> Is SETI set up to look for anything like that?

There are people looking for (and finding) Dyson sphere candidates. And 
in general variable star searches would turn up the arrangement you 
describe.
> 
> Of course, I would never do anything to attract strangers until I was 
> more than confidence that my technology could overpower any hostile 
> aliens I might attract. If possible, I would set up the signal several 
> hundred light-years away from concentrations of my species' population.
> 

-- 
alias Ernest Major