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Re: Earth's intrinsic glow.

At 11:31 AM 7/19/96, Kevin 'Tex' Houston wrote:
>Kelly Starks x7066 MS 10-39 wrote:
>> At 10:21 AM 7/19/96, Kevin 'Tex' Houston wrote:
>> >I wonder what such a probe would reveal about earth?  Assuming a .4 C
>> >fly-by and a
>> >favorable position (ie earth is seen from a distance equal to 60 to 120
>> >degrees of
>> >earth's orbit.) would a standard set of spectrographic instruments be able
>> >to detect
>> >Oxygen or Carbon Dioxide?  Would a wide band radio reciever be able to
>> >detect our
>> >television or satellite transmissions?  Would a good night-side photo
>>show the
>> >rivers and seas of light that populate the north-american continet?
>> >
>> >In other words, if some other world sent a probe here,what is the minimum
>> >sensitivity
>> >required for it to return useful data? (ie. that the third rock from the
>> >sun is a
>> >life-bearing world)  Follow-up question, do we have the required technology?
>> >
>> >--
>> >Kevin "Tex" Houston    http://umn.edu/~hous0042/index.html
>> I know we don't show up that well in the day visually.  But with a big
>> enough scope you can resolve down to any res you want.  We have designs
>> (well concepts) that could resolve objects down to a couple meters from a
>> few light years away.  The geometric structures of our roads, fields, and
>Okay, but could you do it on the fly (at .4C) and keep it small enough to
>be an easy sale to the politicians (you've seen how horrendously expensive
>interstellar flight can be.) and could you have a wide enough field of vision
>to detecty something you didn't know was there to start with

You miss the point.  You could do it from here, to anywhere you'ld want to
go to at .4c.  They are currently trying to propose it to our gov for NASA
to implement.  (No news as of yet.  Concepts probably still being worked

>> agraculture would be a dead give away.  The geometric pattern of city
>> street lights, and trafic flows, at night would be an incredibly obvious
>> hint!!
>So what's the smallest cammera you could get away with to spot this from
>1 AU away?

Don't know, but to spot it from 10 light years it would need an efective
apiture of a couple hundred miles or so.

>> In the radio and EM bands we are VERY bright.  We outshine the sun in some
>> EM bands.  Personally as an ET I'ld be a little suspicious of a planet
>But that's only because the sun doesn't shine in those bands. how far away is
>our power grid visible?  I'd think spillage from a sattelite uplink would be
>more visible than leakage from a power grid over light years, if only due to
>there being a tighter beam from the up-link.

That only helps if your in the narrower beam.  Don't know about distences.
Probably at least a couple hundred light years.  (Your taking about a lot
of power.)

>> where whole continents were syncronized with a 60 cycle per secound hum
>> (I.E. our power grid).  I have no idea what the transmition rating for the
>> power grid is, but I'm sure you could detect it a few light years away.
>I don't know about that, you might be able to chalk it up to some strange rock
>formation that's re-radiating sunlight with some kind of storage ability to
>account for nighttime transmissions.  Kind of like glow-in the dark minerals
>that can stay lit for hours after the light is out.

You probably would, but you'ld also want to aim a scope at us to make sure.

>> The question isn't could they see us, but how closely would they be
>> looking.  We have no official programs looking, and few private ones.  Then
>> again, we'ld be pretty hard to overlook at close range!
>The real question is "how big a system do we need to spot non-intelligent life
>in a system we know nothing about at a decent fraction of the speed of light."

Non-intelegent?  From here, with a big enough scope (couple hundred miles)
and time to watch trends no problem.  There, in orbit, with a couple meter
lens no problem.  Blowing through at .4c, BIG problem.  I'm not sure it
could be done.  Well I suppose you could rig out a wire mesh a few hundred
miles across with scopes on the mesh, and watch it as you approach.  And
again later after you left.  You can't look at close aproach to anything
because it would be sliding to the side of your view.  Assuming you wern't
going to crash into it of course. ;)

>Kevin "Tex" Houston 	http://umn.edu/~hous0042/index.html
>Every time a third party candidate comes up, both major parties say:
>"You can't vote for him, you'll just be handing the election to the other guy"
>Well, Democrat and Republican are just two different names for the same thief,
>So what does it really matter?  This time I'm voting Libertarian.
>Harry Browne for President.  http://www.HarryBrowne96.org/   (800) 682-1776



Kelly Starks                       Internet: kgstar@most.fw.hac.com
Sr. Systems Engineer
Magnavox Electronic Systems Company
(Magnavox URL: http://www.fw.hac.com/external.html)