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Joined: 18 Dec 2015
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09 May 2019, 10:52 pm

There are a few old BOINC & SETI threads. Here's a new general-purpose one.

An interesting essay on how signals could be sent/received using very simple technology that would last a long time.

Mirror in the Sky

An old technology is the key to a new method in the search for extraterrestrial intelligence.

The simple mirror can act as a powerful beacon when it is reflecting direct sunlight. Unlike the surfaces of most objects in the Solar System, which reflect light diffusely in many directions, mirrors display specular reflection. Light that hits a flat mirror retains its directivity, instead of going every which way. Since sunlight comes from the narrow-angled disk of the Sun on the sky, an alien probe with a mirror-like surface would reflect sunlight into a narrow cone, and the reflection would shine very brightly....

There Are Four Lights!


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Joined: 26 Aug 2010
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10 May 2019, 2:09 pm

The article seems incomplete. Like it got chopped off. Its doesn't really SAY anything.

Okay so a meter wide mirror can reflect light from our own sun so sharply that it could be seen 100's of millions of miles away.


So what?

So if we Earthlings were to put such a mirror into orbit around our sun it would be a beacon that anyone could see.... a few hundred million miles away. But that's no where near enough to reach beyond the inner part of our own solar system. An astronomical unit (the distance from the earth to the sun) is about 100 million miles. So if this beacon could reach 5 AU it would only reach Jupiter, and not even reach Uranus or Saturn. It certainly couldn't reach the nearest exo stars (like even Alpha Centauri). So no aliens would see it.

Ditto if alien beings living on a planet orbiting Alpha Centauri tried to signal us.

Okay maybe the author went on to say that you could make mirrors any size that you want. Make one a whole kilometer wide and it would have a million times the surface area of the one kilometer version (and therefore presumably reach a million times as far), and make it still bigger to reach the stars. Okay maybe that would make sense.


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Joined: 21 Aug 2004
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19 Jun 2019, 8:43 am

Another problem is that such a beam would cover only a very tiny fraction of near space.

I've no doubt that there are other intelligences, but for meaningful contact, any such civilisation would have to be in it's technical stage (which on Earth has meant just a century or so, out of 3 millennia or so) and within 50 light years, maximum. That is such a tiny bubble of even our galaxy, let along the entire universe, that I consider the chances of any such contact to be vanishingly small, even if we broadcast a signal in all directions. To make the attempt with mirrors just reduces the possibility further by several orders of magnitude

Not diagnosed "Aspergers" [no option fits, portraying the DSM as the only (it's not) valid (it isn't) standard?]. I'm "very strongly autistic" as shown in a professional aptitude test, developed from the original definition.


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19 Jul 2019, 9:32 pm

I run [email protected] on an i3, i7 & I'll eventually add some larger computers depending on my resources. For now, machines like that would just be workstations for me.,

"Standing on a well-chilled cinder, we see the fading of the suns, and try to recall the vanished brilliance of the origin of the worlds."
-Georges Lemaitre
"I fly through hyperspace, in my green computer interface"
-Gem Tos :mrgreen: