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Alicorn comments on Max Tegmark on our place in history: "We're Not Insignificant After All" - Less Wrong

18 [deleted] 04 January 2010 12:02AM

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Comment author: Alicorn 04 January 2010 02:39:19PM 0 points [-]

The strongest reason that aliens might be invisible to us is that they are deliberately hiding.

Couldn't they just be really, really far away; or have a structure and value system such that their bustling activity looks like natural phenomena; or be trying like hell to get our attention but finding us kind of hard to talk to?

Comment deleted 04 January 2010 02:59:06PM [-]
Comment author: Jack 04 January 2010 03:25:09PM 2 points [-]

They'd want to capture low entropy sources of energy, and radiate away all that energy as high-entropy infra red radiation.

Could we detect Dyson spheres if they were out there?

Comment author: whpearson 04 January 2010 04:03:51PM 0 points [-]

Might we be able to see them if they went in front of galaxies or other highly luminous body?

Comment author: Jack 04 January 2010 06:01:05PM 0 points [-]

Come to think of it, wouldn't they look a lot like black holes?

Comment author: whpearson 04 January 2010 06:31:01PM 0 points [-]

Not really. The black hole might have hawking radiation it should also gravitationally lens the surroundings more than a dyson sphere.

It might also have an accretion disc.

Comment author: MatthewB 04 January 2010 04:37:53PM 0 points [-]

Or if they entered a region of dust or gas that had a temperature differential to the sphere.

If fact, I just realized that if any such structures like Ringworlds existed, they would be trivially easy to spot if they were at the right aspect to us. It would look like a star with either a band across it, or like the star had a single ring. The ring on the far side of the star would also be tremendously bright (if angled to our solar system slightly) and much easier to spot with a telescope that blocked off the light of the central star.

Just an OT thought.

Comment author: Jack 04 January 2010 06:00:54PM 0 points [-]

Stars are too bright and too far away and the ringworld too thin (at least I think there would be stability problems if they were built too wide, but I don't know enough). Worse, I thought the way we were trying to detect planets these days was by looking at the gravitational effect the planet has on the star. But wouldn't a ringworld balance out its own gravitation effect on the star?

Comment author: MatthewB 04 January 2010 08:47:04PM *  0 points [-]

The Kepler Observatory also detects planets by masking the light from the star and then looking for any bright spots (Coronal Masking).

Even more advanced telescopes will use this technique in combination with the gravity wobble. There are also diffraction and coronal masking.

http://www.iop.org/EJ/article/0004-637X/662/1/738/65461.web.pdf

http://spie.org/x24241.xml?ArticleID=x24241

why did I get down voted on that post?

Comment author: Cyan 04 January 2010 03:12:20PM 1 point [-]

you need to think about physics, engineering, thermodynamics and information processing

Like this guy did. Short short version: to get the most out of your star, you drain the energy of the emitted photons until they are (almost) at the temperature of the CMB. Infra-red is still harvestable.

Comment deleted 04 January 2010 08:06:43PM *  [-]
Comment author: Cyan 04 January 2010 08:22:19PM *  1 point [-]

I think the idea is not all the stars in a region -- it's one star per civilization. The basic idea is to maximally exploit energy transfer between the star and interstellar space, so optimal efficiency makes the artifact appear from the outside to be as close to interstellar space as possible.