Dyson spheres

[andygates]

Dyson spheres are cool.  They're hypothetical future-scifi-engineering gone mad: a shell around a star to capture and use all it's energy. 

Theoretically, they'd still radiate a little bit: they'd be big, cool blackbody emitters - leaking a little warmth out into space.  A chap at FermiLab took the IRAS infra-red sky survey and analysed it for just such things (tip: BadAstronomy).  He found just seventeen good candidates.  Assuming their starting criteria are good, that's pretty rare.  Still, every one of those could be a matrioskha brain crammed full of nested computronium, so don't lose heart.

The approach: that life = weird spectral characteristics = detectable, is groovy.  I'm pinning my hopes on getting some visual spectra for extrasolar planets, though.  When we find one with an atmospheric composition that's outside the adiabatic steady state (as Earth is, and Mars is not), then we've got something.

Comments

[skean.livejournal.com]

DA had it right:

Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the drug store, but that's just peanuts to space.

My brain won't compute the scale of such things

[despaer.livejournal.com]

Umm. Can I just say orbital mechanics to the Dyson sphere?

[andygates.livejournal.com]

Which bit?

[despaer.livejournal.com]

The bit where bits of stuff orbiting a larger body all end up in a ring because they are unstable otherwise, like round Saturn. You could probably get odd bits to go round in a different orbit but the time required to set enough of these up that they completely obscured the parent star whilst being far enough out to not be melted by it would result in them all strting to hit each other.

I think it is possible to get some stuff orbiting stars to harvest solar energy but not in an all-concealing mass. Of course, my work here is off the top of my head and unsourced so you never know. I might have a bit of a google on the subject if I have the time...

[andygates.livejournal.com]

Ah well, we'll just build a Culture-style Orbital instead...

[(Anonymous)]

I thought it was because things "orbit" because they fall at a speed that matchs with their tragectory angle. Thus they fall past, but enough gravity vector to keep constant rotational effect.

So in a globe, each item would be falling in a separate loop (ie meridans would cross somewhere) so having timing issues. This would also have to take into account with the gravitation "nudge" from each other item in its position (wobbling).
Eventually they will pull each other into a parallel orbit (at distance ~0 meters, but with different timings (d of T) OR collide and the resultant pieces will crash or orbit (the orbitals again getting the same effect).

In a dysan sphere the opposite gravitationals must balance out (holding it still).
If it were rotating then the tropical band might be orbiting - but the polar regions would just be spinning.
If the tropical band was going faster it would attempt to break orbit ... and the poles would still be spacial stationary.
For the poles to move they would need vectors and right angles to the tropical band...

Cheers,
Carl

[andygates.livejournal.com]

Oh, of course, a polar section would have no motion, no orbit, and so would fall in. You'd need to build it out of unobtanium.

[despaer.livejournal.com]

Also I just remembered. Look up brown dwarfs. these are lumps of stuff large enough to generate heat by gravitational contraction, or sometimes by fusing odd bits of lithium and deuterium in their cores but not large enough to generate P-P fusion. Lumps about 10-80 jupiter masses. These can typically have temperatures around 600K-2000K so I suspect a coldish one might look like a dyson sphere and emit in the IR. Try this for size, if you trust Wikipedia

[andygates.livejournal.com]

Aye, brown dwarfs are a much better candidate for big warm things than Dyson spheres... I guess the most interesting part of the study is that there were a small number, and not, say, a spread of 'em radiating out from a common but astronomically uninteresting centre - which might shout "settlements!".

Non sequitur

[estaratshirai.livejournal.com]

Hey, who was that Web cartoonist we were both grooving on? The one with the RPG featuring Zeno's Paradox? I don't seem to have the link any more.

Re: Non sequitur

[andygates.livejournal.com]

Dresden Codak.

Re: Non sequitur

[estaratshirai.livejournal.com]

Vielen dank.

[teahisme.livejournal.com]

Space the final frontier...I think they made a Star Trek Next Gen episode about a Dyson Sphere. Isn't that the one with Scotty before Doohan died?

I would love to see a picture of a planet like our own in another galaxy though. That would be super cool. I figure with medicine as it is barring strange things I have just shy of another 100 years. Think they can do it in that time?

[andygates.livejournal.com]

Not in another galaxy but in another local solarr system, sure, why not? The limit will be theoretical limits to do with light - so we may not see it in regular colour - but it's not my field of expertise. Watch for the James Webb Infrared Telescope, which is a beast of a thing that is going up next year.

[teahisme.livejournal.com]

Perhaps I shall just watch your blog while you watch James Webb? ^.^

[andygates.livejournal.com]

http://www.newscientist.com/article/mg20026856.300-hunting-new-earths-and-the-edge-of-the-universe.html

Three new super-huge telescopes in the pipeline. Adaptive optics mean they can work from Earth and compensate for atmospheric distortion.