Astronomy Cast Ep. 388: Megastructures

Article written: 19 Oct , 2015
Updated: 28 Dec , 2015

This week astronomers announced an unusual transit signal from another star. Although it’s most likely a natural phenomenon, one remote possibility is that this is some kind of alien megastructure. Freeman Dyson and others have considered this idea for decades. Today we’ll talk about the kinds of structures that aliens might want to build.

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11 Responses

  1. yosemite_yam says

    I so love the “we don’t know what it is, therefore it might be Aliens” thinking. How would an alien mega structure describe what Kepler is seeing any better that some sort of variability or instability in the star? Why are you spoon-feeding the kooks?

    There was a comment from someone in the earlier U-today article on this where mess resulting from a collision of “Jupiters” would create a large clouds that could block a lot of light and not be emitting infrared light. Even if that’s not right, it is testable and a better argument than “Its a Dyson Sphere! That’s not built all the way yet! And doesn’t radiate heat! “

    • Bo Zo says

      A, B) The speculation is fun. This and other media sites are MEDIA sites, they exist to sell ads by attracting the public. (A few are also informative.)

      C) Simpler explanations like ordinary objects and stellar dynamics are problematic. Even though (as all scientists are quick to say) it PROBABLY IS a natural phenomenon, it’s seems like a weird one and may require new ideas.

      D) It might in fact turn out to be an incomplete Dyson sphere! (Do you have a better theory?)

      Edit to add:
      (I’m not entirely unsympathetic to your position. Ordinarily I object to invoking aliens to explain the strange faces people see in their breakfast cereal. But this time, for now, it’s kinda legit to consider ET among the possibilities.)

  2. Bo Zo says

    (I haven’t heard the podcast yet.)

    I’ll go on record as saying I guess I don’t have enough imagination, but I can’t think of many, if any, megastructures worth building.

    In the case of USEFUL things, like solar collectors, lots of little ones would be just as good as one big one, only better, and much easier to build. That pretty much applies to other useful structures too: shipyards, colonies, Maginot lines in space… All are improved by not being bigger than planets. (And I think Dyson spheres et al. are plain silly.)

    Thus a useful megastructure might have to involve some exotic technology that was ONLY POSSIBLE, or much more useful, on an astronomical scale; something like a stargate that has to be huge due to alien physics.

    The other sort of possibility that occurs to me is something USELESS built large for largeness’ sake – something like a shrine or a tomb (compare to pyramids, Taj Mahal) where utility is secondary, where the idea is to demonstrate vanity, wealth or power, and where economy and efficiency are actually negatives. (So human!)

    If I had to guess, I’d bet that either there are no megastructures at all, or else that mega-gigantic tombs are more common than factories or cities.

  3. Member
    robst247 says

    What if the aliens are so advanced that they deliberately assembled and moved megastructures around their star as a ‘smoke signal’ to trigger curiosity elsewhere in the Milky Way galaxy. It’s working! What if they’re saying: “We’re here – the space weather’s nice – come to the party! RVSP.” Sadly, even if we could travel at light speed, we’d miss the cosmic binge by more than 3000 years. We’d probably have to clean disgusting beer- and wine-soaked cigarette ends out of the ashtrays, take the empties back to the supermarket and vacuum the sticky carpet. What a bummer!
    Or what if the aliens don’t need megastructures? What if they are mega-aliens who float bloatedly around their star at their own volition?

  4. Gaugain says

    I think the dyson sphere is a very bad idea. You won`t have gravity on the structure (much like on the ISS) which would be very annoying. If you want gravity you`ll have to spin it very fast, and than you`ll only have gravity on the equatorial zone. So it`s a very bad idea to build a sphere , when you should build just a ring around the star , and spin it, living on the inner side facing the star, feet on the structure.

  5. kkt says

    Larry? Is that you?

  6. FarAwayLongAgo says

    It’s just a glitch in the electronics.

    von Neumann machines could be detected indirectly if they terraform the planets they get to, and we observe a bunch of planets which are very similar to each other in a certain local area of the galaxy.

  7. BlackWolfStanding says

    The thing about a Dyson Sphere is the incredible amount of material it would take to build one that would encompass a complete star at 1 AU (assuming the star is like our sun). There simply is not enough material in the solar system unless you just make ribs and loops around the star and not a complete sphere. Even then, you’ll need more material than what our inner solar system has. So, you’ll need two things to occur. Intelligent space-faring race which we have yet to prove any exist. And a very rocky planet infested solar system which we have yet to find.

    But you never know. Maybe they mined a nearby solar system to enhance theirs? But even this is implausible because of the time involved. I can just see the conversation. “Commander, we have just officially finished the Dyson Sphere just in time to watch our sun start the expansion into it’s Red Giant state.”

    • mewo says

      That would depend on its thickness, wouldn’t it? At a distance of 1AU, a solid spherical shell with the same volume as the Earth would have a thickness of just under 4mm.

      It would depend on how much of the content of a gas giant would actually be useful in making a megastructure, but I estimate that you could get up to a metre in thickness if you converted Jupiter into a Dyson sphere.

    • kkt says

      If they were capable of interstellar travel in a reasonable length of time, wouldn’t they colonize other star systems instead of hauling bunches of ore back to their home system?

  8. Pasander says

    With unobtainium-computium-technologium, couldn’t you just drop a shell over the entire surface of a star? The surface temperature of most stars is not that high.

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