Carnot Efficient Dyson Spheres Are Undetectable by Infrared Surveys (2016)
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An exponential increase in size is not "a relatively small increase in resources and time." It goes from "something that could be built with all the mass in the solar system" to "something that requires the mass from an additional couple of hundred solar systems to construct".
I'm also curious about whether a Dyson sphere which would roughly equal Neptune's orbit would have sufficient sunlight at any given point to sustain life (at least, life as we know it).
I'm not a member of an alien civilization with the technology to create a Dyson sphere, but as a lowly human engineer, the costs don't seem worth the benefits, especially without some other form of energy to supplement the 650x increase in energy needs.
The question is if you could capture the energy and you had the material resources would you let it escape into the universe at 290K?
For better or worse, we have to assume the alien civilizations have the same physics that we do, otherwise the civilization simply has to build their 1au sphere out of artificially created unobtainium to achieve 99% efficiency.
The outer shell does not need to be a single structure. A swam of micro satellites orbiting at 25 AU with 1 atom thick carbon antenna collectors (think black snowflake) would on average be not much more than 1 atom thick and would collect 99% of the energy emitted by the star or inner shell(s).
This is all rather beyond what my post was about which is that only inefficient Dyson spheres can be detected in the infrared and that any civilisation capable of building a 95% efficient sphere is able to build one that is 99%.
If the cost of acquiring and constructing the material into a collector were greater than the benefits of collecting a mere 4% more energy, absolutely!
Plus, for an advanced civilization, if given the choice between 99% efficiency around one star and 95% efficiency around a mere 100 stars - which is more likely to be done?
To make the analogy more relevant to humans: Why - when we're technologically advanced enough and have sufficient materials - do we let so much energy escape Earth?
Anything with sufficiently advanced technology to threaten a dyson sphere wielding species would probably detect the gravitational anomaly of the missing star and go investigate there first.
Taking a tiny portion of the energy from a bunch of stars seems wildly more efficient at surviving from a threat than putting all your resources into creating a system they're sure to investigate.
Entirely off topic, but I love how IANAL style disclaimers found their way to astrophysics discussions. IANAMOAAC anyone? I like it.
(Note: I really like it, this is not snarky sarcasm)
We long ago overcame biological limitations on our lifespans. Since then, the two things they matter to us are not dying by accident, and not getting bored. As you can imagine these can come into conflict on occasion. But building oversized Dyson spheres is fun and not particularly dangerous m.
Or are you guys capable of slowing your perception of time so it seems to go really fast?
I believe the closest equivalent human term is VR MMORPG.
That's assuming the larger surface area is undesired, and the extra space won't be utilized for something else, like habitation, or storage.
Unless they're hiding from something ... something terrible. Coming to a silver screen near you.
Another point worth considering is that if the biology of the aliens were Earthlike, it would be nice to have the "native" intensity of sunlight (or close to it) available everywhere on the inside of the sphere.
Even if the biology were oriented to 4x less insolation, that would only be a 2x increase in sphere radius.
I think the "efficiency" concern is a bit silly also, since advanced alien civilizations will have advanced, high-density power sources available as needed. The only rationale I can see for very high efficiencies would be the desire to hide...and that might be a valid concern.
This provides another thermodynamic reason to make a Dyson sphere as large as possible.
No. It is about abstract computation, which is based on (our best understanding of) theoretical physics.
"The principle is widely accepted as physical law; but in recent years it has been challenged^[how?], notably in Earman and Norton (1998), and subsequently in Shenker (2000)^[10] and Norton (2004,^[11] 2011^[12]), and defended by Bennett (2003)^[1] and Ladyman et al. (2007).^[13]"
So even now, a mere 56 years after its proposal, this principle is coming in to question. How much more questionable would it be after millions or even billions of years of physics research that alien civilizations may have under their belt by the time they start building these sorts of Dyson spheres? How many revolutions in physics knowledge might they have had by that point? They may be able to perceive reality in completely different ways than we do, and have unimaginable intelligence at their disposal.
It is certainly fun to speculate, but I personally find it very difficult to put limits on what beings like that might be capable of, especially when those purported limits are the results of mere human thought.
"using a relatively small increase in resources and time."
A sphere with 99% efficiency would need 25 larger radius according to the article, which is 625x more material assuming the thickness can be the same and doesn't need to be more be be structurally working.
625x to me doesn't sound like a "relatively small increase in resources".
But it looks like some people consider an increase of 62400% in resources a "small increase".
a.) The inner layer is thicker than the outer layer, but not much
b.) The outer layer has a surface area 625x larger than the inner layer
c.) The outer layer needs only a "small increase in resources"
I still don't get it.
The relative small increase is not in reference to a smaller sphere, but to the material resources of the stellar system. If you only need 0.00000001% of the material resources of the system to build an inefficient sphere then using 625x more is not a significant increase.
I am also not a member of an alien civilization with the technology to create a Dyson sphere, but this strikes me as being very good from the standpoint of such a civilization's operational security.
A civilisation capable of building a Dyson sphere should be able to come up with a better use for a star than just lighting up the universe.
Did he ever write that other post? If so it must have a high Carnot efficiency because I can't find it /rimshot
It had always been ruled out previously because astronomers said they'd be easily detectable.
Though who knows what it actually is.
It must be a slow day on HN for this post of mine to make the front page :)