So, for that additional 4% efficiency, the radius must be increased by 25x; making the total surface area somewhere around 650x bigger?
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.
Heh - well, when we're discussing hypothetical super-advanced aliens with technology and capability to create Dyson spheres, it seems sufficiently outside the scope of my knowledge to justify the disclaimer. ;)
Speaking as an alien, we don't have a concept of 'cost' the way humans do.
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.
Aren't there long stretches of time where the nanoreplicators just do their thing and all you can do is watch and/or get another cup of space coffee? (somewhat like the computer program compiling processes on earth)
Or are you guys capable of slowing your perception of time so it seems to go really fast?
You don't need to make a single sphere (swarm more likely). If you arrange the shells in layers the outer layers can efficiently capture the long wavelength radiation using relatively little matter.
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?
> 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?
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?
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.
> 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
Unless they're hiding from something ... something terrible. Coming to a silver screen near you.
I've seen mention before of the Carnot efficiency of Dyson spheres, but what about Landauer efficiency? Assuming the DS is powering a bunch of computers, and assuming sufficiently advanced technology that these computers approach the limits of physics (reasonable for a Type 2 civilization imo), then their computers will use power proportional to kT. The colder the computer, the less power it uses. https://en.wikipedia.org/wiki/Landauer%27s_principle
This provides another thermodynamic reason to make a Dyson sphere as large as possible.
The Wikipedia article you also has this to say about Landauer's principle:
"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.
The Landauer principle applies to any computer made of matter utilizing energy (in a non-thermodynamically reversible fashion). So it applies just fine to biological computers, quantum computers, and even mechanical computers! It's a result in quantum information theory, and doesn't have anything to do with the overall type of computer used. It just determines how much energy it takes to change the state of a quantum (particle), at a minimum. Things like changing the polarization of a photon or the spin of an electron.
The Landauer limit applies to all non-thermodynamically reversible changes of state in a system. I don't know how your biological computer works, so I can't say 100% that it applies - but it probably does.
"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".
Where you are going wrong is assuming the outer layer has to be the same thickness as the inner layers. The outer layer only needs to capture the long infrared radiation emitted by the inner shells. In theory it only needs to be 1 atom thick and can contain gaps half the wavelength to be captured.
...put simply, the emission signal from efficient Dyson spheres will be swamped by infrared noise in any wide-field infrared surveys.
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.
Any civilization advanced enough to build a Dyson Sphere would by definition be one capable of extreme, long term focus. Since ennui is the enemy of long term focus, they'd probably have conquered it.
The article posits that maybe advanced alien civilizations may be motivated to build larger (and hence harder to to detect) Dyson spheres for the efficiency gains. While that's a possibility, it's also possible that being harder to detect is an end unto itself for safety reasons.
Readit News
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.
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?
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?
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?
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.
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.
This provides another thermodynamic reason to make a Dyson sphere as large as possible.
"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.
No. It is about abstract computation, which is based on (our best understanding of) theoretical physics.
"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".
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.