>A civilization that built a Dyson Sphere would have to go to great lengths to avoid detection, either by getting rid of its waste heat in some novel way, or by building massive radiators that give off heat so cool that it would be undetectable against the cosmic microwave background, the faint afterglow of the Big Bang.
So if a civilization were to completely mask itself in the EM spectrum, the only way to detect them would be to look for gravitational distortions assuming those can't be masked. A civilization might do this either to hide from others or because the maximum efficiency of their energy extraction system would occur when their waste heat matched the background ration. So a really advanced (and paranoid or efficient) civilization would be indistinguishable from dark matter.
This brings up another interesting hypothesis: dark matter is actually the computronium of all of the alien civilizations in the universe that have achieved a technological singularity. Unfortunately, this hypothesis can't be tested until humanity gets to the same level.
>This brings up another interesting hypothesis: dark matter is actually the computronium of all of the alien civilizations in the universe that have achieved a technological singularity.
Technological singularity describes the aftermath as an entity achieves an intelligence significantly superior to that of the average unaided human mind. The term gets thrown at a lot of things that don't seem to have anything to do with it. In this case I don't see why humans level intelligence is not enough to build a Dyson Sphere.
It looks really naive that civilizations so advanced to blot out an entire star for its energy can't even find a way to co exist in such a vast universe.
But looking at how fellow humans behave with each other. I would say that is definitely a possibility.
...assuming that the galaxy's most advanced civilizations are protoplasmic. But
beings whose chemistry is based on molten copper, say, would want a hotter
environment. They might have evolved faster, in temperatures where chemistry and
biochemistry would move far faster. There might be a lot more of them than of
us. And their red-hot Dyson spheres would look deceptively like red giant or
supergiant stars. One wonders.
Speaking of Larry Niven, my impression after reading Ringworld (in addition to "holy shit that was good") was that Dyson Spheres were kind of a non-workable, and that a species who'd advanced far enough to actually make one could probably just colonize another system anyway.
A swarm-Dyson sphere, which is the only kind that can be realistically built, is incremental. You just keep building habitats in orbit around the sun, until eventually you capture all the sunlight.
Clearly a solid Dyson sphere is not orbiting its host star, and could eventually drift into the star. However, might it be possible to harvest enough energy from the star to power a propulsion system that keeps the sphere in place?
Won't gravity stop this from happening? Seriously, the shell of the sphere will be balanced on the outskirts of a gravity well right? So if it moves this will move the center of the gravity well and both the star and sphere should fall back towards the center.
It's interesting, but a bit like trying to detect a large and advanced by looking for products of horse manure decomposing in huge heaps. I think it was Mendeleev who thought that getting rid of horse shit will be the main problem of ever-growing cities in XX century.
The need for energy is definite, but the amount and character of such need is debatable. Maybe civilizations shrink and don't use so much energy? Maybe they mine million of stars at once? Maybe they get their energy out of thin vacuum?
Build your Dyson sphere with large gaps in the galactic plane. Then observers at most other stars in your galaxy will see your star, and then you don't have to either build a giant sphere or come up with exotic heat management systems to avoid detection.
The main problem is that the galactic plane is not really a plane :)
Suppose your star is located exactly in the plane, and its axis is orthogonal to the galactic plane. Then, defining "up" and "down" as the opposing directions in that star's axis, you would still have a lot of stars "up" and "down" the plane.
So, even if you only have only one disk orbiting the star, with a high enough orbital inclination, that's still visible from a lot of stars.
And of course, there would still exist a plane containing the disk's orbit, from where the disk eclipses the star.
Even more, the disk itself would still be detectable from other planes, because it's hotter than the background.
Then, if your civilization wants to keep hidden its existance, you still need to develop some kind of stealth tech for the sphere. :)
>the sun beams a total of 120,000 terrawatts per day onto our planet. That's 10,000 times the amount that flows through our industrial civilization.
Should be "terrawatts", not "terrawatts per day". (I stopped reading there. There 100s of 1000s of people who know enough physics never to make such a mistake. I'll read one of them instead.)
While you're at it shouldn't it be "stellar power" etc? Unless the aliens are supposed to be building a Dyson Sphere around the Sun which would be decidedly easier to observe.
The issue I have with Dyson Sphere's is in 1960 the idea of the singularity hadn't really been floated. I think it is far more likely that civilizations either die or upload.
It is not clear to me how that is a contradiction. An uploaded civilization may still desire more computational power, and unless there's an infinite computation escape hatch in physics (and there is currently not even a trace of such a thing), that's going to involve getting more energy from the star. On an exponential growth curve, even improving your civilization's energy efficiency by a factor of a hundred quadrillion still only buys you a blip on the scale on cosmic time scales before you start wanting to expand again.
Is it just me, or is there someone else who thinks theories like these are so naive it borders the ridiculous?
Isn't it too pretentious to think that, not only other similar civilizations do exist (which is a stretch already), but also predict their infra-structure necessities and what kind of solution they are going to come up with?
I known I'm nobody and Mr. Dyson is a Nobel-prize grade genius, but come on... this is (much) more fiction than science.
If they want to affect the environment, or perform computations, they have to use energy. If they have to use energy, they have to get energy from somewhere. Hydrocarbons don't last for more than a couple centuries. Heavy-element fission will get you another century. Light-element fusion will get you another ten thousand years.
Whither comes the energy for a million year civilization? Should they ignore their star? Just let all that power go streaming by?
(Dyson won theHeineman Prize, Harvey Prize, Wolf Prize, Templeton Prize, Pomeranchuk Prize, Fermi Award, and the Poincare Prize; but did not win a Nobel.)
Maybe you proved my point. Just look at how many ifs this theory depends upon.
1. That a civilization similar to ours exists
2. That such civilization exists in the same time frame as us
3. That such civilization's demands on energy are similar to ours
4. That such civilization expands enough to face energy shortcomings
5. That the best source of energy such civilization finds is a nearby star
6. That they arrive to the same conclusion as Mr. Dyson about the best way to harness the power from this star (the biggest pretension by far in my opinion)
7. That they manage to build it
A very interesting chain of propositions, but really? I find amusing that are people willing to take this more seriously than a simple imagination/future prediction exercise.
We can't even reliably predict how our own civilization will look like in a matter of decades. Now imagine how naive is to think we can predict which problems hypothetical begins similar to us are going to face, let alone predict a particular the solution they are going to come up with.
Son, you don't have to start jumping up and down and gibbering excitedly about the singularity. This ain't hard.
All life uses energy. All civilizations will always use energy, because they are made of life forms. (biological or silicon-- who cares)
If civilizations grow steadily, then their need for energy will grow steadily. If they don't flame out, then they'll need to expand beyond their host planet, and intercept more solar energy, until eventually all sunlight is captured, and you've got a Dyson sphere.
If civilizations grow until they hit a threshold, then stay steady-state for the rest of the universe's lifespan, then we'll only be able to detect them if the threshold is pretty big-- if they just stay on their planet, then they'll be hard to spot, without really big space telescopes.
Thanks, but again, you're explaining me the reasoning behind it (I get it, otherwise I wouldn't be arguing it), and losing the point about why I say it's pretentious in the first place.
Let's be realistic. A civilization so advanced as to be able to capture the entire energy of a star, probably also has energy alternatives, and probably wouldn't want to attract the attention of lesser beings (like us) by trapping a star's output in a detectable way.
I've never understood such assumptions of intelligence. "If a civilization could do X, they could also do Y and Z." Says who? It's not like we're experts in alien intelligence. How can we be, when we have never encountered one?
All true, but applying common sense still has a point. For example, do we want to broadcast the fact of our own existence across interstellar distances? This is actually an active debate topic among those who think about stuff like this.
Ironically, after a brief spell of broadcasting our existence with powerful radio and radar waves, we're gradually shutting down the big transmitters for reasons of economy and efficiency. Satellites allow us to accomplish the same end with much less power than the old high-powered transmitters, and GPS-guided aircraft makes more sense that long-range radars for all but military purposes.
There are those who argue that we should transmit the basic facts of our existence with high-powered radio transmitters and lasers, and await a reply. Others argue that we shouldn't. Both arguments have merit.
Yes, absolutely. It is said that, because of radar, we're the brightest object within several light-years in those wavelengths. Add to that the periodic nature of radar, and we're signaling with an obviously unnatural beacon for anyone willing to listen.
I'm just saying the debate goes on, even though we're providing quite a beacon for anyone interested in detecting signs of semi-intelligent life. :)
> True, but we have always been sending radio signals in space and probably will continue to.
I wouldn't say "always". The first reasonably strong, narrow-band radio signals commenced in the 1920s. Not even 100 years. And we're quickly reducing our EM radiation footprint for economic reasons unrelated to anything resembling policy.
I see the point of both arguments -- that we should, and shouldn't, broadcast our existence. I actually prefer the "should" argument overall, considering the difficulty that an alien species would have getting here. We might learn something remarkable from a safe remove.
Sure, they could have their own nuclear fusion reactors or even something more sophisticated, but why let a perfectly good source of energy just go to waste?
I don't think they'd care that anyone could detect them if they're that advanced...
> Sure, they could have their own nuclear fusion reactors or even something more sophisticated, but why let a perfectly good source of energy just go to waste?
TO avoid detection by some other warlike species?
Regardless of the alienness of a life form, there are certain principles one can rely on, under average circumstances:
* Resource aren't infinite anywhere, and an intelligent species won't deliberately waste resources.
* No civilization is invulnerable.
* The duration of existence of any lifeform is finite.
There will always be outliers, but if we're after a set of reliable assumptions, these are on the list.
> I don't think they'd care that anyone could detect them if they're that advanced...
If you wrap a star in collection surfaces, thermodynamics dictates that the result will be a much larger surface at a lower temperature. If that isn't true, then the point of the exercise (energy collection) won't pan out.
Obviously this is rank speculation, but knowing what we do about living species, some speculations are more likely than others.
The most likely shape of interstellar war is lasergrams that say "We hate you" (but here is some harvestable energy...).
The next most likely is probably relativistic projectiles, which are dangerous in proportion to the energy required to send them (i.e., they aren't that likely a threat).
Direct invasions of civilizations that can shape the matter of an entire solar system seem pretty much destined to failure (I guess you could come in on a ship built from an entire solar system, but I wonder if you are war mongering at that point).
It could very well be that the only civilizations that still exist are the ones that are good at hiding. All the others (even if they are the big majority) might have been destroyed after giving a signal of life/existence.
I'm guessing that it's not unlike why we don't leave food out when camping in bear country. If the bear realized what we were doing (hiding food from it), then it would surely come to the bear conclusion that our behavior was unreasonable, but we know better.
I agree. From my limited knowledge of power sources, I understand that fusion and zero point energy would provide more easily accessible and vaster amounts of energy than one could build with a huge solar collector. Solar can only go to the maximum that the sun outputs in that direction. I would speculate that alien civilizations have found far more efficient means of power than a solar array.
It wouldn't just be one direction, it would be a sphere around the whole star. Stars are essentially just large fusion reactors, so it would take one the size of the star to compete with it (within an order of magnitude or so).
A quote: "Alternative energy is an umbrella term that refers to any source of usable energy intended to replace fuel sources without the undesired consequences of the replaced fuels."
It is equally likely an advanced civilization would have found out ways to engineer/create energy unlike how we imagine it. It might even seem irrational to us, magical, impossible even.
You're not thinking very big, or in terribly deep timescales. There's not a lot of easy-to-access hydrogen in the solar system, and most of it is at the bottom of steep gravity wells. (The gas giants)
On the other hand, if you put your solar collector well inside Mercury's orbit, where the solar flux is dramatically higher, then you get plenty of power, without having to maintain and fuel a reactor.
So if a civilization were to completely mask itself in the EM spectrum, the only way to detect them would be to look for gravitational distortions assuming those can't be masked. A civilization might do this either to hide from others or because the maximum efficiency of their energy extraction system would occur when their waste heat matched the background ration. So a really advanced (and paranoid or efficient) civilization would be indistinguishable from dark matter.
This brings up another interesting hypothesis: dark matter is actually the computronium of all of the alien civilizations in the universe that have achieved a technological singularity. Unfortunately, this hypothesis can't be tested until humanity gets to the same level.