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Yes, it's a basic assumption that aliens will build megastructures simply because they can. If alien civilizations are common enough, eventually one of them will do it and they should be obvious because of it. It only takes one.

Personally I think aliens would build artificial worlds tailored to their species where they can rather than Dyson Swarms/Spheres, simply because the maintenance requirements are lower (Earth has hosted life for billions of years without outside assistance or sentient maintenance), even if the living space is lower and the up front cost is much, much higher. Such a race could have multiple inhabited worlds around any particular star and never give away their presence on the galactic stage.

But the idea of using up all of a star's available energy to do stuff is an attractive one and a powerful motivator to build Dyson Swarms.

 Overread wrote:
Blackfang - one problem is you're assuming that alien races would build big things for us to spot. You mention a Dyson Sphere, but we also have to consider that that might be what "we'd" build if we could, but might not be what other alien races could or would build.

They might have no need or desire or even idea of such a structure. They might be totally pacifist and simply explore other worlds in tiny ships leaving little to no trace. So they'd have the technology, but the wouldn't be colonising or building or doing things on other worlds that we might notice.

It could also be that life arose, developed, fell and was rendered to dust generations ago and that what evidence there is is buried in the ground on planets and such. Ergo that it all happened and we missed it. Or rather missed it within our sphere of visual observation.

Or maybe its happening right now, but we don't see it because the light travelling to us is so ancient by the time it reaches us.

There are some assumptions about alien physiology and psychology that are pretty safe bets because of how evolution works. They reproduce. They require sustenance. Ergo they need living space and energy. They can think rationally and so they do things that make sense.

A dyson isn't a literal metal ball. In essence it means that a civilization is capturing a significant portion of a star's emitted energy to do work and this eventually becomes waste heat and the shift in spectrum is easily identifiable and completely unavoidable unless you can dump heat into an alternate universe. It's the easiest known way to get living space and energy. To not see dysons anywhere can only mean two things - that either literally everybody else in our sphere of visual observation figured out something better before even making one, or that nobody is there.

Discussing anything outside our visible universe in both time and space is of course useless, doubly so when talking about alien visits to Earth.

That's a kind of odd way to view it - dysonspheres or nothing. Also surely if its a huge sphere that captures all of a sun's light then, by definition, its going to be pretty darn dark and hard to spot in the first place.

The thing is you also make assumptions like they must reproduce - why? That's how life on 1 planet of a whole universe has developed does not in any way mean that its the only way life can develop.

Plus you're overlooking the fact that they might have reached a point where, if they are similar to us, they could control their genetics down to a very fine level. Removing the need for reproduction and perhaps creating immortal life. Perhaps they have perfected a balanced system of growth within their own ecosystems and don't have need to expand as greedily for resources as humans do. We could be the odd ones out (indeed there's argument that that is one of the big things that does separate us from many other species - our ability and drive to utilize resources to a point where we actively destroy our own resource base through overharvesting)

 Overread wrote:
That's a kind of odd way to view it - dysonspheres or nothing. Also surely if its a huge sphere that captures all of a sun's light then, by definition, its going to be pretty darn dark and hard to spot in the first place.

It'll be very bright in the infrared spectrum.

 insaniak wrote:
Yeah, I'd like to think that any civilisation with the ability to build a Dyson Sphere would have realised long before that point what a horribly ridiculous waste of resources it would be.

Any civilization that would have need of that scale of energy probably wouldn't consider it a waste of resources as they would most likely have the ability to move and shape entire planets so globbing a bunch of them together to make a Dyson sphere isn't necessarily out of the question. The real question was already mentioned. Would such aliens be able to come up with the idea? They might never even think of surrounding a star in solar panels.

Its kinda like in Stargate when the Asgard are surprised by the concept of how guns worked. They had never considered using expanding gasses to propel solid projectiles. Its probably a bad example because expanding gasses > moving objects > moving objects at lethal velocity is pretty basic physics, but the general idea of aliens failing to discover certain concepts is definitely something to consider.

Even in our own history, different human civilizations have had an absence of certain concepts. We today can't really fathom not having the concept of Zero, but many civilizations did not have a concept of Zero.

Now a Dyson sphere would be a ludicrously massive project that would take hundreds or thousands of years for even those capable of doing it. So perhaps a simpler thing to expect would be a half-baked dyson sphere. Massive planet sized solar arrays instead of a whole star encompassing array. Just because it would be an easier project.

Even if aliens landed here the general consensus will be to deny that aliens landed here because humanity is far too narcissistic to think that any other life in the universe could be more intelligent than them. "Of course nobody is using interstellar travel because WE can't figure it out. There's no way a blue skinned thing with 5 asses will beat us to the intellectual punch!"

 Overread wrote:
That's a kind of odd way to view it - dysonspheres or nothing. Also surely if its a huge sphere that captures all of a sun's light then, by definition, its going to be pretty darn dark and hard to spot in the first place.

All the captured light will radiate back out unless they want to boil alive, it'll just be in a different spectrum and if we ever point a telescope at a dyson will will know it instantly.

The thing is you also make assumptions like they must reproduce - why? That's how life on 1 planet of a whole universe has developed does not in any way mean that its the only way life can develop.

Plus you're overlooking the fact that they might have reached a point where, if they are similar to us, they could control their genetics down to a very fine level. Removing the need for reproduction and perhaps creating immortal life. Perhaps they have perfected a balanced system of growth within their own ecosystems and don't have need to expand as greedily for resources as humans do. We could be the odd ones out (indeed there's argument that that is one of the big things that does separate us from many other species - our ability and drive to utilize resources to a point where we actively destroy our own resource base through overharvesting)

Literally every species does that.

The "anything is possible" argument isn't clever, it's ignorant. There are things we know, including some hard limits on physics and biology.

You're also arguing against the exclusivity principle: the problem that, to explain the lack of detectable aliens, the explanation has to apply to literally all aliens. How likely is it that literally all members of all alien civilizations everywhere have decided to deny their basic natures and live as asketic celibate hermits? Because it only takes a handful of individuals who don't do that to quickly outnumber the hippies into irrelevancy.

 John Prins wrote:

 Overread wrote:
That's a kind of odd way to view it - dysonspheres or nothing. Also surely if its a huge sphere that captures all of a sun's light then, by definition, its going to be pretty darn dark and hard to spot in the first place.

It'll be very bright in the infrared spectrum.

only if the Aliens are dump enough and waste that energy

a working Dyson Sphere would be impossible to detect from Earth unless it is very near and circles around another star
or we can see the Aliens building it and a star disappearing over time

and by assuming that evolution takes similar amount of time in different places, if Aliens are outside a 100-1000 lightyear range, we will never see them at all
not even talking about the the universe we can see is a very small part anyway

 John Prins wrote:

But we have no FTL phenomena to point to. At best we can point to enormous regions of space expanding in such a way that the expansion is greater than light's ability to cross the gulf (cosmic event horizon) and we've got no idea why it's happening or what's driving it.

That's the difference between humanity achieving heavier than air flight and achieving FTL. One was just figuring out the physics from an observable phenomena, the other is figuring out the physics from NEVER observed phenomena.

well, FTL as Faster Than Light is an observed phenomena, it is just impossible to exceed c (as universal physical constant)

yet it is also impossible for humans to exceed a specific speed, which we can get around by sitting in an object that can travel faster
but for traveling between stars we are not aiming on high speed or go faster than c but search for something that let us travel without moving, were we already have several concepts, we are just missing the necessary energy to do it

They can think rationally

Can doesn't mean will. Human rational thinking is very easily bulldozed by other natural elements of our brain, like pattern-finding and tendency to care about immediate results and their own small "clan"..and then you have ideologies, which completely override rational thinking and can do so on a population level.

 kodos wrote:

 John Prins wrote:

 Overread wrote:
That's a kind of odd way to view it - dysonspheres or nothing. Also surely if its a huge sphere that captures all of a sun's light then, by definition, its going to be pretty darn dark and hard to spot in the first place.

It'll be very bright in the infrared spectrum.

only if the Aliens are dump enough and waste that energy

a working Dyson Sphere would be impossible to detect from Earth unless it is very near and circles around another star

Captured light doesn't disappear. All energy ends up as heat in the end no matter what happens in between. A dyson is dark but hot and the skewed ratio of visible vs infrared is so easily identifiable astronomers are confident we that we will notice a dyson if it's the field of vision of any radio telescope if as little as 1% of the star's light is captured by solar panels.

the light does not disappear but is transformed to energy

the point of the sphere is to capture all the energy and use it for something

if the sphere gets hot enough on the outside to be detactable by someone lightyears away, there is a lot of energy wasted and building the sphere makes no sense in the first place

and this is why this idea is to dedect aliens because of super structures is problematic
if someone needs to build a structure to catch the energy from a star, only catching and using a fraction of it instead of "all" is a waste of ressources
but if they use all the energy they can get, we won't be able to see it

How many planets worth of matter would it take to construct a Dyson sphere anyways? The material requirements would be ludicrous. And why make one in the first place instead of using fusion generators and cutting out the middle man?

And has anyone checked the population growth of first world countries lately?

the more "realistic" versions are to have many small solar power plants in orbit around the sun either as ring

but those we won't see either as they will change the light of the star only in one direction and it would be pure luck if this would be the one we are looking at

the idea of Dysen that a high developed alien race could be dedected by the difference of visible light and infrared light from the star because they would collect the visible part for energy, was just that, an idea during the 60ies based on SciFi from the 30ies to overcome the limitation of the time

 kodos wrote:
the light does not disappear but is transformed to energy

the point of the sphere is to capture all the energy and use it for something

Yes, it is, but eventually you end up with waste heat. And you can extract energy from heat, but you need a colder medium to do so (that's how a Sterling Engine works). So at some point your ability to extract energy from heat fails because your inside and outside temperatures reach equilibrium. And that point will be well above the background heat level, because you're dumping heat into your surroundings.

Basically it's inescapable that at some point you'll be radiating heat (IR light) well above the background temperature of the universe, and your Dyson Sphere/Matryoshka Brain sticks out like a sore thumb.

That assumes a closed unit, you could be shipping in ice or something else from outside of the sphere to provide cooling. Indeed if you've built something that huge you've surely found ways to mitigate and "hide" yourself so that you're not targeted by any passing alien invasion force.

But it doesn't get around the fact that building such a vast structure is quite insane to start with.

 NinthMusketeer wrote:
How many planets worth of matter would it take to construct a Dyson sphere anyways? The material requirements would be ludicrous. And why make one in the first place instead of using fusion generators and cutting out the middle man?

And has anyone checked the population growth of first world countries lately?

First, you can lift mass out of your own star if you need it. This involves solar panels generating magnetic fields to direct jets of solar wind to giant magnetic collectors. Only a tiny fraction of the stuff is other than hydrogen, but you can still get all the mass you need, because stars are really, really massive.

Second, you do it because solar panels are easier than fusion engines. Like, way, way, way, way easier. The mass to energy extraction is PROBABLY far better as well, unless very small fusion generators are possible. We've yet to figure it out, but solar may provide more energy per unit mass, be easier to produce and maintain, with fewer risks.

Third, yes, first world countries have negative growth rates, but we sort of have to assume that societies with positive growth rates will overtake those with negative growth rates in the long term.


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 Overread wrote:
That assumes a closed unit, you could be shipping in ice or something else from outside of the sphere to provide cooling. Indeed if you've built something that huge you've surely found ways to mitigate and "hide" yourself so that you're not targeted by any passing alien invasion force.

But it doesn't get around the fact that building such a vast structure is quite insane to start with.

Note that the 'equalibrium' temperature we're talking about might be a few degrees above background levels - 3 degrees Kelvin on average. Something 6 degrees Kelvin will still stand out as obvious, and you're not shipping in 2 degree Kelvin ice.

One thing you could theoretically do is dump the waste IR radiation into artificial black holes which you then use as batteries well away from your home base, but gathering all your waste heat for that is rather unlikely. It's a lot harder than just radiating waste heat, and if you have a Dyson Sphere/Swarm, you probably aren't afraid of invasion because you'd have billions of starships and near infinite power for weaponry to fend off attacks - at least compared to an invading fleet of aliens not using a Dyson Sphere of their own.

 John Prins wrote:

 kodos wrote:
the light does not disappear but is transformed to energy

the point of the sphere is to capture all the energy and use it for something

Yes, it is, but eventually you end up with waste heat. And you can extract energy from heat, but you need a colder medium to do so (that's how a Sterling Engine works). So at some point your ability to extract energy from heat fails because your inside and outside temperatures reach equilibrium. And that point will be well above the background heat level, because you're dumping heat into your surroundings.

Basically it's inescapable that at some point you'll be radiating heat (IR light) well above the background temperature of the universe, and your Dyson Sphere/Matryoshka Brain sticks out like a sore thumb.

this assumes that the energy is only used inside the sphere and not used to cellect it to be used somwhere else
the whole point of the idea is that there is different energy in different spectrums which would mean that an alien race collects part of it to be used for something else inside

yet if the sphere is collecting the energy to be used for something outside the sphere, being simple here, like charging up batteries for starships, we won't see it

also the concept of "waste heat" is for our kind of technology if they use something else and their "waste" is not heat but other radiation, we won't see it either

 John Prins wrote:

One thing you could theoretically do is dump the waste IR radiation into artificial black holes which you then use as batteries well away from your home base, but gathering all your waste heat for that is rather unlikely. It's a lot harder than just radiating waste heat, and if you have a Dyson Sphere/Swarm, you probably aren't afraid of invasion because you'd have billions of starships and near infinite power for weaponry to fend off attacks - at least compared to an invading fleet of aliens not using a Dyson Sphere of their own.

And thus we reach the oft forgotten tales of BATTLE PLANETS - who I will note in the UK never quite got the TV exposure they should have but darn if they didn't have some neat and fine toys for them for a while.

 kodos wrote:


this assumes that the energy is only used inside the sphere and not used to cellect it to be used somwhere else

Even redirecting the energy will create waste heat that must be dealt with. If aliens can either reverse entropy or have 100% efficient systems, then they don't need Dyson Swarms to collect energy.

Basically your argument is "We don't see alien megastructures because they violate all our known laws of physics". This seems unlikely, given that such megastructures can be built under known physics (Dyson Swarms at least). IOW an alien race only need be slightly more advanced than us to create one, and aliens reaching technological levels we understand seems a lot more likely than them reaching ones we don't.

 lord_blackfang wrote:
If FTL is possible than the Fermi Paradox just becomes even worse. It becomes even more ridiculous that aliens are nowhere to be seen if interstellar travel is trivial.

Interdimensional travel is pretty much the only made up tech that would allow alien civilizations to expand and not be detectable.

A while ago, a number of UFOlogists speculated that the “aliens” were coming from parallel universes, much like the three-toed apes and other weird phenomena. Author Jerome Clark called this theory the “Goblin Universe” theory. I’m not sure how seriously the mainstream UFO believers took the theory, but it’s at least out there.

Edit: looks like that name didn’t stick.
https://en.m.wikipedia.org/wiki/Interdimensional_hypothesis

Maybe they take the energy from the Dyson Sphere and convert it into chemical energy to power ships.
Thus the energy will be transported away from the sphere before ultimately being used.

It's a bit foolish to say that absolutely, 100%, all the energy is used and expelled at the Sphere itself.
In human society almost none of the energy we produce is used at the point of production, especially not large scale production.

 John Prins wrote:

Even redirecting the energy will create waste heat that must be dealt with. If aliens can either reverse entropy or have 100% efficient systems, then they don't need Dyson Swarms to collect energy.

Basically your argument is "We don't see alien megastructures because they violate all our known laws of physics".

no, the argument is, for something like a megastructure to collect energy make sense, the aliens would need technology to reverse entropy or have 100% efficient systems
and/or use transport the energy away before it gets used/converted

an alien race that has technology similar to ours, just a little bit more advanced, would have no reason to waste ressources to build something that gives back a tiny bit of the energy needed to build and maintain it

and yes, assuming that aliens create technology that we understand is the first mistake

 Overread wrote:
But it doesn't get around the fact that building such a vast structure is quite insane to start with.

There's this notion that a dyson is some gigantic all or nothing project that you have to build for a million years before you get use from it but it's not, the first solar panel or mirror satellite you put up there is already a functional unit and will help fund the next one and it just snowballs from there. Covering an easily-detectible-to-any-casual-observer 1% of Sol is something we could do in maybe a century, which might be sooner than we have fusion.

Exactly; the plausible version is too small to detect.

 Overread wrote:
That assumes a closed unit, you could be shipping in ice or something else from outside of the sphere to provide cooling. Indeed if you've built something that huge you've surely found ways to mitigate and "hide" yourself so that you're not targeted by any passing alien invasion force.

But it doesn't get around the fact that building such a vast structure is quite insane to start with.

This kinda always confuses me when Dyson spheres are discussed. Someone brings up something along the lines of the builders wanting to 'hide' from the rest of the galaxy. I think any race which builds a Dyson sphere would have no need to hide from anything. You're already ludicrously powerful. At least you can use some of that captured energy to defend yourself.

Dyson spheres wouldn't be something you build if you are trying to hide. If hiding is a concern, you'd bury yourself in a nebula somewhere not put a freaking STAR in a cage. Especially since the "stealth" of the Dyson sphere would only exist in bubble around the Sphere itself, a bubble which would expand at the speed of light, but anybody outside that bubble could still see the star before you had closed it off, and if they are looking when the star goes dark that is something that might catch their attention.

I would expect a Dyson sphere creating civilization would be an interstellar power, not a single system species trying to hide in a galaxy of terrors.

 LordofHats wrote:

 lord_blackfang wrote:
You probably don't spend thousands of years to travel to a different planet just so you can do butt stuff on local drunkards.

Wild speculation theory,

What if, the aliens who come to earth and probe the local drunkards are the space version of the local boys who go cow tipping and there's nothing nefarious about it? It's just a bunch off dumbass kids, drunk of space beer, fresh off from space drivers ed, bored out of their minds in a hodunk nebula where nothing happens and they have nothing to look forward to but following Ghlock and Schleel into the minnes, having a laugh at those goof aliens on the blue planet

If you read the Stephen King book The Dome (ignore the awful TV series) - spoiler below for anyone that wants to read the book..


It's an interesting idea certainly! Some future technology point creates space-folding, worm holes or something similar that reduces the vast interstellar distances or at least makes them surmountable. Some kind of legal code (like a Star Trek 'Prime Directive'?) prevents general interference, but a small number of smugglers/kids/space hippies(?!) want to go and play in the backyard, or to bring back souvenirs to sell on to collectors.


Automatically Appended Next Post:

 Grey Templar wrote:

 Overread wrote:
That assumes a closed unit, you could be shipping in ice or something else from outside of the sphere to provide cooling. Indeed if you've built something that huge you've surely found ways to mitigate and "hide" yourself so that you're not targeted by any passing alien invasion force.

But it doesn't get around the fact that building such a vast structure is quite insane to start with.

This kinda always confuses me when Dyson spheres are discussed. Someone brings up something along the lines of the builders wanting to 'hide' from the rest of the galaxy. I think any race which builds a Dyson sphere would have no need to hide from anything. You're already ludicrously powerful. At least you can use some of that captured energy to defend yourself.

Dyson spheres wouldn't be something you build if you are trying to hide. If hiding is a concern, you'd bury yourself in a nebula somewhere not put a freaking STAR in a cage. Especially since the "stealth" of the Dyson sphere would only exist in bubble around the Sphere itself, a bubble which would expand at the speed of light, but anybody outside that bubble could still see the star before you had closed it off, and if they are looking when the star goes dark that is something that might catch their attention.

I would expect a Dyson sphere creating civilization would be an interstellar power, not a single system species trying to hide in a galaxy of terrors.

Yes.. or considering the age and vastness of Space, to leave a monument saying "look, we were once here, we were great and we did this"

 NinthMusketeer wrote:

Voss wrote:
I'm intensely curious how scientists have been listening for 'radio beam emissions' for centuries.

Before more modern means of such receiving scientists were relying on jury-rigged alien technology.

Error on my part. I meant decades.

A Dyson sphere as a monument? Around a star that will eventually destroy itself and likely the sphere along with it?

 NinthMusketeer wrote:
A Dyson sphere as a monument? Around a star that will eventually destroy itself and likely the sphere along with it?

Not all stars go nova.

 kodos wrote:

and yes, assuming that aliens create technology that we understand is the first mistake

No it isn't. All our research points to physical laws and constants that are _extremely_ rigid, and only really 'bend' under the influence of other laws and constants. Various forms of energy (waves, particles, etc) and forms of matter behave in predictable ways and under reproduceable conditions. Really unfamiliar user layouts (and software) would require research and potentially a lot of hands-on experience, but energy sources and effects on physical objects would be very testable and understandable.