Alien Megastructure... or just something we haven't thought of yet?

[braces_for_impact]

If there was a civilization that advanced, they may have stopped using radio as a means of communication eons ago. "Their" radio waves could have passed our planet while the dinosaurs roamed.

 

[Terrell]

Would be interesting if it is an alien megastructure, but I wouldn't rule out some natural phenomenon that we simply don't fully understand.

 

[Jimmy Higgins]

Would be interesting if it is an alien megastructure, but I wouldn't rule out some natural phenomenon that we simply don't fully understand.

I do ponder how long a megastructure could last past a civilization. Comets, asteroids, Michael Bay would all cause issues. Of course, maybe the creators would find solutions to those issues, though probably never heard of Michael Bay.

 

[Loren Pechtel]

They wouldn't be 1500 light years away, though--anybody doing mega engineering in space has the ability to do an interstellar trip. There would be colonization expeditions. If you figure travel at 1% of lightspeed (within the range of an unboosted solar sail or Orion) and 1000 years before a colony sends out a colony ship you get a spread velocity of about 1ly/300 years. At that rate they will have colonized any part of the galaxy they want (but not the surrounding globular clusters) in 30 million years.

I was going by more conservative estimates (like .001c and 1 million years). But in any case, your estimates assume they're interested in large-scale colonization.
Maybe they only want to colonize a few planetary systems just for increased chances of survival of their civilization, and have AI in other planetary systems to keep an eye on everyone else just in case (i.e., to prevent hostile advanced civilizations from arising). But then, maybe even the colonization of a few planetary systems is unnecessary - just small outposts there, capable of growing if needed, will do.
We don't really know what the aliens may want. Your argument seems to work against the existence of advanced aliens with some specific sorts of minds. But the chances of other aliens do not appear to be strongly affected.

They don't need to be interested in large scale colonization. All you need is some groups that want to get away from the main group they're in. If one a million people has the pioneer spirit you'll have tons of colonists. Even one in a billion would do it, albeit slower.

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They wouldn't be 1500 light years away, though--anybody doing mega engineering in space has the ability to do an interstellar trip.

Do they? Aren't we still limited by physics? Doing large scale local projects is one thing. Being able to travel 0.01 times the speed of light in a machine that isn't destroyed in the process? The energy required and the issues of traveling in a near but not quite a true vacuum are issues that can't just be hand waved.

I gave two systems that could do it.

 

[dystopian]

They don't need to be interested in large scale colonization. All you need is some groups that want to get away from the main group they're in. If one a million people has the pioneer spirit you'll have tons of colonists. Even one in a billion would do it, albeit slower.

This argument against alien civilizations in our milky way galaxy really only applies if you're talking about von-neumann probes. It doesn't quite work otherwise because there's simply too many variables that could slow/interrupt/reverse colonial expansion otherwise. The argument only works when you can assume stable behaviors.

 

[credoconsolans]

Would be interesting if it is an alien megastructure, but I wouldn't rule out some natural phenomenon that we simply don't fully understand.

Exactly, scientists got all in a tizzy about another such 'regular signal' decades ago, then with further investigations discovered quasars.

 

[Peez]

This claim does not seem to be supported: "As civilisations become more technologically advanced, they create new and better ways of collecting energy — with the end result being the harnessing of energy directly from their star."

Since we are nowhere near this "end", it is perhaps premature to state with any certainty what sort of technology might be favoured at that time.

Peez

 

[Angra Mainyu]

They don't need to be interested in large scale colonization. All you need is some groups that want to get away from the main group they're in. If one a million people has the pioneer spirit you'll have tons of colonists. Even one in a billion would do it, albeit slower.

I was addressing your view that "At that rate they will have colonized any part of the galaxy they want (but not the surrounding globular clusters) in 30 million years.", also considering that you said that "anybody doing mega engineering in space has the ability to do an interstellar trip" (which indicates the aliens doing the mega engineering are the ones planning the trip).

The new scenario (i.e., smaller groups of colonists) faces (at least) the following difficulties/assumptions.

1. It assumes that there are millions of aliens. That may not be so. For example, it may be one or a few AI that remain after an earlier civilization with greater numbers. Or it may be the cyborgs (resulting from merging between machines and biological organisms) that won a war against others, and see no good reason for increasing their numbers.
2. Assuming that there are millions of aliens in an advanced civilization and 1 in a million want to leave, your scenario further assumes that those particular aliens would manage to do so. But the smaller group of aliens is not the same (or at least it may well not be the same) as the group making the megastructures. This assumption seems to require that the smaller group:
a. Can get the resources that are required for interstellar travel. The larger group may not be willing to give them those resources, or to allow them to take them to another planetary system.
b. Can travel at the speed you suggested. But now we're not talking about sending a robot at .01c, and then spreading every 1000 years or so; rather, we're talking about colonists traveling at that speed in an effort to colonize another planetary system. That's a lot more difficult. For example, it requires a much bigger ship (by the way, did you do the math for solar sails even considering other types of stars?)
3. Even assuming 1. and 2., there is a further assumption: that small groups will become big groups, and from a few you would get millions in 1000 years. But why would that happen?
Even if there are millions of aliens because the numbers used to increase as they reproduced in the past, there is no good reason to assume that reproduction will continue at the same rate - or at all.
So, maybe the colonists just won't reproduce after they settle. Or they will do so, but so slowly that there will be new colonists only every 10 million years or something like that. More generally, there is no good reason to think the total number of aliens will continue to increase indefinitely. If, at some point, reproduction stops, and all of those into colonization already did the colonizing, that's that. If reproduction does not stop entirely but almost, then in practice, the same happens (i. e., colonization stops or becomes so slow that they may well not be detectable yet).

So, your new argument rules out some further kinds of aliens, but there is still a lot of room left.

 

[Bomb#20]

They wouldn't be 1500 light years away, though--anybody doing mega engineering in space has the ability to do an interstellar trip.

Do they? Aren't we still limited by physics? Doing large scale local projects is one thing. Being able to travel 0.01 times the speed of light in a machine that isn't destroyed in the process? The energy required and the issues of traveling in a near but not quite a true vacuum are issues that can't just be hand waved.

They're also liable to be limited by politics. Even if the inference that they have the technological ability and the resources to do an interstellar trip turns out to be correct, it may simply be too hard to convince enough LGMs that it's a good idea for their current generation to put much effort into a project that's guaranteed not to have any return on investment for a thousand years to have any realistic chance of winning the interstellar trip debate, when there's still plenty of mega engineering in space to work on that will bring immediate benefits during their own lifetimes. We find it hard enough to get people to cooperate on stuff that won't do us any good until after the next election cycle.

 

[skepticalbip]

Would be interesting if it is an alien megastructure, but I wouldn't rule out some natural phenomenon that we simply don't fully understand.

I would turn that around. It will be interesting whatever it is. It would be really interesting if it were some natural phenomenon that we don't yet understand but I wouldn't rule out an alien megastructure.

 

[fromderinside]

The only technological life form I have ever come across has very little interest in anything in space further away than low orbit around their home-world. What little effort they have put in to go further is almost all concentrated in the slightly higher geostationary orbit; they have made some desultory attempts to examine the closest celestial body in person, and have sent a small number of automated probes to other planets in the system; and have launched a literal handful of probes at solar escape velocity - only two of which have even reached the edge of their Solar System.

At this rate, the chances of them getting funding to explore in detail the nearest planet to their own (much less any nearby stars) seem slim; Interstellar probes that have the potential to seed colonies in other solar systems seem not to be on the cards at all, even after tens of thousands of years of technological development.

Yeah, yeah, Dr. Wetblanket, er bilby, all you say is on point except we're actually running out of stuff with which to make stuff. We'll be mining the asteroid belt within a hundred years. And we'll be using launch and recovery technology that is reusable. Many mountains will be serve as launch vehicles and we'l have power grids in space on the outer planet side of earth. We'll need it.

Otherwise we'll history as will most of earth's life.

Now when we begin transmitting from from a 400 million mile radius rather from a 93 million, some odd middle, mile orbiting spot there might be larger chance for extrastellar electromagnetic signal detection.

Just sayin' optimistically.

 

[Bomb#20]

... we're actually running out of stuff with which to make stuff. We'll be mining the asteroid belt within a hundred years. ...

The deepest mine in the world is 4 km deep. The earth's crust is about 40 km thick.

 

[Jimmy Higgins]

They wouldn't be 1500 light years away, though--anybody doing mega engineering in space has the ability to do an interstellar trip.

Do they? Aren't we still limited by physics? Doing large scale local projects is one thing. Being able to travel 0.01 times the speed of light in a machine that isn't destroyed in the process? The energy required and the issues of traveling in a near but not quite a true vacuum are issues that can't just be hand waved.

I gave two systems that could do it.

Two propulsions. There is still the whole shield issue.

 

[bilby]

The only technological life form I have ever come across has very little interest in anything in space further away than low orbit around their home-world. What little effort they have put in to go further is almost all concentrated in the slightly higher geostationary orbit; they have made some desultory attempts to examine the closest celestial body in person, and have sent a small number of automated probes to other planets in the system; and have launched a literal handful of probes at solar escape velocity - only two of which have even reached the edge of their Solar System.

At this rate, the chances of them getting funding to explore in detail the nearest planet to their own (much less any nearby stars) seem slim; Interstellar probes that have the potential to seed colonies in other solar systems seem not to be on the cards at all, even after tens of thousands of years of technological development.

Yeah, yeah, Dr. Wetblanket, er bilby, all you say is on point except we're actually running out of stuff with which to make stuff. We'll be mining the asteroid belt within a hundred years. And we'll be using launch and recovery technology that is reusable. Many mountains will be serve as launch vehicles and we'l have power grids in space on the outer planet side of earth. We'll need it.

Otherwise we'll history as will most of earth's life.

Now when we begin transmitting from from a 400 million mile radius rather from a 93 million, some odd middle, mile orbiting spot there might be larger chance for extrastellar electromagnetic signal detection.

Just sayin' optimistically.

With the exception of a bit of Helium, plus the minuscule amount of stuff we turned into space probes, plus a few radioactive materials that disappeared long before humans evolved, every single resource the Earth started out with is still here.

We are not running out of anything (except perhaps Helium). Anything we want, we can make - given enough energy. And we are parked 1AU from an energy source we have hardly started to tap, that is good for a few eons at least.

The idea that we are running out of anything is insane.

 

[Loren Pechtel]

They don't need to be interested in large scale colonization. All you need is some groups that want to get away from the main group they're in. If one a million people has the pioneer spirit you'll have tons of colonists. Even one in a billion would do it, albeit slower.

This argument against alien civilizations in our milky way galaxy really only applies if you're talking about von-neumann probes. It doesn't quite work otherwise because there's simply too many variables that could slow/interrupt/reverse colonial expansion otherwise. The argument only works when you can assume stable behaviors.

I'm not assuming stable behaviors--I'm assuming there would be some with the pioneer spirit, not that any large numbers have it.

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Would be interesting if it is an alien megastructure, but I wouldn't rule out some natural phenomenon that we simply don't fully understand.

Exactly, scientists got all in a tizzy about another such 'regular signal' decades ago, then with further investigations discovered quasars.

Quasars? Aren't you thinking of neutron stars?

 

[credoconsolans]

... we're actually running out of stuff with which to make stuff. We'll be mining the asteroid belt within a hundred years. ...

The deepest mine in the world is 4 km deep. The earth's crust is about 40 km thick.

And those deep mines are already inhospitable to human life.

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Would be interesting if it is an alien megastructure, but I wouldn't rule out some natural phenomenon that we simply don't fully understand.

Exactly, scientists got all in a tizzy about another such 'regular signal' decades ago, then with further investigations discovered quasars.

Quasars? Aren't you thinking of neutron stars?

My bad. I was thinking pulsars aka neutron stars.

 

[Loren Pechtel]

They don't need to be interested in large scale colonization. All you need is some groups that want to get away from the main group they're in. If one a million people has the pioneer spirit you'll have tons of colonists. Even one in a billion would do it, albeit slower.

I was addressing your view that "At that rate they will have colonized any part of the galaxy they want (but not the surrounding globular clusters) in 30 million years.", also considering that you said that "anybody doing mega engineering in space has the ability to do an interstellar trip" (which indicates the aliens doing the mega engineering are the ones planning the trip).

The new scenario (i.e., smaller groups of colonists) faces (at least) the following difficulties/assumptions.

1. It assumes that there are millions of aliens. That may not be so. For example, it may be one or a few AI that remain after an earlier civilization with greater numbers. Or it may be the cyborgs (resulting from merging between machines and biological organisms) that won a war against others, and see no good reason for increasing their numbers.

That's a dead species.

2. Assuming that there are millions of aliens in an advanced civilization and 1 in a million want to leave, your scenario further assumes that those particular aliens would manage to do so. But the smaller group of aliens is not the same (or at least it may well not be the same) as the group making the megastructures. This assumption seems to require that the smaller group:
a. Can get the resources that are required for interstellar travel. The larger group may not be willing to give them those resources, or to allow them to take them to another planetary system.
b. Can travel at the speed you suggested. But now we're not talking about sending a robot at .01c, and then spreading every 1000 years or so; rather, we're talking about colonists traveling at that speed in an effort to colonize another planetary system. That's a lot more difficult. For example, it requires a much bigger ship (by the way, did you do the math for solar sails even considering other types of stars?)

As time goes on the group that can accomplish something gets smaller and smaller. 50 years ago space was the province of governments. Now orbital launches by private corporations are commonplace and a group of amateurs has attempted to send a rocket to the edge of space. (The flight was terminated soon after launch and didn't make it.)

There will come a point when the group of prospective pioneers can do it out of their own resources. Against the timescale of the galaxy this will be an eyeblink. Short a highly repressive government the resources aren't going to stop this.

As for the speed--I'm talking about speeds that can be attained given technologies we already understand. Exactly what performance we will get in the real world is uncertain but both technologies can do well above 1%.

The solar sail math (I'm not the one who did it) is for a star similar to ours--but ETs probably will evolve around something similar to ours. Bright stars don't live long enough, dim stars will tidal lock planets in their golidlocks zone. Perhaps some stars are unsuitable for light sails but there's no requirement that they colonize every star--in fact, it would be very unlikely if they did. It would be a move of desperation to colonize a place like Antares.

3. Even assuming 1. and 2., there is a further assumption: that small groups will become big groups, and from a few you would get millions in 1000 years. But why would that happen?
Even if there are millions of aliens because the numbers used to increase as they reproduced in the past, there is no good reason to assume that reproduction will continue at the same rate - or at all.
So, maybe the colonists just won't reproduce after they settle. Or they will do so, but so slowly that there will be new colonists only every 10 million years or something like that. More generally, there is no good reason to think the total number of aliens will continue to increase indefinitely. If, at some point, reproduction stops, and all of those into colonization already did the colonizing, that's that. If reproduction does not stop entirely but almost, then in practice, the same happens (i. e., colonization stops or becomes so slow that they may well not be detectable yet).

So, your new argument rules out some further kinds of aliens, but there is still a lot of room left.

The numbers were just for illustration--you can plug most any sane value in for either the travel speed or reproduction rate and still get a value less than a gigayear.

 

[Angra Mainyu]

1. It assumes that there are millions of aliens. That may not be so. For example, it may be one or a few AI that remain after an earlier civilization with greater numbers. Or it may be the cyborgs (resulting from merging between machines and biological organisms) that won a war against others, and see no good reason for increasing their numbers.

That's a dead species.

What do you mean by that?
In any case, the aliens would be alive. Or AI.

2. Assuming that there are millions of aliens in an advanced civilization and 1 in a million want to leave, your scenario further assumes that those particular aliens would manage to do so. But the smaller group of aliens is not the same (or at least it may well not be the same) as the group making the megastructures. This assumption seems to require that the smaller group:
a. Can get the resources that are required for interstellar travel. The larger group may not be willing to give them those resources, or to allow them to take them to another planetary system.
b. Can travel at the speed you suggested. But now we're not talking about sending a robot at .01c, and then spreading every 1000 years or so; rather, we're talking about colonists traveling at that speed in an effort to colonize another planetary system. That's a lot more difficult. For example, it requires a much bigger ship (by the way, did you do the math for solar sails even considering other types of stars?)

As time goes on the group that can accomplish something gets smaller and smaller. 50 years ago space was the province of governments. Now orbital launches by private corporations are commonplace and a group of amateurs has attempted to send a rocket to the edge of space. (The flight was terminated soon after launch and didn't make it.)

There will come a point when the group of prospective pioneers can do it out of their own resources. Against the timescale of the galaxy this will be an eyeblink. Short a highly repressive government the resources aren't going to stop this.

Two points:
First, you're talking about aliens with government systems that resemble those of Earth in the present time.
That leaves room for many other social organizations, which may be stable if the aliens are psychologically very different from humans. For example, I don't know how repressive a "highly" repressive government would have to be, but an alien psychology may be very different from human psychology, and their kind may be far more comfortable with a collectivist sort of system than humans are, and much less comfortable with more individualistic systems. Communism is a problem given human psychology. But given alien psychology? It depends on the specific aliens. Who knows?
In reality, their psychology may well be much more alien than that.

Second, even in our social environment, there are physical constraints that limit what small groups (or any groups) can accomplish. If the project requires a certain amount of resources and those resources are not available in a planetary system to anyone but the government, that's that.

As for the speed--I'm talking about speeds that can be attained given technologies we already understand. Exactly what performance we will get in the real world is uncertain but both technologies can do well above 1%.

The solar sail math (I'm not the one who did it) is for a star similar to ours--but ETs probably will evolve around something similar to ours. Bright stars don't live long enough, dim stars will tidal lock planets in their golidlocks zone. Perhaps some stars are unsuitable for light sails but there's no requirement that they colonize every star--in fact, it would be very unlikely if they did. It would be a move of desperation to colonize a place like Antares.

M class stars may tend to tidal lock planets, which makes it less probable that intelligent life will evolve in such systems, given the same number of systems.
On the other hand, they're much more numerous - and in some cases, much older -, and life may well be able to evolve on tidally locked planets. One of the following might work:

a. An Earth-sized moon orbiting a gas giant orbiting an M-type star in the outer part of the GZ, with a thick atmosphere and a high content of CO2, stabilizing temperatures.
b. A superearth orbiting an M-type star in the outer part of the GZ (or further), also with a thick atmosphere, etc.
c. A water-covered planet, superearth-sized (yes, technology is more difficult, but still possible).
d. A superearth orbiting an M-type star, right in the middle of the GZ. It's tidally locked, but there is a strip around the planet where temperature is good enough.

And there are a number of alternatives. M-type stars are about 76% in the cosmic neighborhood (source: https://en.wikipedia.org/wiki/Stellar_classification#Class_M )
G-type are about 7.5%.
There are also K-type stars (about 12%).

But that aside, are you counting the resources needed for life support during the trip? Sending robots is one thing, but people (or biological aliens) may be more complicated.

3. Even assuming 1. and 2., there is a further assumption: that small groups will become big groups, and from a few you would get millions in 1000 years. But why would that happen?
Even if there are millions of aliens because the numbers used to increase as they reproduced in the past, there is no good reason to assume that reproduction will continue at the same rate - or at all.
So, maybe the colonists just won't reproduce after they settle. Or they will do so, but so slowly that there will be new colonists only every 10 million years or something like that. More generally, there is no good reason to think the total number of aliens will continue to increase indefinitely. If, at some point, reproduction stops, and all of those into colonization already did the colonizing, that's that. If reproduction does not stop entirely but almost, then in practice, the same happens (i. e., colonization stops or becomes so slow that they may well not be detectable yet).

So, your new argument rules out some further kinds of aliens, but there is still a lot of room left.

The numbers were just for illustration--you can plug most any sane value in for either the travel speed or reproduction rate and still get a value less than a gigayear.

That's not the case. For sufficiently low reproduction rates, that does not happen. AI may not even be interested in reproducing. And maybe what results on some planet from millions of years of genetic engineering and integration with machines wouldn't, either.
Alternatively, they may reproduce very rarely, and their numbers would never get beyond, say, a few hundred individuals.

 

[Bomb#20]

The deepest mine in the world is 4 km deep. The earth's crust is about 40 km thick.

And those deep mines are already inhospitable to human life.

Not compared to an asteroid they aren't.

 

[credoconsolans]

And those deep mines are already inhospitable to human life.

Not compared to an asteroid they aren't.

They almost are.