Editor’s note: Simon Goodwin is professor of theoretical astrophysics at the University of Sheffield (England).
There are three ways to search for evidence of technological alien civilizations. One is to look for deliberate attempts to communicate their existence, for example through radio transmissions. Another is to look for evidence that they visited the Solar System. And a third option is to look for signs of large-scale engineering projects in space.
A team of astronomers took the third approach, searching data from recent astronomical surveys to identify seven potential candidate stars to harbor alien megastructures known as Dyson Spheres “which deserve further analysis”.
This is a detailed study that looks for “strange” behavior of stars that could be signs of the presence of these alien megastructures. However, the authors are careful not to make any exaggerated claims. The seven objects, all located less than 1,000 light-years from Earth, are “M dwarf” stars — a class of stars smaller and dimmer than the Sun.
Dyson spheres were first proposed by physicist Freeman Dyson in 1960 as a way for an advanced civilization to harness the power of a star. Composed of energy collectors, factories and habitats floating in space, they would increasingly occupy the surroundings of the star until, finally, they would almost completely surround it, like a sphere.
What Dyson realized is that these megastructures would have an observable signature. Dyson’s signature (which the team looked for in the recent study) is a significant excess of infrared radiation. This is due to the fact that the megastructures would absorb the visible light emitted by the star, but would not be able to use all of it. Instead, they would have to “dump” the excess energy as infrared radiation with a much longer wavelength.
Unfortunately, this radiation could also be a signature of many other things, such as a disk of gas and dust, or disks of comets and other debris, in the star’s orbit. But the seven promising candidates are not due to one disc, as they did not fit well into disc models like that.
It’s worth noting that there’s another possible signature of a Dyson sphere: the star’s visible light diminishes as the megastructure passes in front of it. This signature has been found before. There was a lot of excitement about Tabby’s star, or Kic 8462852which showed a lot of really unusual dips in its brightness that could be due to an alien megastructure.
But Tabby’s star’s behavior is almost certainly not due to an alien megastructure. Several natural explanations have been proposed, such as comet clouds passing through a dust cloud. But it’s a strange observation. An obvious follow-up to the seven candidates would be to look for that signature as well.
The case against Dyson beads
However, it is quite possible that Dyson spheres do not even exist. I think it’s unlikely that they exist. This doesn’t mean they couldn’t exist, but rather that any civilization capable of building them probably wouldn’t need to do so (unless it was a mega art project).
Dyson’s reasoning for considering these megastructures assumes that advanced civilizations would have large energy needs. At the same time, astronomer Nikolai Kardashev proposed a scale to evaluate the technological advancement of civilizations that was based almost exclusively on their energy consumption.
In the 1960s, this actually made sense. Looking back over history, Humanity continued to exponentially increase its energy use as technology advanced and the number of people in the population increased, so they simply extrapolated this ever-increasing need into the future.
However, our global energy use began to grow much more slowly in the last 50 years and especially in the last decade. Furthermore, Dyson and Kardashev never specified what these vast energy levels would be used for, they just assumed (quite reasonably) that they would be needed to do whatever advanced alien civilizations do.
But when we look at future technologies, we see that efficiency, miniaturization, and nanotechnologies promise much lower energy use (the performance per watt of virtually all technologies is constantly improving).
A quick calculation reveals that if we wanted to collect 10% of the Sun’s energy at Earth’s distance from our star, we would need a surface area equal to 1 billion Earths. And if we had super-advanced technology that could make the megastructure just 10km thick, that would mean we would need about a million Earths worth of material to build it.
A significant problem is that our Solar System only contains about 100 Earths of solid material, so our advanced alien civilization would need to dismantle all the planets in 10,000 planetary systems and transport them to the star to build its Dyson sphere. To do this with the material available in a single system, each part of the megastructure could be just one meter thick.
This assumes they use all the elements available in a planetary system. If they needed, say, a lot of carbon to make their structures, then we would be dismantling millions of planetary systems to get it. I’m not saying a super-advanced alien civilization couldn’t do this, but it’s a hell of a job.
I would also strongly suspect that by the time a civilization got to the point of having the ability to build a Dyson sphere, they would have a better way of getting the energy than using a star if they really needed to (I have no idea how , but they are a super advanced civilization).
Maybe I’m wrong, but it doesn’t hurt to take a look.
(This article is republished from The Conversation under a Creative Commons license. Read the original article.)
