If you are going to look for evidence of technologically advanced civilizations in the Universe, you must start by considering what, exactly, you might be looking for. My colleagues and I in the NASA-sponsored Categorizing Atmospheric Technosignatures program spend a lot of time thinking about this. But there is a question that haunts me as much as it challenges the project: How far can a civilization go as it advances?
This question relates directly to the Kardashev scale, a topic we have covered before† The Kardashev scale is all about energy harvesting. A Type I civilization in Kardashev’s scheme can capture all of the energy falling on its home planet. A Type II civilization can capture all of the energy generated by a star, and a Type III can do the same for an entire galaxy. Harvesting the energy output of a whole galaxy seems pretty advanced indeed, yet we could take the idea further. Might there be Type IV civilization, or a Type V? Are there any limits at all to the advance of a technological species — and if so, where are those limits found?
Any attempt to think along these lines is speculation of the purest kind. Today, however, I am going to do just that. why? First of all, because it’s fun. But also because this is a route that some of the world’s best science fiction has traveled before, in books such as Stanislaw Lem’s His Master’s Voiceand in the movie Interstellar†
Meddling with dark matter
Kardashev envisioned civilizations that are still subject to the laws of physics. The Universe gives these laws to them just as they are given to us. We cannot change these laws — we can only use them more or less efficiently.
But what if a civilization becomes so advanced that it can in fact change those laws? This civilization would have gone well beyond merely harvesting energy. The very nature of energy itself, with established rules like energy conservation, would be subject to revision within the scope of engineering.
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Astrophysicist Caleb Scharf explored this kind of question in a piece entitled, “Is Physical Law an Alien Intelligence?The work is a masterpiece of creative invention. Scharf explored the rules of physics and asked which ones might have been rewritten by a sufficiently advanced form of life.
One eyebrow-raising possibility concerned dark matter. When astronomers track the motions of galaxies and clusters of galaxies, they find a problem: There is not enough mass to cause the forces needed to drive the observed motions. To solve this problem, astronomers assume there must be a lot of matter that cannot be seen. This means it does not emit light, which means it does not interact with the luminous stuff we see in any way other than through gravity. Hence the claim that the Universe is mostly full of “dark” matter. But for the sake of speculation, Scharf wondered if dark matter’s lack of interactions might not be a consequence of natural law, but rather the engineered result of an advanced civilization’s meddling.
Perhaps, Scharf asked, the best way for life to avoid catastrophes like radiation torrents or blast waves from exploding stars would be to disconnect almost entirely from the Universe. Using a 3-D “normal to dark matter” printer, you could, as Scharf puts it, “upload your world to the huge amount of real estate on the dark side and be done with it.”
Scharf had other ideas, such as a hyper-advanced civilization accelerating the expansion of the Universe — something we now attribute to so-called dark energy. Scharf mused that a sufficiently advanced civilization might actually be the cause of the acceleration. Perhaps they are using it to prevent the eventual heat death of the Universe and to ensure that disorder does not overwhelm the cosmos.
Could an advanced civilization peel back the veneer?
Allow me to enter the fray and introduce some radical speculation of my own.
What if there are actually many laws of physics, but evolution selects the ones that organisms can observe? Perhaps in the process of establishing the difference between the self and the world — which really form a single whole — there is some freedom in how an infinitely rich Universe gets parsed into observers and observed. This idea is implied in the wonderful movie arrival, where a species of aliens who come to Earth have a different cognitive and linguistic structure, and this gives them a very different physics of time. If physics and biological self-creation were linked in this way, perhaps a hyper-advanced civilization could indeed peel back the veneer separating self and Universe, and mix and match physical laws any way they see fit.
Is any of this possible? Well, a lot of things might be possible in the Universe, and many of those possibilities still work within the constraints of what we know about physical law. But it is also possible, and perhaps more likely, that the physics we know today puts severe limits on life and what it can do. These limits might constrain technological development enough to stop well short of what our science fiction can imagine. Perhaps, for example, there simply is no way around the limits imposed by the speed of light, and crossing the distances between stars will always be tremendously difficult and expensive.
You need to hold both these possibilities in your head, for they are equally staggering in their implications.