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Dragon sleeps in a cave
Dragon sleeps in a cave

Researchers: The aliens exist but they are sleeping…

And we wake them at our peril

Recently, science (and science fiction) writer Matt Williams has been writing a series at Universe Today on why the extraterrestrial intelligences that many believe must exist in our universe never show up.

Last week, we looked at the hypothesis that the aliens’ advanced technology ended up destroying them all and… the machines may be coming for us because destroying is all they know how to do.

This week, let’s look at a quite different idea that Williams outlines in “Beyond “Fermi’s Paradox” V: What is the Aestivation Hypothesis?” (August 7, 2020). Aestivation is the summer version of hibernation in winter. The aliens, in this scenario are not dead; they are merely sleeping. Just as many life forms on Earth go into torpor during hot and dry conditions, they are awaiting cooler conditions before they emerge.

Why might the ETs need cooler conditions? Many ET theorists posit three types of civilizations on a Kardashev Scale, depending on their state of development:

The scale was originally developed in a 1964 essay by Russian astrophysicist Nikolai Kardashev. Type I civilizations can harness the energy of a planet, Type II, a star system, and Type III, a galaxy. The structures they could build (and we could detect) would depend on the energy they can harness.

Galaxy redevelopment would generate a lot of heat, maybe too much. In a 2017 study, “That is Not Dead Which Can Eternal Lie: the Aestivation Hypothesis for Resolving Fermi’s Paradox,” physicists associated with Oxford’s Future of Humanity Institute (where Nick Bostrom is the director) suggested that the ETs may have decided to wait till the universe cools down before doing any more calculations; thus they are aestivating:

If a civilization wants to maximize computation it appears rational to aestivate until the far future in order to exploit the low temperature environment: this can produce a 1030 multiplier of achievable computation. We hence suggest the “aestivation hypothesis”: the reason we are not observing manifestations of alien civilizations is that they are currently (mostly) inactive, patiently waiting for future cosmic eras. This paper analyzes the assumptions going into the hypothesis and how physical law and observational evidence constrain the motivations of aliens compatible with the hypothesis.

Sandberg, Anders & Armstrong, Stuart & Cirkovic, Milan. (2017). That is not dead which can eternal lie: the aestivation hypothesis for resolving Fermi’s paradox. JBIS – Journal of the British Interplanetary Society. 69. (open access)

One suggested reason that the ETs might adopt such a strategy is that they have become digital beings anyway:

Indeed, an increasing number of futurists, astrobiologists, and SETI experts are starting to think that advanced intelligence eventually transitions into a digital mode of existence. Living as digital beings within powerful supercomputers, post-biological aliens (or future posthumans) will demand unhindered access to powerful and efficient means of information processing—a hypothetical mode of existence known as “dataism.”

George Dvorsky, “Hibernating Aliens Could Explain the Great Silence” at Gizmodo (May 13, 2017)

How would we know if any of this is true? Two of the authors of the paper

Can we test it?

Yes! The obvious way is to carefully look for odd processes keeping the universe from losing potentially useful raw materials. The suggestions in the paper give some ideas, but there are doubtless other things to look for.

Also, aestivators would protect themselves from late-evolving species that could steal their stuff. If we were to start building self-replicating von Neumann probes in the future, if there are aestivations around they better stop us. This hypothesis test may of course be rather dangerous…

Anders Sandberg & Milan Ćirković, “The aestivation hypothesis – popular outline and FAQ” at Andart: {art of Anders’ Exoself

About the dangerous part, Sandberg told Gizmodo,

Another way to potentially detect these sleeping civilizations would be to mess with their stuff, but that could be very dangerous. “[We could] try to set off some process that really would upset the aestivators—like launching a lot of self-replicating probes to pave the reachable universe with our infrastructure,” said Sandberg. “If the aestivators are halfway competent their robot guardians will show up to stop that. Which might make this a very risky way of testing the hypothesis.”

George Dvorsky, “Hibernating Aliens Could Explain the Great Silence” at Gizmodo (May 13, 2017)

In short, we’d better not wake them up. By way of explanation, in their paper, Armstrong et al. quote a famous horror writer,

The Old Ones were, the Old Ones are, and the Old Ones shall be.

Not in the spaces we know, but between them. They walk serene and primal, undimensioned and to us unseen.

H.P. Lovecraft, The Dunwich Horror and Others

One physics team, more prosaic, disputes the whole notion. They say that the Aestivationists misunderstand the astrophysics principles involved in massive computing: “computer-generated entropy can only be disposed of by transferring it to the cosmological background. In fact, while this assumption may apply in the distant future, our universe today contains vast reservoirs and other physical systems in non-maximal entropy states, and computer-generated entropy can be transferred to them at the adiabatic conversion rate of one bit of negentropy to erase one bit of error. This can be done at any time, and is not improved by waiting for a low cosmic background temperature.”

Williams thinks the Aestivation hypothesis is best seen as a thought experiment. So let’s play along. As he points out, the hypothesis is based on a number of assumptions about the aliens’ approach to life: for example, that they are very advanced compared to us, that they range far in space, that they are so interested in things like dominating galaxies and making contact with us that the aforementioned digital prison or oblivion for a mindboggling amount of time is worthwhile. He suggests that they could be doing this while they wait for us to evolve to the point where we are worth knowing.

All of these assumptions can be questioned. For example, would knowing us really be worth aeons of Sleeping Beauty-style oblivion? If the ETs are so advanced, why couldn’t they just invent us in their spare time without leaving home?

But not to worry, even the authors seem to agree that the idea is just a thought experiment (maybe a movie at some point?). One observer sums it up:

If you’re feeling uncertain or unconvinced about this theory, don’t worry, you’re not alone. I think this is one of the more creative, but less plausible, possible explanations for Fermi’s Paradox, for why we have not observed evidence of extraterrestrial intelligence. Even the primary author, Anders Sandberg, wrote on his own website last year: “I . . . personally think the likeliest reason we are not seeing aliens is not that they are aestivating, but just that they do not exist or are very far away.”

Rev. Jonathan Rogers, “The Aestivation Hypothesis” at NWUUC (July 1, 2018)

The aliens, at any rate, have a gift for being much more fun when they don’t show up.

You may also enjoy considering the other hypotheses:

Seven reasons (so far) why the aliens never show up. Some experts think they became AI, some that they were killed by their AI, and others say they never existed. Who’s most likely right? Science fiction writer Matt Williams delves into seven hypotheses into which scientists and science fiction writers have put a lot of thought.

8.Are the Aliens We Never Find Obeying Star Trek’s Prime Directive? The Directive is, don’t interfere in the evolution of alien societies, even if you have good intentions. Assuming the aliens exist, perhaps it’s just as well, on the whole, if they do want to leave us alone. They could want to “fix” us instead…

7.How can we be sure we are not just an ET’s simulation? A number of books and films are based on the idea. Should we believe it? We make a faith-based decision that logic and evidence together are reasonable guides to what is true. Logical possibility alone does not make an idea true.


6.Did the smart machines destroy the aliens who invented them? That’s the Berserker hypothesis. A smart deadly weapon could well decide to do without its inventor and, lacking moral guidance, destroy everything in sight. Extinction of a highly advanced civilization by its own lethal technology may be more likely than extinction by natural disaster. They could control nature.

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Researchers: The aliens exist but they are sleeping…