The Absolute, Definitive Truth About Alien Megastructures

The title of this post is a joke, or taken literally, an outright lie. The only definitive truth is that no one knows if anyone has ever built a megastructure, or even if they would if they could. I have persistent doubts if such things exist anywhere in the universe, but I can't yet tell you if such doubts are reasonable.

Update 8 December 2016: I left out one type of motivation for building a megastructure - planetary climate control. Although these "Dyson Dots" would be relatively small, they might be detectable for transiting planets. I need to run the numbers...

The Usual Disclaimer

So, we're going to be speculative here yet again, and very probably wrong. I won't be able to cite many facts, so if that is the sort of thing you like to read, perhaps now would be a good time to hit the back button.

But I'm Completely Serious

We are interested in the conjectured alien megastructures because we might have a chance to observe them with technology we have or could well have in the near future. These structures would be bigger than planets (my definition), and since we can observe planets about other stars, we might well be able to observe these things, and so looking for them is a kind of SETI. I've written before about why I think SETI is worthwhile.

Almost certainly wrong: an alien megastructure speculation about KIC 8462852

Update: 20 September 2016 - with the Gaia DR1, we didn't really know which way the 300 micro arcsecond systematics would push, us, but now there is some evidence that the parallax measurements are systematically underestimated. Another nail in the coffin.

Update: 14 September 2016 - it would seem that today's Gaia data release invalidates this, as the the star is no further from us than what Boyajian, et. al., estimated from its brightness, and possibly a fair bit closer.  So what we are seeing is a real dimming.

OK, what follows is highly speculative, but as far as I can tell, is at least internally consistent and doesn't require any exotic new physics. I've got some facts in here, but if all you care about is the facts, this isn't for you.

As I pointed out recently, to find ET technological civilizations, we're going to have to be wrong a lot - unless they are trying to make it easy for us, which they very well may not be. So, I am a long term optimist but short term pessimist. Unfortunately, being persistently wrong is very painful for some people, many of which might be the most qualified to try and set out the theoretical parameters for ET technology.

So, let me have a crack at it for the case of the star KIC 8462852, commonly referred to on this blog as "Tabby's Star," and I could well be proven wrong in a few days with the first Gaia data release. I will stick to known physics exploited with unknown technology, and perhaps it may take a bit longer to prove me wrong.

The conjectured megastructure is actually a swarm (conceivably millions) of light sails flying close to the star, using light pressure in clever ways to maintain their positions (I won't detail this yet, because my model of "near field" stellar sailing isn't very good). The megastructure is a shell of reflectors, perhaps within one or two stellar radii (a few million kilometers) of the star's atmosphere. These sails are steered in a coordinated way such that they concentrate the star's light in a particular direction by a high magnification, for the purpose of accelerating (or possibly deaccelerating) a very large light sail and its payload up to interstellar speeds - perhaps a few percent of the speed of light. It would concentrate the star's light by several orders of magnitude.

The Case for the Wow! Signal

I recommend Robert Gray's book The Elusive Wow! if you want detailed background on the Wow! event of August 15th 1977. The book also describes the author's efforts to replicate the signal. To date, no one has reported a reliable second detection of the Wow! Signal, although efforts to find it have not been persistent.

The Wow! Signal was a single 72 second event detected by the Big Ear radio telescope operated by Ohio State University, which was sweeping past the constellation Sagittarius at the time. This telescope was designed to conduct a survey of the radio sky, not to study individual sources in detail. The survey was successful and a number of new radio sources were discovered. After that, some of the science team thought that a SETI search would be a good use of the telescope.

I think the case against the Wow! Signal as an ET beacon is well known.

We are all well aware of the fallacy of the argument from ignorance. Just because the Wow! Signal has not been proven to be from a known source doesn't mean it's from ET. It's possible that the Wow! Signal was some sort of strange problem with the Big Ear's receiver that only occurred once, or that it was an extraordinarily elaborate and strenuous hoax. For these reasons, you would need to see independent confirmation, and we haven't; Robert Gray's single-handed and largely self-funded efforts to do so have been far from comprehensive.

Since the Wow! Signal was discovered after the fact, when Jerry Ehman went through a stack of printouts, it was too late to get another radio telescope to break off what it was doing, swing over and confirm the signal.  The signal was never confirmed, and no similar signal has been found in that region of space.

The are multiple reasons we think that the Wow! Signal may have been an ET beacon.

Where I am on the Drake Equation at the end of 2013

I'm sure you are all familiar with the Drake Equation. It's straightforward: SETI scientist Frank Drake devised it as a way to estimate the number of alien civilizations in our galaxy that we might be able to detect. It's only intended to be a rough guide, and has survived the last 50 odd years because it serves as a good way to divvy up the questions we will need to resolve to answer the bigger question, "Are we alone"?

There are many fine explanations of the terms of the Drake Equation easily available to you, so I won't repeat them. Here are few:

• Seth Shostak's book Confessions of an Alien Hunter, Chapter 3, explaining each term in detail.
• This page from the SETI Institute
• This video by Carl Sagan

This is how the equation is usually written:

N = R* • f_p • n_e • f_l • f_i • f_c • L

As we move from left to right across the equation, the terms become less and less well known and harder to estimate, even when we know more. The only thing we're sure of with some of the terms is that none of them are zero, since we are here.

In the last few years, there has been progress. We have gone from knowing just the first term with any kind of accuracy ( a factor of 2 or so), to having solid estimates of the first three terms, and we can now begin to conceive of a research program that would give us an estimate of the fourth term.

Remember, we are only interested in rough numbers here: we just want to know, is N a lot or a little?

So, for 2013, I think we are here:

Why Search?

In an earlier post, I argued that the current SETI program is not a silly waste of time if we want to search for ET and answer the question of whether we are alone, and I stand by that.  At the time I wrote that post, I didn't think that anyone would be interested in the why question. Of course we want to search, the only question is how, isn't it?  Maybe not for everyone.

All you have to do is to look at people like Frank Drake, Jill Tarter and Seth Shostak, who have

SETI Pioneer Frank Drake

devoted most of the careers to this topic, and you will realize that is is emotionally involving at a personal level, and not just "scientifically interesting".  It isn't purely a matter of scientific curiosity, and certainly not of ambitious scientific careering. 

Well, of course, the small number of people who study a topic are interested in it, and probably find it fascinating in some way.  What about everyone else?

So here is a question to ask yourself: if it was announced tomorrow that science knew for certain that there was another intelligent civilization in this galaxy, what would change for you?  Most adults are highly accomplished at keeping their own little worlds unperturbed.  Would the announcement of a distant ET civilization affect any major decisions you might make about your own life - your job, relationships, where you live, how many children you have, or any religious beliefs you might have?  Probably not you, but the younger generation, yes, because adolescents have left behind the comforts of childhood, and have yet to build their little worlds.  They don't mind being perturbed, and will often volunteer do some perturbing.  With announcement that we know about ET, their worlds just got much, much bigger.

Now it's not just Earthlings alone in the vast, cold universe anymore.  There are the others, possibly many others.  The universe no longer belongs solely to the astronomers, but is now alive, and belongs to everyone.

The Fermi Paradox - Part 1

This post is intended for those unfamiliar with the Fermi paradox. If you've already read a thing or two about it, I invite you to skip this one and wait until Part 2.

This is a companion post to Episode 2 of the Wow! Signal Podcast.  You can go over there and get the audio version with cool music.

For the purpose of this post, we are going to take as a given the null hypothesis about alien visitors to Earth - that this has never happened.  This is what the controversial astrophysicist Michael Hart called Fact A.

It turns out that accepting Fact A presents an interesting dilemma; first recognized by the distinguished physicist Enrico Fermi in 1950.  The unsolved problem is, that we would expect alien visitors on our planet, given a set of very reasonable assumptions. It’s really not such an extraordinary claim, after all. Assuming Fact A, this presents us with a puzzle. Either one or more assumptions have to go, or something really weird is going on.

Douglas Adams once famously wrote:

"Space is big. You just won't believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space."

But space is also hugely old The entire history of Homo Sapiens is only about one twenty-thousandth the age of the Earth, and the age of the Earth is less than a third the age of the universe. What would seem to be likely is that at least local to our galaxy, time eventually overwhelms space with respect to galactic colonization.

Searching for Bracewell Probes - part 2

In the first part, we talked about some of the variables that I think could control the observables of a Bracewell Probe.  This is essentially a first, crude move toward mapping our ignorance of these hypothetical machines.  We can't know what Bracewell probes are yet, or even if they exist at all, but perhaps we can constrain or at least make some reasonable assumptions about what they could be.

Searching for Bracewell Probes - part 1

Ronald Bracewell

Bracewell Probes were first discussed by Ronald Bracewell in a 1960 Nature paper. The basic idea is send robotic probes to solar systems that seemed promising, and these probes would sit and wait for millenia looking for signs of intelligent life in those systems, and should those intelligent creatures ever reach a certain measure of sophistication, then either radio home for instructions, or simply provide a library of advanced knowledge that would help these lowly beings achieve a kind of galactic citizenship.
that the "Superior Communities" would

Bracewell Probes still seem like a sensible way for superior communities to reach out in their galactic neighborhoods, whether their intentions are benign or defensive. Rather than guessing when to send probes to check out a suspect solar system, they simply strike out for all of them in the neighborhood, and then wait. Would their purpose be, as Bracewell conjectured, to enlighten us, or simply to alert the rest of the superior community that here there be uppity apes?

The Natural Philosophy of Queerer and Queerer

A man's got to know his limitations.

--- Harry Callahan in Magnum Force 

A bit about Haldane's Law, and what it means about the search for other minds in the cosmos.

Haldane

You might recall that in our first post, there was a quote from the great Enlightenment thinker David Hume.  To paraphrase, all we can understand is what we have felt - either internally or externally.  The essential point is that when faced with something unfamiliar we interpret it in terms of the familiar.  We discover the universe in small steps.  Big conceptual leaps are rare, and even they depend strongly on what the "internal sense" has long known.

J.B.S. Haldane (1892-1964) was a distinguished evolutionary biologist and geneticist.  His Law is most often stated as:

I have no doubt that in reality the future will be vastly more surprising than anything I can imagine. The universe is not only queerer than we suppose, it is queerer than we can suppose.

A lifelong study of the evolution and diversity of life on Earth alone could easily have guided Haldane to that conclusion. We are still making sense of the biosphere that is right here in front of us, with the textbooks scrapped and rewritten on a regular basis.

Let's say Haldane was right. We believe we anticipate strangeness, but even the strangeness is strange. What could be stranger than a non-human intelligence, particularly a sophisticated one? Haldane says we can't meaningfully speculate about how strange they could become, and in ways we can't imagine. An alien being isn't just going to offer you a cup of coffee and then tell you about Seven Habits of Highly Effective Cosmic Guardians. Or it might, and then eat you.
Now that's discouraging. If Haldane was right, how can we know what to look for if we are in search of other minds in the universe? We might be looking straight at them and seeing nothing.

In fact, I would bet that we are doing just that. In his excellent book, The Eerie Silence, Paul Davies offers a different slant on the critique of UFO reality - that the UFO mythos taken as a whole isn't strange enough. Davies would fully expect something much weirder, not a phenomenon that falls right in line with millennia of folklore. There are those who would argue that UFOs are in fact plenty strange, but I think Davies has a point. If what is going on is something we can understand or even clearly define, then it's probably not aliens.
And yet when we talk about our first encounter with a non-human intelligences, we often think in terms of Hollywood fantasies like The Day the Earth Stood Still. Klaatu is a mythical man very much of Earthly making, and his landing on the Washington Mall only makes far too much sense to us. Why haven't they landed on the White House lawn? They already did - in our imaginations, which is likely as close as "they" will get. We are going to have to get way beyond that sort of scenario

So, if we are to form any hypotheses, or even conjectures, so we know what to look for when go in search of Other Minds, what hope do we have in light of Haldane's law? I don't have a clear answer, but perhaps we can formulate it in terms of our own limitations, and look for the silence behind our blind spots. What can't we see, and why?  

I am hopeful. Experience shows that we humans can eventually, over generations, get our arms around some pretty strange ideas, primarily using our talent for abstraction. For example, the very odd idea of a black hole was fished out of the mathematics of Einstein's equations decades before the first solid observational evidence that such things existed. By the time astronomers were ready to go looking for black holes, the theorists already had a fair idea of what to search for. Now there is evidence for many billions of black holes all over the universe and they are well incorporated into the astronomical paradigm.

The other bit of hope is that maybe Haldane's law is limited, and doesn't really hold for alien intelligences. Perhaps the constraints on the evolution of sentient life are so tight that we all end up resembling each other in important ways. Perhaps. But don't bet on it.

Dream of the Open Channel by Paul Carr is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.