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.

The Possible SETI Target HD 164595 - more messing around with Aladin

Last Update:  9 September 2016

There been a lot of kerfuffle lately about a possible SETI detection more than a year ago at the RATAN-600 radio telescope in Russia. Some would say far too much kerfuffle, since it was only seen once and may well admit to alternative explanations. SETI scientists like  Eric Korpela are unimpressed.

Aliens, Perhaps, but Not the Aliens of the Gaps

Update (8 August 2016): Audio Interview with Ben Montet.

With the publication of Montet and Simon's arresting new preprint showing even more anomalous dimming behavior by Tabby's Star,  a lot of reasonable people are asking whether it's time to declare this stellar weirdness the work of an ET civilization, or whether it may be soon. While I am emotionally inclined to go this way, and intuitively sense that this may be the ultimate conclusion reached, I am not a believer. There is a fundamental error we still must avoid.

Light curve for KIC 8462852 from Montet and Simon

It is not crazy or deluded to think that this could be the work of ET. Not at all. We know that technological civilizations exist in our galaxy, we just don't know how many. It is easy to get into pointless arguments about whether there is just one, or the universe is swarming with creatures in some ways analogous to dexterous, talking monkeys like ourselves. These arguments are usually based upon probability guesses with very weak, or even non existent empirical support.

The truth is that nobody really knows how common ET civilizations are, or how long they flourish, and the so far null result of our (so far) very poorly funded SETI enterprise isn't much help in resolving it one way or the other, as has been argued by such persons as Jill Tarter for many years now.

Messing Around in Aladin, part 1 - Tabby's Star and the missing star.

Last Update: 11 August 2016

This is another one of those draft entries that I will publish before it is done. I invite comments, questions and criticisms as always.

Looking into some of the stories I've been covering lately that live right in the imprecise border between astronomy and SETI, I've gotten interested in astronomical catalogs. It turns out that there are a lot of them, compiled over the years by a number of different scientific groups for different purposes. With the advent of astronomy outside the visible spectrum, the number of catalogs has multiplied, and it can be a daunting job to sift through them. I invite you to join me in my confusion and delight as I attempt to navigate my way through this glorious mess our civilization has built.

Aladin Sky Atlas is astronomy software made available for free from the University of Strasbourg in France. It gives you a graphical interface to a wide range of astronomical catalogs and image libraries. One thing it lets you do is overlay various catalogs across the electromagnetic spectrum around an object, so you can see for yourself what's nearby an object of interest and what its known properties are.

It turns out astronomers have cataloged far more objects than they have been able to study closely. As a result, there are many things not know about most of the cataloged objects. These are nearly all things that could be known if someone had the time and resources to look into them, but no one has yet.

4 Pi SETI - Why Not Build the Argus Radio Telescope Full Scale?

Robert Dixon

Update: we need to digest this first. All-sky there could be 2000 FRBs per day.

This  post - like nearly all the others - is about the questions I have. I am not a radio astronomer.I want to know how and how much and when about the radio telescope we will discuss below. This was stimulated by my interview with Robert Dixon last year, in which he discussed the virtues of the Argus concept. I lay awake that night thinking about it, and wondering why it hadn't been built yet.
 
The Search for Extraterrestrial Intelligence (aka SETI) is just that - a search. Like any search, it becomes much more difficult when more dimensions are added to the search space, and far easier when one or more of those dimensions are removed.

For example, if you are looking for an obscure little store with the best barbeque ribs in the West, and all you know is that it's in Los Angeles County, then your search space is quite large. However, if you have the additional information that it's on Santa Monica Boulevard, then you you still have some searching to do, but much, much less. You might even find the joint before it closes.

The problem with the SETI search is that it uses telescopes, and telescopes like the Allen Telescope Array or the Arecibo Observatory, only look at a small part of the sky at any one time. In fact, all the radio observatories in the world put together are only looking at a tiny sliver of the sky. If an ET beacon is transmitted for a short time while you are looking at another part of the sky (which you almost certainly are), you would completely miss it. We can dream about adding more telescopes to the search, but we would need a ridiculous number to cover the whole sky at once - or would we?

The Long Delay Echoes

The subject here is a scientific mystery that was well documented by European scientists in the 1920s and 1930s, well before any man made objects were launched into outer space, and then was largely forgotten. The phenomenon has since apparently disappeared, although anecdotal reports still pop up from time to time, and a low level of interest persists. We are discussing it here, because although no one knows for sure what caused the Long Delay Echoes, one plausible explanation is Bracewell Probes. The Long Delay Echoes (LDEs) just possibly might be a clue to how to find such a probe.

Some Basic Background You may Wish to Skip

 I'm sure you know that radio waves generally travel at the speed of light, and can be bounced off of various surfaces and also off the Earth's ionosphere if the radio wavelength is long enough. The speed of radio waves can be a bit slower if they are traveling through a medium such as a plasma or water, but generally the speed is not much less than the 300,000 kilometers per second we are used to. That means, if we send a radio signal out, and see it come back to us, then to calculate the distance to the reflector, we divide the time delay in seconds by 2 (since it went out and back), and then multiply by 300,000 kilometers per second to get the distance. Then, if we send out a radio signal and it comes back 2 seconds later, it must have traveled 300,000 km each way, or most of the way to the Moon. Amateur radio operators often enjoy bouncing their signals off the moon, which generally exhibits a very weak echo delayed about 2 and one half seconds. Strong echoes, or echoes delayed longer than 2.5 seconds, are not moon echoes.

Since the 1960s, there are many radio repeaters in Geosynchronous orbit, but the round trip delay is much shorter than the moon -  less than half a second, and you generally won't see a satellite echo at all unless your signal parameters are just right - and probably illegal.

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:

When is absence of evidence = evidence of absence?

You often hear the old mantra "absence of evidence is not evidence of absence," but I think that this is an oversimplification. The truth is, sometimes it is, and sometimes it isn't. It depends on the experiment, and also how well you understand the implication of the results.

There are times when you can make an excellent case that something is absent because there is no evidence of it. If you are is small, well-lit room, you probably don't need to look under many things to convince any reasonable person that there is no tiger there. In general, you need two things:

1. You need a solid argument for what sort of evidence you would expect if what you are looking for is there, and how that would be different from the null hypothesis (not there). 
2. A set of data that tends to falsify the hypothesis, thus advancing the null hypothesis.

We're not talking about "proof" here. I would just as soon we not talk about proof much at all, unless the topic is logic or mathematics. Rather, simply raising or lowering the odds of the null hypothesis, i.e. that the claim in question is not true.

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 Jaws of Darkness

"Or, if there were a sympathy in choice,
War, death, or sickness did lay siege to it,
Making it momentary as a sound,
Swift as a shadow, short as any dream,
Brief as the lightning in the collied night,
That, in a spleen, unfolds both heaven and earth;
And ere a man hath power to say "Behold!"
The jaws of darkness do devour it up:
So quick bright things come to confusion."
--Lysander from Act 1, scene 1, 141–149, "A Midsummer Night's Dream" 

This is that talk we need to have on the last term in the Drake Equation, mostly commonly denoted as "L". I'd like it to be more of a conversation than a soliloquy, so please share your thoughts here, or come on over to the G+ Community and let me have an earful. Better yet, let's talk in real time, and record our conversation for the Wow! Signal Podcast.

I would also like to point out that Seth Shostak has written thoughtfully about "L" in this document (go to page 399), and covers many of the key points well. Perhaps you should read that first. I'll wait.

A couple of key interviews

Just a short note please check out a couple of key interviews relevant to this blog: Geoffrey Landis and David Grinspoon. 

Also, if you are interested in SETI (of course you are), please read this.

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?

Speculation - the only way to fly

Ronald Bracewell

Here is another speculation, but probably not very original. In fact, it's a variation on the 1960 concept of a Bracewell Probe.  It's hard for me to imagine that some science fiction author or another hasn't treated this in some form.

In the future, we expect to be able solve these three broad classes of technological problem we haven't got a a handle on yet:

1. Very large sensors that can remotely sense distant planets accurately enough to ascertain their habitability with a high confidence.
2. The hosting of a human mind on a machine substrate - i.e. a truly intelligent machine.  This implies that the state of a human mind could be captured - "uploaded" onto a machine and captured in a data set. In other words, we could completely define what we now call the "self" in terms of data.  The crucial thing here (within an order of magnitude or so), is how much data.  Let's say it's about an exabit compressed, or  10^18 bits.  Some estimates are lower that, but I think we need lots of margin.  
3. Travel across interstellar distance, although the problems of doing so quickly ( a significant fraction of the speed of light and exploiting time dilation effects) may prove to be insurmountable no matter how sophisticated our technology is, and at present we have only the broadest concept of how to cheat the speed of light limit.

Let's assume we could do both 1 and 2, but item 3 could only be done slowly, so that it takes hundreds or even many thousands of years to travel between the stars.  This would be a hopelessly tedious journey for a human or superhuman intelligence, and all the mass required for reliable life support would only slow it down and limit options for deacceleration.

So, we would want to send only a small mass to another star system and it would take a long time and cost a lot of energy.   However, we can transmit information far more cheaply and at the speed of light.  You might need a really big and powerful transmitting array, but this is just scaling up from current technology.  To transmit an exabit in a year you would need a transmission rate of about 30 gigabits per second -  well within plausibility, even over interstellar distances.  The size of the receiving antenna you would need on the other side would increase with the distance (roughly 100 meters on a side at 100 light years, given plausible assumptions about  the transmitter, noise temperature and losses), but such antennas can be made from gossamer materials that can be folded compactly.

Is SETI Silly?

No, I don't think it's silly.  It remains entirely possible that simply by carefully studying the photons flying at Planet Earth from all directions, we will find clear evidence of an extraterrestrial civilization.  However, as I have taken pains to point out, we really don't know what we're talking about when we use that phrase, so we're going to have quite a long (and I think, healthy) debate about that the evidence should be, and how best to find it.

The Search for Extraterrestrial Intelligence (SETI) is a loose affiliation of scientific institutions funded by private donations, trying to find a way to search for other technological species in our galaxy.  It's just one galaxy - doesn't sound too ambitious - but where to start?

Review of "An Eerie Silence" by Paul Davies

I want my book reviews to be useful to you, the reader, who may not have read the book in question and are trying decide whether to spend your money and time to do so.  So, my purpose will not be to show you how cleverly I grok the text, but rather to lay out for you what your are likely to find interesting or helpful in the book and how much of your time will be invested.

For non-fiction books, you don't need to read every chapter, so I will break down the content of the book and try to help you decide if these are topics you are interested in.  Of course, I will only review a book I have read in its entirety.

I will also include interesting nuggets or quotes that struck me as particularly interesting.

The Synopsis

The Eerie Silence by Paul Davies

Paul Davies is a physicist and author who has been associated with the Search for Extraterrestrial Intelligence (SETI) much of his career.  He wrote this book inspired by a 2008 workshop he hosted to look for innovative ways to improve this search.

 

Who Should Read it?

Anyone interested in a scientific approach to the problems of searching for alien life in the cosmos. Only a general layperson's background in the sciences is required, although the background explanations in the book maybe too sketchy for some readers. If you want a more in-depth introduction to the science, I suggest reading David Grinspoon's "Lonely Planets", which takes the reader gently through basic science topics needed to understand the questions of alien intelligence.
Science Fiction writers should find a bounty of story premises here, as well.

 

Time investment

Modest. The book is not difficult and is reasonably well organized and written. Only 242 pages, which includes bibliography, end notes and index, and is divided into 10 chapters and an appendix.

 

Is it Worth Reading?

For me, the most interesting Chapters were 3, which discusses the fascinating concept of a shadow biosphere, and Chapters 5-8, which discuss recent thinking about how SETI can be improved and expanded, and the kinds of highly exotic phenomena we might encounter from highly advanced extraterrestrial civilizations if we search well enough and long enough. These chapters are rich in recent, provocative ideas.
Readers unfamiliar with SETI and astrobiology will find the entire book informative, although there are a number of other books and articles on the topic that would serve equally well or better.

 

Interesting Nuggets

Davies knew famed UFO researcher J. Allen Hynek, and even visited him at this home.
Davies is a member of the committee formulating what Earth's response "should" be (if any), should an alien signal be detected.

 

A Few Quotes

"Clearly, there could be a large number of alien probes in the solar system, and we would be completely unaware of them unless they signaled us."

Homework from Professor Shostak

Seth Shostak may be right about UFOs,or he could be wildly wrong, but it is difficult to ignore his critiques of the the notion that UFOs are spacecraft from other planets. The SETI astronomer and podcast host recently appeared on Martin Willis' Podcast UFO to explain his views, which are also laid out in Chapter 4 of his book, Confessions of an Alien Hunter.

What's not wrong with the ETH

Gort is not pleased with us

OK, I just got through slamming the ETH to the deck, and I have it in a sleeper hold, waiting for it to go limp.  Why would I defend it?

Recall that my main problem with the Extraterrestrial Hypothesis (ETH) is the "Hypothesis" part.  It's not so much the answers it offers, but that it fails to ask useful questions that we can answer with real data.  However, I feel that I must also address some the attacks the ETH has unjustly suffered, as well as some of the false distinctions it is included in.