Lucy Ricardo has never been to Sirius.

Not an entry where I’ll be blazing new trails. :o) It’s only a story about my own explorations. And, if I had read and pursued things more systematically, I would have understood everything here much sooner.

***

Somewhere back there, in the recent span of years during which I’ve been writing in OD – did I write about it in OD, and was it lost in the Great OD Hack? because I can’t find it – I tried to figure out how big a footprint our inhabited Earth had so far made among the stars. You know, with I Love Lucy wafting out toward infinity.

Who might at least have had the chance of detecting us? Meaning: How far out might we have been heard, to date?

The first step in getting the approximate answer I sought was to check when radio was invented.

Marconi sent and received the first deliberate radio transmission in 1895, and radio telegraphy proliferated rapidly after that, with (checking Wikipedia for examples) the U.S. setting up radiotelegraphy communication between the Hawaiian Islands in 1901, the first naval battle of the Russo-Japanese War in Manchuria being reported via radiotelegraph in 1905, and so on.

This was all rather blurry for my purpose – I had no idea how strong the signals were in the earliest days, and this bothered me – but, nonetheless, I knew that the amount of time, in years, that had passed since our first radio transmissions was equal to the distance, in light years, that those radio waves would have travelled through space.

So, if I said that the beginning date was 1910, for example – choosing that date in order to give a decent chance that telegraphy would have been being used here and there all around the world, so that I could be asking about the spherical volume that Earth’s transmissions would have expanded through, rather than just the maximum distance in some direction – then that would mean that, in 2011, transmissions from Earth had passed through a volume of space with a radius of approximately 101 light years.

The next step was to get an idea of what that number might mean. How many star systems are within that volume? I knew that the nearest star system, the three stars that make up Alpha Centauri, was only a little over four light years distant…

I cannot find the calculation I made, but I can give you an idea. I didn’t find a reference that directly answered the question, so I went about it crudely. I looked through the tomes in the astronomy section in Powell’s Books until I found a handy list of the twenty nearest stars to our sun, with distances. The distance from Earth given for the furthest star of the twenty told me that, within a spherical volume with that radius, there were twenty stars. I then generalized that density to a spherical volume with a hundred-light-year radius (about; I did this a few years back, I’m not sure when).

I have no idea of whether my math was off, but I don’t think it was too far off. I’m also sure that the stars aren’t distributed evenly, but I gambled that the spacing averaged out.

The answer I got, anyway? I got an answer of thousands of stars within that volume.

I can’t remember the number I got – seventeen thousand? twenty-three thousand? something resembling those, I think. I was agog.

Our radio – and later our TV – transmissions were already wafting through thousands of star systems – around even more thousands of unknown planets, and even more thousands of moons and asteroids…

I daydreamed on that basis, pondering this situation in which Earth had really hung out the shingle. And while remaining hilariously oblivious to the fact.

It now appears to me that I was wrong. :o)

Not wrong (as far as I know) about this calculation that I crudely tried to do; wrong about its implications.

You think of different things when you get a separate bite at the apple. A little over a week ago I read an article about the discovery of a distant planet in the “Goldilocks zone” around its star, and the author took the opportunity to ramble about the Drake equation and Fermi’s “where are they?” The title of the piece was “E.T. Won’t Be Phoning Home Anytime Soon.”

A few things tweaked me in the article, and in the comments. Which is very common for the subject. :o) The problem with the Drake equation, as with the entire topic it encapsulates, is that people tend to be too confident in assigning values and probabilities to the various components of it, there being no examples other than Earth to which to compare anything, and even a good background in some aspects of the topic just serves to bolster the excess confidence.

(And, naturally, their egotistical overconfident assessments don’t match my own egotistical overconfident assessments, which makes me grouchy. :o) Oh, yeah, I have all the intellectual vices. Every one of them. I’m like CDC sample storage, and the containment system is buggy.)

What particularly caught me was this sentence toward the end of the piece:

Given that humanity has been sending signals into space for nearly a century, listening for them for about 40 years, and still hasnt found anything indicates to me that the universe isnt teeming with intelligent life.

Well, that’s certainly a confident diagnosis of an indication. I wondered about it. And this time I picked up the question from the other end:

How far away would we be able to detect ourselves? Assuming a media-busy broadcasting Earth, just like the one we have?

I posted the article on Facebook and typed irritably about it:

I have never had any idea of about SETI: What do our listening capabilities amount to, in this specific sense? Meaning, for example – to use our present-day selves to get a unit of measurement – at what distance would we presently be able to detect the radio noise of an Earth (or to distinguish it, factoring in the noise of the sun next to it)? Has anyone seen an estimate? What can be expected?
All I know is that we have some dishes and we’re listening for anomalies – which is a bit uninflected. Which makes the lines of reasoning based on our not having heard anything a step more unevaluable than they have to be.

And then it occurred to me to try Google on it. (I don’t know whether the detectability angle came to mind back when I did the original wondering, but I don’t think I pointed the Google at the aspect then. When I look back, a huge proportion of my misunderstandings and unnecessary delays in knowledge or comprehension have resulted, not from self-terminating errors in construction, but from it simply not having occurred to me to type search words into a search engine. It’s a bonehead plague.)

Google bore fruit, and I typed what I gleaned into a comment under the article – far too late for much of anyone to actually read it, of course. Here’s the comment I wrote, with italics added for emphasis. (For some OD-glitchy reason, I cannot make that URL a live link! So just copy and paste it into a new window if you want to read.)

I went looking for an estimate of whatwe would be likely to detect. For what its worth, SETI has some information about the distance at which Earths transmissions would presently be detectable, here:

http://setifaq.org/faq.html#1.2.3

The upshot: if the receiving dish were the size of Arecibo, 305 meters across, then even the best-case transmission, UHF TV carrier waves, could be detected at a maximum distance of 0.3 of a light year from Earth. (That doesnt include detecting TV pictures, which could only be detected in the inner solar system.) The nearest star is a little over 4 light years away.

For this reason, SETI is looking for other kinds of transmissions narrowband transmissions, where all the transmitters power is put into a very narrow range of frequencies. However, the reason anyone would be doing that at very high power would be likely to be in order to specifically and deliberately try to communicate at interstellar distances at great expense in effort, energy, initial construction, etc. Its hard to estimate how likely anyone out there is to go to this much trouble to try to be heard by unknown aliens. (Were not doing it.) But anyone who is not doing it is almost certainly not going to be found by accident, and definitely not through their transmissions, because their transmissions will be undetectable.

One reason to try to communicate across interstellar distances is to communicate, not with unknown aliens out of unspecified motivations, but with ones own interstellar colonists or interstellar probes. However, this supposes that they have managed to cross the nearby interstellar gulfs at all, something vastly more difficult and conjectural than making a transmission. Notwithstanding that, if they did have colonists or probes out there to talk to, the best way in which to get the most distance out of transmission power is to make a directional transmission. Any such transmissions have a fantastically reduced chance of being detected by us, because the chance of those transmissions being accidentally pointed straight toward us is so low.

Mr. Lehrer wrote, Given that humanity has been sending signals into space for nearly a century, listening for them for about 40 years, and still hasnt found anything indicates to me that the universe isnt teeming with intelligent life. Based on this picture, Id say neither Mr. Lehrer nor I nor anyone else can make any inferences at all about the rate of incidence of intelligent life or elsewhere in the universe based on not having heard anything. (Cheers reruns could have been airing in every third star system, all precisely at the time in the past that would match with light from their stars reaching Earth now, and we wouldnt know anything.) We wouldnt have the data Mr. Lehrer thinks weve detected the absence of.

So that’s a very different picture: one in which Earth has not “hung out the shingle” at all.

And one in which it looks as though we will not be able to detect any civilizations that might be out there, however technologically advanced and electromagnetically active, unless they are deliberately trying to be detected.

(For what it’s worth, the SETI information also notes that the Arecibo telescope has used active radar to study objects in the solar system, and those transmissions would be detectable ten thousand light years out – but, again, those radar transmissions are directional and very narrowly focused, and have the same problem as the directional transmissions I discussed; they won’t be detected unless they are pointed straight at the receiver.)

We can quibble about the possibility of beyond-our-own-current-science signal-gathering capabilities – we can always do that – and I suppose we can talk about much, much bigger collector dishes than mighty Arecibo. But the problem is there. (And I’ve been trying to pick holes afterward in ignorant-idiot-amateur fashion, but I don’t think a physicist would tell me that thousands and thousands of signals undetectable at a given distance, as from a whole planet, will somehow add up to be more detectable at that distance than one such signal.)

So, for these reasons, SETI is focused on a special case – the specific possibility of alien civilizations that are going to a great deal of remarkable trouble to be interstellar extroverts toward parties unknown to them, with powerful omnidirectional beacons that radiate at frequencies chosen for reaching out.

I wonder if we would, or will, ever go to such trouble.

(One factor: Should we? For reasons of objections beyond the expense? I once read a suggestion about why such friendly, ambitiously outgoing transmissions may be rare or brief… the possibility that they actually do succeed – in that the senders are found by other aliens, who have mastered the problems of interstellar travel… whereupon the transmissions stop. I seem to recall reading the line, “Death is silent, but so is the predator….”) (And, even if those predators finding new life-bearing worlds that way do not actually exist, there’s also the thought that civilizations that are intelligent enough to see the option of starting very slow interstellar contacts for their distant descendants, and the conceivable benefits, would also think of the possibility of such an outcome.)

If we look for such very special, huge activities, and we don’t find any, not finding them doesn’t mean or indicate anything.

(Much like if our only means of finding out whether intelligent life is present on a particular planet were a machine that detects the Mount Rushmore sculptures. If you do happen to detect Mount Rushmore on the planet, that is a good indication. But if you don’t… notice that China, Australia, Denmark, Oregon, and many other fine inhabited regions on Earth would also give a false negative.)

Meanwhile the other way to eventually detect other civilizations, if they are there, would be to, over time, move between stars and expand through more and more star systems until we encounter them. An option of fantastic difficulty, and posing even more questions.

We float amid mysteries too big for us to see.