What is the first radio signal sent by humankind?

February 21, 2011 8:08 PM

What is the first radio signal sent by humankind and could it be understood by an alien race?

I have been doing some reading on the topic of SETI and in particular the Wow! Signal and it got me thinking about the following:

1. If a similar "listening" project to SETI was set up by a distant alien race, what would be the Earth-generated "Wow! Signal"? I assume some sort of test broadcast from the late 19th century, but is there a definitive "first"?

2. Could signals from Earth be decoded? I notice that the Arecibo message created by Carl Sagan et al, was sent in binary. Is such a broadcast easier to interpret than a radio broadcast of something like music or the human voice?

posted by smithsmith to science & nature (15 answers total)

Signals from Earth would be too attenuated to be distinguished from background noise.

The strength of electromagnetic radiation, including radio signals, diminishes by the square of the distance from the source.
posted by orthogonality at 8:15 PM on February 21, 2011 [2 favorites]

First off, the inverse square law works against us with SETI. The antenna a civilization a few light years away would need to capture a non-directed earth signal would need to be the size of planets or solar systems, depending on the distance. SETI works on the assumption that an alien civilization has somehow found us and is sending us powerful targeted communications. Aliens would not be able to detect an earth originating signal using something the size of Arecibo.

The answer is just about any radio signal is detectable with a large enough antenna.
posted by damn dirty ape at 8:17 PM on February 21, 2011

We're not really in any position to judge how intelligent extraterrestrial life would sense and makes sense of external stimuli. Binary is a big deal to us, and we place great weight on the significance of particular numbers, but it's something of a leap to assume some other form of life would think the same way.
posted by obiwanwasabi at 8:17 PM on February 21, 2011 [2 favorites]

For the first years of radio, most traffic was Morse Code which was encoded by turning the transmitter carrier on and off.

But translating an alien language based on a very short sample is pretty much impossible. Natural languages are far too complex to attack with so little information.
posted by Chocolate Pickle at 8:18 PM on February 21, 2011

In the youtube clip "the known universe" it had the farthest extent of Earth's electronic signals as being about 70 light years away, so I guess whatever we were beaming out at the time.

what Orthogonality says is kind of a bummer. since faster than light space travel is probably totally impossible, I would have thought that radio signals would be the only means that different civilizations would have of knowing of each others' existence.

of course in "Contact" the first thing the aliens recieved (and sent back) was television images of Hitler.
posted by moorooka at 8:25 PM on February 21, 2011

"Humans have debated the best ways to contact our interstellar neighbors for centuries. In 1820, German mathematician Karl Friedrich Gauss proposed cutting an enormous right triangle into the Siberian pine forest, creating a monument to the Pythagorean theorem big enough to see from outer space."


It's always been my understanding that it would be of a mathematical origin, using prime numbers in a sequence. Syntax and repetition, such as music or other types of static messaging. The Arecebo mentioned above is already obscure and outdated.

Frankly I think the promise of deliciousness like Krispy Kreme donuts would get them talking.

.
posted by ~Sushma~ at 8:25 PM on February 21, 2011

This blog post is relevant to your interests.
posted by twirlip at 8:32 PM on February 21, 2011 [2 favorites]

The first transoceanic signal was the Morse code for S, sent repeatedly. That's "beep beep beep, pause, beep beep beep, pause, beep beep beep, pause ..." I don't think that would raise too many alien eyebrows, or whatever they might have, because pulsars and other natural emitters can make a rudimentary cyclic pattern like that.
posted by StickyCarpet at 9:13 PM on February 21, 2011

What everyone seems to forget is that we're pretty much the in the galactic version of middle Alaska. Way out on a secondary arm, nowhere near all the fun of the core. Radio signals are gonna take a very long time to get anywhere beyond our immediate area.

Douglas Adams summed it up best:

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.
posted by Sphinx at 9:20 PM on February 21, 2011

To answer (sort of) the first question: discounting any early experiments that involved magnetic or capacitive coupling rather than electromagnetic waves, from it'd have to have come from one of the early experiments that produced a definitively non-random signal, and it would have to be strong enough to (assuming some way of accounting for the noise floor & the Earth's natural atmospheric discharges) be detectable outside the atmosphere.

Experiments prior to Hertz were mostly focussed on magnetic or capacitive coupling; he was the first to definitively produce and demonstrate electromagnetic waves as a separate phenomenon. However, although it would make sense that he deliberately produced non-random patterns to prove this, his experiments were across or between adjacent rooms; unlikely to have been powerful enough to be detected beyond the atmosphere. Tesla publicly demonstrated 'wireless' communication in several times between 1893 and 1897 - all similarly short range between adjacent buildings at most), and so again unlikely to be detectable outside the atmosphere.

My money would be on Marconi's experiments - despite the Tesla-love of more recent times, he was the first to conclusively demonstrate electromagnetic wave transmission over reasonable distances. By 1895 he was transmitting over a distance of a mile; by mid-1897 he'd established 2-way communications over 10 miles; by later the same year he was up to 34 miles; in 1899 he transmitted across the English Channel; in 1899 he claims to have achieved trans-Atlantic reception (on preview: as per StickyCarpet's comment above, but it's disputed); but by 1903 he'd definitely achieved trans-Atlantic communications.

Given the insensitivity of receiving apparatus of the time, I'd reckon those are the sorts of powers you'd need to stand out from natural background noise and be detectable in space. So my money's on 1897-1903 - if (and it's a big if) the receiving civilisation is advanced enough to overcome the problems of noise floor and the inverse-square law.

^{Maybe a very large array, linked by Stargates, that can be precisely steered and focussed to within a tiny fraction of an arc? ;-)}
posted by Pinback at 10:08 PM on February 21, 2011 [1 favorite]

Just to reinforce the comment of sphinx above (earth being in the 'galactic equivalent of middle Alaska') I couldn't resist showing off a picture I came across recently.

The main picture is a depiction of our galaxy (as opposed to one of the millions of others in the known universe). The very small blue dot in the right hand side of the image is the volume of space through which radio waves generated from earth would have travelled in the last two hundred years.

It bends my brain a little to look at these distances and see what 200 years of light speed is equivalent to !
posted by southof40 at 1:52 AM on February 22, 2011 [4 favorites]

Binary is a big deal to us, and we place great weight on the significance of particular numbers, but it's something of a leap to assume some other form of life would think the same way.

If by "particular numbers" you mean primes, then I have to disagree about how much of a leap this is. We are necessarily talking about a species that has invented radios and therefore presumably has some mathematical abilities. Primes are one of the very earliest things you notice once you start doing basic arithmetic. They might not "place great weight" on them, but they'll be noticed.

Different bases (e.g. binary) are somewhat more esoteric but if you think about bases at all then it's natural to consider the smallest possible base, which is 2. And if the species in considering other species, it probably makes sense to think about what base they might use, so some "least common denominator" type base isn't a bad guess.
posted by DU at 4:46 AM on February 22, 2011 [1 favorite]

The main picture is a depiction of our galaxy (as opposed to one of the millions of others in the known universe).

To be accurate, that is exactly a depiction of one of the millions of other galaxies in the known universe. We don't have any pictures of our galaxy from outside of it. None. Our great¹⁰-grandchildren won't have any either.
posted by Netzapper at 6:03 AM on February 22, 2011

Wouldn't it be the crude spark gap stuff they did? That would be the most potentially discernable, because it would be an obvious pattern, across many bands of EM. Lightning is random, dots and dashes are not.
posted by gjc at 6:08 AM on February 22, 2011

I agree with obiwanosabi. We're making wild guess that, even if an alien race picks up the message, they they'll be able to translate it.

That said, considering the discoveries of quantum physics and how, in general, we limit what is capable of achieving in the universe, it may be possible that another life form has developed the ability to capture our radio waves faster than the signal travels... so insisting they won't get the signal for eons is pure hogwash in the grand scheme of things.
posted by Unsomnambulist at 1:55 AM on February 23, 2011