the "Wow" signal

[kun11]

That’s what I was wondering about, engineer_comp_geek. Thanks for the post.

[Francis_Vaughan]

@Chronos

While a highly-efficient compression of data will leave it indistinguishable from random noise, nobody actually uses or even wants compression that efficient. All real compression schemes will put in a little extra information that’s completely predictable, in such a way that deterioration of the signal can be corrected or at least detected. This would actually make alien transmissions easier to recognize, not harder: We probably wouldn’t be able to figure out how to decompress the data, but that’s fine, because we would be able to recognize that it is compressed, and the most important message we could get from the data anyway is the mere fact that the aliens exist.

I think the problem is that this extra information need not be regular in its encoding. The idea that the data would be regularly packetized and we can see regular checksums or the like is still a poor technology. The packet layout need not be regular. Indeed in principle it is better if it isn’t - you can avoid periodic interference issues.

The current examples are some spread spectrum and CDMA encodings. Also the GPS signal provides a good example. Unless you know where you are in the cycle you can’t latch onto the signal. The cycle itself is a psuedo-random sequence. The GPS P channel cycles in a period of weeks, and so is essentially indistinguishable from noise. The S/A channel cycles a lot faster, but you still need to know the coefficients for the generator to be even able to find the boundaries of the packets. In general it is this additional knowledge of the spead of spectrum and time that you need before you can even find the data channel - which itself may be encrypted and/or compressed that makes things appallingly difficult.

Modern military radars work this way too. Spread spectrum operation where the signal intensity at the target is below noise. Unless you know the coefficients of the spread generator you cannot find the signal, and for all useful intents you cannot determine if your are being illuminated by the radar.

[Colophon]

Surely before we can begin to speculate on the aliens’ intent, we need to work out whether they meant “Wow” as in “Like, wow, man,” or as in WoW.

[ivan_astikov]

@ChrisBooth12

This is why I think SETI is a waste of money. They are trying to find signals that we would use on earth. Don’t radio waves become static after a few lightyears or so? It also assuming aliens use a base 10 system. Isn’t base 8 “better” when compared to base 10?

Which is why I think they should concentrate on the near-skies for a few years.

[Milossarian]

Funny this should come up, as I just happened upon this article on the Wow! Signal last night.

I found this part interesting:

In more familiar notation, the signal increased from zero to level 30 “sigmas” above the background noise, and then decreased again to zero, all in the span of 37 seconds.

Two aspects of this signal immediately caught the attention of Ehman and project director John Kraus, who saw the results the following morning.

First of all, 37 seconds was precisely the time it takes the Big Ear scanning beam to survey a given point in the heavens.

Because of this, any signal coming from space would follow precisely the “Wow!” signal’s pattern - increasing and then decreasing over 37 seconds. This practically ruled out the possibility that the signal was the result of Earthly radio interference.

[Lucas_Jackson]

@Chronos

The other reason you wouldn’t want to use the hydrogen hyperfine line itself for a communication is because then your recipient would have to worry about the possibility that it was natural. It’s not too hard to come up with a scenario of something in nature that would emit a big burst right at that frequency; it’s harder to come up with a scenario that would emit at exactly twice that, or pi times that, or whatever.

I just heard a podcast that has renewed my interest. Anyway…

Wouldn’t the above assume it was meant for communication with a random recipient? Maybe it was intended for a known recipient and we just randomly caught it.

Not that I have much of an opinion one way or another regarding its origin.

[bob_2]

Reading all these approximations I am reminded that Everest, when he measured the height of the mountain that bears his name, added 20 feet because he felt that to say it was 20,000 (which is what it was) would sound like an approximation.

[Kevbo]

@bob_2

reading all these approximations i am reminded that everest, when he measured the height of the mountain that bears his name, added 20 feet because he felt that to say it was 20,000 (which is what it was) would sound like an approximation.

29,000’ msl

[Just_Asking_Questions]

@Kevbo

29,000’ msl

29,002.

And it was Andrew Waugh, not Everest, that added the 2 feet.

[Enola_Straight]

In the movie “Contact” the SETI astronomers encountered a signal described as “hydrogen times pi”. Would that frequency be in a “quiet zone” in the radio spectrum?

[Isilder]

@Enola_Straight

In the movie “Contact” the SETI astronomers encountered a signal described as “hydrogen times pi”. Would that frequency be in a “quiet zone” in the radio spectrum?

No.

The Hydrogen line is the quiet line as all the hydrogen absorbed it…

For pi hydrogen to be quiet, there’d have to be abundant atoms with an electron ready to absorb the photon … which is due to electron shells ,so that means the difference in shell energy levels would have to be precisely that energy , as E=HF … so no there won’t be a Hydrogen line * Pi quiet frequency.

[Isilder]

@bob_2

Reading all these approximations I am reminded that Everest, when he measured the height of the mountain that bears his name, added 20 feet because he felt that to say it was 20,000 (which is what it was) would sound like an approximation.

Ah that furfy. I think they say it as a joke.

The idea is that the measurement has two parts
A centre and an uncertainty.

Now the actual error has been found to be 18 or 20 feet…
So I gather t he Great Trigonometrical Survey did identify that their measurement was ± 30 feet, or something like that.

So… the “add two feet” thing is a meaningless… they ALWAYS said 29002 ± 30… I don’t think any sea level model is so accurate.
For example the GPS measurement added another 10 feet… because its model of “sea level” is for the whole earth and not just for the Himalayas.

[Isilder]

However, no the signal was not precisely the hydrogen line nor a precise .00000000 value in MHz.

So Earths use of base 10 is irrelevant to the WOW signal… it would be just the same in any base.

[Ignotus]

@Isilder

However, no the signal was not precisely the hydrogen line nor a precise .00000000 value in MHz.

So Earths use of base 10 is irrelevant to the WOW signal… it would be just the same in any base.

I doubt it would have five consecutive zeroes early in its’ representation in very many reasonably small bases.

[Leo_Bloom]

Volume 103 no2, Summer 2017
Hydrogen Line Observations of Cometary Spectra at 1420 Mhz
Antonio Paris
Washington Academy of Science
The Center for Planetary Science
ABSTRACT

In 2016, the Center for Planetary Science proposed a hypothesis arguing a comet and/or its hydrogen cloud were a strong candidate for the source of the “Wow!” Signal. From 27 November 2016 to 24 February 2017, the Center for Planetary Science conducted 200 observations in the radio spectrum to validate the hypothesis. The investigation discovered that comet 266/P Christensen emitted a radio signal at 1420.25 MHz.

All radio emissions detected were within 1° (60 arcminutes) of the known celestial coordinates of the comet as it transited the neighborhood of the “Wow!” Signal. During observations of the comet, a series of experiments determined that known celestial sources at 1420 MHz (i.e., pulsars and/or active galactic nuclei) were not within 15° of comet 266/P Christensen.

To dismiss the source of the signal as emission from comet 266/P Christensen, the position of the 10-meter radio telescope was moved 1° (60 arcminutes) away from comet 266/P Christensen. During this experiment, the 1420.25 MHz signal disappeared. When the radio telescope was repositioned back to comet 266/P Christensen, a radio signal at 1420.25 MHz reappeared.

Furthermore, to determine if comets other than comet 266/P Christensen emit a radio signal at 1420 MHz, we observed three comets that were selected randomly from the JPL Small Bodies database: P/2013 EW90 (Tenagra), P/2016 J1-A (PANSTARRS), and 237P/LINEAR. During observations of these comets, we detected a radio signal at 1420 MHz.

The results of this investigation, therefore, conclude that cometary spectra are detectable at 1420 MHz and, more importantly, that the 1977 “Wow!” Signal was a natural phenomenon from a Solar System body.

Full article is on line.

[Chronos]

That does seem pretty clear. Huh, I would not have guessed that that particular mystery would be one that would ever be resolved.

[ftg]

The first, recent, thread on this.

(There’s another one that somehow persists.)

[Leo_Bloom]

Mr. Wow is not wowed. And the SETI guys aren’t shutting down either.
“We should have seen the source come through twice in about 3 minutes: one response lasting 72 seconds and a second response for 72 seconds following within about a minute and a half,” Ehman told Live Science. “We didn’t see the second one.”

The only way that can happen, he said, is if the signal was cut off abruptly. A comet wouldn’t produce that kind of signal, because the gases that surround them cover large, diffuse areas. Nor would the comet have escaped from the radio telescope’s field of view that fast.

[Slash1972]

Can someone explain how a comet would give off a signal like that?

[DesertDog]

@bob_2

Reading all these approximations I am reminded that Everest, when he measured the height of the mountain that bears his name, added 20 feet because he felt that to say it was 20,000 (which is what it was) would sound like an approximation.

This is eighteen months after the quoted post, but that’s why scientific notation is used. If Waugh had announced that Mt. Everest was 2.9000x10[sup]4[/sup] feet high (or 2.90 or 2.9) we’d have known the confidence he had of the exact height.

And speaking of static (as in unchanging), LGM-1, the first pulsar identified, was named somewhat tongue in cheek because its regular pulses might have been – just might have been – originating from an artificial source, hence Little Green Men.

That hypothesis was dropped in part because the pulses were too regular. There was no modulation in either time or amplitude to carry information on top of the pulses.