Earth-like exoplanet discovered around Proxima Centauri

[smartcooky]

Here's what you're after .. 'IETI: The Invitation to ETI' .. (these were the dudes and dudettes who first got their butts kicked whilst standing around on top of a building waving placards, in 'Independence Day'. )

The other idea is that ETI probes are lurking within our system and are listening to web traffic via satellite uplinks. Unfortunately, even the most powerful uplink signal emitted is still many orders of magnitude weaker than the solar flux. Thus, even if you access pages from the IETI website above, and they happen to transit a satellite uplink, there would be zero impact on our terrestrial civilisations as a result of ethereal IETI ideas.

 

[lpetrich]

There is a very serious problem with digital transmissions, one that is not often mentioned. Our digital transmissions, at least, are much more difficult to reverse-engineer than our analog ones. They typically include

• Data compression
• Error correction
• Encryption

making them *very* difficult to reverse engineer.

One would have to be covertly present on our planet to be able to interpret them.

 

[SelfSim]

There is a very serious problem with digital transmissions, one that is not often mentioned. Our digital transmissions, at least, are much more difficult to reverse-engineer than our analog ones. They typically include

• Data compression
• Error correction
• Encryption

making them *very* difficult to reverse engineer.

One would have to be covertly present on our planet to be able to interpret them.

(I concur with you here. Also, digital transmission techniques encompass modulation methods which take advantage of digital encoding ... which also then require prior knowledge of these techniques in order to know which channels contain message pertinent information).

Generally speaking, to date, SETI has assumed that signals capable of being received by us, would also contain messages interpretable by us .. (otherwise their whole investigation would be pointless).

SETI has also developed techniques for detecting broad(er)band signals (ie: broader than narrowband beacons or pulses). An example of this, taken from our own terrestrial spectrum, would be certain GPS satellite signals. Although the artificial nature of such signals is not apparent from the power spectrum, the artificial nature of the received signal is obvious following specific digital post-processing techniques resulting in digital domain spectra. This technique would also reveal certain hypothesised multiple-time-sent SETI signals, thereby indicating intelligent origins.

 

[SelfSim]

https://dl.dropboxusercontent.com/u/...eadscratch.gif

Hmm .. I'm taking that as meaning either:

- you haven't seen Independence Day or,
- you don't see one of the ironic outcomes of imagining that satellite transitting web content, could also be imagined as being some form of messaging to imagined local ETI probes?

I'm pretty sure your response could also have some other meaning however(?)

 

[smartcooky]

Hmm .. I'm taking that as meaning either:

- you haven't seen Independence Day or,
- you don't see one of the ironic outcomes of imagining that satellite transitting web content, could also be imagined as being some form of messaging to imagined local ETI probes?

I'm pretty sure your response could also have some other meaning however(?)

It means "I have utterly no idea what you are talking about"

 

[smartcooky]

Digital transmission would be a poor choice for a direct signal for the all the reasons stated by lpetrich.

For this reason, I just cannot help but go back to Sagan et al and his insistence that prime numbers hold the key to radio first contact with distant civilisations. There is no known or conceivable natural phenomenon that will generate prime numbers, so if we ever receive a radio transmission from deep space that, for example, is made up of pulses grouped in batches of sequential prime numbers......

| ___ || ___ ||| ___ ||||| ___ ||||||| ___ ||||||||||| ___ ||||||||||||| ___ ||||||||||||||||| ___ ||||||||||||||||||| ___ ||||||||||||||||||||||| ___

etc... (and only prime numbers) it must have been generated by an intelligence that is at least as advanced as us.

Likewise, if we were to send a powerful transmission containing such content, and there were an advance civilisation on Proxima b, they would be in no doubt either.

I have no fears whatsoever, as regard inviting an invasion from Promixa b. If an inimical starfaring civilisation hell-bent on conquering the galaxy existed there, they would already have invaded by now.

 

[JeanTate]

The biggest issue is sensitivity. See here for the explanation of the design parameters needed for SETI targetted and all-sky surveys leading up to the Phoenix survey which concluded in 2004 with the announcement of:

(I believe Proxima Centauri was within the included search zone, also).

In particular, note Figure 5 here and included below.



.. and note the x-axis is sensitivity in Watts/m².

Also note:



Which, I think, demonstrates the Tarter/SETI's view, which I posted way back in post #118, that when these design exercises were undertaken, (and even up to Tarter's 2004 document), TV broadcasts were beyond the technology of the time. Putting subsequent technology improvements aside for the moment, the Figure 5 graph still encapsulates the theoretical parameter constraints, which are still applicable to the discussion about types of signals, assumed EIRPs, background noise, receiver sensitivities, interstellar distances and search types, needed to establish a proper observational test for ETIs. This test is still the appropriate one for providing the minimum necessary data leading to any scientifically formed hypotheses/questions about ETI's residing on Proxima b.

Also noteworthy is the findings of the most recent 'Project Breakthrough Listen':


Their website mentions they have detected many 'interesting signals', but they have not yet been able to conclude that any of these are isolated to an external ETI source.

Thanks.

This is quite helpful. Among other things, it very much confirms that you and I (at least) have mostly been talking past each other.

Perhaps to oversimplify, the SETI initiatives were (and still are) looking for a very specific kind of signal. I have been posting about a different kind of signal. To the SETI-ites, something that, to a radio astronomer, would look like an odd kind of noise would not be a signal.

Example, polarization: SETi-ites seem to set great store in any ETI "signal" being polarized; from a radio astronomy perspective, some (natural) signals are (quite naturally) polarized. Also, would airport radars, integrated over the whole Earth, be significantly polarized? How about integrated TV transmission?

SETI-ites' focus on their narrowly defined signals also explains why they do not use Jy as a metric, and why their W/m² seems so odd (when you come across it for the first time).

So, here's a challenge for you, SelfSim (if you choose to accept it, of course): the SKA could certainly detect an integrated 'airport radar' signal (defined per radio astronomy, not SETI) from Earth, if it were located on Proxima b (and tuned appropriately, pointed in the right direction, etc, etc); maybe it could detect a single airport's! Where, in the Wolfe+ document, is airport radar-like signals discussed?

 

[JeanTate]

Here are a couple of things that have me thinking.

► Maybe advanced civilizations don't radiate for very much of their existence. If this is true, there are a couple of obvious reasons why that might be;'

1. they get whacked by The Great Filter shortly after achieving the technology, (Cold War ends up in nuclear holocaust rather than peace; their civilsation is wiped out by disease, a planet-killing meteorite or a massive CME.

2. Emissions are reduced because much of their media broadcast goes direct. On Earth, within 20 years there could be no direct terrestrial or satellite media emissions at all. This is already happening. I can listen to almost any major radio station in the world, or watch most of my SkyTV video content, on the internet. Same will apply to TV as providers use high speed fibre internet to get their broadcasts into homes.

► Maybe the S/N ratio really is too low for ordinary "not specifically directed at a star" radio emissions to be picked up over interstellar distances. This is why I think it might be worthwhile directing a very powerful radio signal towards Proxima b. It would be the quickest and cheapest experiment, even if it has a low chance of success. It would be like putting $10 on a horse at 5000:1 odds. Chances are, you will lose your money, but boy, if it wins!!!

(bold added)

Yeah, but ... the most powerful radio emissions, from Earth (that get past the ionosphere) are military, and they have nothing to do with communication (early warning missile systems, 'jamming', etc). And the strongest civilian radio emissions (depends on how 'strongest' is defined, of course) is airport radars, which are also not used for communication.

OK, so maybe the ETIs have not only found a way to avoid getting whacked by The Great Filter, but also have no need for powerful military-purposed radio emission (perhaps they are entirely past the 'military' phase?). That leaves airport radars; not so easy to replace, I should think ...

 

[smartcooky]

Yeah, but ... the most powerful radio emissions, from Earth (that get past the ionosphere) are military, and they have nothing to do with communication (early warning missile systems, 'jamming', etc). And the strongest civilian radio emissions (depends on how 'strongest' is defined, of course) is airport radars, which are also not used for communication.

True, but they would be short lived emissions from the point of view of a distant point in space (think the WOW signal) and they would be on many different frequency bands. Using the moon as a proxy, looking on one particular frequency in the mid GHz range, how often would you be "swept" by the beam of radar.

OK, so maybe the ETIs have not only found a way to avoid getting whacked by The Great Filter, but also have no need for powerful military-purposed radio emission (perhaps they are entirely past the 'military' phase?). That leaves airport radars; not so easy to replace, I should think ...

Many big, high powered 50cm airport surveillance radar systems such as Marconi S264 and the Plessey AR-1 have been replaced with much lower powered systems that rely on finesse rather that brute force to track aircraft. Many have been augmented with squawk (IFF) systems, and now GPS to report aircraft positions rather than relying on a big powerful signal to bounce off the aircraft on order to locate them.

There is now a system called JPALS (Joint Precision Approach and Landing System) which is an all-weather precision approach system that uses GPS to guide the aircraft down its flight path to a safe touchdown. The pilot sees exactly the same instrumentation that he would for an ILS LOC/GS, VOR/LOC or EFIS display but instead of being guided down radio beams transmitted off the end of the runway, he is being guided by a computer and his GPS... no ground emissions needed!!

Ultimately, primary active airport radars could one day be completely replaced with passive secondary radar systems that have much lower RF emissions.

 

[SelfSim]

... Perhaps to oversimplify, the SETI initiatives were (and still are) looking for a very specific kind of signal. I have been posting about a different kind of signal. To the SETI-ites, something that, to a radio astronomer, would look like an odd kind of noise would not be a signal.

SETI are clearly searching for narrowband messages. Your example of the HI line is not the same because we already know where to look for it in the continuum spectrum (its characteristics are very well known to a very fine degree). SETI's isolation technique for message bearing signals is to use an assumed band-limited channel spacing (between 0.1 to 1Hz) across a wide assumed spectrum band and they are then limited in the integration (or observation) time this technique causes. All of this then, is what renders the Jansky rather meaningless to them in their assumed band-limited (at their origins) signal searches, even though it is still a relevant measure of receiver sensitivity of the receivers they make use of. (See below for acknowledgement that I think we are now on a similar wavelength about this).

SETI also use other techniques for detecting broader band signals, too. (As mentioned in my post to Ipetrich).

Example, polarization: SETi-ites seem to set great store in any ETI "signal" being polarized; from a radio astronomy perspective, some (natural) signals are (quite naturally) polarized. Also, would airport radars, integrated over the whole Earth, be significantly polarized? How about integrated TV transmission?

Well, signals that are consistent and tightly polarized, would be worth their while testing for any/all regular patterns. When all of their criteria/tests are passed by some 'emission of interest', I think they'd then classify that as what they've been looking for .. (ie: polarisation is not the only criterion).

SETI-ites' focus on their narrowly defined signals also explains why they do not use Jy as a metric, and why their W/m² seems so odd (when you come across it for the first time).

Agreed (and reaffirmed in my own words above) .. excuse the repetition.

So, here's a challenge for you, SelfSim (if you choose to accept it, of course): the SKA could certainly detect an integrated 'airport radar' signal (defined per radio astronomy, not SETI) from Earth,

I am not yet at all convinced that there's any 'certainty' about this!
For example, radar signals are attenuated by the medium they transit, (and thence beam dispersal). In the case of Earthly based airport radar, this would be caused by our particular atmospheric characteristics. Then there's the effects of the ionosphere, the plasmasphere/magnetosphere, solar flares, CMEs, etc(?)

And its us who knows about some of these things ... (and not necessarily unevidenced Prox b 'aliens' with an SKA ..).

...if it were located on Proxima b (and tuned appropriately, pointed in the right direction, etc, etc); maybe it could detect a single airport's!

Let me ask how many "ifs" (or assumptions) are needed here by you for your hypothetical to fully substitute for the absent data about Proxima b, and are you keeping track of all of these?
I mean, were you aware that the extant Proxima b Centaurians have been plagued by the problem of high thermal noise and radiation levels in designing their receivers, because of their planets' closeness to its host star? (Etc, etc ...)

Where, in the Wolfe+ document, is airport radar-like signals discussed?

Can't find any ... (and so)?

 

[SelfSim]

... For this reason, I just cannot help but go back to Sagan et al and his insistence that prime numbers hold the key to radio first contact with distant civilisations. There is no known or conceivable natural phenomenon that will generate prime numbers, so if we ever receive a radio transmission from deep space that, for example, is made up of pulses grouped in batches of sequential prime numbers......

| ___ || ___ ||| ___ ||||| ___ ||||||| ___ ||||||||||| ___ ||||||||||||| ___ ||||||||||||||||| ___ ||||||||||||||||||| ___ ||||||||||||||||||||||| ___

etc... (and only prime numbers) it must have been generated by an intelligence that is at least as advanced as us.

Likewise, if we were to send a powerful transmission containing such content, and there were an advance civilisation on Proxima b, they would be in no doubt either.

And yet, when he finally got his opportunity that's not what he sent at all!

 

[JeanTate]

True, but they would be short lived emissions from the point of view of a distant point in space (think the WOW signal) and they would be on many different frequency bands. Using the moon as a proxy, looking on one particular frequency in the mid GHz range, how often would you be "swept" by the beam of radar.

Yes, but remember we're talking about the closest star (except for Proxima and A&B Cen). Over a few decades, there'd likely be quite a few WOWs from whatever what we call Sol is called there.

Many big, high powered 50cm airport surveillance radar systems such as Marconi S264 and the Plessey AR-1 have been replaced with much lower powered systems that rely on finesse rather that brute force to track aircraft. Many have been augmented with squawk (IFF) systems, and now GPS to report aircraft positions rather than relying on a big powerful signal to bounce off the aircraft on order to locate them.

There is now a system called JPALS (Joint Precision Approach and Landing System) which is an all-weather precision approach system that uses GPS to guide the aircraft down its flight path to a safe touchdown. The pilot sees exactly the same instrumentation that he would for an ILS LOC/GS, VOR/LOC or EFIS display but instead of being guided down radio beams transmitted off the end of the runway, he is being guided by a computer and his GPS... no ground emissions needed!!

Ultimately, primary active airport radars could one day be completely replaced with passive secondary radar systems that have much lower RF emissions.

Fascinating!

So there will be nothing to track drones? Or planes with malfunctioning (or worse, think 9/11) transponders?

 

[JeanTate]

SETI are clearly searching for narrowband messages. Your example of the HI line is not the same because we already know where to look for it in the continuum spectrum (its characteristics are very well known to a very fine degree). SETI's isolation technique for message bearing signals is to use an assumed band-limited channel spacing (between 0.1 to 1Hz) across a wide assumed spectrum band and they are then limited in the integration (or observation) time this technique causes. All of this then, is what renders the Jansky rather meaningless to them in their assumed band-limited (at their origins) signal searches, even though it is still a relevant measure of receiver sensitivity of the receivers they make use of. (See below for acknowledgement that I think we are now on a similar wavelength about this).

SETI also use other techniques for detecting broader band signals, too. (As mentioned in my post to Ipetrich).

Yeah but ...

From what I read, there seems to be a hole: a broadband signal that looks like noise, but can't be; the integrated radio emission of millions (+/-) of narrowband transmitters, to take one example.

Well, signals that are consistent and tightly polarized, would be worth their while testing for any/all regular patterns. When all of their criteria/tests are passed by some 'emission of interest', I think they'd then classify that as what they've been looking for .. (ie: polarisation is not the only criterion).

Sure, but would an unpolarized or weakly polarized "strange kind of noise" signal be detected? At the least it seems to be considered a low priority.

Agreed (and reaffirmed in my own words above) .. excuse the repetition.

I am not yet at all convinced that there's any 'certainty' about this!
For example, radar signals are attenuated by the medium they transit, (and thence beam dispersal). In the case of Earthly based airport radar, this would be caused by our particular atmospheric characteristics. Then there's the effects of the ionosphere, the plasmasphere/magnetosphere, solar flares, CMEs, etc(?)

And its us who knows about some of these things ... (and not necessarily unevidenced Prox b 'aliens' with an SKA ..).



Let me ask how many "ifs" (or assumptions) are needed here by you for your hypothetical to fully substitute for the absent data about Proxima b, and are you keeping track of all of these?
I mean, were you aware that the extant Proxima b Centaurians have been plagued by the problem of high thermal noise and radiation levels in designing their receivers, because of their planets' closeness to its host star? (Etc, etc ...)



Can't find any ... (and so)?

Well, it was one of your sources that got me thinking about it.

And it turns up as a 'fun fact' in the public-facing part of a main SKA website.

So yeah, given those two things, it seems that airport radars are just the kind of thing that could detect, coming from an us-like ETI on Proxima b.

 

[SelfSim]

Yeah but ...

From what I read, there seems to be a hole: a broadband signal that looks like noise, but can't be; the integrated radio emission of millions (+/-) of narrowband transmitters, to take one example.

I can't see there'd be any such thing as an 'integrated emission'. The only thing 'integrating' point sources from remote a scan of Sol would be the SKA and its receiver(s) on Prox b. In other words all they'd see would be a bunch of very low intensity random spikes, with most of them of such a low intensity that they'd be indistinguishable from the thermal noise of their own receivers. or their own very nearby, host star. Oh .. and maybe faint pieces of the RF tail of Sol's blackbody spectrum(?) They might conceivably see the occasional very faint spike in the 1 to 10GHz (sort of) band, or a powerful, narrowband, repeating patterned (deliberately directed, METI transmission)?

Sure, but would an unpolarized or weakly polarized "strange kind of noise" signal be detected? At the least it seems to be considered a low priority.

The bulk of any noise would be coming from their own detectors (or their own local RF pollution sources).

Well, it was one of your sources that got me thinking about it.

I respect the radio astronomy and engineering behind the SETI search - it has been well thought through.
Their assumptions behind their motivating strategies however, are purely belief based, which adds no weight to their search, IMO.
(One needs to be very cautious when reading SETI materials).

And it turns up as a 'fun fact' in the public-facing part of a main SKA website.

Well I tried to lighten up this sub-conversation too, but apparently senses of humour aren't appreciated (or understood) in such discussions(?)

So yeah, given those two things, it seems that airport radars are just the kind of thing that could detect, coming from an us-like ETI on Proxima b.

Find me a verified remote observation from our own SKAs!

 

[lpetrich]

(Me on digital broadcasts being essentially impossible to reverse-engineer...)

(I concur with you here. Also, digital transmission techniques encompass modulation methods which take advantage of digital encoding ... which also then require prior knowledge of these techniques in order to know which channels contain message pertinent information).

Yes. That makes it even worse.

Generally speaking, to date, SETI has assumed that signals capable of being received by us, would also contain messages interpretable by us .. (otherwise their whole investigation would be pointless).

I don't see how it would be pointless. It would still have value in indicating the existence of radio-transmission technology elsewhere in the Universe. In fact, a lot of SETI efforts are not very well-adapted to receiving messages. Efforts like looking for narrowband signals like signals with bandwidths less than 1 Hz. That means a bitrate of less than 1 bit per second.

SETI researchers call what our society emits "leakage radiation", something intended for internal consumption that nevertheless departs into interstellar space. I will show that one needs very large antennas to receive the full signals, as opposed to carrier waves. Let us look at some bandwidths:

• AM broadcasting^WP -- 20 kHz
• FM broadcast band^WP -- 150 kHz
• Colour broadcast of television systems^WP -- 8 MHz

Since the broadcast power will be spread over these bandwidths, that will make these signals *very* weak. The amount of telescope area required to observe them scales as the bandwidth:
(telescope area) ~ (bandwidth)

So if one needs some area of telescope to see a carrier signal with bandwidth 1 Hz, one will need 10^4 times that area for AM radio, 10^5 times that size for FM radio, and 10^7 times that area for analog TV.

Let us take the Arecibo 300-m telescope. Scaling up for AM radio gives 30 km, for FM radio gives 100 km, and for analog TV gives 1000 km. One will need a planet-sized antenna to watch our TV broadcasts.

There are other strong signals without much interpretable content, like the output of long-range surveillance radars.

So carrier waves and radar pulses are the leakage-radiation counterpart of what SETI researchers called "beacon signals", signals intended to attract listeners' attention.

Digital transmission would be a poor choice for a direct signal for the all the reasons stated by lpetrich.

For this reason, I just cannot help but go back to Sagan et al and his insistence that prime numbers hold the key to radio first contact with distant civilisations.

I agree. One won't need much transmission time to transmit the first few prime numbers.

The first eight of them are 2, 3, 5, 7, 11, 13, 17, 19. Their total is 77. Adding gaps with size 4 gives a total of 109. So with one pulse per second, one can do a complete transmission in 2 minutes.

 

[JeanTate]

I can't see there'd be any such thing as an 'integrated emission'. The only thing 'integrating' point sources from remote a scan of Sol would be the SKA and its receiver(s) on Prox b. In other words all they'd see would be a bunch of very low intensity random spikes, with most of them of such a low intensity that they'd be indistinguishable from the thermal noise of their own receivers. or their own very nearby, host star. Oh .. and maybe faint pieces of the RF tail of Sol's blackbody spectrum(?) They might conceivably see the occasional very faint spike in the 1 to 10GHz (sort of) band, or a powerful, narrowband, repeating patterned (deliberately directed, METI transmission)?

More talking past each other.

Airport A has a radar, sometimes some of its radio emission goes in the (~4 years in the future) direction of Proxima b. Ditto Airport B's radar, which operates at ~the same frequency. And so on. At Proxima b, the individual radars can't be distinguished (assuming a suitably wide bandpass); the only thing detected is the integrated radio emission.

How about cellphone towers? This site gives ~100k in the US. Yes, there are several different bands in which these operate, but not that many; yes, integrated the radio emission is rather broadband (even within one band); yes, like airport radars, there is a strong directional component. However, integrated over the whole Earth, and over an hour (say), wouldn't there be the possibility of some 'unusual noise' being detected at Proxima b?

The bulk of any noise would be coming from their own detectors (or their own local RF pollution sources).

This is - or should be - well understood.

Weakly polarized radio emission with an unusual (broadband) spectrum should be easily detected by an SKA-type system, down to (maybe) microJy levels.

I respect the radio astronomy and engineering behind the SETI search - it has been well thought through.
Their assumptions behind their motivating strategies however, are purely belief based, which adds no weight to their search, IMO.
(One needs to be very cautious when reading SETI materials).

Indeed.

Why they seem to ignore, or downplay, "unusual noise" as potentially being produced by an ETI is something I don't quite understand.

Well I tried to lighten up this sub-conversation too, but apparently senses of humour aren't appreciated (or understood) in such discussions(?)

Well, at least you tried ...

Find me a verified remote observation from our own SKAs!

Well, perhaps not from our SKA, but the DSN routinely detects signals of an obviously artificial nature, from quite remote locations!

 

[JeanTate]

There's a strange entry in Tarter's Table 1 (source), "Ionospheric Radars".

I have no doubt that they do have a P_IERP of 2x10¹¹, but what's this doing in that Table? Especially in the last column ("# of stars within range")?

Or maybe there's something to this ... maybe some significant fraction of the radio emission from such radars makes it "out", and ends up as (potentially) detected by even DSN-like radio facilities on Proxima b?

Question of smartcooky: even if airport radars end up being too weak to be detected, even at Proxima b by an SKA-like system, what about weather radars? The need for them isn't going to go away, is it?

 

[SelfSim]

... At Proxima b, the individual radars can't be distinguished (assuming a suitably wide bandpass); the only thing detected is the integrated radio emission.

Demonstrate your evidence, (please).

... yes, like airport radars, there is a strong directional component. However, integrated over the whole Earth, and over an hour (say), wouldn't there be the possibility of some 'unusual noise' being detected at Proxima b?

'Noise' is noise. If it isn't, then please demonstrate your evidence for distinguishing 'unusual noise'.

.. Weakly polarized radio emission with an unusual (broadband) spectrum should be easily detected by an SKA-type system, down to (maybe) microJy levels.

Please define 'unusual (broadband) spectrum' (measurably so).

Indeed.

Why they seem to ignore, or downplay, "unusual noise" as potentially being produced by an ETI is something I don't quite understand.

They filter it out ... deliberately.
Ruling out false positive explanations, I would think, requires at least temporal persistence of the characteristic over integration timeframes(?)

Well, perhaps not from our SKA, but the DSN routinely detects signals of an obviously artificial nature, from quite remote locations!

... narrowband, well defined, predicted and tested signals.

 

[smartcooky]

And yet, when he finally got his opportunity that's not what he sent at all!

Really?

The message consisted of 1,679 binary digits, approximately 210 bytes, transmitted at a frequency of 2,380 MHz and modulated by shifting the frequency by 10 Hz, with a power of 1,000 kW. The "ones" and "zeros" were transmitted by frequency shifting at the rate of 10 bits per second. The total broadcast was less than three minutes.

The cardinality of 1,679 was chosen because it is a semiprime (the product of two prime numbers), to be arranged rectangularly as 73 rows by 23 columns. The alternative arrangement, 23 rows by 73 columns, produces jumbled nonsense (as do all other X/Y formats). The message forms the image shown on the right, or its inverse, when translated into graphics, characters and spaces.



Besides which, Sagan didn't write the message, Frank Drake did, with some assistance from Sagan.

 

[JeanTate]

Demonstrate your evidence, (please).

Can't.

It's a model, just like almost everything else we're discussing (the Sullivan integrated TV emission detectability is the exception; see post #128).

'Noise' is noise. If it isn't, then please demonstrate your evidence for distinguishing 'unusual noise'.

It looks like noise to a standard SETI search, but is most peculiar to a radio astronomer. For example:

• it has a rather odd variability (~24 hour period if it comes from the Earth)
• its spectrum is also odd, not at all like the spectrum of any known continuum noise
• it seems to be coming from the direction of Proxima Cen only

Please define 'unusual (broadband) spectrum' (measurably so).

Known astrophysical continuum sources have spectra that are pretty boring: they're nearly always 'flat', 'steep', or 'peaked' (the peaks are often in the GHz range, hence they're "GPS"), and as you pointed out, the lines are relatively few and well-known. The kind of integrated artificial radio emission we're discussing would not be like this at all.

They filter it out ... deliberately.
Ruling out false positive explanations, I would think, requires at least temporal persistence of the characteristic over integration timeframes(?)

Indeed.

And this is what, it seems to me, is a weakness of the SETI protocols ... the ETI signal could be in the 'noise' ...

... narrowband, well defined, predicted and tested signals.

Indeed.