how does seti really work?

[bwanaaa]

if i were looking for a repeating pattern in the EM signals of space, I could argue that such a find is NOT a hallmark of intelligent life. After all, do you think someone is being intelligent when they stutter or keep saying the same thing?

What are the criteria that SETI uses to determine interesting stuff?

 

[DrPizza]

So, you're suggesting that if an alien life form wanted to say, "Hey, we are here. Is there anyone else out there?" sending out a chaotic random signal that completely blends into the background would be more intelligent, but something that would be easily detected would be less intelligent?

 

[bwanaaa]

I think that intelligent life would NOT want to be found. After all, wasn't it Feyneman who suggested that CETI be canceled. The rationale was that we are so young in our technological development that if we invite any alien to visit, and the alien has the ability to hear and decipher our signal, they are likely to be more advanced than us and they are more likely to want to use us as food. I think this is the rationale that any intelligent life would have regarding ET.

I think therefore that if intelligent life wanted to be found, they wouldnt mess around with trivial EM radiation, rather they would detonate a nuke in deep space where its signature would not be confused with a star. Based on that, I think they would look for a similar event and begin communication using a pattern of such high energy events. The EM crap in space is too befruddling. And in fact, the letters of this paragraph are a sequence not significantly different from random by statistical measure, yet they are arranged in a meaningful pattern. The chaotic random signal that completely blends into the background may in fact be just that-myriad conversations.

If you want to be heard in a room, you have to shout.

 

[bwanaaa]

But my question still remains unanswered. What is seti looking for-what is THE target pattern or perhaps I should rephrase and ask, what is the algorithm used?

 

[irishScott]

SETI SRC: Have fun analyzing it.

http://setiathome.berkeley.edu/sah_source_code.php

This also appears to have good information (I just skimmed it)
http://science.howstuffworks.com/seti.htm

 

[irishScott]

Originally posted by: bwanaaa
I think that intelligent life would NOT want to be found. After all, wasn't it Feyneman who suggested that CETI be canceled. The rationale was that we are so young in our technological development that if we invite any alien to visit, and the alien has the ability to hear and decipher our signal, they are likely to be more advanced than us and they are more likely to want to use us as food. I think this is the rationale that any intelligent life would have regarding ET.

I think therefore that if intelligent life wanted to be found, they wouldnt mess around with trivial EM radiation, rather they would detonate a nuke in deep space where its signature would not be confused with a star. Based on that, I think they would look for a similar event and begin communication using a pattern of such high energy events. The EM crap in space is too befruddling. And in fact, the letters of this paragraph are a sequence not significantly different from random by statistical measure, yet they are arranged in a meaningful pattern. The chaotic random signal that completely blends into the background may in fact be just that-myriad conversations.

If you want to be heard in a room, you have to shout.

The idea is to detect inadvertent signals, not invite aliens to Earth. We're transmitting EM signals into space all the time. The idea is to pick up similar transmissions. SETI and Arecibo are insanely sensitive, so this isn't as unrealistic as it sounds.

That said, any transmissions may have simply not reached us yet (unless an advanced civilization was pathetically close), so I personally don't believe in the project as it currently stands.

However, SETI is the sole reason that Distributed Computing even exists, and it was the SETI developers at UC Berkely that developed BOINC. Stanford's Folding@home, the most powerful computing network in the world, was also inspired by SETI.

Many of these projects have extremely valid goals and extreme potential benefits, from curing cancer to proving physics theories to predicting climate change to designing/optimizing particle accelerators.

http://forums.anandtech.com/me...=1818634&enterthread=y
http://www.distributedcomputing.info

 

[silverpig]

SETI doesn't look for a repeating pattern. The way it works is this:

Imagine you have a directional microphone hooked up to some headphones and a speaker playing music some distance away. When the microphone is not pointed at the speaker, you hear nothing in the headphones. When the mic is pointed directly at the speaker, you hear the music. Now, let's say you have no idea where the speaker is. How would you find it? Well you'd probably spin around, wave the mic up and down and try to scan all around you.

Now, let's say you are doing a scan across the "sky" with your mic and happen to be pointed at the right elevation and are scanning towards the speaker in such a way that your mic will pass over it. What do you hear? You hear nothing, then a little sound, then the sound is loud, then it drops off, then it goes back to nothing. This increase, peak, decrease follows the form of a gaussian (bell curve).

The SETI telescopes basically just scan back and forth across the sky all the time and record what they "hear" to magnetic tapes. The information on those tapes is then cut into small pieces and sent to people on the net where their computers look for gaussians where the telescope scanned over a radio signal. Once the gaussians are identified and confirmed, you can then go ahead and actually point a large telescope at the source to see what it's putting out.

 

[bwanaaa]

so it really is like trying to hear someone at a party who is shouting above everyone else- you listen for where the sound is loudest-not necessarily for anything intelligible. i would think that another angle might shed some light as well--natural processes might produce a smooth gradient-intelligent processes might selectively use specific em bands.So when SETI is scraping the sky for em radiation it might also look for 'coarseness' in em band intensity-to give an analogy-something like one might see from a spectroscope. But natural processes would smear all over the spectrum.

is this a valid cnsideration or a phallacy?

 

[Gannon]

Originally posted by: bwanaaa
I think that intelligent life would NOT want to be found. After all, wasn't it Feyneman who suggested that CETI be canceled. The rationale was that we are so young in our technological development that if we invite any alien to visit, and the alien has the ability to hear and decipher our signal, they are likely to be more advanced than us and they are more likely to want to use us as food. I think this is the rationale that any intelligent life would have regarding ET.

I think therefore that if intelligent life wanted to be found, they wouldnt mess around with trivial EM radiation, rather they would detonate a nuke in deep space where its signature would not be confused with a star. Based on that, I think they would look for a similar event and begin communication using a pattern of such high energy events. The EM crap in space is too befruddling. And in fact, the letters of this paragraph are a sequence not significantly different from random by statistical measure, yet they are arranged in a meaningful pattern. The chaotic random signal that completely blends into the background may in fact be just that-myriad conversations.

If you want to be heard in a room, you have to shout.

I think actually the reverse is true, the more advanced you become the LESS BARBARIC you are...

Thinkof our modern economic system : Totally barbaric because we're too stupid and not powerful enough to extract the energy and configure matter in the most efficient ways possible.

Poverty and war could be gone tomorrow if we weren't so blimin stupid.

 

[Markbnj]

Originally posted by: bwanaaa
But my question still remains unanswered. What is seti looking for-what is THE target pattern or perhaps I should rephrase and ask, what is the algorithm used?

The programs that analyse the signals are looking for stuff that isn't cosmic background noise. There are all sorts of ways that ordered, purposeful transmissions are different from naturally occuring noise. The topic is thoroughly explored online in various places.

However, we will never hear anything through SETI. Mathematically speaking it is just about on the order of impossible. It may have been Feynman who made the argument, I don't really recall, but if you take into account the very limited time in which we as a species have been able to transmit and receive signals, and consider the chances of our being near to another civilization in that same tiny slice of the developmental timeline, then either any such civilization is long gone, or they transcended the things that usually cause the end of civilizations and the universe should be full of their communications.

 

[bwanaaa]

@Gannon

please dont take this the wrong way but i think your statement is somewhat self serving-just as the church enforced the view the world is flat.

"I think actually the reverse is true, the more advanced you become the LESS BARBARIC you are"

We are clearly more barbaric today our ancestors. We no longer kill for food or material needs. Now we kill others for things as ephemeral as ideas and we are teaching our children to kill themselves for the conflicts of our ancestors. Our advancement is simply a reflection of how much more efficient we become. Our nature as catalysts that increase the entropy [disorder] of our environment is unchanged. Any other living thing in our universe that is subject to these laws would evolve and behave the same way.

Originally posted by: Markbnj

... transcended the things that usually cause the end of civilizations and the universe should be full of their communications.

I love that word 'transcend'-it leaves out the connotations of 'ascend' or 'descend' while emphasizing the fundamental nature of life that is change.
yes i remember that argument. the specific problems i had with it were:
1) if communications were had and the civilizations are extinct, the messages (like the light from the edge of the universe) should still be around.

2) as communications become more efficient they are packetized (TCP/IP) and compressed (LZ, ZIP,rar, etc). They begin to resemble the chaotic almost random flavor of noise. we may already be listening to ET and not know it. you said that "There are all sorts of ways that ordered, purposeful transmissions are different from naturally occuring noise. The topic is thoroughly explored online in various places. " Please help me a little because my googling has only giving me disinformation.

The ruse of SETI to enable our cooperation through joint computing is a sort of X-prize. A reward is offered that inspires orders of magnitude more investment than it is worth. (at the time it is offered). SETI also has that flavor of serendipity that characterizes most discoveries. In fact, it goes one better than that, it gets millions of people to contribute resources and yet we really have no idea what we really are doing-like bees in a hive. How would you feel if you found out that your calculations contributed to the prediction of outcome of a biological or cyber attack on another nation? That your calculations helped the policy makers decide something like this. I know that's ridiculously extreme, but I am just trying to illustrate a point. PPlease forgive the hyperbole.

 

[silverpig]

Originally posted by: bwanaaa
so it really is like trying to hear someone at a party who is shouting above everyone else- you listen for where the sound is loudest-not necessarily for anything intelligible. i would think that another angle might shed some light as well--natural processes might produce a smooth gradient-intelligent processes might selectively use specific em bands.So when SETI is scraping the sky for em radiation it might also look for 'coarseness' in em band intensity-to give an analogy-something like one might see from a spectroscope. But natural processes would smear all over the spectrum.

is this a valid cnsideration or a phallacy?

Natural sources are detected with SETI. Actually SETI has discovered several new radio sources we hadn't known about.

SETI does look in a specific band. Okay, so when astronomers try to figure out how the galaxy works, they need to know what kinds of matter exist where. Most of the time you can do this by looking at spectral emission lines. Point your telescope/spectrometer at some spot in the sky take some spectra, see a few sodium lines and you know that there is ionized sodium in that direction.

The most abundant element in the universe is hydrogen. Hydrogen comes in two forms, molecular H2 (two hydrogen atoms stuck together) and atomic hydrogen H (just a single hydrogen atom). H2 is easy to see. It exists wherever there is ionizing radiation. Ionizing radiation both helps the H2 to form and also lights it up. Easy.

It is also important to map out atomic hydrogen. However, this is much more difficult to see. As soon as you hit it with light, it ionizes, then forms molecular hydrogen. So how do you see it if it only exists where there is no large amounts of light? Some smart guy figured out that when a hydrogen atom forms, the spins of the electron and proton can be either aligned, or anti-aligned. The anti-aligned configuration is energetically more favourable, but the difference in energy is so tiny that the half life for the spin-flip reaction is several billions of years (IIRC). Luckily, there is enough atomic hydrogen out there, half of which has its proton and electron spins aligned that there is enough decaying to produce a measurable signal. That smart guy calculated that when the spin of the electron flips, it emits a photon at 21 cm, in the radio spectrum.

Any species intelligent enough to look up at the stars with radio telescopes, able to figure out that 21cm radiation is important, will also realize that if there is some other species out there at the same level of development they will also have an army of radio telescopes scanning the cosmos at 21cm. Thus, it only makes sense that if one wanted to be detected, one would have the best luck by sending out signals at 21cm. This is where SETI looks.

 

[silverpig]

Originally posted by: bwanaaa
so it really is like trying to hear someone at a party who is shouting above everyone else- you listen for where the sound is loudest-not necessarily for anything intelligible. i would think that another angle might shed some light as well--natural processes might produce a smooth gradient-intelligent processes might selectively use specific em bands.So when SETI is scraping the sky for em radiation it might also look for 'coarseness' in em band intensity-to give an analogy-something like one might see from a spectroscope. But natural processes would smear all over the spectrum.

is this a valid cnsideration or a phallacy?

Oh and by phallacy, are you suggesting this is all a big chunk of dick?

 

[irishScott]

Originally posted by: bwanaaa
@Gannon

please dont take this the wrong way but i think your statement is somewhat self serving-just as the church enforced the view the world is flat.

"I think actually the reverse is true, the more advanced you become the LESS BARBARIC you are"

We are clearly more barbaric today our ancestors. We no longer kill for food or material needs. Now we kill others for things as ephemeral as ideas and we are teaching our children to kill themselves for the conflicts of our ancestors. Our advancement is simply a reflection of how much more efficient we become. Our nature as catalysts that increase the entropy [disorder] of our environment is unchanged. Any other living thing in our universe that is subject to these laws would evolve and behave the same way.

Don't mean to hijack the thread, but define "We". The world is not on the same playing field. 1st world countries are far more civilized and advanced than 3rd world countries.

Humans can evolve, and human nature can evolve. It may take millions of years, but it will happen.

HTF do you or anyone know what "any other living thing" in our universe would be remotely like? We can speculate on the near infinite possibilities, but we know so little about the Universe that doing so would be similar to toddlers' explanations for simple facts (ie: "Leaves fall in Autumn because the trees get tired of holding them.", "Water comes out of the hose because it wants to play with the air.", etc)

Besides, logic does not dictate everything. Lets say there was an alien race who relied entirely on highly developed instinct. Not logic. Logic and intelligence were never developed, yet it could function on the same level as a human. How do you explain it's behavior oh Omnipotent bwanaaa? You can't? Now is that because it's impossible, or because we simply don't know how it's done yet?

I tend to go by: Nothing is impossible, therefore the possibilities for anything are limitless, therefore the accuracy of speculation decreases exponentially with respect to the scale of the issue. The only way to know for sure is to gain knowledge, and not pull ignorant logical shit out of our asses for explanations.

 

[bwanaaa]

Originally posted by: irishScott


Don't mean to hijack the thread, but define "We". The world is not on the same playing field. 1st world countries are far more civilized and advanced than 3rd world countries.

i object to your archaic nationalistic concept of the world into 1st, 2nd and 3rd tiers. There are 'third world' parts of our own nation where life has little value. Are you old enough to remember the combat zone in Boston, downtown newark or parts of miami? The incidence of HIV in the Newark hospitals is on a par with that of parts of Africa. I might agree if you tried to say that barbarism can be suppressed by wealth and income, but to ascribe evil to certain parts of the world is to ignore the potential for good and evil that is in all people.

HTF do you or anyone know what "any other living thing" in our universe would be remotely like? We can speculate on the near infinite possibilities

I do not know. But if you have any education in physics, you would know that educated guesses begin with what we know. Have you ever heard of the words 'null hypothesis'? That begins with a premise that you try to disprove. Wild speculation does not lend itself to education nor does it give a direction for research.

Besides, logic does not dictate everything. Lets say there was an alien race who relied entirely on highly developed instinct. Not logic. Logic and intelligence were never developed, yet it could function on the same level as a human. How do you explain it's behavior oh Omnipotent bwanaaa? You can't? Now is that because it's impossible, or because we simply don't know how it's done yet?

I tend to go by: Nothing is impossible, therefore the possibilities for anything are limitless, therefore the accuracy of speculation decreases exponentially with respect to the scale of the issue. The only way to know for sure is to gain knowledge, and not pull ignorant logical shit out of our asses for explanations.

Omnipotent. I like that. Are you referring to my 'phallacy' comment above. Truthfully, it's kind of sad that I cannot find a woman who likes sex as much as I do. But seriously, your statement is that logic does not dicktate everything. Could you elaborate. Flesh that out for me-how would highly developed instinct work? Are you referring to a beehive? Do you mean logic in the narrow sense of boolean operators or a broad sense of causality as defined by deduction and induction? Anyway, I dont think I ever talked about logic, or even approached defining intelligence.

I am sticking to my question, what is seti looking for? Yes thank you silverpig for that discourse on flipping hydrogen. Yes I read about the water hole and why we look where we do (as well as the other me-too projects looking at other freqs) But what are we looking for?

A beacon of a constant tone? How long is 'constant'?

A sinusoid? What freq modulation withing the waterhole?

any pattern different than random? What's the 'word length'?

I cannot seem to find that out.

 

[Markbnj]

2) as communications become more efficient they are packetized (TCP/IP) and compressed (LZ, ZIP,rar, etc). They begin to resemble the chaotic almost random flavor of noise. we may already be listening to ET and not know it. you said that "There are all sorts of ways that ordered, purposeful transmissions are different from naturally occuring noise. The topic is thoroughly explored online in various places. " Please help me a little because my googling has only giving me disinformation.

Compressed and/or packetized (translated, formatted, whatever) information is not necessarily of higher entropy that the source that it was created from. There's no reason why it should be. The translation of intent and meaning from one symbology to another doesn't inherently have to increase randomness. Perhaps it feels more random to you because it is no longer directly comprehensible, but it is still based on the original ordered meaning.

Here is a decent technical overview: http://www.openp2p.com/pub/a/p...03/19/seti.html?page=1

 

[bwanaaa]

tnx. what i gleaned is that:
* Signals observed in the same location in the sky on two or more telescope passes
* Signals observed on similar frequencies during different passes (some frequency drift is allowed to compensate for Doppler shift)
* Strong signals that generated a power-versus-time curve closely matching that expected for the Arecibo telescope (this is known as a Gaussian curve)
* Signals that were not associated with known sources of terrestrial interference or satellite transmissions
* Sources adjacent to a known star or galaxy (sources in empty space were discarded)
* Sources adjacent to a main sequence star similar to our sun (other types of stars are thought to be unlikely to support habitable planets)
* Sources closer to our solar system

some of this stuff is bogus.

Why wouldnt you look for a signal in deep space--i think that's precisely where an artificial signal would originate from.

why would you expect an arecibo like telescope to be a source? wouldnt you rather think a hubble type telescope would be more likely to be used as a transmitter?

i give up.

 

[silverpig]

Originally posted by: bwanaaa
tnx. what i gleaned is that:
* Signals observed in the same location in the sky on two or more telescope passes
* Signals observed on similar frequencies during different passes (some frequency drift is allowed to compensate for Doppler shift)
* Strong signals that generated a power-versus-time curve closely matching that expected for the Arecibo telescope (this is known as a Gaussian curve)
* Signals that were not associated with known sources of terrestrial interference or satellite transmissions
* Sources adjacent to a known star or galaxy (sources in empty space were discarded)
* Sources adjacent to a main sequence star similar to our sun (other types of stars are thought to be unlikely to support habitable planets)
* Sources closer to our solar system

some of this stuff is bogus.

Why wouldnt you look for a signal in deep space--i think that's precisely where an artificial signal would originate from.

why would you expect an arecibo like telescope to be a source? wouldnt you rather think a hubble type telescope would be more likely to be used as a transmitter?

i give up.

If you look in deep space (ie, out of our galaxy), then the signal must have taken at least 10 million years to get here. If it's farther than Andromeda, you're looking at hundreds of millions to billions of years. First off the chances of a civilization being advanced enough a billion years ago vs a thousand years ago greatly favour looking close by. Also, the signal power drops off as the square of the distance, so the signal you are trying to detect would be about 1 trillion to 1 quadrillion times weaker than something in our neighbourhood. And Arecibo already would have trouble detecting a signal from that close.

Do you even know how hubble works? It has a pitifully small power for transmitting as it just transmits data back to earth. Other than that it's a big mirror attached to some lenses attached to a digital camera that is pointed in space. Try using your digicam to send me a signal. Furthermore, hubble is an optical/near IR telescope. Arecibo is radio. They don't speak the same language.

 

[irishScott]

Originally posted by: bwanaaa

Originally posted by: irishScott


Don't mean to hijack the thread, but define "We". The world is not on the same playing field. 1st world countries are far more civilized and advanced than 3rd world countries.

i object to your archaic nationalistic concept of the world into 1st, 2nd and 3rd tiers. There are 'third world' parts of our own nation where life has little value. Are you old enough to remember the combat zone in Boston, downtown newark or parts of miami? The incidence of HIV in the Newark hospitals is on a par with that of parts of Africa. I might agree if you tried to say that barbarism can be suppressed by wealth and income, but to ascribe evil to certain parts of the world is to ignore the potential for good and evil that is in all people.

HTF do you or anyone know what "any other living thing" in our universe would be remotely like? We can speculate on the near infinite possibilities

I do not know. But if you have any education in physics, you would know that educated guesses begin with what we know. Have you ever heard of the words 'null hypothesis'? That begins with a premise that you try to disprove. Wild speculation does not lend itself to education nor does it give a direction for research.

Besides, logic does not dictate everything. Lets say there was an alien race who relied entirely on highly developed instinct. Not logic. Logic and intelligence were never developed, yet it could function on the same level as a human. How do you explain it's behavior oh Omnipotent bwanaaa? You can't? Now is that because it's impossible, or because we simply don't know how it's done yet?

I tend to go by: Nothing is impossible, therefore the possibilities for anything are limitless, therefore the accuracy of speculation decreases exponentially with respect to the scale of the issue. The only way to know for sure is to gain knowledge, and not pull ignorant logical shit out of our asses for explanations.

Omnipotent. I like that. Are you referring to my 'phallacy' comment above. Truthfully, it's kind of sad that I cannot find a woman who likes sex as much as I do. But seriously, your statement is that logic does not dicktate everything. Could you elaborate. Flesh that out for me-how would highly developed instinct work? Are you referring to a beehive? Do you mean logic in the narrow sense of boolean operators or a broad sense of causality as defined by deduction and induction? Anyway, I dont think I ever talked about logic, or even approached defining intelligence.

I am sticking to my question, what is seti looking for? Yes thank you silverpig for that discourse on flipping hydrogen. Yes I read about the water hole and why we look where we do (as well as the other me-too projects looking at other freqs) But what are we looking for?

A beacon of a constant tone? How long is 'constant'?

A sinusoid? What freq modulation withing the waterhole?

any pattern different than random? What's the 'word length'?

I cannot seem to find that out.

Lol yeah sorry I was in a bad mood yesterday. Technically we could debate this forever. That said, I used "Omnipotent" correctly.
http://www.google.com/search?h...Omnipotent&btnG=Search

 

[silverpig]

Originally posted by: bwanaaa
I am sticking to my question, what is seti looking for? Yes thank you silverpig for that discourse on flipping hydrogen. Yes I read about the water hole and why we look where we do (as well as the other me-too projects looking at other freqs) But what are we looking for?

A beacon of a constant tone? How long is 'constant'?

A sinusoid? What freq modulation withing the waterhole?

any pattern different than random? What's the 'word length'?

I cannot seem to find that out.

I already said what it is looking for. It scans for gaussians which are indicative of a signal. Once a signal is determined to be real, you point a bunch of radio telescopes at it and see what you hear. If they are like us, you could pick up tv stations, radio broadcasts, a HELLO UNIVERSE!!! signal, whatever.

You don't look for anything specific beyond that. You just look for a signal, then see what it is. If it's a known natural object, move on. If it is more complex, then announce it. Requiring SETI to say they're specifically looking for SOS in morse code is a pointless question.

 

[bwanaaa]

....scanning for gaussians.... hmmmm

well, this book -http://www.amazon.com/gp/reade...TF8&p=S00T#reader-link

isalittletoodenseforme.

If this is what you are referring to, then I do not understand what a gaussian signal is. Yes I think I know what a gaussian distribution is. I also hae used gaussian surfaces in analyzing math problems in the distant past. but a gaussian signal--never been there, never done that.

here is one explanation of a gaussian signal, but i am not sure if this is what you refer to:

http://www.prosig.com/signal-processing/prob/gauss1.gif

 

[Fayd]

Originally posted by: Gannon

Poverty and war could be gone tomorrow if we weren't so blimin stupid.

Poverty and war are direct results of wealth and power. they are not possible to solve.

 

[silverpig]

Originally posted by: bwanaaa
....scanning for gaussians.... hmmmm

well, this book -http://www.amazon.com/gp/reade...TF8&p=S00T#reader-link

isalittletoodenseforme.

If this is what you are referring to, then I do not understand what a gaussian signal is. Yes I think I know what a gaussian distribution is. I also hae used gaussian surfaces in analyzing math problems in the distant past. but a gaussian signal--never been there, never done that.

here is one explanation of a gaussian signal, but i am not sure if this is what you refer to:

http://www.prosig.com/signal-processing/prob/gauss1.gif

They are looking for a gaussian peak in the intensity of power received in a narrow band of the radio spectrum. Basically they are looking for their telescope to be recording low level background as it sweeps across the sky, and then to record something getting louder, peaking, then dropping off as the telescope scans past it. All they are looking for is that increase in intensity. It's just called a gaussian because, well don't even worry about why it's called that. Just know that they look for the signal to get loud, then quiet, as the telescope moves across the sky.

 

[bwanaaa]

thank you, that's what i gleaned from the image i had posted but wasnt sure. no for the 64,000 dollar question-why look for a gaussian? isnt a normal distribution the hallmark of random variation around a mean? isnt starlight a gaussian?

 

[silverpig]

Originally posted by: bwanaaa
thank you, that's what i gleaned from the image i had posted but wasnt sure. no for the 64,000 dollar question-why look for a gaussian? isnt a normal distribution the hallmark of random variation around a mean? isnt starlight a gaussian?

You look for a gaussian because that's how the intensity goes as you pass over a signal. It doesn't mean that the signal is gaussian, or that they are sending gaussians, it's just the shape that a steadily moving telescope passing over a source will produce.