h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Flake said: "Does that not 'presume' too much as well? If so, then you are as 'arrogant' as you claim Fermi to be."

Whoa, I sense some bad feelings here. I have had some experience with Fermi's work in my schooling and casual reading, and he is nothing less than a brilliant man - I admire him. I have had the unusual privelege of meeting and working with some of his contemporaries, and continue to meet and work with those who followed him at the premier nuclear research laboratories in the US Department of Energy complex. I believe that gives me enough of a knowledge base to speculate what he might also have felt about our (the human race's) own space exploration at the time without having the accusation of arrogance projected upon me when I express that speculation. I think it's a significant difference for me to state, based on what I know from my own readings and people I've met who knew Fermi the man and his time and the way society was then, that my statement of his attitude towards space exploration has a more solid basis than that of his statement we're discussing.

In any event, you're right about the most important part though: I shouldn't have used the word "arrogant." So, I will state here, for the record, that I should not have used the word "arrogant" to describe his statement. Seriously, that was a pretty bad gaff on my part. Whether I agree or disagree isn't really a justification for that sort of sentiment.

So, uhm ... 'nuff said I guess.

- JD

Fair enough.

Acid Override,

In reply to post 98, I have to say yes, we would contact them. Even if they were 'less advanced', for the simple reason of learning their biology, chemistry etc.

I think we would if they were the only species we could contact. What I was getting at was that if we advance enough to contact one species we could probably contact several. I reckon we would favor contact with more technologically/socially advanced races.

Reminds me of Calvin and Hobbes

"We have enough nuclear weapons to destroy the planet several times over, we are slowly but surely destroying the planet, we fight constantly amoung ourselves and we have caused the extinction of several species on this planet."
"I think the surest sign that there is INTELLIGENT life out there is that it has not tried to contact us"

What about philosophies? I forgot about that.

Analiese: "For example, the intelligence we get from the repeating signal of a pulsar would be way different from the repeating signal of a tv raster wouldn't it? Or would it? I think there's a mathematical theory about this stuff. Maybe you could make that a little clearer?"

Sure...

When you receive a radio wave, you lock onto a carrier frequency. That carrier frequency has been modified in some way so that the intelligence has been superimposed upon it, in a process called modulation. There are two ways to modulate a signal. We can make it change amplitude (similar to volume), which is what the AM on the crappy old radio stations stands for... amplitude modulation. An advanced race would use this very little, because it has such poor range... the amplitude part of a radio wave is the part most affected by its travel through the air, so when you demodulate it, you get a fuzzier signal the further from the transmitter you are.

Then there's the other way, which is frequency modulation (FM). Everything from your cell phone, tv, to your computer's modem use this type, because the intelligence doesn't get affected as the signal gets weaker. The carrier wave's frequency gets slight increases and decreases to match changes in the intelligence.

Today we've found that digital signals modulate and demodulate so much cleaner than analog signals. Without getting into too much technical detail, the digital signal only has to shift the carrier frequency a bit to indicate a one, and then return to normal for a zero. Analog signals, on the other hand, would shift it in varying directions and degrees, and each shift increment would indicate a variation on the intelligence, from + to -.

If we assume that anyone advanced enough to be using radio waves has advanced to the point of using frequency modulation and digital intelligence, then what we're looking for is a frequency that, when demodulated, gives us non-random ones and zeroes. Even if they're advanced to the point of multi-state transistors (our current transistors can only switch between "on" and "off", which gives us our ones and zeroes, but research into 3 and even 4 state transistors is underway), then we'd still be looking for numbers on these demodulated signals, even if they were 0-15.

So that's how we look for intelligence. We read a frequency, demodulate it, and see if there are patterns in what we have left. It would differ quite a bit from the pulsing of a pulsar.

Fascinating tangent. I wish you were there when I watched the great "Contact" the first time, Blathers.

- JD

wrong thread I know blatherskite.. but can you explain more why seti is doing what is doing...

Are there any indications that frequency modulations might occur as the result of natural processes such as doppler effects, Mr. Mugwump?

Part of my mind has just imploded.

Wrong thread? I'm not so sure about that... topic drift is the first immutable law of the internet.

"but can you explain more why seti is doing what is doing..." - The why is pretty simple. Until we have the ability to search out life on other planets, this is the only method we have for finding it. So while we're getting interstellar probes off the drawing board and into production, we can do this.

"Are there any indications that frequency modulations might occur as the result of natural processes such as doppler effects, Mr. Mugwump?" - All possible causes have to be examined before a signal can be determined to be of alien nature. Not only to we have to look to make sure it wasn't a natural signal, but we also have to make sure that it wasn't some anomaly generated by interference with a ham radio, for instance. And then we have to make sure it wasn't some glitch with the equipment itself.

A naturally occurring doppler shift, would look like a sine wave when demodulated (if you took trig and ever had to graph a sine formula, you know what I mean... and if you don't, it's basically the shape of the surface of wavy water, alternating peaks and troughs). A digital signal, when demodulated, is a square wave... or it can be spikes appearing at fairly regular intervals.

cheers mugwump.. but I meant why are they looking for fm signals, surely there are a whole bunch of different types of signal to llok for other than radio..

I'm not sure what you mean...

If you're interpreting "radio" to mean the type of signal we listen to music on during the morning commute, that is only a tiny part of the picture. Radio, cable television, cell phones, digital satellite tv, GPS locator satellites, radars, military communication equipment... all this stuff uses radio waves.

And electric bears...

Thank you for the clarification, Mr. Mugwump. Yes, I'm familiar with trigonometric functions. I come from a culture that developed the base 20 numbering system, among other things, presaging the hexidecimal system commonly used in computers, and which, unlike the classical Greeks for example, assumed the existence of zero as well as the concept of limits in reconciling lunar and solar calendars.

So the next question that arise in this digital frequency modulation assumption is what if anything we can determine from it. I would presume the message, if it exists, is probably not intended for us. We'd be more or less eavesdropping. So how would we determine that it does in fact represent a message, what you've termed "intelligence", and what that message might mean?

Obviously, SETI assumes that messages must have some sort of discernable content or pattern, and I believe Mr. Sagan, among others, may have expressed that assumption mathematically. Do you know if that's the case? And if so what the mathematical representation was?

I'm not familiar with Sagan and his works, and if SETI has published some sort of formula to determine if a signal has intelligence, I haven't seen it. The formula you may be referring to is the one concerning the possibility of intelligent life on other planets by Frank Drake: http://www.seti-inst.edu/seti/seti_science/drake_equation.html

Or it may not.

Determining that a message has intelligence is really fairly simple. If it's digital, for instance, then all those squares (or spikes) would begin at a multiple of a particular interval. That interval is determined by how fast the message can be coded/decoded by the receiving/transmitting hardware.

For illustration purposes, let's suppose a simplistic binary signal is transmitted as a square wave, a high state always indicates a one and a low state always indicates a zero. The data transmission 10100110001 has been sent.

The wave would start high, then switch to low after a time interval of t microseconds. It would then switch to a high t ms later. Then is would switch state to low for 2t ms, then high 2t ms, low for 3t ms, and then back to high for t ms.

The one constant through all of it would be t. That's what tells us that the signal is intelligence. The values can shift (apparently) randomly, but the time intervals in which they change would be constant.

As for decoding it... that's a whole different story. SETI isn't necessarily concerned with decoding an extraterrestrial message, though. Finding one would be their big success.

So you're saying that any alien intelligence, would use low energy radio waves as we do on earth, as a preferred way of communicating, and if they don't use these low energy radio waves, then we're not going to even recognise it...

aren't there any other ways of communicating over large distances that don't involve the modulation of low energy radio waves as carrier signals...

is it not possible to use other higher energy em waves, such as light, x-rays etc

Low frequency does not necessarily mean low energy.

With higher frequencies there are problems associated with absorbtion by the intervening medium and other types of signal degradation.

A good natural example of this is the centre of our Milky Way galaxy.
Due to dust and other matter in the line of sight between Earth and the centre in Sagittarius we cannot see the postulated black hole. (Contrary to popular belief, black holes are made visible by their hot accretion discs.) However there is a very strong radio source called Sagittarius A which is believed to be the black hole.

The emitted radio waves cut through all the intervening matter and can be detected by us.



turvy

I believe what you're describing, Mr. Mugwump, is the concept of a delay line, which I understand was employed during the Cold War for directing surface to air missiles. It was thought to be jam proof because the controller and missile would "know" the duration of "t", but the enemy wouldn't so the message would still get through.

It's an interesting presumption that such a thing would be used for communication over interstellar distances. I can't really say if it would or wouldn't, although a thought does come to mind about what sort of utility it might have to some so-called civilization. Do you suppose they would be needing to control surface to air missiles too?

I suspect there are probably methods of modulating signals we haven't even thought of yet. Whether Drake's theory concerning the number of relevant civilizations existing at any given time in the universe holds up or not, we still seem to presuming a lot of things, even from a strictly technological standpoint, that might not be valid.

Indeed, I would be surprised to learn that aliens found "our" technology so effective that they would necessarily devise it independently and in parallel at precisely the same time as we have or at least at a time that would correspond to a signal reaching us at the appropriate time in our history.

Still, I suppose somebody will justify it as a longshot worth taking as apparently they already have.

Can we not just stand on a high mountain and speak really loudly?