PDA

View Full Version : Discussion: Would We Mistake Signals from ET?



Fraser
2004-Dec-02, 07:06 PM
SUMMARY: Researchers from the University of Michigan think that the current programs to search for extraterrestrial intelligence (SETI) might not be able to distinguish signals from the noise of nearby stars. They showed how an efficient message sent through radio waves is nearly indistinguishable from the ordinary thermal radiation coming from stars. If extraterrestrial civilizations have been transmitting for a long time, they'll probably have optimized their communications to save power, and so we won't recognize it when we hear it.

View full article (http://www.universetoday.com/am/publish/mistake_et_signals.html)

What do you think about this story? Post your comments below.

antoniseb
2004-Dec-02, 07:14 PM
I had thought about this a few years ago. I suspect that more advanced ET's will mostly be using highly directional broadcasts for most anything that isn't handled by cables of some sort. I think that mostly when we look at an ET infested planet, if we see amy radio at all, it will be purely EMI, which will have some characteristic frequencies that it is strongest at.

Duane
2004-Dec-02, 07:15 PM
The bad news? They might be out there but we can't hear them. The good news? Maybe they can't hear us either.

lswinford
2004-Dec-02, 08:35 PM
When pulsars were discovered, people were excited because of the seemingly unnatural repetition of regular spikes, commonly associated with minor irregularities. Some people thought they were beacons, like some advanced civilization's equivalent of saying "We're over here" or perhaps like a lighthouse for navigation. This very paragraph would represent a strange, but hopefully curious jumble of signals no matter what code encrypted them. There is a lot of guess-work making an intelligible signal over such a long expanse of space and time. What time-sequence, what regular framing signals should they use? etc. Or, like one conjecture (the source escapes me) what if they are sending pictures and we haven't caught something like header codes to interpret them. If its a very big picture, possibly sent too fast so the signal fuzzes the data over this distance, what if they assume we would apply an-obvious-to-them filter which would make star noise come clear? Earth-bound spy's have been doing similar things in passing information. Maybe their puzzle to us is that if we can't sift through the noise we don't deserve to hear from them. ;)

Richard_K
2004-Dec-03, 06:22 AM
I don't think SETI ever hoped to eavesdrop on ET's cellphone message. Space is big, and messages take a long time to jump between stars, so any point-to-point communication would probably be based on coordinating and synchronizing the emission and the detection, so the chances of us intercepting any waste signal are pretty poor. In addition, the original paper notes that any decent compression system should reduce the signal to close to the maximum entropy state, where the next character (if the term 'character' is appropriate) is equally likely, and the signal will be indistinguishable from noise.

If we hope to detect anything, we must either hope for a broadcast that was intended to be recieved by us, or a broadcast that could be received under less than ideal conditions. If you were sending out a signal that would take 50 years to make the trip, you might start off with an informationless, highly identifiable signal to herald the start of transmission, and allowing the receiver to focus accurately on the following signal. People have tried fractal signals with a range of structures that would transmit more levels of information depending on the quality of your reception. All is not necessarily lost, but the message must be intended to be heard.

Guest
2004-Dec-03, 04:05 PM
Bah, Humbug!
It is true that eavesdropping would be difficult if this is true. But what if an alien civilization wanted to be found? If so they would have already realized that their transmissions are undetectable and intentionally devised a signal random enough to be found. If they do not want any visitors or to meet new friends, then we probably won't find them. So I wouldn't exactly call it a waste of time. Rather I would rename the SETI mission as a search for FRIENDLY alien civilizations that want to find us. Or maybe a search for socially outgoing civilizations rather than xenophobic and aloof ones?

alfchemist
2004-Dec-06, 06:06 AM
You're right, Iswinford! just like college books are not meant for kids, these "indistinguishable" signals are not meant for us. If they really are so advance in communications, they would have found a way to get to us since they would go thru the kind of technology like ours before they could achieve a far more advance technology.

If indeed, such an advance civilization exists and we found a way to eavesdrop, wouldn't it be prudent to stay away from something or somebody who don't wanna to communicate with us? Our "guest" is correct in saying that SETI should look for a "FRIENDLY CIVILIZATION" though this may seem like a blind, deaf, or mute with limited ability to communicate looking for one another in a very vast space

Matthew
2004-Dec-06, 06:45 AM
Lets say we could decode the aliens mobile phone messages, they would be speaking in another language and we would have no reference point to begin deciphering it! :o

damienpaul
2004-Dec-06, 06:46 AM
sort of like talking to my ex....:P

zephyr46
2004-Dec-06, 07:09 AM
Lets say we could decode the aliens mobile phone messages, they would be speaking in another language and we would have no reference point to begin deciphering it!

Yeah, and the techniques used in decoding messages here, don't even help us translate what the animals are going on about! Let alone ET! :D

Damo is your ex a bit of a Demonic Ape (http://www2b.abc.net.au/science/k2/stn/newposts/1402/topic1402380.shtm) ?

damienpaul
2004-Dec-06, 07:34 AM
Yup, she is a regular planet of the apes

btw, I wonder if its ever been considered to listen to 'animal' noises

alfchemist
2004-Dec-06, 08:08 AM
Hey DP! Is that ex-gf or ex-wife? :D I'm no linguist but when you have decoded or made sense or pattern in their transmission, I believe that you have started decoding their language as all languages have pattern or structure. And that's a great start!

Nick4
2005-Apr-24, 03:28 AM
This could be a problom i never thought about picking up signals from stars and mistaking it for ET