SETI technology for communication

The article "The Case for Transmitting to Space" ( www.space.com/searchforlife/seti_transmit_060525.html ) says

What about how to do this? It seems to require some thoughts - the movement of the other star system around the galactical center has to be taken into acount very very precisely, the movemnet of the planet of that system as well, the movement of our own system and our own planet... Next the time the signal requires for the distance is very important.

If the signal is a short message then each bit is required to be sent to another direction which may differ by a nearly nothing here on Earth but will differ largely at the distance of the other system.

What thouights, ideas, soluations and so on?



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

SHUSH!!!!

Don't transmit anything to other systems! They'll might decide to exterminate us. ( I know I would if I was an alien. We look like trouble...)

Too late, Voyager is already all but out of the Solar System with a map to earth and a blueprint of what to 'exterminate' first when they get here.

I'm reminded of a scene from a classic Twilight Zone, "How to Serve Man."

A priceles shot when the guy finally figures out that its a Cookbook!

And just how far have our radio and television signals gone already? Fifty light years, a hundred? If they're out there, they'll be able to speak English by the time they get here. That'll make things easier. What what!!

And the Voyager maps were etched on solid gold. Great, not only will they know where we are, but they'll know we're rich enough to throw away precious metals.

We're doomed, doomed I tells ya.

I, for one, will welcome our new esteemed overlords and their benevolent despotism.

Especially if they bring teleportation technology. Yeah!

Do you think it'd be good to send out a really really powerful signal burst every so often? Sort of store up a tonne of energy and blast it out three times a year. A big "Hello, here we are, come join the party! Drinks are on me!"

What's our most powerful tranmission? Oh I suppose when we were letting off air burst test nukes would have been a fairly powerfull indicator of intelligent life. Well, maybe not intelligent, but concious techologicaly capable life.

How loud do we need to shout anyway? I hear that we can pick up a mobile phone strength signal from Saturn, but the stars are oh so much further away.

The most powerful signals routinely being sent into space are from air defense radars. Of course they are not aimed at particular stars, so as the beams accidentally sweep through space the aliens would detect random intermittent pulses with basically no information content. Still, it is a dead giveaway that we are here and have technology.

I really don't understand why the effort on interchanging messages with extrasolar intelligence is undertaken with electromagnetic waves, while we know quite exactly the propagation speed of those waves. Maybe LISA receives some spacetime ripples containing some information. But I guess higher developed civilizations won't transmit waves of detectable origin or decodeable content. They are probably a bit more fearful and transmit all messages in background noise without detectable signature as our military is doing it with its Pseudo Random Noise transmission techniques.

Hello, frankme,

up to now SETI doesn't think about interchanging messages as I understand them. They simply think about of telling distant civilisations of our existence - which is allways positive under the aspect that other civilisations then will or even might remeber our existince and we aren't left to oblivion.

A dialog via electromagnetic waves is impossible if we keep in mind dialogs as we know them between humans talking to each other via radio or telephone or even internet.

So regarding what I said in the initial post think of Venus Express which sent a first signal via reflection by the venusian surface. I suppose that there are a lot if signals that have been reflected into space by the earthian surface. These signals might arrive at distant civilisations in space one day and they might be identified as artificial and sent or caused by intelligence - if and only if any layer of the atmosphere, the Van Allen belts, the Terminations Shock, the Heliosheath etc. of our system or of the other system have NOT blocked or wiped out those signal(s).

What about sending via such reflections? The reflections also would have the advantage that hostile aliens identify the wrong planet even if they identify the correct star. The planet or body used to reflect the signal could be a moon of a gas giant that orbits outside the radiation belt of that gas giant - or it could be one of the recently detected small planets orbiting far beyond Pluto. Plus the night side of that planet could be used. Then the danger of hostile aliens is reduced and the question of energy is left and the focus can turn to it.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

Knowing the correct star system is all the information the aliens would need. When communicating at interstellar distances it is difficult to target anything smaller than the entire solar system anyway. And if the aliens decided to travel to our star system it would be trivially obvious which planet harbors the civilization, even if they didn't know before arriving. So letting them know which star is just as good as letting them know which planet at that star.

No telling what wavelength of communication a particular alien civilization would use, anyway. If they're like us and are using easily-created em signals that won't harm us bodily every time we use them then most likely the signals won't be detectable by the time they get here (spread out, interfered, filtered by dust, suns and blackholes, not to mention our own solar system and planetary magnetic shields).

I would think that some truly advanced civilizations probably use Xrays, gravitational pulses or other forms of radiation we don't monitor wrt alien signals.

I am despondent that we shall never have an alien broadcast to watch on TV (I mean, imagine their commercials!).