How to recognize transmissions from alien life?

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zuz
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SETI is searching for a signal from space. What is this signal supposed to say? Hi, here we are.? We were broadcasting signals into space for 50 years before we actually knew we were doing it. Those first signals are still going, but they are not traveling in a big sphere. They're going in the direction that those first transmitters were pointed. Eventually we started transmitting from all over the world. Those first signals are what we should be looking for. If we detect a signal from a point in space, and it's not there tomorrow, maybe the planet that broadcast it is just pointing in a different direction. Instead of looking for a "We are here" sign, shouldn't we be looking for ET's equivalent of Howdy Doody?
 

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berkeman
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SETI is searching for a signal from space. What is this signal supposed to say? Hi, here we are.? We were broadcasting signals into space for 50 years before we actually knew we were doing it. Those first signals are still going, but they are not traveling in a big sphere. They're going in the direction that those first transmitters were pointed. Eventually we started transmitting from all over the world. Those first signals are what we should be looking for. If we detect a signal from a point in space, and it's not there tomorrow, maybe the planet that broadcast it is just pointing in a different direction. Instead of looking for a "We are here" sign, shouldn't we be looking for ET's equivalent of Howdy Doody?
Think about what you would try to do with an exploratory signal that you would transmit into space to try to make contact. What would you use? A common thought is to use mathematical relationships to show your basic intelligence to start a conversation. Like transmitting the first few primes...

https://en.wikipedia.org/wiki/Communication_with_extraterrestrial_intelligence
 
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zuz
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Yes I agree. But when a civilization first starts using radio they don't know what they have. The first signals they send out are going to be jibberish. Hence the nod to Howdy Doody.
 
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Vanadium 50
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Most searches are not looking for radio. They are looking for radar.

At any given TV frequency there are dozens of broadcasters. The interference will surely preclude any successful interpretation.
 
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Klystron
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SETI is searching for a signal from space. What is this signal supposed to say? Hi, here we are.? We were broadcasting signals into space for 50 years before we actually knew we were doing it. {snip}
Pardon the contradiction but scientists, engineers and tech knowledgeable people certainly knew we were broadcasting/leaking electromagnetic signals off planet. Literature including science fiction and popular electronic publications abounds with 'First Contact' stories.

I worked with several scientists and engineering managers from NASA's SETI programs. We often discussed 'signal to noise' SNR difficulties detecting intelligent signals from background noise including natural radio sources. Speculating that alien civilizations can learn about Earth cultures by analysing old television broadcasts can be fun to imagine, but outsiders are more likely to detect heavy pulsed radar transmitters, particularly outside the Earth's magnetosphere.

One publication described searching for 'traffic control transmissions' alongside actual communication attempts; assuming advanced civilizations even use EM transmitters.
 
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