The Theory of Nothing

How will we understand an alien radio transmission?

How will we understand an alien radio transmission?

This question should be: how will we know when a radio signal that originates from space is from an intelligent species? By now, every science fan knows about the 'Wow' signal that was detected by a SETI project on August 15, 1977 by Ohio State's Big Ear radio telescope. The signal was intense and far above the background noise. Unfortunately, no confirmation or additional signal has ever been detected, and certainly this is not the fault of a large effort to duplicate the momentous event.

The question is: was this a signal from an extraterrestrial intelligent species or was it just an accident. I propose an even more fundamental question: what constitutes an extraterrestrial intelligent species signal? What should we be looking for?

SETI or the Search for Extraterrestrial Intelligence program has been trying to find an intelligent alien signal since 1960, and since then the program has been expanded with many new radio telescopes and better technology, which include the ATA or Alien Telescope Array. This facility has a bunch of radio dishes northwest of San Francisco. They currently have 42 dishes but plan even more, and their plan is to monitor a million stars for alien signals as well as do a lot of other astronomical work.

At this point in time, all they're looking for is a signal that's not from a natural source. Here are some of the sources for radio signals from space: old satellites or NASA probes. A signal from NASA's Pioneer 10 probe was picked up by a radio telescope at Arecibo, Puerto Rico, and that's just one example; neutron type stars emit radio signals, and in the case of pulsars, they are regular; spurious signals from billions of miles away, probably from an ancient supernova; comets sometimes emit radio signals, as in the case of a comet detected by the RPC or Rosetta's Plasma Consortium. I could go on and on, but you get the picture. Radio signals are always bombarding Earth from outer space. The trick is trying to determine if any of them are from aliens.

Let's say that an alien decides to send a signal out to see if anyone is out there listening. What type of signal would they send? As you know, the further a radio wave travels, the weaker it gets. However, our radio telescopes are powerful enough to detect a microwatt signal from Voyager probes that have gone to the edge of our solar system, billions of miles away. So, we should be able to detect a signal from an alien on a planet around a nearby star. By this I mean within a hundred light years of Earth.

Radio signals we've sent out into space are modulated. When Marconi invented radio in 1894, a signal was just a pulse of electromagnetic energy. Communication was done using Morse code, a serious of dots and dashes or on and off pulses. In order to send voice or music, one has to modulate the radio carrier wave. The first modulation was done with amplitude modulation or AM. The sound wave is impressed upon a continuous carrier wave during transmission and then separated or detected by the receiver. A better way to modulate is by frequency. In this case changing the carrier wave's frequency to match the sound wave is called FM or frequency modulation. Digital modulation is slightly different. In this case an analog signal is digitized and used to modulate the carrier wave by means of digital tones, essentially musical notes, which can be detected using digital to analog techniques. This is how modems work, if you can remember what a modem is. Obviously, this is a more complicated method of modulation.

The question I ask is: how would an alien send a signal? That's where we get into a problem because we have no idea how aliens think. Maybe they don't use radio, instead using light to transmit information. There's no way we'll be able to detect light signals unless they were extremely powerful laser beams.
It all comes down to how we'll know that it's an alien generated signal. But, before we get into that argument, we first have to find a radio signal that's not from a known source. We're still waiting for that to happen.

Thanks for reading.