Would we be able to detect an alien message if we got one?

Emma Sackville put this question to Dr Duncan Forgan at the University of St Andrews...

Duncan - If we received an encrypted message from space, it depends on how good the encryption is. If a message is very well encrypted, we wouldn't be able to understand it as an artificial message - it would look just like noise. Just like the kind of noise you see in the cosmic microwave background or the noise you see on your old fashioned television set.

If the encryptions not quite as good then there are certain things we can do to understand the quality of communication. We do this with communication from animals. For example, we can give it a rating to say how much information is contained in the signal and so we could certainly say this is very informative. But what the information actually is, is going to be very challenging to figure out.

Emma - Have we ever had anything similar in the past that could have been a message that people were excited about?

Duncan - The one that everyone remembers is what's called the "wow signal," which came in , I think, the early 70s, and it was a very strong, narrow band transmission being sent to the Earth. We think now that it was a natural signal; it was actually something bouncing off something else, but that signal had no information in it, it was just a pulse. But then even if the signals just a pulse, that still tells you something because a single pulse is basically "hello."

Emma - Ooh, that could be interesting. Okay - ultimate question. If we got a message, and if we could understand it, do you think we should respond to it?

邓肯——好吧,问题是我们没有一个合法的framework for figuring out what to do next. We have what's called the reply protocols that SETI scientists wrote down saying well, this is what we should do, but not-ones going to follow those protocols because they're not in international law. So, if a message was received and say, for example, America wanted to respond but China didn't - tough - America could still send the message on behalf of all of Earth, which is not great.

My personal opinion is that we shouldn't send any replies because, speaking as a human being, I'm not particularly impressed with how well human civilization copes with its responsibilities as a steward of the Earth. A little bit of time maybe before we become more respectable as a galactic civilization.