Some of you may have noticed the Berkeley SETI Research Center's statement on sending messages to other stars. Some of you may be surprised at our stance against transmitting. We put out our statement because the SETI Institute has been indicating that they want to start transmitting. They had an invitation-only workshop on transmitting at the SETI Institute on Feb 13, 2015 (I was not on the guest list) where according to the Guardian, opponents of transmitting were called "paranoid." It seems a little harsh. Here's why I think transmitting is a mistake in more detail than the statement gives. This is not necessarily the view of the other people who signed the statement.
The proposal ignores that human civilization changes over time. If we are broadcasting signals that could be returned in 1200 years, we will not be the same civilization in 1200 years. According to the Guardian, at the meeting, one of the proponents said "a civilization only three hundred years ahead of ours could detect Earth's TV signals at a distance of 500 light years." If that's the case, won't we know through other means if there is a technological civilization around the stars they target long before our signals even arrive there?
Nobody will be listening for a response, so what will we have learned from our efforts? About 1200 years ago, the Caliphate was at its maximum, and Muslim scholars were deriving algebra based on Hindu texts. Charlemagne was Emperor of the West. The Chinese were inventing printing using wooden blocks. Matches had not yet been invented in Europe. There was a flourishing civilization in North America that extended from Wisconsin to Florida. We wouldn't be able to understand someone speaking English, nor would they understand us. Europeans wouldn't discover the New World for another 700 years. Regardless, of what happens humans will have long forgotten the SETI Institute and the signals they sent. We may be extinct, civilization may just be a memory, or we may be colonizing space. But nobody will be listening in any case.
It's impossible to do a cost benefit analysis of transmitting. Nobody can tell you the probability that these signal will be detected, or if they are, what the reaction of extraterrestrials will be. Is there a 1 in a million chance that ET will decide we're a threat and eliminate us? Is there a 1 in a million chance that ET will call off the planned colonization of Earth when they receive a signal from us? Of course the most likely result is that there will be no response, but that result isn't certain. There is no way to determine the probabilities. ET could be just like us (which would be frightening) or so different that we don't even recognize each other as intelligent (which would be frightening). We simply cannot predict intent, capabilities, or response. We can't even predict what our own response to an extraterrestrial signal would be.
- Nobody elected us. I'm a scientist. I don't have the right to speak for the people of Earth even though I have access to a telescope that could. Same goes for any group of scientists. There's even a Declaration of Priciples that SETI scientists supposedly adhere to that says I won't transmit a message in response to a signal without global agreement. But it's OK to transmit messages without first receiving a signal? The representatives of the people of the world (the UN General Assembly) need to set the rules for this game.
The future doesn't get a vote. How many people will live in the next 1200 years? We can't consult them. Proponents seem consoled by the idea that any bad outcome won't occur in our lifetimes. If a bad outcome were to occur, those living at the time might not be so consoled by the fact that it didn't happen to us.
The signals that proponents claim we've already sent (TV, radio, Arecibo radar) are not nearly as likely to be detected as they claim. We couldn't even detect TV and radio signal at the nearest star with Arecibo. The Arecibo Planetary Radar is detectable at distances of thousands of light years, but doesn't repeatedly target the same spots on the sky. Someone receiving a single pulse is likely to discount it because it isn't repeatable.
As a comparison risk analysis, suppose a 10km asteroid were going to pass through the Earth's atmosphere, igniting fires that would kill a million people. You could divert it, but there would be a 1% chance it would hit the earth destroying all life. Which choice do you make? There are ways to decide. No such analysis can be done for METI.
Scientists can debate each of these points, except the first one. It shouldn't be my decision, and it shouldn't be decision of any small group of scientists.