Well, we’ve heard a lot about the terrible circumstances in Japan over the last week or so. Honestly, I don’t feel very qualified to comment on the situation. There are excellent descriptions of the nuclear physics online, the one thing I’m most likely to be able to contribute intelligently to, so I’ll direct you to Frank Shu’s refreshingly thorough analysis (even if developing events make it a little out of date – thanks to @telescoper for the heads up). Instead of talking about earthquake magnitudes then, I’ll remind you of a lesser known scale. If we ever record a value of 8.9 on it, it will have equally significant results for our world.
Imagine you’re part of SETI (The Search for Extraterrestrial Intelligence). You’ve been “manning” the telescopes that are searching for signs of intelligence in the Universe. You’re jolted awake by your computer terminal bleeping – there is a signal. What do you do next? We’re all familiar with the idea of culture shock – the knowledge that we are not alone in the Universe will change the world’s opinion of itself dramatically – perhaps we will find it difficult to cope?
It’s clearly a delicate situation to handle, but not a situation that hasn’t been carefully considered by SETI. There are in fact a set of protocols in place, to guide any scientists who might be sitting on the biggest scientific discovery in all history. So what happens? You might expect that the military swoops in and gags all those concerned, but that’s not in the protocols. Instead, the astronomers responsible do several things. First, they go over the results with an exceptionally fine toothcomb – false alarms about this sort of stuff are not well received by the scientific community (or the public for that matter). Once they’re happy the signal is extraterrestrial and not a natural phenomenon, they inform the other signatories to the protocols, and the national authorities.
Whether the military decides to swoop in at this point is not entirely clear – I imagine that the signatories of the protocols would do their damnedest to execute the next stage of the protocols, which is to disseminate the data widely to all the world’s astronomers, and then to the general population.
But there are many potential sorts of detections. We could stumble upon a multi-directional beacon from an active civilisation transmitting to the entire Galaxy, or uncover relics from a long-dead species in the Outer Solar System. There could be an invasion fleet in Earth orbit, or merely indirect evidence that a distant star system has been meddled with by an intelligent species – maybe their star has an unusual spectrum, or they have engaged in significant asteroid mining (let’s leave that topic for another post, as I have some work in progress on that one). The nature of the signal itself is also important – is it a strong signal? Is it periodic (i.e. can you repeat the measurement)? Did you see the signal coming in, or did you find it by scouring the data archives?
Clearly, some signals are more important than others, and this is where the Rio Scale comes in. This scale is constructed by expert opinion, and estimates exactly how important the signal is. If it hits zero on the Rio Scale, then we ignore it, as it has no significance. If it’s between 1 and 3, it might be of a little significance. As we get towards its maximum value of 10, the signal becomes increasingly important (until at 10, it basically rewrites human history). There’s a nice little applet that lets you play with certain scenarios, and tells you what value they have on the Rio Scale. OK, it’s not founded on the rigid physical principles that earthquake magnitude scales are, but it’s a sort-of rigorous way of categorising how amazed/awed/scared you should be.
As I understand it, the maximum value recorded on the scale to date is about 1 (there was a recording of 4 in 2003, the first case where the Rio Scale was calculated in real time rather than after the fact, but that turned out to be a hoax). We’re yet to really see even the moderate section of Rio yet, but observations with the Kepler Space Telescope could have the potential to record 4 on Rio, or higher.
There is a lot going on in the world right now – revolution, earthquakes, tsunamis, nuclear crises, orbiting Mercury for the first time, terrible music and Royal Weddings – and the chances of detecting aliens are pretty remote. But if you do open the paper tomorrow and SETI is in the headlines, ask yourself: “What’s the Rio on that?”