Fasten your seat belts, friends: we are leaving for a journey that combines the mysteries of the depths of the earth with the secrets of infinite space. We're talking about an odd couple: earthquakes and cosmic rays.
They look like two protagonists from completely different worlds, don't they? A recent study found that they may be more related than we think.
Where does this strange friendship come from?
If you think earthquakes and cosmic rays have nothing in common, you're not alone. Also the same Piotr Homola, lead author of the study (that I link to you here), admits that the connection seems strange at first glance. But here's the surprise: There seems to be some pretty solid evidence of a correlation between these two phenomena. Mind you: Researchers aren't saying that cosmic rays trigger earthquakes.
The discovery lies in the terrestrial core, the beating heart of our planet. Here there is a continuous ballet of liquids that move in often unpredictable patterns. And not only that: our magnetosphere is born from this nucleus, a "shield" that protects us from quite a few space "threats".
Among these threats, cosmic rays, which are divided into primary and secondary. The primary ones are those that our magnetosphere manages to stop, while the secondary ones are the ones that manage to pass.
The dance between earthquakes and cosmic rays
The researchers noted that particularly intense earthquakes often appear to be preceded by significant changes in the amount of secondary cosmic rays passing through the magnetosphere.
And here our friend the earth's core comes into the picture. If it shakes, not only could it increase seismic activity at the surface, but it could also affect the magnetosphere, visible through the behavior of secondary cosmic rays.
It's not just a random correlation
Again, that sounds like a pretty bold statement: but the researchers are pretty confident in their findings. “In the scientific world, it is accepted that a discovery can be said to be made when the statistical confidence level of the confirmatory data reaches five sigma or standard deviations“, says Homola. “For the observed correlation, we got more than six sigma, which means less than a one in a billion chance that the correlation is due to chance."
Because it can't be a coincidence
Imagine having a darts competition with friends. Every time you throw a dart, you can hit the target, or be close to it, or far away. If we measure how far each dart lands from the center, we get a kind of “average” or average position of where the arrows land.
Now, not all arrows land exactly at this midpoint. Some are a little to the right, some are a little to the left, some are a little higher, some are a little lower. How much these positions vary from the midpoint is what we call the “standard deviation.” It's a way to measure how much our darts (or whatever we're measuring) spread or disperse around the midpoint.
If all of your darts land very close to the center of the dartboard, you have a low standard deviation, because the darts don't spread out very much. But if your darts are landing all over the place, then you have a high standard deviation (and maybe a bad aim).
Now, when scientists talk about “sigma,” they are talking about the unit of standard deviation. So if they say “six sigma,” they are saying that something is six standard deviations from the mean. In practical terms, it's like saying you threw a dart so far from the center of the target that it seems impossible it ended up there. If a discovery is “five sigma” or “six sigma”, it is as if that absurd shot far from the target also happened five or six other times. It can't just be a coincidence: there must be a reason why the darts land there. And that's what researchers will now try to find out.
Cosmic rays and earthquakes: in conclusion
The discovery, sensational in itself, does not yet have practical use: perhaps we may never be able to derive a device that accurately predicts earthquakes from cosmic rays.
Certainly, however, the discovery of a link between the cosmic radiation recorded on the surface and the seismicity of our planet deserves new research opportunities.
