Sorry to get all evidence-based on you but I’m hearing people panicking and fleeing Tokyo because of the oncoming radiation apocalypse. Now this is the sort of thing that could easily be overtaken by events but let’s have a look at how much radiation is hitting Tokyo right now.

Radiation is a funny thing. I remember growing up in the 80s with both Chernobyl and the threat of nuclear war hanging over us and geeking out on information about the effects of fallout. I remember learning that there are three types of radiation: alpha, beta and gamma. Alpha does loads of damage but is very slow and can be stopped by a piece of paper; beta is a bit faster but can’t get you if you’re inside; gamma rays are fast and do damage but there are relatively few of them. But we talk about “radiation” as if it were all the same. Anyway, let’s measure some radiation.

Here’s a screen-grab from an online Geiger counter in Tokyo:

There are two things to notice: a spike in the middle, and the fact that radiation generally appears to have gone up a bit. The important question is, how much? To answer that you need to know what the background radiation was. Thankfully, the site owner has put up a background sample, and here’s a screen-grab of that:

You can see from these images that the radiation levels have gone up from a background count of about 15 CPM to more like 20, an increase of 5CPM. (Tokyo appears to be on the low side for background radiation, the world average is between 25-30CPM.) The site also helpfully notes that 100 CPM is about 1 microsievert per hour. So an increase of 5 CPM is about 0.05 microsieverts/hour.

1 Sievert makes you sick and gives you a roughly 5% increased risk of cancer. So how long would it take to absorb one Sievert at this increased rate? 0.05 microsieverts is 0.00000005 sieverts. It would therefore take you roughly 2283 years of living in this environment before you started to feel ill, at which point you may have other problems. (Actually, it would take a lot longer than that, because radiation decays.)

What about the spike? After all, it went all the way up to 80CPM at one point. Taking away the background radiation that’s going from 0 to 60 in 180 minutes. That’s about 5400 counts in three hours, or 30 counts per minute - one third of a microsievert per hour. For the period of three hours, that’s a microsievert. That’s like smoking one tenth of a cigarette. It might actually have been a plane passing overhead.

I hope you now know why the government is telling you that there isn’t a problem. It’s because right now, there isn’t a problem.

Continue to read the news, continue to be vigilant, but please make decisions based on evidence.

One more thing. Here is a picture of the Fukushima reactor complex:

There’s something that the media is not telling you about that picture. That is that, after one of the biggest earthquakes in history, plus a tidal wave, plus a series of explosions, dammit, so far it’s still there. There are buildings. Fukushima is not presently a sea of radioactive glass. This is astonishing. This is really, really impressive engineering.

What is happening in Fukushima is only going to entrench those who have an opinion about nuclear energy. For those against it, this is evidence of why nuclear is unsafe; for those in favour of it, this is what really good safety procedure and defence in depth looks like. I don’t think it changes anything either way.

But I am very impressed that it’s still standing. Those engineers deserve a medal for this one.