And that proud look as though she had gazed into the burning sun,
And all the shapely body no tittle gone astray.
I mourn for that most lonely thing; and yet God’s will be done:
I knew a phoenix in my youth, so let them have their day.
–William Butler Yeats
Before the industrial revolution, between the 17th and 19th centuries, the life expectancy of Norwegian peasants followed an unusual pattern. The records show they would drop every ten or so years, before bouncing back up again three years later. This wasn’t the result of a weird disease affecting the farmers and fishermen of the fjords, nor the consequence of periodic bouts of war. Instead, the answer may have been hovering over them.
W.B. Yeats may well have won the Nobel Prize for Literature, but he was never going to win the Physics Prize* with his rather inaccurate description of a “Burning Sun.” The Sun doesn’t burn in a conventional sense like a fire on earth, instead it is an incredibly large nuclear explosion.
Normal nuclear explosions blow themselves apart pretty quickly, however the sun is so large that its own gravity pulls it back together: the sun is constantly blasting itself outwards and collapsing back inwards.
As a result, a more accurate description would be “The Throbbing Sun,” and it’s this throbbing that’s believed to be responsible for the cyclical reductions in Norwegian peasants’ life expectancies.
The Sun’s throbbing cycles every 11 years. For 8 years the Sun behaves like normal, but for 3 years it churns out particularly intense amounts of energy. Astronomers can tell when the Sun is in a particularly intense phase because it gets covered in a large amount of sun-spots. These dark splodges on the surface of the star are easy to see if you have a telescope, and accurate records of their existence go back to 1674.
Using parish records from local churches in two separate towns in different parts Norway, researchers at NTNU in Trondheim compared the life expectancies of children born during periods of intense solar activity (solar maximum) and periods of average or less activity (solar minimum).
It was found that children born during solar maximum had a lifespan that was, on average, 5 years shorter. Also women born during solar maximum had a reduced fertility, meaning they were less likely to have their own children. A large portion of this drop in life expectancy was due to a large increase in infant mortality amongst children born during solar maximum.
We now know that a lot of UV light is bad for you. During solar maximum, the amount of UV light hitting the earth increases. Amongst the peasant population in Norway who spent a large portion of time outdoors – and let’s be honest, the Norweigans aren’t genetically predisposed to resist the suns rays – this appears to have been enough to have a measurable effect on their livelihoods. So if you wanted to live a long time in pre-industrial Scandinavia, you had to choose the right time to be born.
Matt was born in 1989 which was during a solar maximum, however his life expectancy probably took more of a battering from his decision to do a PhD in chemistry than from the number of dark splodges on the surface of the sun. He tweets @mattallinson
* Which in that year (1923) was won by Millikan for measuring the charge on an electron
Gine Roll Skjærvø, Frode Fossøy, Eivin Røskaft Proc. R. Soc. B: 2015 282 20142032; DOI: 10.1098/rspb.2014.2032