Thursday, 22 October 2009

Sharing your bed with radiation

So, last night I gave my "Field Guide to the Isotopes" talk at my home institution, the University of Surrey. It went, I think, pretty well, though the turn-out was on the low side for our evening lectures programme. I guess people must have been paying attention, as there were a few very pertinent questions along the way, and some interesting comments and questions at the end.

One of the comments was about the isotope potassium-40 (K-40). Potassium is an alkali metal, element number 19, which sits under sodium in the periodic table. It sits there because it has chemical properties similar to sodium, so it readily forms salts which are vital in the human body for the proper functioning of cells.

So, potassium is element number 19, which means that every nucleus of potassium has 19 protons in it but there are a few naturally-occurring isotopes which differ in the number of neutrons they have. The most common is K-39, next is K-41. They are both stable, but about 0.01% of potassium atoms has a K-40 nucleus at its centre. K-40 is radioactive (it will decay either to argon-40 or calcium-40), with a half life of around 1 billion years. Now, the earth is not so very much older than this (at around 4 billion years) so there is still some remaining K-40 that was created some time before 4 billion years ago to be found on the earth. Unlike the other main long-lived naturally-occurring radioactive isotopes (of Uranium and Thorium), Potassium is actually a biologically useful element, and so we all have some small amount of radioactive K-40 in us.

I expressed this in the talk by saying (and I don't take credit for it - it's been pointed out before) that if you sleep with someone else, you are getting an increased dose of radiation from their body by doing so - and vice versa. A questioner at the end was quite worried. Fortunately, humans have been sleeping with other humans for a long long time, and the doses are clearly not high enough to cause any trouble.

Still, all other things being equal, single people have a lower radiation dose!

Sunday, 18 October 2009

First Post!

Hello and welcome to my new blog about nuclear physics; Blog of the Isotopes. I've been occasionally writing a personal blog for many years, and often going off and talking about nuclear physics as part of my job as an academic nuclear physicist, also for many years, so it seemed like it was about time to join those two things up. So here we are: the blog of the isotopes - all about nuclear physics. The blog's name comes from the fact that nuclei - the tiny clusters made of protons and neutrons at the centre of each atom - come in different isotopes, just meaning a unique combination of a number of protons and neutrons in the same way that each chemical element differs from the others by having a different number of electrons in an atom.

Of course, it might be that blogs are on their way out and that I should be tweeting about nuclear physics instead, but maybe that will come too :-)

Anyway - a little about me: I work at the University of Surrey, which has the largest nuclear physics group in a UK university#. I call myself a nuclear structure theorist, which means that I do calculations of the structural properties of nuclei (things like their size, shape, mass, and the ways in which they can vibrate) using our knowledge about the nuclear force - then I see how well these ideas about the nuclear force really agree with what my experimental colleagues observe and refine my theories based on that. No doubt I will be talking about this in future blog posts.

I plan to keep an eye out for topical nuclear physics news stories and talk about them from the point of view of a nuclear physics researcher, and also to share some of my interests in the wider field of nuclear physics beyond what I do research into... but I don't want to do it all in this first entry; so let me just justify the fact that I have chosen to start today by saying that I will be giving a public lecture at the University of Surrey this Wednesday (21st October) in Lecture Theatre M at 7pm on nuclear physics. The title of the talk is "Field Guide to the Isotopes," and it will be a little tour of some of the exciting things that nuclei are used for elsewhere in science and society from understanding climate change and other geological processes to medical diagnosis and treatment, to determining the ways that astronomical processes take place. If you wish to come, please just turn up in time for a 7pm start. Details are at or leave a comment here.

more soon!

# probably - it's slightly hard to count