Hey : )
The last week has been fun—one of my friends from home came down on Tuesday and we went to see Taylor Swift in the O2! One of the best things about living in London is that you don’t have to force people to come and see you—they come themselves for the attractions and then can sleep on your floor. Taylor, as I now affectionately call her, was brilliant—a very professional performer and though she did talk some rubbish in between her music and dancing she was so compelling about it that I was completely swept along.
Tubing there was easy—straight from labs to North Greenwich tube station, but unfortunately by the time we were heading home the infamous tube strike of last Tuesday/Wednesday had begun so we and a million other confused pop fans were stranded at the O2. Luckily, our carefully honed D of E skills set in, so we were able to navigate to alcohol and then, eventually home.
Continuing the good news theme, Atomic Physics has finished! Yey! *tiny celebration* It has been replaced by a new lecture course called Soild State, which so far seems to be about crystals and things.
Also I have discovered another physics mystery! In last week’s astrophysics course our lecturer announced that the sun’s temperature gets hotter the further you go away from it, and nobody really knows why.
I planned to elaborate on this, but the summary papers I tried to read are a bit beyond me at the moment (or else the fact they don’t know themselves makes it badly explained, but probably the beyond me thing). The exact problem is that what we think of as the surface of the sun (the photosphere) is about 5800K hot. This is fine, but the sun actually has three more chunks of atmosphere extending beyond that bit, called the chromosphere, the transition region and the corona, which stretch far out into space. The weird thing is that the temperature in the corona reaches 2 million kelvin.
That heat is not coming from the sun’s surface. My favourite second law of thermodynamics says that hot stuff can’t continuously heat up hotter stuff. So where is this energy coming from?
Well, if you read the sort of layman’s section of the NASA website about this topic it says something very intriguing. Most scientists think that the main source of heat comes from the rapidly changing magnetic field lines in this area of space generated by the swirling plasma in the sun. The laws of physics say that magnetic field lines cannot cross, so every time they are about to, something must intervene and rearrange them to stop this occurring, producing heat.
This effect is seen in other stars too, and seems to be more dramatic in those that are spinning faster, which does seem to suggest that the stretching and reshaping of magnetic field lines may have something to do with it.
I will probably have a look at some more papers on this later, because writing that down has made me interested again—but for the life of me I couldn’t tease out any explanation from all the maths that I saw. Hmm. The only thing I really understood was a tentative explanation for why no explanation has yet been found (an excuse in other words). It is likely that the important heating effects seem to happen at all scales—both incredibly large and incredibly small, which are almost impossible to simulate simultaneously on a computer and the small scales hard to observe by satellites.
And so it remains a mystery…
By the way, the histogram I showed you last time has turned out not to be quite as neat as I thought… I am just about to go and finish writing up the experiment, so I will fill you in on the final value of e that I manage to scrabble to.