Thursday, July 30, 2015

New discovery in subatomic physics

This is a bit exotic but I have nothing else bookmarked for this month. The first pentaquark has been reported. This is a particle composed of five quarks - very strange but predicted. Normal particles such as protons are composed of three (see diagram) so it is like one and two-thirds of a proton - kind of.

Here is a good article explaining this starting from Rutherford's discovery of the compact nucleus of the atom over a hundred years ago.

Sunday, June 28, 2015

CXC Physics on-line resources update

Following changes the CXC website now offers syllabuses and past papers as downloadable ebooks through their 'store'. Past papers cost money to get but the syllabus has a cost of $0 which means it can be downloaded free but it is neccessary to create an account and go through the shopping cart thing.

Saturday, May 30, 2015

Inside a radiation detector

This picture shows the board of a gamma-ray detector known as a Geiger-Muller counter.  Gamma rays are detected by the tube, counted and the count shown on the LCD. The words at the top of the board warn of high voltage (400-500V).
The type of radiation detected depends on the tube used.
See Wikipedia for more.

Monday, March 30, 2015

Closing off modeling climate change

Have just finished the course at EdX which I mentioned in two previous posts (first, second).

As part of an assignment I looked at historical temperatures for Georgetown and Timerhi. Georgetown has one of the most complete sets of data for this part of the world. Here is a graph showing the annual average temperatures (degrees Celsius) from 1850 (Georgetown orange, Timerhi green). It is clear that there is an upward trend which has accelerated from about 1950. The trend for Georgetown is about 0.2 degrees rise per decade and the mean temperature seems to have risen by about one degree since 1950. Global temperatures show similar results.
One closing topic was short-term mitigation - what we can do now to reduce the problem. The lecturer pointed out that there are things that can be done such as reduce heat loss by homes in cold countries, change agricultural practices to trap more carbon and increase energy efficiency of transportation. Another is to change our life style and diet.

It seems to me more than ever what we need is better working together to tackle world problems and less short-term politics.

Friday, February 27, 2015

More on modeling climate change

Am still doing this course as mentioned in the previous post. Heavy going at times with topics such as:

  • greenhouse gas physics
  • atmospheric feedbacks
  • carbon cycle
  • perturbed carbon cycle
  • solar and glacial cycles

Most weeks have models to set up using spreadsheets or programming. Some assignments require access to one or more of the Climate and Carbon Cycle Models available from University of Chicago.

One interesting prediction - if we stopped producing carbon dioxide today it would take the earth thousands of years to recover, may be hundreds of thousands. And we would not feel the full effect of what we have produced so far for hundreds of years during which the ice sheets would continue to melt and the sea level to rise...

Thursday, January 29, 2015

MOOC - climate models

Am now doing another course at EdX called "Modeling Climate Change". Again this involves quite a bit of physics. The focus really does seem to be on modelling and so far seems to be a good introduction to some serious computational physics. A good course for linking with physics at the University of Guyana. More next month.