Wednesday, 20 August 2014

Wednesday Science Limerick - Comet 67P

There’s a comet named 6 7 P
That Rosetta has wanted to see
And it looks like a duck
Though with plenty of luck
They’ll find water among the debris

Comets are astronomical objects consisting of a mixture of rocks, dust, water ice and frozen gases which orbit the sun in an extended orbit. When they approach the sun they heat up and some of the water and frozen gases evaporate, releasing some of the dust. The escaping material  is blown by the solar wind (caused by plasma escaping from the sun) to form a tail which can sometimes be visible to the naked eye - although the central rocky body is too small to see. Every time it comes close to the sun it loses more material and may break up into fragments. Meteor showers can be associated with some comets - representing small fragment which have become detached and spread out along the orbit over millions of years.

In recent years robotic space craft have approached and photographed comets and at the present time the spacecraft Rosetta is in orbit round the comet 67P/Churyumov–Gerasimenko. (Sorry for the long name - and the fact that I didn't include the full name in my limerick - but comets are named after their discoverers.) It has proved to be most interesting in that it is anything but spherical - and its shape has been likened to that of a rubber duck. Before 1959 it didn't approach the sun closer than about 400 million kilometers but a "close" approach to the planet Jupiter altered its orbit so that it now comes to within 190 million kilometers. Obviously the closer it comes the hotter it gets and the more material it looses each orbit. Some of the smoothest areas appear to be in the "neck" and if the comet consists of two large rocky masses cemented together with water ice it may not be that far from splitting into two. 

There will be much more active research over the next couple of years, with much more detailed photographs plus other scientific measurements of the material escaping from the surface. In addition there will be an attempt to land a probe and sample the surface. I will be following the discoveries with interest and I note that the Wikipedia page is being kept well up-to-date - the last amendment being yesterday.

Monday, 18 August 2014

Do Chimps have a bigger Short Term Memory than we do?

In thinking about the brain's internal language one of the interesting features relates to the size of our short term memory, and the number of thoughts we can handle at any one time. This video suggests that chimps may be better equiped in this area than we are!

Saturday, 16 August 2014

The Wiring of the Human Brain

A bird’s-eye view of nerve fibres in a normal, healthy adult human brain. The back of the brain is on the left of the image and the left side of the brain is at the top of the image. 
I am impressed with what can be done using MRI Scans.
Picture and more information from the Welcome Trust Blog

Thursday, 14 August 2014

Last month I criticised Jeff Hawkes book because he used the term "invariant" when discussing human memory. I pointed out.
Since when has the world been invariant? And even if it was our memories change continually with time, and my memory of my mother when I was six would not have been the same as my memory of her forty years later, or my memory of her 15 years after her death at the age of 90. One of the well-known limitations of the human mind is that long term memory is not a reliable record of what happened.
If you want to know how unreliable our memory can be watch the above lecture by Elizabeth Loftus.

Wednesday, 13 August 2014

Wednesday Science Limerick: Helium

They say one degree Kelvin is cold
Liquid Helium’s quite uncontrolled
When put in a jar
It’s behaviour’s bizarre
It climbs out – that’s a sight to behold

Helium is a most interesting element. It is the lightest of the chemically inert noble gases and the second commonest element in the universe. It was first discovered because of its spectrum in sunlight – which is why it is called Helium – after the Greek word for the sun ἥλιος (helios). The nucleus, the alpha particle, is also a product of radioactive decay.

It has the lowest boiling point of any substance (4.22 degrees Kelvin) and it is still a liquid at absolute zero, although a solid can be formed at high pressure. Below 2.1768 degrees Kelvin it become superfluid. This is a strange property where a thin film spreads out over all surfaces connected to the liquid and the liquid flows through the film from higher to lower levels. In the diagram the film covers all surfaces of the sealed container and from the outer to the inner bowl until the levels are equal. If the container was not sealed the liquid helium would escape.

In fact there are two isotopes of helium, He4 (2 protons and 2 neutrons) – as described, and He3 (2 protons and 1 neutron) which does not become superfluid until a much lower temperature. These strange properties are hard to understand without some knowledge of quantum physics and the meaning of words like "Boson" and "Fermion" – but should you want to know more the articles on Wikipedia are well written.

For more about the background to these Wednesday Science Limericks, and this one in particular, see below the fold.

Tuesday, 12 August 2014

Rural Relaxation - Whirlwind at College Lake

On Sunday we had a bit of a storm at Tring but once it had passed I decided to got to College Lake for a walk and cup of coffee - but couldn't get there as the road was closed because power lines had been brought down near the bridge over the canal at Bulbourne. So on Monday I went to see what had happened.
OK I was a day too late to photograph the whirlwind but had come from the west and cut a gap (see above) in the tall poplar trees that border the Canal.  Between those trees and the smaller ones closer to the water there is a small hay meadow and the second photograph shows broken branches that were lifted by the wind and drop in the meadow. Other branches could be seen on the track leading back to the Visitors Centre.

The whirlwind swept across the lake, a visitor's photograph showing the water whipped up by the island on the right in the first photograph. It then crossed out of the reserve and brought down a tree in Northfield Road, about quarter of a mile away.