The Christmas Pudding Model

Well, OK, it's technically called the Plum Pudding Model, but it's the same thing. John Dalton from Cockermouth, just down the road from here, revived the idea of atoms. When JJ Thomson discovered electrons in 1896, that caused a problem. Electrons were negative but atoms were neutral. That meant that there must be positive stuff in the atom. No positive particles had been discovered so the hypothesis was that the electrons were like negative currants in the positive dough of a Christmas pudding. The positive was smeared throughout. This meant a prediction that when positive alpha particles were fired at atoms, there would be no resistance because the positive in the atom was spread out so thinly. Turned out to be wrong ...

Constellations

Constellations are a wonderfully silly idea but I love them. The idea of seeing patterns in the stars - space is 3D and the stars we link together are just stars that are in the same direction as viewed from Earth. They may be vastly different distances along that common direction. But the seeing of patterns is a way that humans make sense of the world. And it helps us to find our way round the sky. These boards are in the cable car station for Mount Teide on Tenerife. The night sky is supposed to be very good up there!

Igneous intrusion on La Palma

I was able to catch up with much more recent volcanic features on the Canary Islands. Most striking was the fact that it has never been smoothed and widened by glaciation like the features in northern Britain. Today I've picked out a volcanic dyke in the Caldera de Taburiente on La Palma. I don't speak Spanish but the display board shows molten magma welling up through cracks in pre-existing rocks, It shows the temperature gradient from the middle of the feature and cooling as it moves out. The molten rock bakes the country rock, resulting in a zone of metamorphism. The bottom photograph is a detail of this. But look how much harder the dyke is than the surrounding rock, which has worn away leaving the dyke standing out like the ones I saw on Arran.

Xenolith at Skinburness

 We found this rock on the beach at Skinburness. It is Criffel granite. You can just see Criffel under the cloud across the water.

Criffel granite is an igneous intrusion. The hot magma welled up under the surface but never broke through. Granites can take up 1 million years to solidify so they grow big crystals. However, the grey lump is not a crystal. As the magma came up, it pushed into rock that was already there. They call this "country rock". Sometimes bits break off and fall into the magma. The rock solidifies around the intruder. The intruder is called a xenolith.

Relative speed

Here is the Queen Elizabeth passing the identical Queen Victoria out in the Atlantic. We'd been tipped off that it was about to happen. Things happen slowly at sea but this happened twice as fast as expected. We were steaming north at 20 knots. She was steaming south at 20 knots. That means that the distance between us was shrinking at 40 knots. That was our relative speed. To us, we could have been still with the Elizabeth approaching at 40 knots. To them, the Elizabeth was still and we were approaching at 40 knots. That was all fine until Einstein got hold of it and started thinking about what would happen when you get to the speed of light .... but that's another story.

Full Moon on Christmas Day

Here it is, the first full Moon on Christmas Day since 1977, as seen somewhere out on the North Atlantic. I wondered why it had taken so long and what factors affect how often any given date gets a full Moon. It turns out that there is more than one way to measure a complete orbit of the Moon around the Earth. One is to measure a complete 360 degree rotation, but you have to do this against the background of the stars and it turns out to take 27.3 days. It is called the sidereal month. My next task will be to figure out how to observe this. More logical is the month from New Moon to New Moon ie measuring the time it takes between occasions on which the Moon and the Sun line up. Here it rotates more than 360 degrees round the Earth because the Earth itself has moved on round the Sun. It takes about 29.5 days but varies during the year because the Earth's orbit is not round. This is the synodic month. 12 lots of 29.5 days comes out at 354 days, so each full Moon will slip by 11 days in a regular year but 12 days in a leap year. I started trying it out on a calendar but gave up. Anyway, next full Moon on Christmas Day is something like 2034 so it will be a while.

Volcanic insulation on Gran Canaria

The southern end of Gran Canaria is very arid. They have put in a lot of tourist apartments by the sea. The flat roofs seem to be covered in the local volcanic rock. I assume that this is insulation to maintain a cooler temperature inside, which is the opposite of what we need up north in the winter. The rock is porous due to gas bubbles in the lava flows and thus it traps air. This makes it a poorer conductor of thermal energy thus causing it to take longer for the thermal energy to get through into the house.