Saturday, 8 April 2017

Up close and personal with James Joule

I got to meet James Joule in the lobby at Manchester Town Hall. He was a local brewer who did an experiment where falling weights pulled a paddle wheel in a vat to do mechanical work on the liquid. The temperature of the liquid was raised and thus the First Law of Themrodynamics had its beginnings. I am finding it hard to get used to the convention that it is capital J for the abbreviation as in 100J and small j for the full name as in 100 joules.

Friday, 7 April 2017

Linear air track

The linear air track is a long metal tube with tiny holes in. Air from the outflow of a vacuum cleaner is blown down the tube and comes out through the holes, leaving a layer of upwardly mobile air on which gliders float.
 I use it in conjunction with light gates to try to show conservation of (linear) momentum but also to illustrate Newton's First Law. Once you get the glider moving, it does not require a constant application of force to keep it going. It will keep going in a straight line at a steady speed until it hits the other end and an external resultant force acts on it. Then it will change direction and come back in a straight line at a steady speed etc. Aristotle thought that objects needed force on them all the time just to keep them going at a steady speed. His problem was that he inhabited a world of friction.
The odd thing about our vacuum cleaner is that the tube is kept inside. You have to pop the black handles at the top of the silver drum and list the top off carefully.
Then screw the hose onto the outflow of the vacuum cleaner as shown below. It connects to the linear air track as shown in the top photo. When you put it away, coil the hose so that it doesn't get crushed when you put the lid back on.

Thursday, 6 April 2017

Simultaneity on the train to Winchcombe

Sat in the steam train at Cheltenham I was reminded of Einstein's work on special relativity. He suggested that someone stood exactly in the middle of the carriage and had apparatus that was able to shine a light beam instantaneously in both directions. The doors at either end have light activated locks that open the doors when the light beam hits them. The person in the middle of the carriage sees each beam hit each door at the same time so both doors open at the same time. The light has traveled equal distances in equal times. Someone on the platform as the train goes by would see it differently. The back door would be moving forwards towards the backward travelling light beam. The front door would be moving away from the forward travelling light beam. So the person on the platform would see the back door open first and the front door second. Both witnesses of the same event but they see a different order of door opening.

Wednesday, 5 April 2017

Geology on Rosthwaite Fell

I found this wonderful paper on the geology of Rosthwaite Fell which explains its place in the Scafell Caldera. http://jncc.defra.gov.uk/pdf/gcrdb/GCRsiteaccount289.pdf The summit rocks pictured yesterday are Crinkle Tuffs and the abstract suggests that these might be ignimbrites. As such it would be the result of a pyroclastic flow. If I ever go again I'll know to look more carefully https://en.wikipedia.org/wiki/Ignimbrite . The rock under Tarn at Leaves is Rosthwaite Rhyolite. Scafell must have been a pretty impressive volcano.

Tuesday, 4 April 2017

Evidence of ancient earth movements on Rosthwaite Fell

These are the summit rocks on Bessyboot. Notice the diagonal planes from top left to bottom right. These will be layers of ash. I think from previous reading that we are somewhere on the edge of the ancient Scafell Caldera. They may have settled in water perhaps and so they would have been laid horizontally. But the fact that they are at an angle now is evidence that the whole earth must have tilted sideways. Notice that later pressures have split the rock vertically. Evidence of ancient earth movements...
 But in places the rocks have also split along the bedding planes.

Monday, 3 April 2017

Lenticular clouds from Bessyboot


These fabulous lenticular clouds were visible from the summit of Bessyboot at the end of Borrowdale. They stretched almost from Cockermouth to Penrith. The wind was strong and the clouds form in stationary waves after the wind has passed over the mountains. https://en.wikipedia.org/wiki/Lenticular_cloud says that the isolated lens-shaped clouds form when the air is taken to the peak of the wave and the temperature is below the dew point. So the clouds should be at the peaks and the distance between isolated clouds would represent the wavelength. I would estimate a wavelength of at least a mile, more likely 2 miles. It says that the gaps between are when the air goes down to the trough and the temperature is above the dew point. It has reignited my interest in the idea that the wave shape is fixed but that matter moves through the pattern. On the way down, the main pattern from the top picture was still visible - it is a stationary wave after all - although more clouds had filled in.
Back in Wigton, there were some weirdly twisted clouds visible which might be the remains of lenticular clouds as the front comes in and stratus starts to dominate.

Sunday, 2 April 2017

The Hill Reaction

We took delivery of centrifuged crushed spinach leaves. They are kept iced so that they last longer away from the plant. There was a solid pellet in the bottom of each tube and a liquid called the supernatant above the pellet. We poured the supernatant into a separate beaker.
 Then we added 3 cubic centimetres of isolation medium to the pellet left at the bottom of each tube and gave it a shake. The isolation medium helps to extract the chloroplasts. We called the resultant medium the LEAF EXTRACT.
 We labelled 5 tubes. We used syringes to measure 5 cubic centimetres of DCPIP into tubes 1, 2, 3 and 5. We used smaller syringes to add 0.5 cubic centimetres of leaf extract to tubes 1, 3 and 4. We wrapped tube 3 in foil. Tube 2 got 0.5 cubic centimetres of isolation medium. Tube 4 got 5 cubic centimetres of distilled water. Tube 5 got 0.5 cubic centimetres of supernatant. We put the tubes 10cm away from a bright light. DCPIP is an electron acceptor.
When light is absorbed by chloroplasts, the energy is used to split water molecules. Two electrons are released. These can be accepted by the DCPIP which loses its colour. Tube 1 is on the left. It is now paler than tube 2. Tube 2 should stay blue because it contains only isolation medium which releases no electrons. Tube 4 is pale green. It contains no DCPIP and is the colour that tube 1 will become when all of the DCPIP has been decoloured. Tube 5 is paler blue/green, showing that the supernatant still contained chloroplasts. The centrifuging hadn't been perfect.
 Every 5 minutes we put samples of tubes 1 and 5 into cuvettes for testing in the colorimeter to quantify the colour change.
Tube 3 in the dark stays blue. This shows that the Hill Reaction is indeed the light dependent reaction. No light: no electrons for the DCPIP to accept.