Precambrian rocks in Charnwood

 

We went up the Beacon to look down on Loughborough. The board says that the rocks are volcanic sediments that settled in the sea 600 million years ago. This is older that the Lake District. It counts as Precambrian. I am interested in the discussion of life in the Precambrian era because the Quantum Biology book I've been reading talks about the discovery of potential fossils in really, really old rocks in Greenland. The board talks about bedding planes in the rocks, which show the layers in which the ash landed on the seabed. Put later heat and pressure made the mineral crystals mobile and lined them up pointing up out of the beds, often at 90 degrees. This makes a cleavage and in slate is what gets cut to make the sheets.

Kinetic picture

This amazing picture is apparently called a "kinetic picture". It is 3 pictures. One is on the base and the other two are on vertical slats. Kinetic because you have to move to see the different pictures. It could have been called a parallax picture because what you see changes depending on where you are looking from.

Three norths collide!

 

Here's an interesting quirk from the Ordnance Survey: for the first time ever the three types of north they identify on their maps will coincide - they will all be pointing in the same direction. But only at a certain place and at a certain time! True north means the direction you go to head directly to the geographic north pole - the axis of the Earth's rotation. Because the Earth is curved, these lines get closer together the further north you go. Try drawing lines going from the stalk of an apple to the bottom - they start close but spread apart round the middle of the apple and then come back together again. Now look at a map: all north pointing grid lines are parallel and do not get closer as you head further north. This is an approximation to make curved space sit on a flat paper. It is arranged so that one special grid line is actually true north. Then there is magnetic north. The magnetic pole of the Earth wanders and in the next year or two, there will be times when if you stand on that special true north grid line, your compass will also point along that line. Three norths collide!! It's well explained in this film. 

Resolution with rollerblades at Watchtree

We talk about the ability of waves to detect particles. If the waves are about the same size as the particles, then the particles can be detected. Above, the stones in the tarmac were easily detectable by the wheels because they were much bigger than the ones below. Below, it felt smooth when in fact it is still made of small grains. The closer to wheel size, the more detectable.

This is one aspect of resolution of measuring instruments. The rollerblades were unable to resolve the smaller particles.

 

How tall is Caldbeck Transmitter?

 

We had an interesting walk up to Caldbeck Transmitter. My little finger held out like that subtends1 degree of my vision. That means the mast subtends 8 degrees. I was stood 1500 metres away. By trigonometry, tan(8) = height/1500 so the height of the transmitter is 210 metres. It is actually 337 metres high. Now the first few tens of metres are out of sight over the horizon - you can't see the terminal buildings. But that's now very accurate if I should be expecting say 300 metres. That would need an angle of 11 degrees and there's no way I can get that out of it. If my little finger were worth 3/4 of a degree, it would work. However, the usual problem would be that my finger was not far enough away - that would make the angle bigger not smaller. Perhaps more of the mast was hidden than I'm estimating.

Momentum: collisions with coins

 When I started teaching, the game of "shove ha'penny" was massively popular. How times have changed! Today I fired coin A into a stationary coin, coin B. Coin A stops and coin B moves on. Try A at different initial speeds.

Then I stuck two coins together.

When you repeat the experiment with coin B being twice the mass, it won't go as far. It's velocity after the collision is reduced. Or swap it round and fire the heavy one at the lighter one. If done correctly, the lighter one should go twice as far. All this shows that velocity after a collision depends on two things - velocity before the collision and mass. Hence we use momentum in calculations. TOTAL momentum of both coins together before the collision remains unchanged after the collision.

Then for fun, try this! Predict what you think will happen first!

Trying a cymatics experiment

 I took my inspiration from this film. I realised that I could do the experiment here by prising the front off my stereo speaker and playing sine waves tones generated in the Audacity app. I wasn't expecting anything given the rudimentary nature of the equipment but I was amazed to get patterns that look like those in Nigel John Stanford's film.

Above is 25 Hertz. Below is 50 Hertz. I'm not sure the photographs look much different but it seemed different looking at it.

The circular ripples in the film turn out to be a transient feature that appears just at the beginning. Thank you to Kay for telling me about cymatics. Although I've done experiments covered by the term, I'd never heard that word. It is about finding ways to make sound waves visible. I'm keen to try the corn starch and water mix next!