Whatever next?

Well, it turns out this variety was named in the 1940s when Einstein would still have been alive. It shows his reach in popular culture!

Useless protractors

I liked this display in the Whipple Museum of the History of Science  in Cambridge. You can't use these lovely coloured protractors because you can't see the measuring point through the opaque plastic!

Decimal clock

 This is in the Fotzwilliam Museum in Cambridge. If there were 10 hours in a day, each decimal hour would last for 144 of our normal minutes. Nearly two and half normal hours! Each decimal minute would last for 86.4 normal seconds. The decimal hours would seem ridiculously long compared to normal hours but decimal minutes and decimal seconds might not seem so far out.

Not Newton's Apple Tree at Trinity College, Cambridge

I was excited when I saw that Newton's apple tree was outside Trinity College, Cambridge but a little perplexed as well because I have visited it at Woolsthorpe Manor. This is actually a graft from the original tree http://www.creatingmycambridge.com/songs-creative/resources/local-history-topics/newtons-apple-tree/

Four years later and the pattern is still there

There was a pattern in this gill on the slopes of Rest Dodd when I last went past four years ago http://wigtonphysics.blogspot.com/2015/08/interesting-wave-like-pattern-in-gill.html It was in a slightly different part of the pool but was still there. This time I could see progressive waves moving through the pattern. There is a vertical stone at the back which would reflect them so this should be a good site for a stationary wave to appear so perhaps the pattern shows nodes and antinodes. It has occurred to me that I could test this hypothesis in the lab by setting up a ripple tank with a reflective barrier and adding detergent.

Cyclotron

The few times that I have seen a cyclotron I have been surprised about how small it is. It is in the order of 30cm diameter. It is one of the earliest particle accelerators. The two metal halves are called Ds. The Ds are metal so that they can be given an electric potential. Hence there is a potential difference across the gap. positive particles are injected into the centre. A strong magnetic field acts perpendicular to the D - ie into the plane of this picture. The magnetic field is perpendicular to the motion of the charged particle so by Fleming's Left Hand Rule a force acts of the particles which acts towards the centre and pulls the particle round in a circle. The potential difference is alternating so that when the particle completes a half circle and returns to the middle, the potential switches which accelerates the particle across the middle and into the other D. Each time the particle crosses the middle, it gets faster and so orbits at a bigger radius. The clever thing is that no matter what the radius, it takes the same time to complete a half circuit so all particles in the apparatus can be accelerated at the same time. The limit on the size is that if it were biggest, relativistic effects would increase the mass and thus cause a particle to go more slowly, not reaching the middle at the same time.

Moseley and X-ray spectroscopy part 2

 The apparatus consisted of a rack of pure samples of elements inside a vacuum tube above.

 When that element was in the centre of the tube, it came under a cathode that fired a beam of electrons down onto it, shown above.

To avoid having to break the vacuum every time a new element was tested, there was an ingenious pulley system where turning a knob at the top turned a cotton reel which moved the line to which the rack of elements was attached.

The beam of X-rays from the sample then went into this chamber where it hit a prism made of a salt. The beam was then deflected round the chamber and the results photographed at different angles recorded on a scale inside.