Diffraction in the TV screen

This seemed like a perfect diffraction pattern but on closer inspection I noticed a few features. The first order had a lot of violet and was wider than the second order. The second overlapped with the third which then seemed to give magenta - red and blue. 

Minette Lamprophyre dyke on Sale Fell

 

We found this dyke close to the summit of Sale Fell on the Cockermouth side. The rock is a type of Lamprophyre called a Minette. I'm just getting to grips with this type of rock so seeing a known example was helpful. It seems to have large pink crystals. The dark patches look like lichen where some crystals have eroded out.

Looking for the Bouma Sequence on Sale Fell

 I'm new to the idea of the Bouma Sequence. Today we went looking for evidence of what happened at the bottom of the Iapetus Ocean 480 million years ago. We climbed up from the back car park between Ling Fell and Sale Fell and examined the first narrow exposure on the south-west edge of the fell. Bouma suggested that when there were "landslides" down the continental shelf under the sea, the sediments would settle out in a particular order. The explanation is here. The second example picture at the bottom of that article is particularly helpful. A good diagram is here. We think we found part C of the sequence, stood vertically on end.

You can see the curved structures in the sediment. That would make the layers on either side. B and D if that is true.

Microgabbro on Carrock Fell

 

This feature is on the Mosedale flank of Round Knott, just below the summit. It turned out that the bands in the rock were tiny - see foot in photograph for scale. I hadn't figured that the picture in the book we were using had a pencil in the photograph, not a pole!! It's this one if you're interested. The big trick here is the differential precipitation and settling of different minerals. The book says that augite with iron and magnesium precipitated first and settled, leaving a mixture heavy in calcium and aluminium (plagioclase) so this then precipitated, until the original balance was restored and then the process repeated forming the bands.

Wavelength at Maryport Parkrun

We had a lovely time at Maryport Parkrun - a very flat and fast course with lovely marshalls. Having posted about the wave sculpture in Whitehaven, I was interested to see the pattern of the waves against the pier. I counted 10 waves when I blew up the picture and measured a 200m distance from my map. That means wavelength is 20m. Not an easy thing to measure on the see and only approximate, compounded by the slight angle of incidence.

Newtonian Reflector

 

The other type of telescope used on the astronomy night was a Newtonian Reflector. I used to teach the advantages and disadvantages of the Cassegrain Reflector but I've had to look this one up. With the Cassegrain, you look in at the bottom of the telescope along the axis. With this, you look in at the side near the top. A concave mirror focuses the light near the top and it is reflected sideways by an angled plane mirror. The lack of lenses means no chromatic aberration. The Newtonian only has one mirror that needs shaping unlike two in the Cassegrain. 

Telescope counterweights and equatorial mounts

 

I'd always wondered what the bits sticking off the side of an astronomical telescope were, but up close they turned out to be counterweights to stop gravity pulling the telescope down. This doesn't happen on my birdwatching telescope because it sits directly over the top of the tripod. So why is an astronomical telescope off to one side? To simplify the answer, stars move over time because the Earth is turning. You need a drive to make the telescope move to compensate for this. There are two axes for movement - stars move sideways across the sky but also up and down. By aligning one axis with the axis of the Earth that never changes, the other motion can get a constant speed drive. I've not yet worked out why being off centre makes that possible. It is called an equatorial mount.

Wigner Energy and the Sellafield Fire

 

I have posted before about Wigner's contribution to Quantum Mechanics so I was excited to see he was featured in the exhibition about Sellafield in The Beacon at Whitehaven. Turns out that the Wigner Effect is that a neutron going into a moderator like graphite knocks a whole atom out of its position in the lattice if the neutron has sufficient energy. This can knock out other atoms etc. Some of these atoms don't make it back into the lattice but stop in the gaps between the lattice atoms, in the interstitials. The lattice is the place with least energy so these interstitial atoms have more energy. If there are enough of them and they all release their extra energy at once, that will raise the temperature enough to be dangerous. See here for my source and more details.

Ribbed stratus cloud

The sky at Watchtree on Sunday was interesting. It is stratus but ribbed. The repeating pattern is reminiscent of a stationary wave, like the one  you get if you hold a knife blade under a laminar flow from a tap. Now I have seen lenticular clouds in this very gap between the mountains and they are caused by stationary wave patterns being set up. Perhaps this is the same.

Tektites

 

Tektites are a type of meteorite that was made when a bigger meteorite created such a big impact that it melted the surrounding rocks and knocked some fragments of the melted rocks back out into space. They fell back to Earth. Tektites are glassy like obsidian but the composition is not the same. See here for details. It turns out that there are only 4 areas on Earth where they can be found and that dating techniques have tied them in with nearby impact craters.

Chondrite meteorite

 

I have to confess to knowing little about meteorites, nor even the difference between them and meteors. All this was put right by the Border Astronomical Society evening at Watchtree. Meteors get hot and burn up; essentially what I'd call a shooting star. Meteorites reach the ground intact. There's even a word I didn't know: meteoroid for the rock that can become either but for the time before it hits the atmosphere. And meteorites come in types. This is a chondrite meteorite. That means it is rocky rather than metal. The article explains that radioactive decay dating suggests it is as old as the Solar System at around 4.5 billion years old.

Physics in the pub

 

Spotted on the back of a fruit machine! A useful warning but you'd need some Physics or a painful experience to understand the implications. The problem will come when you tilt the machine to move it. The higher the centre of mass, the greater will be the resultant torque when the centre of mass is moved away from its equilibrium position, hence more strength will be required than if the centre of mass were lower.

Trying for an ice prism

 

Last time it was frozen at Watchtree I found a prism-shaped lump of ice a couple of centimetres thick. I fished it out to try for a prism effect. I think the problem is that to get the spectrum, you need a thin beam rather than the ambient light round. I wonder what effect the flaws in the ice would have. Sadly couldn't get it home for experiments.

Wavelength in Whitehaven

I counted 4.5 wavelengths on the wave sculpture in Whitehaven. From the map, it seems to be 200m long. That means the wavelength is about 44m.
 

Sir John Cockcroft

 

We went round the Sellafield exhibition at The Beacon in Whitehaven. Not as wonderfully physicsy as the original on the Sellafield site 30 years ago but much better than its last on-site iteration in the visitor centre which was only aimed at young families. I thought I knew the name John Cockcroft. Turns out he won the Nobel Prize for Physics for inventing a particle accelerator that was the first to "split the atom". I now need to work out how the capacitors and diodes on the Cockcroft-Walton generator work to increase the voltage. In the context of Sellafield, he's seen as the man who saved us all by insisting on the now-iconic filters on the tops of the chimneys.

Looking for xenoliths on Criffel

 

We used Chapter 8 from this book to look for the boundary of the pluton below Millour (page 465 onwards). We couldn't find the contact in the stream because it is now a jungle of gorse and brambles where the leat leaves the Kirkbean Burn. But we did have success on the slope just above. The map on page 467 promises strong foliation and dipping outwards at 50 degrees. And that seems to be the angle of the slope on these crags. The highlight was what appeared to be a paving slab cemented onto the granodiorite at the same angle in a place that cannot possibly be artificial. Turns out we had found a huge xenolith. Page 466 says that they are country rock and that they align with the foliation. And it can't have been much more that 100 metres from the pluton boundary. I like it when what you find matches what you've read!

Foliated granodiorite

I went to Criffel having heard that what I was calling granite is actually foliated granodiorite. I wanted to see what foliated looked like. Apparently it is the lining up of the minerals - they are no longer randomly distributed. Well, there was little convincing evidence on the mountain but 3 days later I found this on the beach at Allonby. I'd say it is convincingly foliated.

4 day old Moon

Having managed to find the ISO settings, I can now take pictures of the Moon without it over-exposing. I found this website with labels for the same picture - well, mine is just a few hours after the one shown. The big dark patch is the Mare Crisium. Mare is Latin for sea. That's what these features looked like to the first observers with telescopes. Now we know that they are darker, newer rocks, probably lavas released on impact.

Photographing the stars

I was alerted to the idea that by playing with the Pro settings I could extend the exposure time and change the ISO. I had to wait for a clear night to experiment. To my amazement, the maximum exposure time allowed, which is 8 seconds, worked provided that I let it do Auto ISO because that gave a higher value than any of the manual settings. It was about 6400. I'm staggered by what I can see.