A bit over precise?

Exciting that the clearance on the lorry was given to the nearest mm. Load or tyre wear would be at mm level 

Eclipse

The partial eclipse was way more impressive than expected. It was visible despite thin high cloud and was noticeably darker at its peak, which I hadn't expected. The old telescope projection method proved best for viewing. 

Insulated Floor

I was being shown how to drive a steam train at Shildon. The guide asked us why the floor was wooden. The answer is that wood is not a good conductor of heat so it stays cool enough to stand on. Steel would conduct heat from the boiler so well as to burn your feet. 

Mug design

The holiday home mugs are shorter but wider than the ones at home. The volume is the same. It has dawned on me why they are more difficult to handle when full. The centre of mass is further from the pivot so I have to create a bigger counter moment with my hand. 

Quantum Radio

 This is a brilliant little programme on BBC Sounds. The presenter goes to Helgoland to ask quantum physicists "what is quantum?". 

Light detection in the eye

 

This explained clearly how we see colour. I read an interesting report in Physics World recently about seeing brand new colours. Each type of cone cell detects over a range of wavelengths. There is overlap of these ranges which means that certain wavelengths trigger two different cone cell responses. This masks them so we don't see those colours independently. Researchers have used very narrow laser light to hit single cone cells so that the response comes from only one type of cone cell, avoiding the overlap problem.

Dog Vision

 

The exhibition at Tullie House on Colour was a lovely mix of basic science and art. I was left playing spot the difference with these pictures but I did figure out which end of the spectrum is missing for dogs.

Colour Blindness

 

Doing the colour blindness test is one of my earliest memories from Primary School. Interesting to see them again all these years later.

Curved space-time

This trellis at The Newt near Glastonbury reminded me of the diagrams of space-time when it is curved by gravity in General Relativity!

Sun dial for the dead

Spotted in the cathedral at St Davids. It must work on light through a window. I don't think I've ever seen an indoor sundial before and certainly not one on a tomb!

Levelling the Land

Every bridge on the Lancaster Canal seemed to have a benchmark. Then the penny dropped. Benchmarks were used for linear surveys - ideal for a canal. The canal needed to be level to retain the water so surveying must have gone from bridge to bridge. But does that imply that the bridges were built as each section was dug? I suppose I'd assumed they dug the whole canal and then added the bridges but actually that wouldn't make sense in terms of access for local residents ...

Saltburn Cliff Railway

We enjoyed the cliff railway. It doesn't give the mass of an empty car but the 1500 litres of water in a full tank at the top would have a mass of 1500 kg and a weight of 14.7 kN. This must be enough to lift 12 people and overcome frictional losses. Let's estimate 12 adults at 80 kg each. That's roughly 1 tonne so say 10 kN. The frictional losses are therefore worth about 5 kN. 207 feet is around 60 metres so work done against friction might be in the region of 5 kN x 60 = 300 kJ. That doesn't actually sound that much

Polarised colours

Back to a phenomenon I've recorded before but not been able to find any theory about. Compare the bottom fence posts in the two pictures. The fence posts should be green but appear purple in the top photo. The top photo is taken through my polarising sun shades. Rotated through 90 degrees for the bottom picture. I've noticed before that my polarising filters seem to preferentially let through the blue end of the spectrum.

Robert Recorde

It was wonderful to come across this in Tenby Parish Church - the person who invented the equals sign. I suppose I have thought these things have always been there and wouldn't have a specific inventer.

Changed Meaning

The new Tullie House sign reminded me of the unit for magnetic flux density. That is T for Tesla named after the great Nikolai Tesla. I wonder now if students will think it is named after the cars.

Vector Field

I loved the two large concrete arrows on Mawbray Banks, used to guide bomber training in the war. 

Pressure and temperature

It was a mistake to store a bottle of Prosecco in the loft. The high temperatures in August must have increased the pressure of the gas in the bottle to such an extent that it was able to overcome the strength of the glass. The bottle was at the orange arrow but one shard ended up a couple of metres away by the pink arrow. The temperature must have been sustained for some time to allow the thermal energy to conduct through the glass. 

Watching the Wind on Loch Keose

The wind gusts were stirring up dark patches on the loch. These must be tilting the water in a direction that reflects less light in my direction. Then these sections moved as coherent wholes down the loch. They can't have been moving as fast as the wind itself.

Branching time lines

These apple trees at The Newt reminded me of branching lines that form in the time dimension as a result of decision making. Schrodinger's Cat is a famous example. Opening the box can be said to start two lines - or some would say two parallel universes. One would have the cat alive and the other dead. This branching is one way to get round the Grandparent Paradox and allow time travel.

Roman pottery

We had a brilliant pottery demonstration at The Newt. The potter explained that the minerals in clay can become aligned under pressure to form cleavage planes - this is what happens when slate is formed. This wouldn't be good in pottery so the point of working the clay on the wheel is to make sure the crystals don't form cleavage planes.