A "hot" metal cover in the snow

 

It snowed yesterday morning. All morning, the snow refused to settle on this access cover for the drains. Metal feels cold to the touch so this seems weird. However, metal feels cold because it conducts heat well. The air trapped in the drain space will have been warmer than the air above so conduction will have been from below. This will have been enough to melt falling snowflakes. The ground around is loose and traps air. The trapped air acts as an insulator so cannot conduct from potentially warmer ground below. It's interesting that people talk about "stone cold" which suggests that rocks could also be good conductors.

Clocks in and out of phase

 

There are two clocks in our room that both have loud 1 second ticks. Last week they were out of phase by about 0.5 seconds so you could hear them both distinctly as individual devices. This week they are ticking in unison. The mechanisms will not be perfectly calibrated to 1 second so they should slide in and out of phase. 

Checking a gamma source with a mirror

 

It is good practice to check radioactive sources for damage before use. The safe way to do it, as recommended by CLEAPSS is to use a mirror. This is a gamma source and the gamma rays are not reflected back in the way that light is even though they are both electromagnetic waves. It ensures that the source is always pointing away from you. Always hold in 30cm tongs at arm's length.

Calcium silcate? A view from the Slag Bank

 Last week I was dealing with a question on metamorphism about the reaction between calcium carbonate (limestone) and sand (silicon dioxide) to produce calcium silicate CaSiO3. This must be wollastonite. But I finally got to climb to climb the slag bank at Barrow yesterday and I am wondering if this is largely artificial calcium silicate.

The layers in it look like lava flows or some of the banded volcaniclastic sediments in the Lakes. The pieces I picked up with very light and full of holes like pumice. Essentially, in steel making there is sand in the ore still. It is not pure haematite. To get rid of the sand, it is reacted with limestone. Both iron ore and limestone were readily available around Barrow. So calcium carbonate and silicon dioxide could indeed get to react. There is more information here and here.

The views were so good that I could see Snowdonia, the Isle of Man and Scotland. In the picture above looking up the Duddon, the Scafells are in the distance.

Sound insulation at Wasdale Head

 These barriers were in operation around a generator at Wasdale Head. 

I was very interested in the set of symbols that went with it. I'm not sure whether it adds kN to the load or is resistant to forces in the kN range. Also, does it reduce by 43dB or is what comes through less than 43dB?

So I tried their website. I really liked the frequency graphs lower down. This seems to show 43dB REDUCTION but at high frequencies only. This is important because I know from experience that it is the frequencies around 4000Hz that are most sensitive to the ear.

The Green Flash

 I had forgotten about NASA's Astronomy Picture of the Day site. Going back to it I found this wonderful film of the Green Flash. I have seen the Green Flash twice from the school trip to Normandy. I got very excited. It lasts a fraction of a second. 

Petrol price and American gallons

 

The price of diesel has topped £1.50 a litre for the first time in Wigton. We've paid that once in a remote place in the very far north of Scotland. We wanted to know what it would have been in gallons, knowing the fuss that was made when petrol first went over £1 a gallon. I work on the idea that there are 8 pints in a gallon and that a litre is roughly 2 pints so 4 litres to a gallon. It's actually 4.546 litres to a gallon, meaning diesel is £6.91. The problem is that I've discovered that an American gallon is different.https://en.wikipedia.org/wiki/Gallon It looks as though we were running different sizes of gallon in the UK for measuring different things until the mid-1800s when it was standardised. We seem to have gone with the liquid gallon but the Americans went with the corn gallon. Anyway, there are 3.78 litres in an American gallon. Our American friends reckon to have reached about $3.50 max meaning 92.6 pence per litre.

The Boyle's Law apparatus has leaked

 I had a surprise with the Boyle's Law apparatus because the readings didn't match those I took a decade ago. Here it is on 180kPa and the air volume is 33cm^3. A decade ago, the volume was 22cm^3. The ideal gas equation is pV=nRT. pV is 180 x 33 = 5940. A decade ago pV = 3960. So nRT must be bigger. The room temperature won't have changed much and R is a constant. Hence the number of moles of gas must have increased. Air must have leaked into the apparatus.

But it still gives results that show that pV=constant (roughly). Below we get 160 x 38 = 6080.

And finally 100 x 58 = 5800. So pV is always around 5900. This is one way of illustrating Boyle's Law.

Colorimeter photos and resolution

 

We used the absorbance scale, which is the bottom scale with the black numbers. The smallest scale divisions are every 0.05, which means that the resolution is therefore 0.05.

Here are the filters we used to find lambda max.

Here is the all important zero button.

Meniscus

 Liquid has surface tension. The particles would normally bond in all directions but at the surface they can only bond sideways and downwards. This means more bonds than usual are formed sideways creating tension. Where the liquid touches the side of a container, these bonds hold on. Gravity makes the liquid sag downwards in the middle. The sag is called the MENISCUS.

We always measure to the bottom of the meniscus.

Here are the two pieces of measuring equipment we used in class so that you can see the resolutions.

Rain before seven, fine before eleven

 Here is the scene first thing this morning.

By quarter to 11, the first sign of fine weather was beginning to appear in the west over the Solway.

My parents taught me the weather saying "rain before seven, fine before eleven" when I was a child; we were trying to be optimistic on wet holidays on the west coast of Scotland. When I became a teacher, an early lesson was that very few students had been taught it by their parents! It is based on the four to five hour transit time of an Atlantic front across the UK. It often doesn't work in mountainous areas like this one because the mountains can catch the cloud, especially if the weather is coming up from the Azores as it was the other week. But today it looks as though it's going to be all right.

Angles morts: blind spots

 

In France, the warning to cyclists and motorists about where they cannot be seen seems to have been called the "angles of death". In English, we call them "blind spots". The French is better. It is the physics that fixes this. Light travels in straight lines and cannot pass through metal. I'm interested that it includes a space right in front of the vehicle where the driver would not be able to see down.

Thirlmere Aqueduct at Greenhead Gill, Grasmere

 

The water from Thirlmere goes to Manchester through a tunnel that needs no pump - the water flows due to gravity alone. However, there are points where the gradient of the tunnel takes it above ground level. One such point is Greenhead Gill at Grasmere so they had to build two bridges to take the aqueduct out of tunnels and above ground. This included a change in direction. There is a brilliant film about the project that includes a visit to the site to be found on the Institution of Civil Engineers website https://www.ice.org.uk/what-is-civil-engineering/what-do-civil-engineers-do/thirlmere-aqueduct-and-reservoir

Gassy lava near Dockey Tarn?

 On the way up towards Nab Scar from Alcock Tarn, I found this boulder inn the path. There are rows of little indentations.

I was wondering if it was artificial but it continued into rocks nearby. This means that it is probably due to gas bubbles in lava. But why would the bubbles be so uniform in rows? It doesn't look as though there were repetitive layers forming on layers and that in each the bubbles rose to the top. So a mystery.

We went on to visit lonely Docket Tarn which sits on one of those wide ledges that is characteristic of the lava flows in the Borrowdale Volcanics around St John's in the Vale.

Optical corona: reflections in Alcock Tarn

 The Sun was shining through thin high cloud, enough to produce an optical corona. Having posted last year about optical coronae in steamed up glasses due to mask wearing, I thought this was an unusual way to capture the optical corona of a different kind. This isn't the corona that is the outer layer of the Sun; rather, it is what happens is diffraction through water droplets. In fact, I think the bit I saw is the aureole - see http://www.atoptics.co.uk/droplets/corona.htm