Goethe and Newton's prisms

I was lent this journal which has a lot about Goethe's views about science.

Most interesting was his work on colour theory. Apparently he wrote polemics against Newton's views. I was interested to read that one big thing was about the distance of the screen from the prism when projecting a spectrum. That explains a lot of the difficulties I had getting classes to see a proper spectrum over the years. Here's the spectrum from the edge of my mirror. Note that green is missing and it is white down the middle.

I'm also interested in how he managed to get a spectrum of "darkness".

Solar rotation

The sunspots have kept their pattern but clearly moved showing that the sun is rotating on its axis. It turns out that because the Sun is not solid, the matter round the equator is able to rotate faster than that at the poles. This must result in some shear. Amidst the complications, it is going to take about 28 days for these sunspots to rotate all the way round the Sun, if they survive that long. So the higher double spot should be visible for the next 8 or 9 days.

Sunspots

Having heard that there are sunspots at the moment I went looking this afternoon. Not perfect conditions but I found some.

Hybrid power batteries

The plate on the battery unit says 25.6V 280Ah *6 = 51.2V 840Ah so there are 6 batteries inside. The sum shows that there must be 3 blocks of two in series which are then wired in parallel together. The advantage of batteries in parallel is that you add the storage in Ah. They are connected in series pairs first because that doubles the voltage without affecting the Ah. Problems arise if the batteries have different voltage ratings. Then one battery can discharge through another. This is known as cross-discharge. Diodes can be used to prevent it.

Lining up like interference patterns

I noticed that this viewpoint allowed me to line up tiles on the roof. There is one set straight on with a couple of sets to the right at different angles and one set to the left. The way they line up is reminiscent of the patterns that get drawn for the interference of light. It's like the interference fringe numbers.

Wall ties at Carlisle Cathedral

The centre of a roof has weight pulling it downwards. This pushes the edges of the roof sideways on the top of the wall. To prevent collapse, there needs to be an equal and opposite horizontal force acting inwards on the wall. This is provided by struts between the two walls. Originally this was a wooden beam. These were later replaced with metal struts which can be seen if you look carefully. The wooden beam was cut off I the middle and the ends decorated with angels! 

Stars and Saharan dust

This was the night sky at the start of last week, looking west. Arcturus is in the lower middle above the building.

Here it is again later in the week after the arrival of the Saharan dust. I can only imagine that the dust is scattering the light from the west more effectively and making the sky brighter.

Driving in hot weather

I read an article that said that cars don't go as well in hot air because the air is less dense. Now I know that air resistance is directly proportional to the density of the air, which would mean they would go better in hot air. It turns out that the article is talking about engine performance. If the air is less dense, a given volume contains less oxygen and the engine might thus be prone to incomplete combustion. I can find no formula relating engine performance to air density but there's an explanation of the issue here.

Cider Apple Periodic Table

This is a lovely graphic but I'm still trying to work out why they are in the order they are!

Solar Farm

There were a lot of solar farms in the south west. This is Tower Hill Solar Farm by the M5 in Gloucestershire. I worked it out from the brilliant interactive renewables map. The planning page gives the power is 6.5MW with 8.05MWp. I was interested in the latter units. It stands for peak MegaWatts, the peak power. There is a lot more info here. Essentially, in practice a solar panel gets hot and does not generate as much. Also, they generate DC but the grid is AC so they need inverters to make that change. To reduce the cost of the inverter, one that is smaller than the peak power is usually used and the power clipped if it exceeds that of the inverter, so the inverter is a limit on the output power.

Saharan dust reaches Wigton

The amazing sunset last night and the hazy conditions that accompanied it turned out to be the forecast Saharan dust. Dust storms in the desert coupled with strong southerly winds carry the dust into the upper atmosphere and to us. The small dribbly attempts at rain have brought it down.

I had seen recently that Saharan dust supplies phosphorus to the Amazon. It also provides iron for the Mediterranean Sea when the wind is blowing as it is at the moment.

Static hair and the triboelectric series

I have seen different accounts of whether hair is charged positively or negatively. It turns out that there is a way to work it out called the  Triboelectric Series. Hair is close to the top of the positive end and there is a big separation to balloon rubber. Hence the hair loses electrons to the balloon and in this instance the balloon ends up positive. The only material that would leave the hair negative would be glass.

Diesel vs electric?

Having been working on my own diesel fuel efficiency, I was interested to see this advert which suggests an electric car can be charged for £10. That would buy me 6.45 litres of diesel or 1.42 gallons. At 70 miles to the gallon, that's 100 miles. Electric cars of similar size to my car seem to have nameplate ranges of 200 miles on a full charge so this charging overnight scheme might be cheaper even accounting for the actual range of the electric car being less. 200 miles would not have got us to the south without an expensive and time consuming motorway service station charge, though.

Fuel efficiency in motorway jams

We spent hours in queues on the M6 and M5 - never really stationary but crawling in a stop-start fashion.

I had thought this was supposed to ruin the miles per gallon values. However we did 389 miles  over nearly 12 hours, mostly on motorway and with maybe 4 hours in queues. We used 24.74 litres of diesel which is 5.44 gallons. That gives us 71.5 miles per gallon. This is better than last week. One difference has been taking off the roof box - but given the queues I wasn't expecting an improvement!

Exploding balloons

We had a great time at the Ruby Wedding party. An odd thing was happening with the balloons. Any that escaped outside were exploding. I think the sunlight was giving thermal energy to the gas particles which meant they had more kinetic energy. They move faster and hit the balloons walls harder. The pressure increased above the strength of the plastic and thus made the balloon explode. 

A sign to Gravity

I was amazed by the road sign near Bridgwater. Apparently it is to a business park. I want to live there! 

Carbon footprint of a car journey

On page 62, Mike Berners-Lee discusses the carbon footprint of driving a mile. He links this to the miles per gallon. On our trip to the south and back, we drove 495 miles. This needed 36 litres. Using a conversion from litres to gallons, this comes out as 62 miles per gallon. Rounding his figures because the comparison is not perfect, this might be 300 grams of CO2 per mile or about 150kg of CO2. The actual figure will be higher because we were in traffic jams for a while on the A1.