Phases of Venus

Venus is low in the southern sky after sunset at the moment. Nigel Henbest's 2024 annual suggests looking through a telescope against the brighter sky before darkness to allow the phase to be seen. On normal settings it over-exposed (above). But a faster shutter speed got something that might be what I was looking for.

Interesting field pattern?

If these arrows were showing the shape of a vector field, it would be a really weird field.

Series circuits with resistors

One thing that was evident with the fairy lights when attempting repair was that the leads had no indication of live or neutral. And that's because it doesn't matter. Resistors like a filament have no preferred direction for current. The fuse will work either way round and there was no Earth lead so it is double insulated.

Filament bulb

This is an old-fashioned outside Christmas fairy light bulb. The filament is the loop shown by the orange arrow. The pink arrow shows a wire strand that holds up the filament. The green arrow is a glass bead to provide insulation. The aim is to keep the wires apart to stop them shorting out.

It is a 12V 3W bulb. Using P=V^2 /R gives resistance of the filament as 48 Ohms. It looks like the filament loop is about 12mm long so resistance per unit length is 4000 Ohms per metre. Tungsten has a resistivity of 5.6 x 10^-8 Ohm.m at 20oC. Using R=rho.L/A and ignoring the temperature rise when turned on, cross-sectional area of such a filament made of tungsten would be 1.4 x 10^-11 square metres so diameter would be 2 x 10^-6 metres. That is surely much thinner than the wire in this bulb.

Thinking about thermodynamics

Mrs B was musing about the thermodynamic implications of this cafe sign. We only talk about heat moving, not cold. And we stress that it is "heat energy" - and modern syllabuses change that to "thermal energy" because we need to stress the difference between heat energy and temperature. Thermal energy is essentially atom wobble. Things with a high temperature have furiously wobbling atoms. We say they are hot. The universe is quite egalitarian and tries to equalise out the amount of atom wobble so ones with more can give to ones with less, but not vice versa. The actual situation is even more complicated because we normally deal with whole objects - collections of millions of atoms. Even an object that feels cold can have a few atoms that wobble massively. So a cold object could pass energy to a hot object but the net flow would be from hot to cold. So physicists tend not to draw arrows labelled "cold"!

Pressure is falling

This was the pressure this morning. You can see from the marker where it was a week ago. What I find odd is that outside the weather is very much like that for high pressure - settled with clear skies. However the barometer reading is not much higher than when Storm Ashley came through last month and I posted about bombogenesis. With Storm Bert on the way, I will need to watch the barometer.

Not quite the Sea of Tranquility...

... but Tranquility on the sea in the marina. It reminded us of the Apollo 11 landings. The Mare Tranquilitatis was named in 1651 by two Jesuit priests who were early physicists. It escaped being a called the Mare Belgicum. It was an assumption by early astronomers that the dark flat areas on the surface of the Moon must be bodies of water like they would be on Earth but they are actually vast basaltic lava flows.

Looking for the Winter Hexagon

I am trying to get reacquainted with the late autumn sky after the weeks of cloud cover. It took me a while to tell the difference between Auriga and Gemini. So it is Auriga top left. Looking into it brought up another asterism to look for - the Winter Hexagon. I could see the bit from Capella down to Aldebaran but Orion had not yet risen so Rigel was behind the garage. I've now got something to look forward to this winter,

Nuffield Physics

This old tractor in the Penrith Christmas Lights parade was a Nuffield ie one from the works of Lord Nuffield, William Morris. It reminded me of the money he put into Physics education. The Nuffield A Level Physics course was so innovative and was more about developing thinking than learning facts. A lot of the ideas live on here

Kirkwall Power Station

 

I am always interested in how islands are powered. It turns out that this power station is now a back up. It is worth 16MW total. It is oil fired. 

Clouds form over islands

 

It was noticeable approaching Orkney, that in an otherwise cloudless sky, convection cumulus was forming over the islands. My guess is the differential heating of land and sea by the sun. Earth has a lower albedo and a lower specific heat capacity so should get warmer. The vapour later maritime air would get forced up by convection over the islands as a result and condense to form cumulus.

Up to 175kW

 

I've been interested in how quickly you can charge an electric car. This station was claiming up to 175kW. I looked up electric car battery capacities. This source suggests between 60 and 120kWh. Assuming all could be charged at the full rate, and that probably is a big assumption, then it would be between 20 and 40 minutes here.

Jupiter again

Jupiter is back in my evening skies. Two years ago it was prominent in September. Last year it was October. Each year it slips by a month. It has taken the Earth a year and a month to catch up with Jupiter again. Obviously in the mean time, Jupiter has also been moving along its orbit. One month forward every year. There are 12 months in an Earth-year so after 12 years, Jupiter would be back to the same place. The orbit of Jupiter round the Sun must be roughly 12 Earth-years.

Even higher pressure

The new high pressure is even higher than the last one. This needs recording as it may be set to drop quickly over the weekend. 

End of coal

Last time we drove past it was still burning coal to generate electricity but that stopped last month at Ratcliffe-on-Soar. That means no more coal burning to generate electricity in the UK.

Waves taller than a church

  During Storm Ashley we found a link to this site. It gives the live data from the buoys in the Atlantic used to feed weather information to the Irish Met Office. At the time, buoy M6 was recording waves 20m high. That's taller than our church tower!

Anti-cyclonic gloom...

... was a phrase used by Tomasz Schafernaker to describe the weather in the UK under a continent-wide high pressure. It's about as high as I've seen my barometer go and is a good time to calibrate them against a known reading. Mine is really close to the BBC reading for Carlisle so that will do.

The conditions won't be doing much for renewable energy. No sunshine, no wind and no waves!

Cumecs

I was interested in the board for the river flow gauge at The Hermitage near Perth. I'd never come across cumecs as a unit abbreviation. 

Durham Geology Map

I loved this map on the pavement outside the Bill Bryson library. They have done their best to make the stones in the pavement match the correct type found in that location.

Here's Cumbria. Wigton is indeed on some lovely red sandstone - but clearly not our easy wearing type!

Units for pressure

This came through my door. Pressure can't possibly be measured in joules. Those are units for energy. 

Durham Cathedral Meridian Line

I found this notice and looked across the cloisters to see one covered over section.

And below is the view from the other side.

Their website says it is quite recent: 1820s. They made a mark at noon when the Sun was highest in the sky on summer solstice. The mark is on the floor.

Repeated at winter solstice and the lower sun puts the mark higher up the wall.

They drew a line between the two. On any other day, when the Sun hits the line it is noon. Watches and clocks can be set by this. The website says this was necessary because devices were less reliable in those days. This was still before train timetables so there wasn't a standard time across the country. This fixed local Durham Mean Time.

Which I guess means I was wrong about Murdoch Mackenzie's Meridian in Kirkwall. It probably wasn't for surveying purposes as a base line but was to fix accurate local time.

And the pressure has gone right back up again!

An impressive rise of 0.5 inHg in 12 hours. 

Bombogenesis

With Storm Ashley raging around us, I was interested in an article that told me about bombogenesis. This article spells out the definition. My barometer works in inches, so it would be a fall of 0.71 inHg in 24 hours. I last set the reading marker a few days ago and it has come down 0.6 inHg in that time. Not bombogenesis but quite a fall. Reading the article carefully shows that it depends on latitude. I can see how but not why. We are 54 degrees North and would then need a fall of 22mb. I converted my readings and had a fall of 21mb, but I think that was over 3 days not 24 hours. It's got me paying more attention to the baromter.

Murdoch Mackenzie's Meridian in Kirkwall

I found the line in the pavement in Kirkwall. 

I was wondering if Murdoch Mackenzie had been working on the time problem on ships. It turns out he was mapping North Ronaldsay. I thought that this must have been the base line for his map against which he made the measurements. But if you read the post on Durham Cathedral Meridian Line from 22 Oct 2024, it's most likely this is a line to fix local Kirkwall time.

Interesting scale

 

This was in the Botanic Gardens at Oxford. Apparently the Scoville Scale is based on chemical analysis. I was trying to work out whether it was logarithmic. But as it seems to be ranked against variety, which is not a linear scale, there shouldn't be a clear spacing between each level.

Colder inside than out

Strange conditions with a wad of warm damp air coming after the house got cold. There is condensation on the outside of the windows because the cold inside is making the glass surface temperature low enough. 

Projecting onto an oblique curved surface

I went to see the brilliant Katherine Priddy play in a tent. The blue spotlights were circular so the beam must have started circular. It hit the tent canvas in the middle top of the photo, spreading out into an almost parabolic shape. A very clear visual mapping from a circle to a parabola. 

Vapour trail

There is a whisp of vapour trail in the middle of the picture. I watched the plane pass. It seemed to go through the high cirrus cloud. Why did the contrail persist there and not elsewhere? Is it that the humidity is high there so it can't evaporate? Is that why there is a cloud there in the first place?

Tare

 I have been aware of the TARE button on electronic balances for several decades but thanks to Mrs B for pointing out the definition in an old dictionary from over a century ago, as being the mass with the container removed. In recent years, it has often been labelled as the "zero" button. Place the container on the balance and press it to make the reading set to zero. It's interesting that it had a usage similar to algorithm. And its other usage: I thought tares were generic weeds but it seems to be specifically Vetch.

Slight aurora

I was out at 9.30pm on an Amber alert and was able to photograph a faint aurora. I was not able to see anything directly with my eye.

Below is another 9.30pm image

At 1.30am after a Red alert, even the camera was struggling to pick up the aurora. The effect is very variable.

Heavy electric cars

This is because electric cars are so much heavier due to the batteries. Can be a bit of a nightmare at festivals if it gets muddy.

The Perseids

Last night the conditions were perfect. A beautiful clear sky. Sadly I missed any trace of the aurora but in my half hour out I did see two meteors. I had a lovely view of Perseus. I have learnt a new word: radiant. I have enjoyed reading about comet Swift-Tuttle. It is interesting that after its discovery in 1862 that they predicted incorrectly the date of return. With something that has a 133 year orbit, it is hard to figure out on one viewing how long its orbital period is because you have to wait so long. It turns out it had been seen before so that made it predictable. And the dust that it left behind perhaps 1000 years ago gives us our annual spectacle.

How long does a solar panel last?

It finally occurred to me to ask what the lifespan of a solar panel is. I found this information from the States. They are suggesting maybe 25 years. It suggests that they will go past the break-even point but it is not as long as I'd expect a roof to last.