Porphyritic granite on the Pentland Road

Hello There's a cutting on the Pentland Road about 2 miles east of Carloway with an obvious vein of big crystal granite in it. Looks like it has intruded  between earlier layers. BGS viewer suggests a vein of Uig Hills - Harris Igneous Complex which could be around 2 billion years old.

The phenocrysts are very like those in Shap granite. 
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But it's quieter inside the car!

Sat inside the car it is 10dB quieter. 

Motorway noise

From right by the motorway. In the 80s of decibels. 

Snowshoes!

These are how snowshoes were in old physics books. They are on the wall of the Tiso cafe in Perth. My feet are approximately 25cm long by 10cm wide. Total area of both feet = 500 square cm. One snowshoe looks to be made of 2 triangles that are 30cm x 30cm and 70cm x 30cm giving area of one snowshoe as 1500 square cm. Total area of both = 3000 square cm. So with the snowshoes the pressure is 1/6 of what it would be. I still find it hard that they are not solid. How does the mesh work?

Not a sundial!

I have got so used to public sundials that I was confused by this. The "gnomon" points east. Then I realised there were no times on the seats.And then that the seats were on the wrong side. Whoops! I'm getting conditioned. 

How long do rainbows last?

This year I am trying to count the number of rainbows that I see. Sometimes the shower stops and the rainbow disappears only for it to start again in roughly the same place a couple of minutes later. Is that a new rainbow or a rainbow that has been paused? There was one part-rainbow that endured for over 10 minutes. There were a series of rainbows that followed the one above and due to the lengthy gaps between the showers, the position of the sun had shifted which meant you could tell the rainbow was not aligned the same way over the loch. Rainbows in waterfall spray can presumably last all the daylight hours and must subtly shift orientation as the sun moves. Philosophically, is a rainbow even a thing at all? Anyway, the questions on ephemeral phenomena are keeping me entertained.

Solar powered!

This truck intrigued me. I wondered if it were a portable solar power unit. But looking at the other side, I wonder if it is actually a solar-powered advertising display. 

Coldest house in the country?

If this cottage really is at 17 Kelvin, then it must be the coldest. Not quite cold enough for the weird quantum properties of liquid helium, but close. 

Further away from a wind turbine

Now about 200 metres away. 

Definitely quieter on average - quiet enough to pick up kids on bikes behind! 

Wind turbine loudness

I stood this close to the turbine and used the dB meter. 

60dB is like the gale through the poplar tree. I wondered if the time interval for the large scale oscillations matched the turbine's rotations. 10 turns in 20 secs means time period is 2 secs. It doesn't match. 

Headphone volume

There was an article in The i on Monday about an epidemic of tinnitus. It links it to prolonged headphone use at high volume. Over 85dB for long periods is bad. It suggests using maybe 60% of full volume on your device to avoid this. I tried my dB app on my headphones. Not sure how good the reading is but it is mostly in the 60s.

Fight gravity!

I loved this car sticker. In a sense, just standing up is fighting gravity. I suppose it means "doing work against gravity" and that is how I have gravitational potential energy. 

Weighing the length

I've been knitting hearts that can be filled with stuffing. I don't have much wool left and was wondering if I had enough wool to knit the two halves. I normally measure length but I don't know how long a section I need.

I'm a bit late to the party on this one but I realised I should weigh it instead. I used the empty tub to get over the low mass cut off - it won't read below 10grams though after that the resolution is 1gram.

And there is enough for the two halves. So an odd bit of metrology.

Magnet recycling

There is a good piece in this month's Physics World about the recycling of rare-earth magnets, citing their roles in wind turbines and electric car batteries. It states that 259 million hard disk drives for computers were shipped in 2021. They tend to go to the tip every few years as a new computer is needed. I have extracted several of the magnets to play with. Previously long-loop recycling was used and the whole thing was broken down, the rare earths being recovered as oxides. Energy is then needed to convert the oxides back into metals before casting alloys, reducing this to powder and then turning the powder into metals. Under a new short-loop process the rare-earth alloys break apart to form a powder after treatment with hydrogen. Much less energy is needed so if it scales up well, this process is probably the future!

How loud is the storm?

I've posted about the sound spectrum of the wind in this big tree but now I've got a dB meter. We were sat in the greenhouse sheltering from the wind and Storm Kathleen was raging. Peak volume from the tree was over 80dB. Some sources have that as being "busy traffic", which seems about right.

There were quiet lulls as well. Interesting to note that these lasted about 5 seconds.

Energy in petrol

This wrecked exhaust silencer shows the energy in even a small amount of petrol. An Internet search reveals varied answers but one gallon of petrol contains the same energy as over 10 sticks of dynamite. This has led me to find more information on the energy density of fuels. This site gives diesel as containing more energy per litre than gasoline whereas this one has them about the same for energy per kilogram. This is because petrol is a little less dense than diesel. That said, it is litres that I put into the tank, not kg. I was also interested in the Gasoline Gallon Equivalent.