Norwegian Jade on the horizon

We spotted the Norwegian Jade cruise ship from the beach at Rosemarkie. If my little finger subtends 1 degree then the ship subtends 1/6 of a degree or 0.0029 radians. If the ship is 50 metres high, it means by the arc length rule that it is about 50/0.0029 = 17188 metres away. 17 km is about 10 miles.

Feedback about my band

I'm in a band. We played a well received gig recently. Parking the guitar in front of the amp is a god way of attracting feedback. What's happening? Well, I knew that the amplifier sound waves coming out of the amplifier make the vibrations bigger, but which vibrations? I had thought it would be by making the strings vibrate more - a resonance effect. According to the Fender website, it is that the sound waves make the pick up coils vibrate and this is called having the pick ups go "microphonic". https://www.fender.com/articles/tech-talk/friend-or-foe-a-feedback-primer The frequency at which pick up coils vibrate is very high because of the thin wire from which they are made, hence the very high frequency squeal.

96 dB: the sound of the summer

My lawn mower claims to be 96dB. I used a digital meter to test that claim. Sat right on top of the grass box, it was claiming >100dB. But intensity diminishes with distance and it turns out that the claim is correct where my head is. I have read that 120dB is the threshold of pain. This is nowhere near. A source suggested you might be all right for 4 hours at this volume. It wouldn't be a pleasant 4 hours though because it's not a nice noise.

Hugh Miller of Cromaty & American Gods

We visited the house of Hugh Miller, the Scottish 19th Century geologist and social activist. The lovely modern garden had the above quotation from him carved in stone. I've been reading Neil Gaiman's novel American Gods. On page 152, the lead character says: " All we have to believe with is our senses:the tools we use to perceive the world, our sight, our touch, our memory. If they lie to us, then nothing can be trusted." Hugh Miller is now lauded as an acute observer rather more than as a theorist. Senses were everything. 

More polarised light at Loch Brandy

Here are two photographs taken with a polarising filter at 90 degrees turn between shots. Notice that a small cloud bottom centre looks black in the top photograph and bright gleaming white in the bottom photograph. My shoulder was to the sun so the sky should be polarised. I think the blue is polarised but the white scattered light isn't. Top photo features more white.

A trace of lenticular cloud in Glen Clova

This picture will need expanding to see the detail. It had all but disappeared by the time I was able to stop safely for the photograph. The main bit of the lenticular is middle left but to the right of this there is the trace of the top of a wave shape - just the upper whisp of the lens shape. Maybe here we have to "loops" of a stationary wave, as I call them in class. Putting the two together gives a full wavelength. Sadly, there is nothing to measure the scale against. There is no knowing how far away the clouds are.

French power lines

I'm always a sucker for foreign power lines. These ones in Normandy look like the pylons have horns. That's because there are two earth wires running along the top. These earth wires protect against lightning strikes. I wonder whether these offer more protection than our single lines.