Modes of oscillation of tractor aerials

 

The tractor pulling this trailer had two very flexible long radio aerials that showed two modes of oscillation. The first was the waving backwards and forwards from the base, like a tree in the wind. I'd have said the time period was roughly 1 second. The second mode seemed to be the third harmonic - so that there were two discernible nodes dividing the length by three. This would make the frequency 3Hz and thus the time period to be 1/3 of a second. I tried to count oscillations in 10 seconds but it was too quick, suggesting that the estimate for time period is probably correct.

A natural magnifying glass

 

Look how well these rain droplets are magnifying the cells on the back of the leaf. The droplets are vaguely lens shaped. That said, there is no distance at all from object to lens so it would make drawing the ray diagram difficult.

Light Water at Bannisdale

 

This is the bridge over Light Water at Bannisdale near Kendal. There's supposed to be a parking place here but it was coned off when we went. There is better parking just off the A6 at 545013. The use of Water as a stream name is not common in the Lake District; it is used in the south of Scotland. However, it got us thinking: Light Water as opposed to heavy water. Heavy water is water where the hydrogen is the isotope deuterium - ie the hydrogen nucleus contains a neutron as well as a proton. I was amazed to discover that the concept of light water does indeed exist - it is called deuterium-depleted water. It turns out that ordinary water contains a very small amount of deuterium and any water with less than this naturally occurring amount can be called light water.

Under pressure at St Mary's

 

I've begun to notice that the floor in some pews is very pitted. Physics text books always give examples of stiletto heels being banned on wooden dance floors. Here's the evidence. The books go on to explain that the small surface area on the end of the heels means a high pressure and that it is pressure that results in damage, not the size of the force itself, at least if that's the weight of a human being.

Little tunnel with echoes; big tunnel without on the way to Threlkeld

 

We walked the old railway line from Keswick to Threlkeld. The longer tunnel has been reopened. A child was trying to make echoes inside but it was acoustically dead. Later we went into the much shorter tunnel. This one had very clear echoes.

So question of the week is about why this happens. We noticed that the long tunnel was not at its original depth. You can tell because the recesses for the workers to hide in when the train came past would only accommodate very small children now! The short tunnel is much deeper. Is that the reason? Or is it to do with the length? I also need to think about possible changes in acoustic impedance as the air goes from the enclosed tunnel out into the air. Is that enough to cause a significant reflection? We were in the middle of the big tunnel when we concluded that there were no echoes. Might there be echoes closer to the end. I have found no answers yet but I have found this brilliant webpage about a tunnel in Sheffield that might need a visit!

A circular spectrum

 This amazing umbrella was being used as a sunshade. I love the circular idea because of the way it suggests that violet blends into red. I can see the logic in this because the secondary colour magenta is a mix of red and blue. You can't say violet is a mix of red and blue but by blurring it all with a secondary colour.

The 2022 warm period

 

It is very rare for the Galileo thermometer to shift in our house. I'd say that the temperature range 0f 18 to 26 degrees Celsius is too high - 14 to 22 would capture most eventualities. This week warm weather has finally reached Cumbria and we've reached the dizzy heights of 22 degrees Celsius. In this thermometer, the clear liquid in the column reaches thermal equilibrium with the room. This probably takes a long time through the glass. Today the liquid's internal energy increases as the particles gain more kinetic energy. The liquid expands and becomes less dense. The glass balls are sealed so their mass and volume are fixed, and hence their density. Things float if they are less dense than the liquid in which they find themselves. As the liquid becomes less dense around them, they sink.

Not the Medieval Warm Period

 

The history displays in Kentmere church are awesome. I was interested in two things here. The first is the error range in the radiocarbon dating. That should mean the absolute error is +-150 years to give a range of 300 years but sometimes usage slips. The second is Medieval Warm Period. I know nothing about this so looked it up here. It's the period that Greenland was colonised by Vikings. And as it is said to start in 950, that means the +-150 years reading must be correct.

Great film about the Jet Stream

 There is always talk about the Jet Stream in weather reports these days. Click here for a brilliant short film about it from BBC weather. It interested me that the biggest temperature difference is in the winter, meaning that the cooling of the Arctic in the 24 hour night must give a bigger differential than the heating of the lower latitudes in summer. Will this change as the climate warms? If there is a warmer Arctic, could the Jet Stream be less pronounced.

Force not Force: a trip to The Forces in Deepdale

 The waterfalls at the head of Deepdale near Brothers Water are named "The Forces (waterfalls)" on the map. I know that the word "force" for water fall comes from a Viking word. I was wondering if "force" in Physics was the same. I should have remembered - it comes from the Latin word "fortis" for strong. This is a bit like a linguistic convergent evolution.

And here's the view down from Link Cove.