Brilliant programme about gravity

You've got a few weeks yet to watch Jim Al-Khalili's brilliant BBC4 programme about gravity. I enjoyed the road trip to try to measure the strength of gravity on Snowdon and on the Dartmoor Tors. I was also pleased that a professor refers to mass as the"stuff you are made of". It's not just me then. http://www.bbc.co.uk/iplayer/episode/b08kgv7f/gravity-and-me-the-force-that-shapes-our-lives

Strange foam stripes on Hayeswater

An odd day in the autumn: the wind was blowing down the length of Hayeswater. The plane waves stretch out sideways across the width of the tarn. But foam made lengthwise stripes along the tarn. The foam was perpendicular to the wavefronts. I have seen similar before but have no idea why as yet.

Testing for products of combustion

We set out to prove that water is made when you burn a fuel. the problem is that it is in the form of water vapour and you can't see it. So we used a beaker of ice to make the water vapour condense on the outside. We used anhydrous cobalt chloride paper, which is blue. It turns pink when it touches water. There's our proof. The colour change must be related to a change in the electron energy bands on accepting water into the molecule.

Roche Moutonee in Windgap Cove

I spotted this roche moutonee from Steeple. It shows the direction of ice movement during the Ice Age. Ice flowed from the top of the corrie on the right hand side and was able to wear this hard rock into a ramp. At the bottom of a glacier the ice melts because there is a massive pressure. In ice the water molecules are spread out. We know this because ice is less dense and floats on water. But pressure forces the water molecules close together making them back into the liquid water configuration. Look at the phase diagram for water half way down this page https://science.nasa.gov/science-news/science-at-nasa/2000/ast29jun_1m It looks as though ice at 0 degrees Celsius will be melted if the pressure increases above 10 atmospheres. Anyway, the melt water trickles down the far side of the rock where it gets into gaps, is no longer under direct pressure so that it freezes and expands, shattering the rock. As the glacier moves on, the ice is dragged along taking the shattered rock with it. Hence the broken crag on the downstream side.

Low Ling Crag: diffraction around

I love Ronald Turnbull's work and I found an interesting picture on his website http://www.ronaldturnbull.co.uk/pics/geopix/Pages/16.html It reminded me that I'd seen a tombolo at Low Ling Crag on Crummock Water. Waves diffract around objects that are roughly the same size as the object if the object is round. The island looks far too big for it to be this. I have posted before about knife-edge diffraction round the ends of a long narrow island http://wigtonphysics.blogspot.co.uk/2014/06/knife-edge-effect-diffraction-and.html I would suggest that it is this that has happened here. The diffracted waves will have brought sediment from both sides and deposited it.

Flame tests

We soaked the splints in aqueous salt solutions and put them into flames. The cations were lithium, potassium and sodium. The colours are produced because the thermal energy moves electrons up through the energy levels. As the electrons lose energy and de-excite, they emit photons of visible light. The frequency (and hence the colour) of that light is proportional to the energy lost in the de-excitation. This experiment shows that the electron energy levels are arranged differently in each element.

Alpha source also emits gamma

 This is the alpha source. It is being detected through the sides of the GM tube. Since paper will stop alpha radiation, it can't be detecting alpha. The emission of an alpha particle leaves the nucleus in an excited energy state. It then loses energy by emitting gamma ray photons. I was interested in using the alpha source as another option for showing the inverse square law decay in gamma ray intensity with distance. As the photographs show, the range of readings is not really good enough. I was using the most sensitive setting and still only getting readings precise to 1sf.

Counting cars on the M6

We were travelling north at 60mph. Let's assume that the cars travelling south were doing the same. I counted cars for one minute. That would be the same as me being still and them coming towards me at 120mph. We passed 60 southbound cars in one minute. That would the equivalent of 30 per minute at normal speeds. Not too bad. I once counted about 100 cars per minute south at Leicester Forest East one Sunday night.

More About Bat Radar

More About Bat Radar were an 80s student band fronted by my brother's friend. Here's a TV programme that tells you more about bat radar and you can actually see bat ultrasound (so it's really sonar not radar). http://www.bbc.co.uk/iplayer/episode/b08h9ctd/sound-waves-the-symphony-of-physics-series-1-2-using-sound I watch a lot of Science TV but this is one of the best I've seen because it tackles things that I've never really bothered with and yet turn out to be really interesting. And the moment when a deaf woman gets to hear again is fabulous...

Least action on Birkhouse Moor

I've been reading a lot of Classical Mechanics recently. I've come across the Lagrangian for the first time and the Principle of Least Action. Lagrange based his mechanics on the arithmetic difference between kinetic and potential energies summed over different paths. The actual path was the one with least action. The book by Leonard Susskind that I'm reading is adamant that it should really be stationary action. He says that dA should be zero. I was looking at the book and then thinking about it on Birkhouse Moor yesterday.

This is a saddle point. From where I was looking the ground goes down and then up to the summit. From the left it comes up to the saddle and then down to the right. If A were to be the height about sea level, then going from where I was stood to the top of the fell, A would go down and up again. If I stood in the middle of the saddle and moved a tiny distance in any direction, A would not change. It would be stationary. This seems to be connected to going from the Lagrangian to the Euler-Lagrange equations.

Huygens' Construction at Glencoyne

We sat on the beach at Glencoyne looking at the view down Ullswater. Then I noticed the action on the shore line...

Incoming plane waves were reflecting from individual pebbles to produce a whole series of semi-circular ripples that spread back out into the water. You can see in the next two pictures that as the semi-circles expand, they coalesce to form another plane wave. This is Huygens' Construction. Huygens worked out what happened to a plane wavefront by breaking it down into point that sent out semi-circular ripples called secondary wavelets. He then worked out where the next wavefront would be by seeing where the semi-circular ripples coalesced. I have known the theory for years but had no idea that it was possible to see such perfect examples. Perhaps this is how he came up with the idea himself.

An odd thing about gamma rays

One problem with using a gamma source and a Geiger-Muller tube to detect gamma rays is that we can't be certain whereabouts in the metal case the actual gamma source is and we cannot be sure whereabouts in the GM tube the detection occurs. This causes a systematic error in the results. An odd way round is to turn the source so that it fires into a solid plate and to turn the GM tube on its end. Enough gamma rays still escape the side of the source to be detected and they can get through the sides of the GM tube to be detected. The centre to centre distance is more certain.

Hutton's Unconformity: A pilgrimage to Siccar Point

 This lonely headland between Edinburgh and Berwick is said by some to be the most important geological site in the world. It was the evidence that James Hutton needed 250 years ago to prove that the world is far older than the 6000 years claimed by interpreters of the Bible. He'd been watching the erosion of rocks on his farm and the deposition of sediment. He realised that sediment forms in horizontal layers with the youngest on top. The sandstone in the top picture is almost horizontal, just tilted slightly towards the sea. But look at the vertical layers in the picture below:

 The rock in the vertical layers is greywacke. This was formed when there were avalanches of debris down the edge of the continental shelf into deep water. The rock is formed of coarse grit and is hard enough to resist erosion. Between the avalanches, layers of fine mudstone formed and these have been worn away to leaves the gaps you can see. Hutton realised that the greywacke formed first because it is under the sandstone. Earth movement tipped it on edge and then it was eroded. Later the sandstone formed. The lowest sandstone layers even have greywacke pebbles in. The unconformity shows that the rocks on Earth were not produced in one seamless event. The events described don't take 6000 years.

Calibrating the tea leaves in Gourrock

We went to Gourrock on the Clyde to see their Bonaparte's Gull, over from America. We enjoyed a trip to the coffee shop whilst waiting for it to appear. The tea timer was a novelty. It's been calibrated and the scale divisions look even - which assumes a constant rate of tea leaf ascent. But the slightly imprecise labeling of the scale made me smile.

                                       

More water in South Wales

The tall thing in the middle of the picture is a kind of fountain in the square outside the opera house in Cardiff Bay. It's metallic and water runs down the sides. The water had clearly reached terminal velocity by about 1/3 of the way down. It was no longer accelerating. This is because the water is hugging the surface so there are drag forces between the surface and the water. By 1/3 of the way down, they must equal the pull of gravity on the water.

Misunderstanding Cardiff Bay barrage

I've always associated barrage schemes as being ways of generating electricity. The problem is that they need the tide to flow through the barrages. The barrage in Cardiff Bay was built to create a freshwater lagoon - a permanent artificial lake - and to stop it being tidal. So the barrage is not an electricity generator although it must let water out from the river Taff or else the water levels would rise and rise. However someone has proposed building a proper tidal lagoon outside the barrage and into the Severn Estuary in the area shown below

See http://www.telegraph.co.uk/news/earth/energy/11445579/Cardiff-tidal-energy-lagoon-could-power-every-home-in-Wales.html The article explains well how such a tidal lagoon generates electricity. There are turbines in holes in the dam wall. Start with the lagoon empty and close the holes whilst the tide is coming in. The water level outside is higher than inside. Just as the water level peaks, open the holes and the water flows into the empty lagoon, generating electricity in the turbines as it goes. When the water levels are the same inside and out, shut the holes again and wait for the tide drop the water level outside the lagoon. Then open the holes again and let the lagoon empty, with the water generating electricity as it flows out.