The Blob: slime mould and networks

 This week's science TV turned out to be fascinating. I'd noticed in the Biology text book I was reading that slime moulds don't fit in normal 5 Kingdom categories. I was interested that Toshiyuki Nakagaki at Hokkaido University is referred to as a biophysicist and I can see why because of the way he is using slime moulds to come up with optimal networks. You've got nearly a year to watch the programme https://www.bbc.co.uk/iplayer/episode/m00103fr/the-blob-a-genius-without-a-brain

Systematic error in reflection experiment

 This is how it should be. The angle of incidence from the normal line (90 degrees) is 50 degrees and so is the angle of reflection.

Here the mirror has not been set on its base line correctly. The incident ray is still where it was but the angle of reflection is 56 degrees. This is a SYSTEMATIC ERROR because every single reading made from now on will be 6 degrees out for the same reason.

Note that the mirror is only 3 degrees out along the base line. That moves the normal line by 3 degrees increasing the angle of incidence to 53 degrees although the incident ray looks as though it is in the same place. Hence the angle of reflection also increases by 3 degrees. 3 degrees on each side of the normal means the line seems to have moved by 6 degrees in total.

LED bollard lights

 Having seen a grey cone inside the pedestrian light bollard on the camp site during the day, I was interested to see how it worked.

Close up there was a circle of LEDs out of sight. I wondered whether the grey cone was fluorescent or just reflects. 

One reason for ruling out fluorescence would be that the LEDS emit visible light. The coating on a fluorescent tube is because the light emission process in the gas produces ultraviolet that we can't see. I suspect reflection because of what you can see in the two photographs. In the first photo I must have been at the angle to which the curve is designed to reflect. Dropping down to photograph the inside meant the angle wasn't correct and it wasn't as bright.

White-tailed lapwing: telescope eye ring or Airy Disc?

We went to see the White-tailed Lapwing at Blacktoft Sands. I have a primitive system of taking photographs through my telescope.

 

I have problems getting the camera aperture into the right place for a photograph and you get odd effects like the one below. 

My first thought was the Airy Disc for an aperture because it is a bright central disc. But it is a true image around the edge instead of the required black circle minimum. So is it to do with the eye ring of a telescope. The eye ring is put in place so that the eye is positioned at the place where all of the light from the objective lens is focussed: it all passes through a disc at that point. The total image disc is smaller for the this effect. I need to come up with a different way to test this.

A strange model of the ear

 

I made a functional model of an ear. The funnel is the pinna, focussing the waves into the cardboard tube that represents the ear canal. This takes the vibrating air inside the head where it hits the ear drum, represented by a stretched balloon. The whiteboard pen represents the ear bones and a balloon filled with water represents the cochlea with the wires representing the auditory nerve. The ear bones are necessary because when sound travels through gas to hit liquid most of it is reflected. This is why in an ultrasound scan, gel is put between the transducer and the body. In the ear, the bones act to stop this happening. I've seen it called an example of impedance matching. The way that the bones act as levers also magnifies the oscillation so in a sense the bones act as an amplifier.

This week's amazing TV documentary: neutrinos

 I can remember being told when I was at school about an experiment with a large vat of dry cleaning fluid deep underground and I've heard lectures on neutrino oscillations in recent years. But this week's BBC4 documentary explains it all really clearly https://www.bbc.co.uk/iplayer/episode/m000zwqr/neutrino-hunting-the-ghost-particle

Biomass of a sunflower

 This sunflower has been the subject of much speculation this summer as to how tall it is. We decided to find its biomass as well.

It was 3 metres 2ocm long.

We weighed it like this, having cleaned as much soil from the roots as possible.

Repeat readings for mass were 4.7kg, 4.6kg, 4.5kg and 4.4kg. The balance kept turning itself off. Not sure if there was some drift there but mean is 4.5kg if we round down.

Almost all of that is from carbon dioxide and water over the space of 4 months. It is a wet biomass because it has not been oven dried so contains liquid water. The flower head is about a quarter of the total mass.

The Last Artefact: brilliant TV

 There's a brilliant programme on the BBC iplayer explaining the problem of having a lump of metal in Paris as the definition of the kilogram and how work has been done to stop the kilogram being dependent on a single object. It says the programme is available for over a year. https://www.bbc.co.uk/iplayer/episode/m000znw3/measuring-mass-the-last-artefact

Using Vernier callipers

 We've been using Vernier callipers to make measurements. There are two scales. The fixed scale has a resolution of 1mm but is actually marked in cm on these callipers. The sliding scale has not numbers on it and is etched into the bottom of the window.

The left hand mark on the sliding scale is used as the marker for where we are on the fixed scale. I've used a red arrow to show this. The asterix marks the 1mm mark. Our marker has just gone past it so we have a reading of of 1mm + a bit. We get the bit by seeing where the marks on the two scales actually line up. I've marked that in green. I now count how far along the sliding scale that happens: 5 marks. So  my reading is 1.5mm. This Vernier scale allows us a resolution of +-0.1mm.

Looking for stone axes on Pike of Stickle

 I ventured down into the gully in search of the famous stone axe factory.

I didn't get down as far as the cave but I did find the reason they were working up here.

Quite clearly these rocks are not pre-historic but they do have very sharp edges on them. It's that property that made them so valuable. This shows that the axes made it all over the country and says that the rock is greenstone. Searches suggest greenstone is quite a vague geological name. This area is geologically very complex. This brilliant guide has a picture of the Langdale Pikes towards the end with bands of volcanic rocks labelled. Did I get down as far as Crinkle Tuffs? My rock is very fine grained. More research to be done.

The power of plants

 We found plants growing through the asphalt on the cycle track at Allonby.

I was wondering what force a plant would have to apply to puncture the asphalt and whether it is easier to do from above or from below. Experimental data would be helpful but in the absence of that, here's an idea that will probably lead to a wildly wrong answer. I looked up the compressive strength of asphalt as being between 20 and 35 MPa. Now Pascals are a measure of pressure. Take the lower figure and equate with force/area. Estimate the area as 2cm x 2cm. That gives a force of 10kN or 1 tonne mass, half of a car. It seems unlikely that this small plant can deliver that and a flaw is that for compressive strength there is usually equal push inwards from top AND bottom surfaces. Thus there is no chance of bending so the figure will be lower here where the upper surface has distorted and cracks made it weaker. Even so, the plant must be delivering quite a force.

Halteres on a crane fly

 I bothered to look at a crane fly through a magnifying glass for the first time this morning. I noticed two stalks coming out of the body with a blob at the end, one on each side, a bit like dumbbells. It occurred to me that these could be to do with stabilisation in flight.

It turns out that they are called halteres. They are actually sensors that give information about rotation in flight. The article compares them to gyroscopes and says that the Coriolis Effect comes into play. I'll need to consider how that actually works here.

The Fake Lava Experiment

 We got a test tube containing a white solid chemical called salol.

We placed it in a beaker of boiling water and the solid melted to form a clear and colourless liquid.

Then we poured the liquid onto two microscope slides. One had been in the freezer until just before the experiment and was noticeably cold. The other microscope slide had been in a warm oven. It took about 5 minutes for the liquid to solidify and form crystals on the cold slide. It took 45 minutes to solidify on the warm slide. In the picture below, the cold slide is on the left and the warm slide is on the right.

The crystals on the cold slide are smaller because they solidified first and did not have as much time to grow. The crystals on the warm slide are bigger because it took a long time to solidify so the crystals had more time to grow. Rocks that solidify from hot molten liquid are called IGNEOUS ROCKS. If the molten rock reaches the surface by coming out of a volcano, we call it LAVA. If it gets trapped underground and cools we call it MAGMA. In the picture below, GRANITE on the left forms when molten magma underground cools very slowly to form large crystals. BASALT on the right forms when lava comes out of a volcano in the air or water which cools it really quickly so it has tiny crystals that are really hard to see.

All igneous rocks have randomly arranged interlocking crystals. There are no layers or any obvious structure. The basalt is called an EXTRUSIVE igneous rock because the molten lava came out onto the surface of the Earth through the EXit of a volcano. The granite is an INTRUSIVE igneous rock because it never escaped from the inside of the Earth and was kept IN the Earth to solidify.

What's in a capacitor?

 Whilst ratching in the cupboards, I found a capacitor that one of my predecessors had cut open. I've always been too compliant to wreck things!

I teach capacitors as two metal plates with a gap between usually filled with an insulator. Here we should have two aluminium foil strips with paper in between that has been soaked in an electrolyte. Now if you roll that up, you'd have the aluminium shorting as the strips touched each other and so a second paper strip makes a four layer stack to be rolled. It doesn't look like this one has survived intact. 

There are good pictures and diagrams here.

Motor glider

 

Yesterday afternoon I heard the quiet hum of a motor above but instead of a micro-light, I saw a conventional glider. The picture is confusing - I was too late to get a good picture of the glider and inadvertently photographed an insect as well. https://en.wikipedia.org/wiki/Motor_glider explains what is going on. I will take a closer look next time.

Invisible ink at the wedding

 I was shown this trick at Sarah and Matt's wedding reception. You can't see anything on this paper.

Now you can. Guess who wrote it for me!

What's going on here ties in with what I was telling my Applied Science class. This is how reflection works. A photon of light enters an atom, as shown below. The energy helps an electron to go several energy levels.

When the electron falls back, it loses energy again by firing out a photon, which is what we see.

The electron arrangement in the ink is clearly such that ordinary light does not have enough photon energy to allow emission of photons that we can see. Ultra-violet light has more energy in its photons. However, surely the re-emitted photons would be the same invisible high frequency. What must be happening is that the electron doesn't fall straight down but jumps from one energy level to another, releasing some photons that can be seen by the eye.

Thinking about the diabolo

 

Thomas Trilby did some great diabolo tricks. I know that these are based on the physics of Conservation of Angular Momentum. I found a nice short film that explains what this means as applied to some of the tricks. Apparently the diabolo is related to the yo-yo,

Thomas Trilby's amazing thin film interference patterns

 Thomas Trilby's Circus act at Prospect Farm was the best thing I've seen in years. So skilful and also so funny. He made huge soap bubbles using string on poles.

The thing I noticed about the bubbles was the way the colours graded at the bottom to produce a rainbow spectrum with red at the bottom of the bubble up to violet towards the middle.

I know that bubbles produce colours by thin film interference. Some light bounces off the outside. Some continues through the bubble's liquid shell. When it hits the end of the liquid layer, more bounces back and the rest carries on through the bubble. White light is made of colours - light of different wavelengths that mix. If the precise distance the light has gone from the front of the thin film of bubble mix through to the inner edge of the bubble mix, if that is precisely a multiple of the wavelength of a particular colour, then that's the colour you see. Red has the longest wavelength and at the bottom of the bubble, the liquid is most curved. So from my viewpoint the light will have travelled furthest. This explains the grading of the colours.

Ancient oscillations in Wigton?

 

The initials SHM will always excite a physicist. I've been walking past this stone on Station Road for years. Simple Harmonic Motion is when the acceleration is proportional to the displacement from the equilibrium position and the acceleration is always directed back towards the equilibrium. Pendulum motion is approximately SHM for small displacements.

Absolute and apparent magnitude

 St Mary's in Wigton is famous for having gold stars painted on the ceiling of the chancel.

Some of the stars are bigger than others. It's like that in the night sky - some stars look brighter than others. The Greek astronomer Hipparchus decided that he could discern 6 levels of brightness and this has turned out to be reliable to this day. The brightest stars he called 1 and the dimmest 6. This is called the apparent brightness because it is what it looked like to his eye. But the differences in brightness could be because one identical star is further away than the other - or that two stars of different intrinsic brightness are the same difference away. This intrinsic brightness is called the absolute magnitude. To put this on a scientific setting, it was decided to calculate how bright each star would seem if they could all be moved to the same difference away - 10 parsecs. This distance appears in the equation linking apparent magnitude m and absolute magnitude M. It is m - M = 5log(d/10) where d is the distance to the star in parsecs.