Nine o'clock Oxford time

I had a room opposite Tom Tower in my second year. The bell rings 101 times at five past nine in the evening which was a nuisance at times! I understood that it was to summon the students back in for the night but I could never understand why five past nine. It turns out that it is a result of G.M.T. When the railways made a common time for the UK vital to keep trains running on time, the idea of using the Sun highest in the sky in that town as noon went out the window. Time was now fixed by noon at Greenwich. Noon at Greenwich is five minutes ahead of Oxford, so by ringing at five past nine G.M.T. the bell was still being rung at the true 9pm local time.

Brilliant programme about Einstein

To celebrate 100 years of General Relativity, the BBC have made a great documentary. Here's the link http://www.bbc.co.uk/programmes/b06s75vs It will be valid for a couple of weeks.

Max Min Thermometer

 I got a wonderful present from Mrs B at the weekend - a Max Min Thermometer. This is also known as Six's Thermometer after its inventor. It is a U-shaped thermometer which records the same temperature on both sides. If you look carefully you'll see that the number scales go in opposite directions on each side. Each side also has a small steel marker in the tube. These record the maximum and minimum temperatures in a given time period. They stay where they are and you have to use a magnet to pull them back to the end of the coloured liquid to allow the process to start again.

 It works because there is a clear liquid in the tube that records the minimum temperature (left hand side above and right hand side below). This expands and contracts with temperature pushing the blue temperature recording liquid round. Above the blue liquid on the other side is a vacuum - nothing to stop the blue liquid moving round the tube.

Earthshine - lighting up the Dark Side of the Moon?

Look at this picture of a crescent Moon, taken around dawn. The bright crescent is all we can see of the half of the Moon that is facing the Sun, given the angle that we are viewing from. You'd think that the side facing the blackness of space would be dark. But you can see it because sunlight reflects from the Earth back up onto the Moon, lighting it dimly. It's like the full Moon shining on Earth - that was bright enough for us to walk in the hills last year. Now I am aware that the phrase Dark Side of the Moon doesn't mean the side out of the light - that's another story - but it sounded nice in the title!

Isaac Newton's prism experiments at Woolsthorpe

I had my "fan boy" trip to Woolsthorpe - as close as it comes to visiting a shrine in Physics! The top picture is the window that Isaac Newton used for his light experiments. A later owner enclosed that part of the room so these days light can't go as far as it did in Newton's diagram. I knew that he had used one prism to split the white light into a spectrum and another to pull it back into a white light. I was only vaguely aware of his other experiment: he took the spectrum and used a slit to take only the red light which he then put into a second prism. Only red light came out of the second prism. He was intent on disproving a theory then that light was colourless and that the glass itself gave the light all the colours of the spectrum. Each experiment shows that the glass is not adding colour. I need to read more about the nuances of why both experiments were considered necessary.

Making measurements with Searle's apparatus

We have been using Searle's apparatus to gather data that we will use to find the Young Modulus for steel wire. It is the same sort of scale as on a micrometer screw gauge. The vertical scale on the left hand side is measured in mm from 0mm to 10mm. One complete turn of the central barrel moves the leveling apparatus by 0.50mm. You start by taking a reading on the left hand vertical scales using the top of the rotating barrel as your marker. The problem is that it takes two complete rotations to move the 1mm between scale divisions on the vertical scale. So you have to make a decision about whether you are below or above 5.5mm for the situation shown in the picture.I think we are below, so we take 5.0mm and add the reading from the barrel, taken where it meets the vertical scale. It is 36 to the nearest whole number. Hence the reading is 5.0 + 0.36 = 5.36mm.

Planets in line and the ecliptic

This was taken on Tuesday morning. The Moon has since disappeared but as well as Venus along the diagonal line with the Moon in the photo, I was able to pick out Mars and Jupiter this morning. They are all in a line because they are all in the same plane in orbit around the Sun. The dust and ice from which the planets formed was pulled into a single plane as the Sun rotated in its formation. The line up in the sky is called the ecliptic. So why do I see them along a line at 50 degrees to the horizontal and not along a nice horizontal line? In part, it's because the Earth doesn't sit properly upright. It is at an angle of 23 degrees to the ecliptic. I then tried to work out how much of the rest is because of the latitude. Wigton is about 54 degrees north so we are standing at an angle to outer space! The 3D geometry is beyond me tonight.

Gales in Wigton: what causes the wind?

Gales in Wigton again today! One of my classes asked me what causes wind. The answer is basically convection. Hot sunshine on the Equator makes air expand, become less dense and float upwards. What goes up must come down. In the Northern Hemisphere it comes down over the latitudes of the Sahara desert. Then at ground level it flows back to the Equator. There is another cell like this taking air up from Europe and down over the Arctic. It is symmetrical in the two hemispheres. It is the joing up at ground level to complete the loop that gives us our winds. They don't go north/south because of the turning Earth but that's another story.

Measuring Storm Desmond in Wigton

I posted the picture above a couple of years ago to show the base level of the Wiza on Station Road. I took the picture below on Saturday afternoon. By comparing the two, the water level is 1.9 metres higher.

I hadn't thought to empty our bucket rain gauge in the garden ahead of the deluge, so this is what collected in a Wigton garden over the last 2 weeks:

That's about 180mm. Nearly twice that fell in a day over the highest ground in Cumbria.

Angular velocity at Isaac Newton's house

I finally made it to Isaac Newton's house at Woolsthorpe in Lincolnshire. This exhibit was in the science centre. You push the ball round the circle and it decays into the centre. I am thinking about the shape. If it represents gravitational potential in the Solar System, then perhaps it is a 1/r shape. The photograph exposures should represent equal time periods. Thus we can comment on the angular velocity as the ball moves from the outside to the centre. In the top photograph, it manages 90 degrees. By the second photograph, the trace of the ball is twice as long - the angular velocity has doubled. In the final photograph, it has doubled again to complete a full 360 degrees. It is true for the Solar System that angular velocity is bigger closer in. I will look in to making measurements of radial distance from the photographs to quantify the relastionship.

Meine Tasse ist in der Einleitung von Physik im Advent

Sie müssen die Filmen von Physik im Advent zusehen.  http://www.physik-im-advent.de/index.php?language=de&MODsid=utjljpou0jlq0oqloborvo44p5 Da können Sie meine Tasse sehen. http://wigtonphysics.blogspot.co.uk/2015/11/verdunnen-schwerkraft-auf-meine.html

Isaac Newton and the Wigton floods

I was fortunate to be able to go to Isaac Newton's house at Woolsthorpe near Grantham at last. His most famous work is the Principia Mathematica. What I didn't know was that the middle section of the book was about fluid mechanics. And the pictures below show a body of fluid in Wigton today...

Apparently Newton wrote about the effects of friction and viscosity on the flow of fluids. At the edge of the river, friction from the bank acts on the water, slowing it down. Then he modeled the water as moving in layers, each one affected by the pull of the one outside it. This pull of a liquid is called its viscosity. Hence the fastest water flows in the middle. So important was the work that they now talk about Newtonian fluids. I used to know about these things so I need to re-read it.

Laser distance measurer

I got to play with a laser distance measurer. It fires a pulse of laser light at the wall and times how long it takes to come back. See below for the distance. You can shine it an angle.The light scatters a bit so no matter which angle you shine it, some comes back to the handset.

 It was more fun with a mirror where the scattering didn't work. So the laser light bounced off the mirror up to the ceiling, scattered from that and then back the way it had come, Impressive.