What happens to all that water?

 

On Christmas Eve the wind was blowing hard from the south creating large waves on Coniston Water. If you enlarge the pictures you might see the waves. You can see the raised water level in the second picture. It made me wonder what happens to the water. If the surface water is all being pushed to the northern end of the lake, what happens? Does that mean that the water level is higher at the northern end and that the lake acts as a sort of pumped storage scheme? Or is there a counter current below the surface moving water back south in a manner akin to a convection current? I've been considering how to make lab models to check these hypotheses.

White water

 

The weather has been miserable recently - one big Atlantic storm after another. We got the edge of the awful pre-Christmas storm that battered the south. There were high winds and a lot of rain. If you enlarge the picture you'll see the prominent white water in the waterfall on this outlier of Wetherlam at Coniston. It got me thinking: why is turbulent water white? The water is full of bubbles and split into lots of drops. There are many reflecting surfaces and light is reflected in many directions, a form of scattering. White means that all colours are being reflected equally in our direction. This is a sketch of an answer - what I've been thinking about the issue.

The final quarter

 

This was the final quarter waning Moon taken on Christmas Eve at breakfast time. The evenings were much darker in the last week or so with the Moon rising after midnight. This morning we were back to the final crescent which was the first photo graph in this series, taken a month ago. I think the New Moon is New Year's Eve.

Oxford's Christmas Light Festival

Oxford was geared up for Christmas. Many religions use the metaphor of light in the darkness. So Oxford hosted what they called a "Christmas Light Festival". As a physicist I'm programmed to study things dispassionately - objectively, we like to say. But human animals are also programmed to respond to things emotionally. So in the pictures below you see scenes in which photons are travelling towards you at 300,000,000 m/s - or you might prefer to say that you are seeing the result of self-sustaining sinusoidal electric and magnetic fields that are perpendicular to each other. You might also just say that it is very pretty. I'm sure I've quoted Bertrand Russell's remarks about light already this autumn. He pointed out that someone blind from birth could experience a wave motion on a ship and learn the Physics of light waves. But they would have no idea of our experience of light.

 

Coniston Hydro-electric Power

We climbed up to Copper Mines Valley at Coniston on Christmas Day.

 

 

At the top of the stream we found the feed for the Coniston Hydro-electric Power Station. I found the details of the scheme on-line http://www.gilkes.com/case-studies/Coniston It's actually an old scheme from the 1930s which fell out of use and was then restored. 



 
 

 

The water travels 700m and falls through a height of 72m to reach turbines that generate 300kW of electrical power. It says that it takes the water 25 seconds to fall that distance. If it fell vertically in a vacuum, my calculations show that it would take only 3.8 seconds. The drag in the pipe means that it won't reach its theoretical maximum speed.  

 

Waning gibbous Moon

 

Not the world's greatest photograph but note that the whole Moon is no longer illuminated. More than half but less than whole = gibbous. It is the right hand side that fades away - or wanes. I had to wait until gone 10 o'clock to see the Moon last night and this picture was taken at 8 o'clock in the morning facing west. The waning Moon is seen late at night.

Santa in space

If you didn't see the story in the newspapers, do yourself a favour and follow this link to watch the film http://www.stratodean.co.uk/ It's very similar to the project by students from a neighbouring school up here. I love the flight data at the bottom of the screen.

Winter solstice on the M6 Toll

 

It was the shortest day of the year in the northern hemisphere - or to be more precise, the shortest number of hours of sunlight. We say that the Sun has reached its most southerly declination - ie it is not very high in the sky at midday. I took this picture at 3pm GMT from the services on the M6 Toll motorway near Birmingham. The Sun is already near the horizon and ready to set. It won't be quite as early tomorrow. Summer is on the way!

Dry ice bubbles

When we had the dry ice a couple of weeks ago we found an experiment in a book which said to add water and washing up liquid. The water heats the dry ice causing it to sublime and turn directly from solid into carbon dioxide gas. The gas then blows bubbles in the washing up liquid. We even added food colouring for effect. I realise now that I missed a trick: I should have added a burning match and watched it go out because carbon dioxide is a fire extinguisher. We noticed an odd phenomenon in that the bubbles stopped after a while. The water got so cold in contact with the dry ice that it turned into familiar water ice right around the dry ice pellets. This stopped the carbon dioxide escaping and occasionally there were odd sounds as it forced its way out.

The Full Moon

 

We've reached the Full Moon. I took the photographs early evening and the Moon was low down in the east. I got my telescope out which is really for watching wildlife. It is a refracting telescope but does get to 40x magnification. At first the camera was over-exposing as in the first image. Far too many photons were hitting the CCD in the camera which removed any detail. I shortened the exposure time to get this image with better contrast.

The human wind speed measurer

It was incredibly windy yesterday. A tree even blew over on Lowmoor Road so we had to make a diversion going home. However, we made the most of the day before the rain came. Here is the author of this blog on top of Latrigg. It was one of those days when it was possible to lean into the wind and not fall over. So I've done some Physics to measure the wind speed.

 

Essentially we need to consider two forces. The red arrow shows my weight acting through my centre of gravity. It causes anticlockwise turning around the pivot so my weight would make me fall forwards. The green arrow is a representation of the force of the wind. This will act all over the front of me but I have assumed that it can be averaged in such a way as to act through my centre of gravity. It produces clockwise turning around the pivot. Provided the clockwise and anticlockwise moments (technical term for turning) are equal, then I won't fall over.

 

Anticlockwise moment = weight x distance from pivot = 65kg x 10 x 0.15m roughly = 100 Nm roughly.

 

To calculate the force of the wind I'm going to use Impulse = change in momentum.

I am assuming that the air stops dead when it hits me.

Momentum = mass x velocity.

If I take a time of one second, a volume of air hits me that I will assume is rectangular in area and cuboid in shape. It's area will be my area, roughly 1.8m x 0.30m. It's depth will be the distance the air travels in 1 second ie the velocity of the wind v. Volume of air stopped in 1 second = 1.8 x 0.30 x v. The density of air is about 1.2 kg per cubic metre so mass of air stopped in 1 second = 1.2 x 1.8 x 0.30 x v = 0.65v roughly.

So change in momentum = mv = 0.65 x v-squared.

Impulse = force x time but time was 1 second so finally

Force of wind = 0.65 x v-squared. This is the green arrow

 

Clockwise moment due to wind = force x distance from my feet to my middle = 0.65 x v-squared x 0.9 = 0.6 x v-squared to 1sf

 

Set the two moments equal to each other:

0.6 x v-squared = 100

v-squared = 170 ish

v = 13 metres per second

This is about 30 mph.

 

It's impressive that this rough method gives a not unreasonable answer. Consulting the Beaufort Scale suggest it might have been nearer 40 mph.

 

 

A gibbous Moon

We went to Watchtree last night to hear a talk about astronomy by the Border Astronomical Society http://www.astronomyclubs.co.uk/ Sadly Comet Ison has vanished but we did look at Jupiter and the Moon. The Moon didn't reach its zenith until mid-evening and 3/4 of it was lit up. It's called a gibbous Moon. The Moon is said to be waxing for the first half of the month when more and more of the surface is being lit up.

First quarter Moon

 

The Moon is waxing at the moment. That's an old fashioned term that means that the Moon is getting more and more lit up as the days go by. I posted about the first crescent last Thursday. Technically the New Moon is when you can't see anything I think. Today we have reached the first quarter. Oddly named because half of the face is lit up.

 

The New Moon coincided with awful flooding on the east coast - a tidal surge. At the New Moon, the Moon and Sun are in line on the same side of the Earth. They pull together on the sea and produce bigger tides. This coincided with a major storm to cause flooding.

Making "smoke" with dry ice

I had some dry ice to use up before it melted. For those who've missed the concept, dry ice is solid carbon dioxide. It is at about -80 degrees Celsius. However, when it melts it turns straight into a gas. You don't get liquid carbon dioxide at normal pressures. We say that the dry ice sublimes - the technical term for turning straight from a solid to a gas. A favourite trick is to pour water onto the dry ice. The water might be at 5 degrees Celsius at this time of year but that is considerably warmer than the dry ice. The dry ice sublimes and releases the carbon dioxide gas. Look at the picture. Carbon dioxide is invisible so why is there a white gas? The answer is that the carbon dioxide gas is still very cold. This make the water vapour in the air condense to form clouds. We've made fog! It was how they used to make "smoke" on stage.

 

The fog is much colder than the air around it. It contracts and is therefore more dense so it sinks. That explains the "waterfall" of fog over the lip of the tray. I have seen cloud do this between valleys on days when there is a cloud inversion.

The secret cave in Langstrath

We spent a day out in the rain looking for the secret cave in Langstrath. We knew roughly where to go but it took about 20 minutes to find the cave entrance. It's an unusual cave because it is really just a space under massive boulders from a crag which collapsed. As you can see, the entrance is very small. You have to crawl inside. You can stand up in there though. Someone has put down boards so that four or five people can sleep in there. There are metal supports and there used to be a metal door.

 

We tried to estimate the mass of the boulder above it. We estimated 5 metres long by 5 metres high by perhaps 4 metres deep means 100 cubic metres. The density of andesite, a common volcanic rock in these parts, is about 2.5 tonnes per cubic metre. So the rock will have a mass of maybe 250 tonnes. And you sleep underneath it! It was hard to take photos inside but here is one of the cooking shelf. There was even a dust pan and brush in the bag. We signed the visitors' book but it is full so if you go consider taking an empty exercise book.

 

So where is it? It's a secret. No one on the Internet tells you exactly where but we worked it out. All I'll add is that it is at the very bottom of the crag. I climbed too far up at first.

 

New Moon Over Wigton

 

Enlarge this picture and you'll see that as predicted, the crescent has moved from the left hand side lit up to the right hand side lit up. And the Moon has moved from the morning to the evening. It's the start of a new lunar cycle - a New Moon.

The Physics of Leo Houlding

We went to see Leo Houlding talking about two amazing expeditions last night in Lancaster. No photographs allowed but you really ought to watch the trailers to his new films to why I thought the mountains were awesome: http://www.youtube.com/watch?v=WzBaPd3OxmM and http://www.youtube.com/watch?v=IqkxeZza5mM

I noted down several bits of Physics.

He stated that a stone dropped from the top of El Capitan in Yosemite falls 1000m in 27 seconds. Simple calculation ignoring air resistance using the equation s = ut + 1/2 at(squared) suggest 14 seconds. There is the possibility that he has timed it but that would mean reaching terminal velocity very quickly. I'll need to think about the calculations involved to figure that out.

About the film of climbing on Ulvetanna he claimed that it went from -5 to -20 degrees Celsius in seconds when the shadow of the mountain moved across the climbers as the day wore on. What a marvellous example of radiant heat - that the heat from the Sun comes as infra-red at the speed of light, even in Antarctica.

He also said that the most efficient way to melt ice for drinking water was to constantly boil 3 litres from below with two stoves and then add a few snowballs at a time. This sounds like a do-able but tricky calculation for the Upper Sixth after Christmas!

No Moon This Morning

 

No sign of the Moon this morning at roughly the same time as Saturday. As predicted the time for the Moon's zenith will have moved forward about an hour a day. It will be highest in the sky at around midday. The shadow side will be facing us so we won't see a Moon. Note that the dim light needed a longer exposure time with the shutter open for a longer time than usual to let in enough light. I couldn't hold the camera perfectly still so the photograph is slightly blurred.

Sliding away in Wigton

 

There was an ice rink on the car park over the weekend. I didn't go on but I'm told that it wasn't really ice. In fact, I've found the Wikipedia page for "synthetic ice" http://en.wikipedia.org/wiki/Synthetic_ice The Physics issue will be that the surface has a low coefficient of friction. The skates have a very small surface area and a polished metal surface also has a low coefficient of friction. If it had been real ice I could have written about the high pressure under the blade causing the ice to melt and you sliding along on a sheen of water which refreezes behind you. 

Luminites and the Wigton lights

It was the switching on of the Wigton Christmas lights tonight. Here's our MP Rory Stewart counting down to the moment that the lights came on.

 

He was followed by the Luminites. I thought they were great on BGT and they were great again this evening. They were very nice about Wigton. And RESPECT to everyone who put on a great event that brought so many people out.

 

Here comes the Physics: Light is an odd thing. I'll tell you that it is an electromagnetic wave. It consists of a moving electric field wave with a moving magnetic field wave at 90 degrees. Each field generates the other so light can be self-sustaining through a vacuum. It does not need particles. However the philosopher Bertrand Russell made a good point. He said that you could take a person who was born blind and put them onto a boat. They could feel the waves moving the boat up and down and you could tell them that light is like that: light is a wave. But he pointed out that they would have no idea what light is really. We don't define it; we just experience it. Physics take note.