Light in Berwick

We spent the week in Berwick upon Tweed, the most northerly town in England. The caravan park was on a hill above the estuary, looking back across to the town and out to sea. I began to notice that the sea looked different shades of blue, depending on which direction you looked relative to the Sun. That got me thinking about how we see things. The picture above is Berwick by night. We only see the luminous objects that make light, and a few that reflect light ( you might make out the arches of the railway viaduct). Below is a picture from the oldest bridge, looking into the Sun. It is obvious that we see the river because it reflects sunlight. The light patch at the bottom of the picture is a true reflection of the Sun in the "angle of incidence = angle of relection" sense, but I'm still thinking about the bright patch at the top of the picture. It must be a reflection of the Sun, but the angles don't quite work...

This picture of the viaduct is taken with the Sun behind me. You can see that it reflects sunlight back at us directly because it looks bright, and that sunlight reflects from it onto the water and up to our eyes. So to some extent, the river is lit up by reflections from elsewhere. It's just that, when I stop to think about it, not all of the angles seem to make sense.

 

The Skeptical Environmentalist

This year I have decided to get to the bottom of some controversial issues. I want to know what the scientific evidence is concerning Global Warming. Many Cumbrians seem convinced that there is no such thing. A related issue is that of the switch to renewable energy sources. Many people round here do not like windfarms. Two or three years ago, people round here who are opposed to windfarms routinely said to me that they favoured nuclear power as the "good for the environment" option. I wonder what they are thinking now about the debate concerning the burial of nuclear waste. Clearly, nuclear power creates radioactive waste so something needs doing with it. I think that as a Physics teacher, I should have researched all opinions, sorted out the scientific evidence and decided how I read that evidence. I should be able to give some sort of confidently expressed researched opinion as a Physics professional. So I'm reading. I have started by borrowing the book in the photograph from Cumbria Libraries. Bjorn Lomborg is a Professor of Statistics from Denmark. A decade ago, he went over all of the data he could find about the state of the environment. He wanted to see if things were as bad as they say. He concludes that the environment is actually getting better. This is very controversial. But if even half of his claims are true, then we should be OK. Wikipedia reckons that Jeremy Clarkson likes this book. Those who know me will realise that I'm worried by that! However, I can't fault his logic so far. It is a fat book: 350 pages of analysis and 150 pages of references. He has a great writing style. It's an excellent book to start with. I'm keeping an open mind. I will have finished it by next week so you can request it from your local library in Cumbria.

Frozen water butt problems

The other winter, the spell of freezing weather that went on for weeks caused a problem with our water butt. Water freezes from the top down - that's the reason life survived on Earth as it could survive under the ice sheets on frozen oceans. Here, the problem is that it also explands as it freezes. The stuff that freezes first at the top doesn't expand upwards anticipating the lack of space. This means that the stuff that freezes last at the bottom has no space into which to expand. It thus expands downwards, pushing out the flat plastic bottom into a rounded shape. The water butt was free to wobble on its round bottom and it fell over. Water is H2O. The hydrogen atoms in one H2O molecule are attracted to the oxygen atom in the next water molecule. This is called hydrogen bonding. At ordinary temperatures, the heat energy is enough to wobble the molecules out of fixed bonding patterns. But as water freezes, the molecules can form fixed hydrogen bonds, making the H2O into a solid. These fixed bonds give the water a rigid molecular structure, like scaffolding, and this opens up gaps, pushing the molecules apart. Google it for a more scientific explanation and diagrams!

"Copenhagen" radio play

On Sunday night Radio 3 broadcast a long radio play (2 hours) about a meeting during the Second World War between two of the greats of quantum physics, Niels Bohr, who was Danish, and Werner Heisenberg, who was German. The meeting took place in the capital of Denmark, hence the title. It is an important incident for the ethics of science. No one really knows exactly what happened but Heisenberg seemed to want to talk to Bohr about the German atomic bomb programme. I had always thought Heisenberg was regarded as dodgy for continuing to work in Germany at this time, but a bit of Internet research suggests that his "crime" may well have been to avoid becoming a martyr and refusing to defect to America. Here's the link. Listen and see what you think.

http://www.bbc.co.uk/programmes/b01ppwn6

Bragg on Bragg

Lord Bragg of Wigton, a former pupil of the school, has a great interest in Physics and has done a lot to promote Physics through his Radio 4 programmes. I've posted about his book "On Giants' Shoulders" before. You can borrow it from Wigton library.

This week, Melvyn Bragg's In Our Times programme has been about Crystallography. This is basically when you fire X-rays at the atoms in a crystal. The gaps between the atoms act like slits so the the X-rays spread and interfere with each other as they pass. The complicated pattern that you get can be interpreted to give the structure.

Here's the link to the programme. I think it's valid for a year.

http://www.bbc.co.uk/programmes/b01p0s9s

Two of the key founders of this area of study were William Henry Bragg and his son Lawrence Bragg. William was born at Westward, very close to Wigton. They both won the Nobel Prize for Physics, the only parent/child duo to have done so.

Time

Castlerigg Stone Circle near Keswick must be one of the earliest scientific sites, if you think about it. Scientists make careful observations and record them. These ancient people made careful observations about the movement of the Sun through the seasons and recorded it. It will be impressive if modern scientific findings are as durable. The study of time is one of the most important areas in Physics. What exactly is time? One of my teachers said that it was the thing that meant that two objects could occupy the same space. (Think about it!) Isaac Newton thought that time was independent of space - as if there was a big clock sat outside the Universe so that there is the same time everywhere. Einstein showed that isn't true. First, light has a fixed speed, so that when I look at the Sun, it is like it was 8 minutes ago because that's how long it takes the light to get here. What does that do to the concept of NOW? Secondly, Einstein showed that time can be stretched if you travel fast. A second takes longer if you are travelling faster. To understand this, read Einstein for Beginners. It's in the school library. See my other blog for details: http://www.idareyoutoborrow.blogspot.co.uk/2012/10/einstein-for-beginners.html

Brilliant science podcasts

One of my fellow science teachers found this brilliant set of explanations of scientific ideas:

http://www.nakedscientists.com/

"Naked" as in stripped down to the bare essential ideas, rather than, well, you know what.  Try telling that to the school's locked down Google!