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February 2016 Archives

I shudder to think what it must have been like in the path of Cyclone Winston. It is hard to conceive of winds 230 km/h sustained for minutes at a time. I remember vividly what is now known as the Great Storm of 1987 (an extra-tropical cyclone) which pulverised south-east England on 15/16 October 1987. There were (according to Wikipedia - ahem!)  gusts close to 200 km/h recorded in Sussex (where I lived), but there were possibly higher ones than these - the anemometers failed.  I spent the night listening to trees falling one by one around our house. Opposite the house was (and still is) a very tall Wellingtonia - one of the earliest specimens of this tree planted in the UK - and if that had fallen on us there wouldn't have been much house left. It stood firm, thankfully. That is frightening stuff.  But that's probably small fry compared to what Cyclone Winston did. 

One thing that I didn't personally experience in 1987 was the storm surge. (Being about 40 km inland kind of protected us from that.) Storm surges are a major cause of deaths in cyclones. The sea level can rise substantially during a storm - and coupling that with a high tide can lead to widespread and sudden flooding. 

There are lots of ways that a storm can raise water level. Winds can blow water towards the shore, and the Coriolis force acting on moving water can cause a build up. One simple effect is that the low-pressure in the storm simply 'sucks' the water level upwards.

Atmospheric pressure (about 1000 millibars or about 100 kPa) can hold up about ten metres of water. If you had a thin tube, filled it with water, sealed one end,  put the other open end in a bucket of water, and lifted the closed end ten metres into the air, you'd see that you got to the point where the water in the tube couldn't be supported any more. A vacuum would form above this height. See it here! In fact, what you have is a barometer - the height of the water is proportional to the atmospheric pressure. A 1 millibar change in pressure corresponds to about a 10 mm of water. With Cyclone Winston, the pressure dropped to 915 millibar, meaning about an 85 cm increase in the height of the ocean to this effect alone. This may not sound much but the disturbance doesn't remain localized - it will propagate out in a similar way to a tsunami. A fairly small shift in sea level in the ocean can correspond to a much more considerable shift when the wave slows down close to the shore. Throw in the effects of wind and rainfall and so forth, and one can end up with a devastating and sudden increase in sea level.  

At a more gentle level, atmospheric pressure is what holds up the water in a pet water dispenser, like the one we use with our chickens. There would be no point having a dispenser more than 10 metres high (that would water a lot of chooks indeed) - there would be no water supported above this height. 

 

 

 

 

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Yesterday I was part of a very interesting workshop on Science in Society, in Auckland. There was a plethora of good examples of science communication discussed - including forest restoration on the East Coast, biological control of pests in vineyards in Canterbury and improvement of health outcomes for Native Americans in Montana. For me, it was clear that there were some resounding messages coming through about science communicaton. 

1. It needs to be driven by the community. Here, community could mean a town or village, a marae, an industry group, a school - any group of people with an interest in achieving something. The participation of the scientist is as a partner, often as a junior partner. In other words, the community takes the lead. The scientist(s) doesn't go out and say "Right, now I am going to do some science communication." If she does, no-one will listen. Instead, she needs to be listening and responsive to the (scientific) needs of others. 

2. Communication is about relationships. Richard  Faull gave a very humbling talk about his work on Huntington's Disease, done in partnership with several Maori families across the country for whom Huntington's is tragically real.  It is a true partnership. To achieve what he has done has taken decades of building relationships. Listening to people's stories, spending weeks on Maraes, being available Christmas Day for someone to offload their fears for the future.  

3. There is a difference between outputs and outcomes: It is easy(ish) to write journal articles about science communication projects. That's an output. An outcome is a lasting impact for the people concerned:

Communication isn't complete until it is put into practice for the people for whom it makes an impact  - Polly Atatoa-Carr

Now here's the problem for the scientist (i.e., me). We are all tasked to be science communicators. (Yes, we are - if you're a member of a professional organization you'll probably find it's part of your responsibilities as a member - and, if nothing else, it is your duty as a professional to talk about your profession.) But it isn't something we can do (as in "Right, I need to do some science communication in the next few months - what shall I do?") Soana Pamaka, of Tamaki College in Auckland, summed it up "Schools are sick and tired of being 'done to'." Instead, we need to build relationships with community groups and be open to respond to opportunities that arise. Almost certainly, those opportunities will not be in our specialist areas. I mean, how many community groups have an interest in neural field models? But if we have good relationships, then groups will come to us because they know us. And we have to respond to that. For example, at Tamaki College, which has a fantastic science programme, the science communication is driven by the school, which means the children, with guidance from teachers. The scientists work in partnership with them. 

Better science communication needs better relationships with communities, and be community-driven. The scientists need to be open to respond to those opportunities. How ironic then, for a workshop on 'Science in Society' nearly all participants were scientists or educators.

 

 

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The big breaking physics news is the detection of gravitational waves. These waves are distortions in space-time, caused by a large mass doing something spectacular (two colliding black holes in this case)  that propagate across the universe and create tiny changes in space when they reach us. The commentary here describes what goes on. Essentially, things change their length/width. When a gravitational wave passes through my office (say ceiling to floor) one can imagine the length of the office increasing slightly, coupled with a decrease in the width of the office, followed by the reverse - a decrease in the length and an increase in the width.  But its not just that the bricks that make up the room vibrate (e.g. as in a seismic wave) - its the whole of space that does it. 

These waves were predicted by Einstein in 1916, just after the publication of his theory of General Relativity. Their discovery is further evidence for the theory. But it's not just about Einstein. Gravitational waves provide another way of observing the universe - 'seeing' what's going on. Up to now, we've been stuck with light-based observations (be it visible light, infra-red, microwave - they all are electromagnetic waves). There are neutrino observations too, but these aren't exactly easy. But gravitational waves are something else - it's like seeing AND hearing something, rather than just seeing it. 

So how are they detected? The concept is rather simple, as explained in the commentary. Build a (large, meaning 4 km in the case of LIGO) interferometer with two arms. Pass light up and down each arm. The light from the two different paths will interfere - such interference could be constructive (if a peak from one arm comes at the same time as a peak from the other) or destructive (if a peak comes with a trough). If everything is stable, the interference is stable. But when a gravitational wave passes, the arms change their lengths. Not by much. The light takes longer to pass up and down one arm, and shorter to pass up and down the other. Now the timings of the peaks and the troughs change, and the interference signal changes. We detect a gravitational wave. 

The difficulty to now has been detecting the tiny signals amongst larger 'noise' signals, but a recent upgrade to the LIGO detector has done its job. Well done LIGO team!

 

 

 

 

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