Features

A helping of seasonal science in which Oxford's Federico Formenti tells me about research into the origins of ice skating:

OxSciBlog: How were ice skates invented/what were they used for?
Federico Formenti: Archaeological evidence shows that ice skates have been used for at least 4000 years. Where skates were invented and why is still a matter of debate in the field of archaeology. The most ancient ice skates are found across a vast area of Europe (from Germany to North Scandinavia) and some argue that they were made for fun. I think that 4000 years ago, in countries where there were long freezing winters and only a few hours of light per day (and neither supermarkets nor cars!), people would have used these few hours of light to get food and any other items necessary for their survival, rather than to have fun.

My doctoral research suggests that they were invented in the South of Finland, where the number of lakes per square mile is the highest in the world. In this environment humans were forced to find a way to cross lakes (so as to avoid having to walk around them).

On average, compared to walking, travelling with ice skates between two locations offered a much greater gain in Finland - in terms of time and energy required for the journey - than anywhere else in the world. This led me to suggest that they were invented in order to save the time and energy required for necessary journeys.

OSB: What materials do we think they used to make them?
FF: The most ancient ice skates were made of animal bones, mostly horse and cattle. This varies quite a lot, depending on the animals which were present in the area where the skates were made. Apparently, the size of the bone skate matched the size of the skater's feet (kids had shorter bone skates).

Bone skates did not have a blade so the movement pattern of 'ice skating' looked rather different from modern ice skating technique: propulsion came from the upper limbs pushing a stick on the ice between the legs whereas the lower limbs, being kept almost straight, provided balance. The first wooden skates with a metal blade were made 'only' in the 13th Century AD, when people skated using their lower limbs as a means of propulsion; since our lower limbs are more powerful than our upper limbs, we could than skate at higher speeds (similar to running) for a limited effort, and making turns became easier.

OSB: How well did these early skates work?
FF: Measured speed on bone skates was similar to walking on firm terrain for a similar effort, although this was measured on a track with curves, so it's possible this was underestimated. Going on a straight line on bone skates is very easy (and relatively fast), but making turns requires slow speeds (because they do not have a blade).

Federico Formenti is based at Oxford's Department of Physiology, Anatomy & Genetics where his current research is in studying how the human body responds to low oxygen. 

As part of our 'Any questions?' campaign a question sent in by Silvan Griffith is answered by Claire Vallance from Oxford's Department of Chemistry.

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Q: I have always understood that pressure, temperature and appearance of a substance are directly related: the higher the pressure, the lower the temperature, the more solid it becomes due to the atoms moving less. Water reaches its highest density at +4°C. If one would decrease the pressure, would it become colder or warmer?

Claire Vallance: You are correct that both the pressure and the temperature affect the ‘appearance’ or ‘solidness’ of a substance. However, temperature and pressure are not locked together in quite the way you describe.

An equation known as the phase rule (described in detail in any thermodynamics textbook) predicts that for pure water we can vary both pressure and temperature independently. For example, liquid water may be turned into solid water (ice) either by reducing the temperature or by increasing the pressure sufficiently.

When we reduce the temperature we reduce the kinetic energy of the water molecules, so that they move around more slowly. Within a liquid, molecules are constantly colliding with each other, and at high temperatures the collisions are energetic enough that the relatively weak attractive forces between individual molecules have little effect and the molecules simply bounce off each other.  However, once the temperature approaches the freezing point, collisions occur so slowly and with so little energy that the intermolecular forces take over and the molecules start to stick together.

As the temperature falls even further we eventually end up with the molecules locked into the lattice structure of solid ice. A similar result may be obtained by reducing the pressure, but in this case the mechanism for crystallisation into the ice structure is not that the collisions become less energetic (assuming that we keep the temperature the same as we increase the pressure), but that the molecules are forced closer together on each collision.

Intermolecular forces are strongly dependent on distance, and are much stronger at smaller separations. At high enough pressures, water can be made to form ice even at room temperature and beyond.

This behaviour can be summarised on a phase diagram. The phase diagram for water [part of which is shown below] reveals which phase (solid, liquid or gas) is most stable at a given temperature and pressure.

 At low temperatures and high pressures (top left of the diagram), the solid phase is most stable, while at low pressures and high temperatures (bottom right of the diagram) the gas phase is most stable.

At intermediate temperatures and pressures we have the liquid phase. The lines, or ‘phase boundaries’, on the diagram show conditions under which two phases can exist together in equilibrium. For example, the line separating solid and liquid allows us to determine the freezing point of a substance at any pressure, and the line separating liquid and gas does the same for the boiling point. We can use the diagram to explore what would happen in your example of water at 4 °C.

Starting at a pressure of 1 atmosphere and a temperature of 4 °C (filled circle), reducing the pressure corresponds to following the vertical line in the direction of the arrow – note that the temperature doesn’t change. As we reduce the pressure, the liquid will become less dense, until when we reach a low enough pressure (just less than 0.01 atm on the diagram, the pressure you would find at an altitude of 32,000 m!) we cross the phase boundary between liquid and gas, and the water evaporates.

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Dr Claire Vallance is based at Oxford's Physical & Theoretical Chemistry Laboratory.

This week sees the launch of Accelerate! a programme of interactive physics show for Oxford schools.

The aim is to bring the excitement of particle and accelerator physics to ages 11 and up: the fun kicks off with a launch event this Friday.

Those going along to the Martin Wood Lecture Theatre in Oxford's Clarendon Laboratory (6pm-7:30pm) will be treated to displays featuring liquid nitrogen, exploding hydrogen balloons and levitating superconductors.

Lots of audience participation will ensure that everyone gets a taste of the hands-on science behind scientific mega machines such as the Large Hadron Collider.

It's a free event and the launch is open to teachers, media and the public.

Accelerate! is organised by Oxford DPhil student Suzie Sheehy (top image).

Highlights from OU science in the news this week:

Could your electricity meter save £££s and the planet?

That's the hope behind the smart meter technology being developed by Oxford spinout Intelligent Sustainable Energy, as Martin Arnold reports in the FT.

The technology is being commercialised with the help of Oxford University Innovation and Navetas and is the brainchild of Oxford engineer Malcolm McCulloch.

Martin writes: 'His eureka moment came when he noticed that he was using less petrol after switching his car's digital display from mileage to fuel consumption. Professor McCulloch felt there could be a similar drop in home electricity bills if people could see how much power each device was using. So he decided to make one.'

It's a nice piece in which Martin highlights Isis Innovation's recent successes: 'In the past eight years, Isis has helped the university raise more than £335m to create about 60 companies. With a staff of 52 and a budget of £2.5m, it concluded 74 licensing and option deals last year alone.'

Elsewhere more investment was on the cards as EPSRC ploughed £250m into doctoral training.

Oxford was a major beneficiary with £25-£30m going into its four Doctoral Training Centres (DTCs) offering interdisciplinary DPhil training for some of the UK's brightest scientists and engineers.

In The Times Mark Henderson did a nice piece mentioning the work of Oxford DTC student Susannah Fleming into automatic monitoring systems that can detect serious illness in children. 

I remember chatting with EPSRC's Lesley Thompson about how Oxford's Life Sciences Interface DTC helped to pioneer this new type of doctoral training when it first opened its doors way back in 2002.

Finally, pain may be an unavoidable part of life but could some binoculars send it packing?

As The Independent's Jeremy Laurance reports, Oxford researchers have found that those suffering chronic pain could decrease that pain by observing the affected limb through the wrong end of a pair of binoculars. Even more amazingly this 'minified' image of their limb can actually reduce its swelling.

The work, published in Current Biology, was carried out by Lorimer Moseley (whilst still at Oxford), Charles Spence of Oxford's Department of Experimental Psychology, and colleagues.

One of the mysteries of Venus is the strange patches in the clouds that show up in ultraviolet light.

As BBC Online discuss [with a nice mention of OxSciBlog] Oxford's Fred Taylor and colleagues report in Nature on observations from Venus Express that shed light on this phenomena. I asked Fred about Venus and its strangely seasonless climate:

OxSciBlog: What do these UV patterns tell us about the atmosphere of Venus?
Fred Taylor: The features seen on Venus in ultraviolet light have been a puzzle to astronomers for nearly a century. The Venus Express spacecraft has revealed the structure in the clouds that produces them, and how they result from complex meteorological behaviour on the Earth's nearest planetary neighbour.

OSB: What can they tell us about Venusian weather?
FT: The cloud patterns outline the weather systems, just as they do on Earth. It is fascinating the way the meteorology on Venus is similar to Earth in some ways, and different in others. Some of the differences are due to the slow rotation of Venus compared to Earth, and some to the great depth of Venus's atmosphere. Other features we don't understand yet, like the detailed nature of the great vortices at the pole.

OSB: How do they help us compare and contrast the Southern and Northern hemispheres?
FT: Unlike the Earth, Venus's atmosphere is nearly symmetrical about the equator - the two hemispheres behave very similarly. In other words, Venus has no seasons. This is explained by the small tilt of the rotation axis - less than 2 degrees, compared to about 23 degrees for the Earth.

Read more about Volcanic Venus on the OxSciBlog. 

Professor Fred Taylor is based at Oxford's Department of Physics.