James Dewar, frozen air and a new way to store energy

Today is the second time we meet up with Scottish scientist James Dewar. We’ve already discussed his ingenious Dewar flask, made famous by the Thermos company. As mentioned at the time, Dewar worked with some rather chilly subjects – liquified and frozen gases, to be exact – and he created his insulating flask to serve his practical need for a container that could maintain the low temperatures of the liquified gases he studied.

The reason Dewar pops up on this blog today, is again related to his low temperature work. It was on this day, 9 March 1893, that he informed a meeting of the Royal Society that he had succeeded in freezing air into a clear and transparent solid. As reported in The Manufacturer and Builder Volume 25 Issue 7, he requested additional funding to further study the exact properties of this frozen air; he postulated that “it may be a jelly of solid nitrogen containing liquid oxygen, much as calves’ foot jelly contains water diffused in solid gelatine. Or it may be a true ice of liquid air, in which both oxygen and nitrogen exist in the solid form.” Part of this confusion on the part of Dewar was that he had not been able to freeze pure oxygen, hence it was not clear how the oxygen part of the frozen air behaved.

I have no idea how frozen air would look, but it will surely be very, very chilly!(© All Rights Reserved)
I have no idea how frozen air would look, but it will surely be very, very chilly!
(© All Rights Reserved)

Interestingly, frozen air has recently resurfaced as an subject of research interest. As reported last year on various sites such as ecogeek, sustainable business.com and NBC News, a UK-based company Highview Power Storage has developed a proprietary process using cryogenic air (actually nitrogen, liquified at -321 degrees Fahrenheit) as a way to store energy. Available energy is used to freeze/liquify the nitrogen, which is then kept in its frozen form in a highly isolated, giant vacuum flask. When energy is required, the nitrogen is allowed to warm to ambient temperature, and the energy released during its transition to a gas phase, is harvested to drive a turbine that generates electricity.

While the technology is not yet able to achieve the efficiency of current battery technologies, it is a potentially less environmentally harmful, greener approach.

Now there’s a reason to raise a glass of very chilled liquid to James Dewar and his frozen air!

Pyotr Lebedev and the pressure of light

Today we celebrate the birthday of the Russian physicist Pyotr Nikolayevich Lebedev (8 Mar 1866 – 1 Apr 1912).

Working in the field of electromagnetism, Lebedev was responsible for a rather famous physics experiment in 1899 – measuring the pressure a beam of light exerts on a solid body. By doing this, he was the first to quantitatively confirm James Clark Maxwell’s theory of electromagnetism. Not only did he prove that the pressure exerted by light, although minute, is very real – he also proved that the pressure of light on a reflective surface is twice as great as on absorbent surfaces.

Thanks to Pyotr Lebedev we have proof that light exerts physical pressure on a solid body.(© All Rights Reserved)
Thanks to Pyotr Lebedev we have proof that light exerts physical pressure on a solid body.
(© All Rights Reserved)

Lebedev’s discoveries led him to postulate that it was the pressure exerted by sunlight on tiny particles of cosmic dust that made the tail of a comet point away from the Sun. However, it is now generally accepted that solar wind has more effect than light pressure in determining the direction of a comet’s tail.

Lebedev died quite young, yet his achievements was significant enough that the Lebedev Physical Institute in Moscow and the lunar crater Lebedev are named after him.

Stanley Miller, primordial soup and the origin of life

Today we celebrate the birthday of Stanley Lloyd Miller (7 March 1930 – 2 May 2007), the American chemist and biologist known for his experiments into the origin of life.

The most famous of his experiments was the so-called ‘Miller-Urey experiment’, where he and his research partner Harold Urey showed that it was possible, using simple chemical and physical processes, to create organic compounds from inorganic substances. This was considered a logical explanation of how organic life could have started on an planet made up of inorganic chemicals.

In my minds eye I've always imagined primordial soup as a rather ominous-looking pond of bubbling and steaming chemical liquid, very much like the thermal geysers at Rotorua, New Zealand. (© All Rights Reserved)
In my minds eye I’ve always imagined primordial soup as a rather ominous-looking pond of bubbling and steaming chemical liquid, very much like the thermal geysers at Rotorua, New Zealand.
(© All Rights Reserved)

The famous Miller-Urey experiment, conducted in 1952 at the University of Chicago, tried to recreate the conditions existing on the early Earth before organic life existed. The experiment combined a number of chemical compounds – water, methane, ammonia and hydrogen – sealed in an connected loop of glass tubes and flasks. The first flask, containing the chemical mix, was heated to cause evaporation, and the gas was allowed to flow into a second flask where sparks (simulating lightning) were fired between electrodes installed in the flask. The ‘electrocuted gas’ was then cooled again in a subsequent flask, and the condensed liquid was allowed to trickle back into the first flask. This cycle was continued over an extended period.

After about a day, the chemical liquid was reported to turn pink, and after about 2 weeks of operation, Miller and Urey found that some of the carbon in the system had turned into organic compounds. By this stage the mixture included amino acids, sugars, bio-molecules and hydrocarbons.

The Miller-Urey experiments showed, quite compellingly, that simple organic compounds – building blocks for proteins and other organic macromolecules – could be created from basic chemical compounds with the addition of heat and electricity.

The spontaneously created brew of life-yielding organic compounds support the ‘primordial soup’ theory first proposed by Soviet biologist Alexander Oparin in 1924. Very simply stated, the theory suggests that the early Earth’s atmosphere, exposed to various forms of energy, produced simple organic compounds, which accumulated as a ‘soup’ in various locations, and through further transformations, more complex organic polymers were formed, leading ultimately to the formation of water-based organic life forms.

Laplace and the floating needle

Today we commemorate the death of the man sometimes known as the ‘French Newton’Pierre-Simon Laplace (23 Mar 1749 – 5 Mar 1827).  Laplace was a bit of a super-scientist, excelling in mathematics, physics, statistics and astronomy.

Among other things, Laplace performed fundamental mathematical analyses of the solar system, studied the thermochemical effects of combustion, and did groundbreaking work in mathematical calculus and the solution of linear partial differential equations.

In addition to all his other achievements, Laplace built upon earlier work by English scientist Thomas Young, to explain surface tension in liquids (essentially it’s ability to resist an external force) in terms of the attraction between the molecules in the liquid (known as cohesion). This cohesive force existing in a liquid results in some very interesting natural phenomena, such as enabling a needle to float on water. Some insects use surface tension to allow them to walk on water.

The phenomemon of surface tension can make the seemingly impossible possible, such as allowing a needle  to stay afloat on the surface of normal tap water.(© All Rights Reserved)
The phenomemon of surface tension can make the seemingly impossible possible, such as allowing a needle to stay afloat on the surface of normal tap water.
(© All Rights Reserved)

Laplace also used inter-molecular attraction to developed the theory of capillary action, where a liquid gets ‘sucked into’ a narrow tube due to a combination of cohesive forces within a liquid and adhesive forces between the molecules in the liquid and those in the containing tube.

The capillary pressure difference existing at the interface between two static fluids (e.g. water and air) can be described by a nonlinear partial differential equation, which is, fittingly, known as the Young-Laplace equation.

Despite being one of the great minds of all time, Laplace remained very aware of the limits of his own insights. As he wisely stated near the end of his life, “What we know is little, and what we are ignorant of is immense.”

Celebrating exploding food on Popcorn Day

Today, 19 January, is Popcorn Day, a day to celebrate one of nature’s fun foods – those crazy little corn kernels that, when exposed to heat, explode violently and morph into cushiony white snacks many times their original size.

We’ve all enjoyed popcorn, but have you ever wondered what makes ’em pop?

Exploding starch frozen in action. (© All Rights Reserved)
Each piece of popped popcorn is a totally unique example of exploding starch frozen in action.
(© All Rights Reserved)

The secret to popcorn’s popping ability lies in the composition of the kernel. The popcorn kernel consists of a hard, watertight outer shell, containing starch and a small amount of water and oil.

When the kernel is heated, the water inside tries to expand to steam, but the hard shell prevents this. The heat also gelatinizes the starch inside the shell. Once sufficient pressure has built up (to an incredible 930 kPa), the kernel bursts open in a violent explosion, freeing the steam and starch.

As the hot starch bursts out of the shell, it expands rapidly to as much as 50 times its original size. At the same time it experiences rapid cooling as it comes into contact with the air outside the shell.   It is this rapid cooling that sets the gelatinized starch into the familiar foamy popcorn puff.

So a popped popcorn is basically a starch explosion frozen in action!

Celebrating Wham-O’s ‘frisbee’ flying disk, a toy for all ages

Today, 13 January, is the date back in 1957 when the Wham-O toy company first began production of their plastic flying disk, or ‘Frisbee’, as they trademarked it.

The concept for the flying disk came about much earlier. While there are different tales regarding its invention, the most plausible story is that it came from the pie tins that the Frisbie Baking Company from Connecticut used to bake their pies in. The pies were popular with students at various New England colleges. Apart from enjoying the pies, they discovered that the empty pie tins could be tossed and caught, resulting in many hours of fun and games.

In 1948, Walter Morrison from Los Angeles created a plastic version of the flying disk that could be thrown more accurately than the pie tins. Morrison marketed his disk, which contained a specifically sloped design and thicker outer edge, as the ‘Pluto Platter’, and this became the blueprint for future flying disk designs. Rich Knerr and Spud Melin of the Wham-O company quickly saw the potential of Morrison’s invention and convinced him to sell them the rights to the design.

The flying disk of 'frisbee' is a truly age-defying toy, and can offer hours of fun to players of all ages.(© All Rights Reserved)
The flying disk of ‘frisbee’ is a truly age-defying toy, and can offer hours of fun to players of all ages.
(© All Rights Reserved)

Shortly after Wham-O started producing their version of the flying disk, the Frisbie Pie Company closed down, and Wham-O named their disk the ‘Frisbee’, acknowledging the role the Frisbie pie tins played in the invention of their toy. Thanks to Wham-O’s clever marketing of the Frisbee disk, sales soared, and the toy even caught on as a serious sport. By 1964, Wham-O released the first professional version of the Frisbee, with better accuracy and more stable flight. The key innovation in the professional version was the introduction of raised concentric ridges, called the ‘Rings of Headrick’ after its inventor, Wham-O’s Ed Headrick.

Physically, the flight of the frisbee works very similar to a standard asymmetrical air foil, accelerating airflow over the disk resulting in a pressure difference causing a lifting force. The ‘Rings of Headrick’ help by causing the airflow to become turbulent as soon as it passes over the ridge of the disk, thus reducing flow separation. In addition to the lift caused by its shape, the torque created by the heavier edge of the spinning disk also has a gyroscopic effect, stabilizing the disk in flight. Higher rates of spin results in greater stability.

Minor adjustments to the shape of the disk can cause significant changes to the flight dynamics – something that can be utilised effectively in specific applications like disk golf where the aim is to cover a course and throw the disk into a basket – similar to sinking a put in golf. Disk golf players use different design disks for ‘putting’, ‘driving’ etc.

The Frisbee even gained scientific legitimacy when, in 1968, the US Navy spent a whopping $400 000 studying the flight of the frisbee in wind tunnels, following its flight with high speed cameras and performing advanced computer flight simulations. The project even included the development of a special frisbee launching machine. (The mind just boggles at all the potential conspiracy theories regarding UFO flight that this must have caused…)

Today the Frisbee trademark is owned by Mattell Toys. More than 100 million frisbees were sold by Wham-O prior to selling the toy to Mattel. Beyond this, many millions more flying disks were sold by other manufacturers, so one can only speculate how many flying disks have been sold since its invention more than 50 years ago.

Christian Doppler and the sound of speeding vehicles

Today we celebrate the birthday of Christian Doppler (29 Nov 1803 – 17 Mar 1853), the Austrian physicist who first described how the observed frequency of sound and light waves are affected by the movement of the source of the waves relative to the observer. The phenomena became known as the Doppler effect.

Simply put, sound and light waves would have a higher perceived frequency if the source was moving toward the observer and a lower perceived freqency if the source was moving away from the observer.

No matter how cool the rider, your Harley will still have a slightly more girly pitch as it races towards the observer.
(© All Rights Reserved)

It is said that Doppler first tested his hypothesis by using two groups of trumpeters – one group stationary on a train station, and the other group on an open train car. Instructing them to all play the same single note, he found that, as the open car passed the station, the pitch of the two groups did not match. Approaching the station the trumpeters on the train appeared to play a higher note, and leaving the station they appeared to play a lower note.

One of the places where the Doppler effect is very obvious is at a motor racing event – I am sure everyone has heard (either live or on TV) the effect of the sound of a racing car, or motorbike, changing quite dramatically as it comes screaming past. As the car races forward, the sound waves emanating from the engine effectively gets compressed in front of the car, resulting in a higher pitched sound, while they get spread out behind the car, producing a lower pitch.

Because the extent to which the frequency changes is dependent on the relative velocity of the source, observed changes in frequency can be used to calculate the speed at which the source is traveling.

The Doppler effect finds application in a wide range of fields, from astronomy to radar to medical imaging to flow measurement to satellite communication and more.

As mentioned before the effect does not apply to sound only – it applies to all waveforms, including light. A light source moving towards the observer will appear to have a higher frequency than one moving away from the observer. However, because very high speeds are required to achieve an effect visible to the human eye, this is less easy to observe than the sound example.

There’s a classic physics joke that says the most effective way to observe the optical Doppler effect is to look at cars at night – coming towards you, their lights are all white, while moving away from you, their lights are red!  (Think about it, it makes perfect sense…) 🙂

Celebrating Anders Celsius and his temperature scale

Today we celebrate the birthday of Anders Celsius (27 Nov 1701 – 25 Apr 1744), the Swedish astronomer who gained fame for developing the Celsius temperature scale.

Celcius’ original scale defined 0 °C as the temperature where water freezes, and 100 °C as the temperature where water boils (at one standard atmosphere). This was the definition of the scale until 1954, and remains a useful, pretty accurate approximation, and is still taught in most schools today. However, to be exact, the Celsius scale is currently no longer defined by the freezing and boiling point of water, but rather by the absolute zero temperature and the triple point of purified water. The absolute zero point is defined as -273.15 °C, and the triple point as 0.01 °C.

It’s boiling water, but it sure ain’t 100 °C.
(© All Rights Reserved)

Based on this slightly redefined scale, the real freezing point of purified water is -0.0001 °C, and its boiling point is 99.9839 °C. Of course these values only apply at exactly one standard atmosphere pressure (approximately sea level) and with specially purified water, so actual ‘real life’ freezing and boiling points only approximate 0 °C and 100 °C anyway. An altitude change of as little as 28 cm causes the boiling point of purified water to change by a thousandth of a degree.

Interestingly, the rule set forth by the International Bureau of Weights and Measures for writing Celsius values (most units of measure, in fact), is to write the numerical value, followed by a space, followed by the °C sign. So the correct way to write a temperature is 37 °C, not 37°C or 37° C.

Currently the Celsius scale is the temperature scale most widely used for all kinds of purposes. Only the United States (bless them) and a handful of other countries still give preference to the Fahrenheit scale. The UK also used to prefer the Fahrenheit scale, but over the last half century the Celsius scale has gained dominance (although they prefer calling it centigrade).

So, whether you prefer an icy, a close to 0°C Scotch on the rocks, or an almost boiling, close to 100 °C cup of coffee or tea, join me in a toast for Anders Celsius, the man who defined it all in the first place.

James Clerk Maxwell – the man who changed everything

Today, we commemorate the life and work of James Clerk Maxwell, the Scottish mathematical physicist who died on this day in 1879.

James Clerk Maxwell, 13 June 1831 – 5 November 1879
(wikimedia commons)

While most people will have heard of arguably the two most prominent physicists of all time – Isaac Newton and Albert Einstein – far less are likely to recognise the name of the third person on the list: James Clerk Maxwell. Maxwell, who formulated classical electromagnetic theory, has been hailed as the 19th century scientist whose work had the greatest influence on 20th century physics, and Einstein described it as the “most profound and the most fruitful that physics has experienced since the time of Newton.”

What makes Maxwell’s electromagnetic theory so important is that it is one of the great unifying theories in physics, combining the fields of electricity, magnetism and optics into a single, consistent theory. He showed that electric fields and magnetic fields both travel as waves, and they travel at the speed of light. This led him to postulate that light, electricity and magnetism behave the same, and can be described through the same equations and theories. In his own words, “We can scarcely avoid the conclusion that light consists in the transverse undulations of the same medium which is the cause of electric and magnetic phenomena,” and “The agreement of the results seems to show that light and magnetism are affections of the same substance, and that light is an electromagnetic disturbance propagated through the field according to electromagnetic laws.”

Maxwell’s electromagnetic theory has been reduced down to four fundamental differential equations, known as ‘Maxwell’s Equations’, first presented in his book “A Treatise on Electricity and Magnetism” (1873).

Another contribution by the great man, possibly less grand than his electromagnetic theory, but fundamentally important in its own way, came in the field of colour and optics. His theory of colour vision made a key contribution to colour photography.

Thanks to Maxwell we now understand that a colour image can be split into red, green and blue channels, and that the full colour image can be recreated by combining these channels.
(© All Rights Reserved)

Maxwell was the first to show that a colour image can be created by photographing the same subject through red, green and blue filters, and then projecting the three resultant images through the same colour filters onto a screen. This showed that the additive primary colours are red, green and blue and not red, yellow and blue, as was previously assumed. It introduced the principle of additive colour synthesis used to this day in colour displays.

So here’s to Scotsman extraordinaire James Clerk Maxwell, one of the greatest minds of modern times and, to paraphrase his biography, ‘the man who changed everything’.

Blue skies, blue eyes – its the Tyndall effect

Tell me why the stars do shine 
Tell me why the ivy twines 
Tell me why the sky’s so blue 
And then I’ll tell you just why I love you…

Well, if you could have sung this little tune to the Irish physicist John Tyndall, born on this day back in 1820, he would have had some strong opinions, at least on the blue sky question.

In addition to many other achievements, Tyndall published studies on acoustic properties of the atmosphere and the blue colour of the sky – he suggested the colour was the result of the scattering of light by small water particles. He discovered that, when light passes through a substance containing small suspended particles, the shorter wavelengths (blue side of the spectrum) are scattered more than the longer, red wavelengths. Since the blue light is scattered in all directions, the substance appears blue.

This phenomenon became known as the Tyndall effect.

What we see as a lovely blue sky, John Tyndall saw as a scientific challenge.
(© All Rights Reserved)

Thus, a clear day-time sky is blue because molecules in the air scatter blue light from the sun more than they scatter red light. Towards sunset, when we look towards the sun, we see reddish colours, because the blue light has been scattered away from the line of sight.

The Tyndall effect also causes other interesting blue colourings in nature, including blue eyes, opalescent gemstones and the wings of some birds and butterflies. When colour is caused by scattering of light it is known as a structural colour, as opposed to a pigment colour.

Now about those stars and ivy…

(Source: Why is the sky blue?)