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Radar
Radar (Radio Detection And Ranging) is an electromagnetic system for the detection and location of objects. It operates by transmitting a particular type of radio signal and then detecting the nature of the echo signal. The original pulsed signal is fed to a movable aerial from which it is transmitted as a beam. If the is interrupted by a solid object, part of the energy of the radiation is reflected back to the aerial. Signals received by the aerial are passed to a receiver where they are amplified and detected. An echo from a reflection of a solid object is indicated by a sudden rise in the receiver's output. The physics involved gives it the ability to measure the distance (range) to the object producing the echo. This is probably its most important quality. In some systems the speed at which the solid object is travelling can also be measured.

Radio Waves
Kenneth Linn Franklin was an American astronomer who discovered, in1955, that the planet Jupiter emits radio waves. Together with his colleague Bernard F. Burke at the Carnegie Institution in Washington, he found that the waves appeared to be short bursts of static, similar to those produced by thunderstorms on conventional radio receivers. The surprising discovery was made entirely by chance while they were scanning the sky for radio noises from galaxies. No radio sounds from planets in our solar system had previously been reported. Burke and Franklin observed that the signals were arriving four minutes earlier each day and they confirmed that the signals indeed came from Jupiter. Later it was discovered that the radio waves were circularly polarized and this means that a magnetic field is involved in their propagation.

First Railway Passenger Service
This was inaugurated on March 25th 1807 on the Oystermouth Railway in Wales. The railway had been established in 1804 to enable horse-drawn goods traffic to travel the 71/2 miles between Swansea and Oystermouth. The passenger service, resulted from a deal between the railway company and Benjamin French. He undertook to run a wagon for the conveyance of passengers for a year and to pay £20 in tolls for the privilege. The train ran twice a day in the summer months and the fare was one shilling for a single journey. There were not stations but there were check gates on the termini at Brewery Yard and Hughes' Forge. Writing in 1813, Richard Ayton described the experience:

It is a very long carriage, supported on four low iron wheels, carries sixteen persons, exclusive of the driver, is drawn by one horse, and rolls along over an iron railroad, at the rate of five miles an hour, and with the noise of twenty sledge hammers in full play. The passage is only four miles, but it is quite sufficient to make one reel from the car at the journey's end, in a state of dizziness and confusion of the senses that it is well if he recovers in a week.

Raoult's Law
This is one of the basic laws of chemistry which allows us to calculate the amount of each substance present in a solution. It states that the vapour pressure of any constituent in a solution will be the same as the vapour pressure which the unmixed constituent would exert at the same temperature multiplied by its mole fraction - the relative amount of it present in the solution. Any solution which obeys Rault's Law is said to be an Ideal Solution. In general it only holds for dilute solutions although some mixtures of liquids obey it over a whole range of concentrations.

Red Tide
The red tide, which appeared in the Gulf of Mexico, produced huge blooms of reddish algae in sufficient quantity to kill fish and cause severe respiratory problems for humans. There was an unparalleled outbreak in 1946 that devastated the fishing stocks in the Gulf. It was not until 1992 that the source of the excessive amounts of phytoplankton was discovered. Scientists at a conference on the ecology of the Gulf identified a "green river" that started sixty miles inland in Florida as the source of the algae. The wind and water currents that bring nutrients from the floor of the ocean to the surface provided the food that caused the algae population to explode once it reached the Gulf. On April 14th 1998, a red tide appeared in the waters off Hong Kong and resulted in the death of thousands of fish and the closure of beaches.

Reflecting Road Studs
The first reflecting studs were Follsain Gloworm studs patented by Jean Neuhaus. They were first laid in England by Market Harborough Urban District Council in March 1934. The first in London were also Gloworm studs and they appeared in Bedford Avenue, also in 1934. The Catseye studs were invented by Percy Shaw of Halifax. It is said that he had the idea for them as he drove between Halifax and Bradford in dense fog. The reflection of the eyes of a cat in his headlamps alerted him to the fact that he was about to drive off the road. Had he not stopped he would have driven through a fence and over a sheer drop.
He experimented for years and finally laid, at his own expense, the first fifty studs on April 29th 1934. These were at a notorious accident blackspot near Bradford and proved such a success that he set formed a company Reflecting Road Studs Ltd. To manufacture them. The Catseye consists of a cast-iron well weighing about four and a half kilograms and which is sunk into the road surface. A rubber pad set into the centre of the well is depressed when a car's wheels pass over it and automatically polishes the glass reflectors. In 1937 the Ministry of Transport decided to test all ten of the reflecting studs then available. They laid all varieties out on a five mile stretch of road and monitored their performance and resilience over a two year period. Only the Catseye remained in perfect condition and fully functional at the end of the trial. All of the others had either fractured or stopped reflecting.

Relativity
Einstein's Theory of Relativity was designed to account for deviations from Newtonian mechanics when very high relative velocities are involved. In 1919, striking confirmation of the theory was accomplished during a total eclipse of the sun. At sites in both Brazil, and off the west coast of Africa, measurements were made of the position of stars visible close to the sun during a solar eclipse. These observations showed that the light of stars was bent as it passed through the gravitational field of the sun. This was a key prediction of Einstein's theory that gravity affected energy in addition to the familiar effect on matter.

Richter Scale
The magnitude of most earthquakes is measured on the Richter scale, invented by Charles Richter and his colleague Beno Gutenberg in 1934. The Richter magnitude is calculated from the amplitude of the largest seismic wave recorded for the earthquake, no matter what type of wave was the strongest. The scale also takes into account the instrument's distance from the epicenter. Richter used a seismograph (an instrument generally consisting of a constantly unwinding roll of paper, anchored to a fixed place, and a pendulum or magnet suspended with a marking device above the roll) to record actual earth motion during an earthquake. However, his seismograph was highly specific and only measured shallow earthquakes in Southern California. Scientists have now made other magnitude scales, all calibrated to Richter's original method, which allow the use of a variety of seismographs to measure the depths of earthquakes of all sizes around the globe.
The Richter Scale ranges from 0 to 10 and the magnitudes, and at Gutenberg's suggestion, are based on a logarithmic scale (with base 10). Put simply, this means is that for each whole number change on the Richter scale, the energy released by the earthquake has changed by a magnitude of ten. Using this scale, a magnitude 5 earthquake would result in ten times the level of ground shaking as a magnitude 4 earthquake. The actual numbers are calculated by dividing the log of the amplitude by the period (the time/distance between wave peaks) of the dominant wave. The different effects of earthquake magnitudes and the average number of times they occur in a year are summarised in the following table.

Earthquake Magnitude Classes

Class	Magnitude
Minor	3 -3.9
Light	4 - 4.9
Moderate	5 - 5.9
Strong	6 - 6.9
Major	7 - 7.9
Great	8 or more

Andrés Manuel Del Rio
Del Rio (1764-1849) was a Spanish-American mineralogist who in 1801 believed he had discovered a new element. While a professor of mineralogy in Mexico, Del Rio examined a specimen of brown lead from Zimapan and found a new metal, similar to chromium and uranium, which he name erythronium, after the red colour of one of its chemical compounds (from the Greek erythros, "red"). Other chemists were sceptical and he eventually accepted their criticism and came to regard it as impure chromium. The Swedish chemist Nils Gabriel Sefström, rediscovered the element in 1830 and named it vanadium, after Vanadis, the Scandinavian goddess of beauty, because of its beautiful multi-coloured compounds. Since the early 1900s, vanadium has been used as an alloying element for steels and iron.

Roller skate
In 1869, the American Isaac Hodgson received a patent for his "roller skate." It was not the first. The earliest known type, using two large wheels on each skate, was invented in 1759 by Joseph Merlin, a Belgian musical instrument maker living in London. In 1760, Mrs Cornelly gave what has become her famous masquerade at Carlisle House, in Soho Square in 1760. Merlin astonished the assembled guests when he sailed into the ballroom mounted on his skates and playing a violin. However, could neither change direction or stop himself with the result that he crashed into a large mirror valued at more than £500. It was smashed to smithereens, his violin was destroyed and he suffered severe injuries.
On April 22nd 1823, Robert John Tyers, a London fruit merchant, took out a patent on his Volitos an "apparatus to be attached to boots ... for the purpose of travelling or pleasure," which used five small wheels in a single line. He first demonstrated them in the safer surroundings of the tennis-court in Windmill Street, also in Soho. Somewhat similar skates with rollers were used to simulate ice skating in a scene of Meyerbeer's opera Prophète Paris, on the 16th of April 1849. Another American inventor, James L. Plimpton of New York, had a patent for four-wheeled roller skates from 1865, whose right was affirmed at a trial for infringement on the 28th of January 1876. These skates had small boxwood wheels and were cushioned by rubber pads. These skates allowed the wearer to maintain a proper balance and also to execute quite intricate movements and gave rise to the roller-skating craze which swept across America in the 1860s and Europe in the 1870s

Roman Horses
There is a direct link, via London, between the rumps of the horses used in ancient Rome and the modern space shuttle. The pivot was the railway system.
The railway gauge in Britain is the very odd figure of 4 feet 8.5 inches. That was used because the people who built the railways had already built the tramways and that was they gauge they had used then. The trams had that gauge because the builders used the same gigs and tools which had been used to build horse-drawn wagons and stage-coaches, so the trams had the same wheel spacing. The wagons and coaches had to have that wheel spacing because the paved roads which led from London the rest of the country had deep and well established ruts with that separation. Any other spacing would have resulted in a much more bumpy ride and many broken wheels. These roads had been built by the Romans and their chariots made the initial ruts. These chariots either came from, or were modelled on those used in, Imperial Rome. They were drawn by a pair (or team of pairs) of war horses so the design was built about the need to incorporate the width of two horses. The rump, of course, is the widest part of the horse so the chariot had to be wide enough to incorporate the rumps of two war horses.
The American Space Shuttle incorporates two booster rockets attached to the sides of the main fuel tank. These are known as solid rocket boosters (SRBs) and are manufactured by a company called Thiokol at a factory in Utah. Utah is along way from Cape Caneveral and the SRBs have to be transported by railway. The railway route out of Utah includes a long tunnel through the Rocky Mountains. The SRBs had therefore to be designed so that they would fit through the tunnel when loaded on an open freight wagon. The tunnel is only slightly wider than the railway line itself, which is the American Standard Gauge in width. That Standard Gauge was adopted when the railways were first being built in America. When they were being built, the authorities used expertise, and workers, brought over from England. That meant that the English gauge also became the American Standard Gauge. Therefore, a major design feature of one of the world's most advanced transportation systems is ultimately derived from the width of a horse's rump in ancient Rome!

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