WORLD ACHIEVEMENTS

Bay of Plenty Beacon, Volume 1, Issue 93, 27 November 1939, Page 7

WORLD ACHIEVEMENTS

HOW LONG IS THE YARD?

I We learn at school a table of meas-' ure which tells us that twelve inches equal one foot and three feet equal one yard. Yet it has taken the scientific men to tell how long the yard is. | The English standard yard is the length between two points on a tablet on the outside wall of the j Royal Observatory at Greenwich, or of a similar measure set in the stones of Trafalgar Square; though in 1855 a revision of the length of the yard was made, a microscope and a micrometer being used. The length was then fixed as being that between two fine lines on two gold plugs near the end of a bronze bar kept always at a temperature of 62 degrees Fahrenheit at the Exchequer. But clever as this calculation was it did not satisfy the* experts of the National Physical Laboratory at Bushy Park. They wanted a measure that would not only be known by all the world but by the Universe —somethong that the men of Mars would be able to understand. Knowing that light and its wavelengths are the same on Mars as on the Earth, the measurers have fixed the yard in terms of the wavelength of a line of light emitted by the metal cadmium when it is vapourised. Believing the foundations of the stars are the same as of the Earth, and if there is cadmium on our (Continued at foot of next column)

globe it will be present throughout . the Universe, the scientists claim that when it is vapourised anywhere the wavelengths of its red line will L always be the same. ! Therefore, if you ever meet a Mar - tian who asks: "How long is Hhc 5 yard?" just reply: "The yard is , 1,419,818.3 times the wavelength of * cadmium vapour," and he will uni derstand.