For an explanation, see the main splats page

The principles of measurement science

• Old units of measurement include the grain and the line, the yard and other units which were at best poorly-defined and which varied from place to place.

• In 1832, Karl Gauss pointed out that a few fundamental units, once defined, could be used to generate many more derived units in a consistent system.

• Around the world, SI units are the standard units of science, based on the meter, kilogram, second and ampere and a variety of combinations of these units.

• Many of the things that we measure are scalar quantities, having a value but no direction component, like length, speed, but not velocity, and mass.

• Some of the things that we measure are vector quantities, having both a value and a direction aspect, like velocity (but not speed) and acceleration.

• We can use various observations taken from a distance to measure where we cannot go, so that we can measure the distance to the Sun, or its temperature.

• One of the standard units of astronomical distance is the light year, the distance that light could travel in one year at 300,000 kilometres per second.

• All measuring instruments operate within limits of accuracy, and when several different measurements are combined, the possible error is increased.

• Indirect measurements of values like the distance to the Sun or the Sun's temperature, are more open to error, because of the indirectness.

• A correlation between two measurements that seem to vary together does not indicate with any degree of certainty that one of them causes the other.

• In 1784, Charles Coulomb described the operation of the torsion pendulum, later used to measure very small electrostatic and gravitational forces.

• Before electronic surveying equipment, a chain was commonly used to measure a long baseline, from which sightings were then taken on prominent landmarks.

• Given time and patience, it is possible to use a theodolite and chain to take enough measurements of bearings and distances to map a whole continent.

• The process of mapping by chain and theodolite involved building a sequence of triangles linked together, so it was called triangulation.

• Classic major surveys were done by Mason and Dixon (America), John McDouall Stuart (Australia) and assorted French scientists in France, Lapland and Peru.

• Some of the key mapping exercises were to measure the length of a degree at different latitudes on the Earth's surface, some at the equator, some further north.

• Once the degree had been measured at different latitudes, scientists knew the true shape of our planet was not a sphere, but more like a flattened sphere.

• Very large distances on land can be measured using radar and similar signals, much more easily than the old survey method of 'chaining' the distances.

• The Fahrenheit scale was designed to avoid any temperature that was negative, since Fahrenheit felt ordinary people could not cope with negative numbers.

• Until there were reliable thermometers to use, it was not possible for scientists to recognise the important difference between heat and temperature.

• Temperature may be measured as absolute temperature on the Kelvin scale. It is possible to approach a zero temperature, but it cannot be reached.

This file is http://members.ozemail.com.au/~macinnis/scifun/splatsmeasure.htm, first created on February 19, 2008. Last recorded revision (well I get lazy and forget sometimes!) was on February 19, 2008.

©The author of this work is Peter Macinnis, who asserts his sole right to the product as it is packaged here, recognising that many of the ideas are common. You are free to use this as a model to do your own version. Copies of this whole file or site may be made and stored or printed for personal or educational use. You can contact me at macinnis@ozemail.com.au, but only if you add my first name to the front of that email address -- this is a low-tech way of making it harder to harvest the e-mail address I actually read.
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