For an explanation, see the main splats page
SPLATS about measurement science
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.
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