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Science and Physics · entry 39 of 52
The meter was originally defined as one ten-millionth of the distance from equator to pole.
The longer version
Early scientists wanted a length that anyone could reproduce without referring to a particular object. They chose a fraction of the planet itself, taking the distance from the equator to the pole along a meridian and dividing it into ten million parts. Expeditions measured the relevant arc with surveying instruments over many years.
Later measurements showed the original survey was slightly off, and the definition moved to a carefully kept bar, then to a wavelength of light, and finally to the distance light travels in a fixed fraction of a second. Each step traded a physical artefact for something any laboratory can realise.
Where this entry sits
Everyday physics and chemistry hide small wonders in plain sight, from kitchen reactions to the light in the sky. These short facts explain matter, energy, electricity, magnets, sound, and the simple units we use to measure the world. The full list sits on the Science and Physics page, where every entry is listed in order.
More From Science and Physics
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Read 43An atom is mostly empty space, with tiny electrons orbiting a dense central nucleus.
Read 44Molecules in a gas move freely, while those in a solid only vibrate in place.
Read 45Density compares mass to volume, which explains why a small rock can feel heavy.
Read 46Dropped objects fall at the same rate regardless of weight when air resistance is removed.
Read 47Water expands as it freezes, which is why ice floats instead of sinking to the bottom.
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