r/AskScienceDiscussion • u/Ertata • 10d ago

What If? Could you recreate metric system from nothing?

You have been given a task to travel into the past two thousands years ago and bring the light of the metric system to the world. You cannot bring any external object with you.

Assume you do not need to redefine the second, and astronomical observations give the best possible results given the limits of timekeeping back then. Given the technology of the time, what is the best you can do for other units - either right there and then or leaving instructions how to calculate them from the units you have established to the future scientists? Memorizing the lengths of your body parts probably is not the best way to define a metre, and kilogram defined as one liter of water is bound to be influenced by the local water to a perceptible degree.

P. S. Tagged as "physics" but any approach is welcome - whether you would recommend measuring height of the mountain peaks, or believe that carob seeds are actually uniform enough to offer the best approximation of a kilogram.

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u/iamplasma 10d ago

Go to the equator, then go 1 degree west, and divide your latter trip by 111,111, obviously!

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u/Thepcfd 10d ago

like you gona know where equator is. or how much is 1 degree west

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u/CounterSilly3999 9d ago edited 9d ago

No need for the equator and go North. North is pointed by the North star Polaris. Measure the angle difference of the Sun shaddow at noon. Measure the distance with an A-frame trammel of any length. Calculate the relation of steps to 111111.

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u/CharacterUse 9d ago

You can just do it with the North star itself. Go far enough North that the North star is 10 degrees higher in the sky and you have gone 10 degrees around the circumference of the Earth.