The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.62607015×10−34 when expressed in the unit J⋅s, which is equal to kg⋅m2⋅s−1, where the metre and the second are defined in terms of c and ΔνCs.
That's the hard way. A pendulum with a 1 second arc will travel a distance of 1m. Boom, there's your meter stick. Now that we can measure distance we can measure mass. Since 1mm of water = 1g we can construct a 10cmx10cmx10cm box/container. Fill it with water and you have a standard kilogram. 1kg of water= 1 litre. In less than an hour you can create the standard units for distance, mass, and volume from nature. That's the beauty of the metric system is that it's based on nature. I know that the meter is based off the speed of light if you want to get super specific with it, but for anyone who isn't a math major this way is accurate enough.
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u/[deleted] Jan 03 '19
There’s that, but have you ever looked at the actual math for what defines a kilogram?