Our standard unit of length is the metre, m. This is useful for things of a human scale but less good for measuring very small or very large objects. That is why we use other units that are multiples ...

Length, time and volume are all examples of quantities close quantityA property that can exist as a magnitude, usually with a numerical value. For example, speed (quantity) is measured in metres per ...

Brian Resnick was Vox’s science and health editor and is the co-creator of Unexplainable, Vox’s podcast about unanswered questions in science. Humanity has a new definition of the kilogram, the ...