Statistics from Altmetric.com
WHAT IS A SECOND?
Since 1967, the international standard for a second has been defined as the time it takes for 9 192 631 770 oscillations of the microwave radiation corresponding to the transition between two hyperfine levels of the ground state of an atom of celsium-133. It sounds complex and an extremely accurate method for measuring time although a more recent proposal using a ytterbium standard is superior by a factor of more than a hundred times.
WHAT IS A METRE?
The origins …
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.