Why do scientists and researchers use SI unit in their work
As the name suggests, it was designed to be used all over the world. Moreover, unlike the 18th century, today's scientific research is a global effort and experts from all around the world collaboratively work together. In such a scenario, it is wise to use a uniform system of measures. Nobody likes discrepancies in data that arise due to shabby conversion.
Another major reason for the widespread acceptance of the SI system is that the magnitudes suit most needs. Take a look at the more than helpful CGS (Centimetre-Gram-Second) system. Nobody measures distance by the centimetre or weight by the gram for everyday purposes. Unless you're a particle physicist working with electrons and bosons, the SI system should work well.
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