# Why has the Kilogram been redefined?

November 19, 2018

Students around the world are frowning as to why the kilogram has been redefined. Will it impact the way they solve numerical problems involving mass/force? Does 1 kg still remain equal to 1000 g?

If these questions are puzzling your mind, do not panic as we try to answer what exactly most of the young people are looking for.

So let’s head on to the first question…..

### Why has the Kilogram been given a new definition?

The first chapter in modern day science books (usually college/university level) often explains the definitions and the physical significance of SI units. But since we are lazy, we tend to ignore this part and move on to the following chapter.

Thus, one shouldn’t be surprised coming across students who don’t know anything about the kilogram, except for the fact that it is the SI unit of mass.

Basically, until this ‘revolutionary’ change, the kilogram was defined (physically) by the weight of a platinum-iridium lump called “Le Grand K”, which is locked away in a safe in Paris. However, despite being shielded by as many as 3 glass jars, Le Grand K gets ‘dusty’ and ‘dirty’, which in turn lead to its deterioration. Hence, it does not weigh the same each time.

Although the fluctuations are very very minute- around 50 parts in a billion, even less than the weight of a single eyelash, these still play a huge deal in the fields of nanotechnology, drug development, precision engineering, etc. Therefore, the scientists were looking for a more robust and reliable technique to define the kilogram.

### Then how will the kilogram be defined now?

The kilogram will now be defined in terms of Planck’s constant (h) which is equal to 6.63 x 10-34 J s.

The process involves an apparatus called the Kibble balance, which makes use of the planck’s constant to measure the mass of an object using a precisely measured electromagnetic force.

Thus, the new definition is formula-oriented, while the previous one was based on the mass of a physical-object that had discrepancies in weight.

### For Students….

Students and layman shan’t worry about this as 1 kg is still equal to 1000 grams and there will be no changes whatsoever in the way numerical problems are solved!