Let’s Get Physics-l: S.I. Units

S.I. Units or Système international d’unités are used by 99% (Just under, if we are being picky (98.96907216% (If we agree on the fact that there are 194: World Atlas) if we are being extremely picky) of world’s countries (The USA and Thailand being the only exceptions (A little odd to say the least)). Initially devised by the Father of Chemistry (A well earned title to say the least) Antoine Lavoisier and further developed by William Thomson (Lord Kelvin (Ring a bell? (The unit for Thermodynamic Temperature are Kelvins))) and James Clerk Maxwell, they provide a way for scientists all over the world (almost) to understand and communicate more efficiently.

There are 7 base units that are referred to as the S.I units. The table below shows what these are:


Symbol Unit Name Unit Symbol Colour

(Wait and see)

Length L Metre m Red
Time t Seconds s Blue
Mass m Kilograms kg Green
Thermodynamic Temperature T Kelvin K Black
Electrical current I Ampere A Yellow
Amount of substance n Mole mol White

Luminous intensity

Iv Candela cd


The S.I. Units provide the foundation for all units which can then be used to quantify other units. To some extent, if you’re one for visualising this sort of stuff, you could describe the S.I. units as Lego bricks. Let’s say, for example, a red brick and a blue brick are put together. If you then substitute in the unit symbols (see above) you get metres second. This isn’t strictly a unit so this may seem like a pointless system to use. However, if you arrange them in such a way you can achieve metres per second which is the unit for speed. How, I hear you ask, can you achieve this? See below:

Displaying IMG_3549.JPG
Metres over seconds = Metres per second (Do you see where I’m going with this?)

This system is all well and good for simple units but another issue is posed when we take into account the fact that some units contain squares and even cubes. However, there is a way you can also represent this:

Displaying IMG_3550.JPG
Kilogram x Metres over (Second x second) = Kilogram x metres per second squared or Force (Newtons)

You can, to an extent, achieve several different units by using multiple bricks to represent squares and cubes. Noted: there are far simpler ways of achieving this sort of system which are less complicated than Lego but it does, to an extent, show an accurate representation of the unit (If you use your imagination) and is mildly enjoyable (For me anyway).

In summary, S.I units provide the basis of all units and are widely used across the globe as the means of quantifying stuff. There are 7 base units which can be seen above in the table. If you have any thoughts or questions on the topic please leave them in the comments. What did you think of the Lego idea? Do you have any suggestions yourself on representing units? In addition, as this is the first proper post for this feature,  feedback would be greatly appreciated on whether or not this is effective and/or useful.


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