Joules For You

Why waste time use lot units when few units do trick

What do calories, watt-hours, megatons of TNT, electron volts, BTU, erg, and foot pounds all have in common? They're all actually Joules in disguise! Specifically they are 4.184, 3600, $4.184\times {10}^{15}$, $1.602\times {10}^{-19}$, 1055, $1\times {10}^{-7}$, and 1.356 Joules respectively!

Joules represent the SI unit of energy. In raw metric units they are represented by $1\text{kg}·{\left(\frac{\text{m}}{\text{s}}\right)}^2$ which is easy to remember since $E=m{c}^2$, thanks Einstein!

I'm sure all of these other units have their place in history, but I don't understand why the others are still in use. People who want the US to switch to the metric system should get onto the Joule train first.

Understandability

Conceptualizing a joule is kind of hard for me. I don't have a good mental scale like I do for distances or mass.

I'm sure putting these different concepts onto the same scale and having that scale hammered into me during early schooling would go a long way!

Do I need to know how many days I could live on a nuclear bomb worth of energy? Or how much I would need to pay in electricity and gasoline to keep my body working? Probably not, but by treating these units for what they are, this sort of mental arithmetic becomes a lot easier. (It's 20,000-1,400,000 years depending on the bomb, $0.35 vs $0.24 per day depending on the cost and of course assuming the energy could be converted directly.)

Watt-hours

This unit is particularly offensive to me. In most cases when time is involved in a unit, it's a derivative with respect to time (meters per second, miles per hour, coulombs per second). The watt-hours is an exception to this since it's an integral term - take the number of watts and add them up over an hour. This would be like measuring distance with knot-hours (which I'm sure is done somewhere)!

For me, this makes it unnecessarily confusing. I dream of a world where we can treat energy like a first class citizen, and power the same as we do speed: Joules per second. Horsepower, watts, decibels - all just Joules per second in disguise!

Orders of Magnitude

This point is common with other metric system arguments - why create multiple units for the same quantity when one unit with different scales will do?

Making it more common to use units with an associated order of magnitude, like kilojoules instead of (kilo)calories or watt-hours, petajoules instead of megatons of TNT, etc. would make thinking in orders of magnitudes easier and make everyone happier.

Try using Joules in your daily life and see what happens!