Cursed Units 2: Curseder Units

Friendly reminder that the pH of the sun is approximately -3.

how could people complain about the music??? it's literally the best part with how much character and emotional weight it gives every part of the videos!

I put milk powder in my milk to get more milk per milk

Chemistry is best described as “Dimensional Analysis: the game”.

Materials science: "We will not cancel the cm." Electricity: "resistivity is totally measured in ohm*meters, just trust me."

chemist here. we love our cursed units! one of my favourites is the rate constant of a chemical reaction, whose units depend on the order of the reaction. For a 0th order reaction it is mol/L/s, for 1st order it is just s^-1, for 2nd order it is L/mol/s, for 3rd order it is L^2/mol^2/s, and so on. The real fun comes in because some chemists prefer to use dm^3 instead of L, which gives you beautiful units like dm^6/mol^2/s

As everywhere I see cursed units, I have to add: The ounce. As a thickness. In PCB-manufacturing, the thickness of the copper layers will be gives as ounces (of copper per square foot). So if you are working in imperial units you will have to look up the density of copper. If you are working in SI and planning to do anything useful, say calculate the max current, you will need to get the density of copper, and also what a foot and an ounce are in SI.

You gotta make a full section on radioactivity units. There's at least 7, and it's painful. (Becquerel, Curie, Gray, Sievert, Ren, Rad, Roentgen, etc.) Also explain why we have so many measurements for pressure (bar, torr, psi, pascal, inHg, cmHg, mmHg, ATM, technical ATM (?), inH2O, kg/cm², the list goes on and on.)

I could write a big effusive textwall, but I'll keep it simple and just say that everything about these videos is sublime and the 40 minutes we've gotten are an absolute gift. Thank you.

Electronic engineer here, i had a good dose of cursed units when i was learning why Inductances and Capacitances behave like resistances in complex variable

I'm an optometry student and i remember when our teacher told us about the barrier units that we use in a contactology class and said that it was a complete mess that he wasn't going to explain to us the mathematical meaning. Now i understood why, it had blown my mind hahaha 😂

As an engineering student, I absolutely LOVE these videos. In high school, my physics teacher always let us use a unit reference table on every test. When someone asked why, he spent a whole class explaining how you could technically use some advanced physics to express just about every unit in terms of any other unit using universal constants. The "standard" units we choose, at the end of the day, are just a point at which someone decided that we should just abbreviate, and aren't always the best/most practical way of understanding things (he brought up mpg expressed as cm^2 as an example). We aren't taking physics to memorize all of these standards, we're taking it to gain a further understanding of how the world works and so shouldn't have memorizing the standards as an obstacle.

I've got a fun one for you that comes out of meteorology: CAPE, or Convective Available Potential Energy, is a measure of the amount of convective energy that a hypothetical lifted parcel of air has available to it once it is able to convect adiabatically through the column of air above it. This is expressed in J/kg, as in joules of energy per kilogram of air. That's pretty sensible, you might think, except that joules are expressed as kilogram-meters-squared-per-second-squared. So the unit is actually meters-squared-per-second-squared. Now, here's where the accursedness comes in: You can get a crude estimate of the theoretical updraft velocity within a supercell by square-rooting the CAPE value. The updraft velocity is in meters per second after you do this, which suddenly makes sense when the dimensional analysis is done.

When the world needed him the most

11:30 I'm very proud of myself for immediately guessing c. While I don't know WHY it's there, it only makes sense to me that these stupid units must involve it somehow. It's the only constant that makes sense to me.

5:54 Physics student here, I'm feeling very relieved right now because I felt like I was going mildly insane learning reaction coefficients for my biophysics course. Also, I'd like to nominate Specific Impulse as a cursed unit. Not because it's that bad to use, it's just inexplicable. It's the measurement for the efficiency of rocket engines, which is measured in seconds. Why? Well, if you do the calculations, you find that the amount of velocity change you can get from your ship is proportional to the velocity of the exhaust gases, in m/s. Except, for some reason, it is then divided by the earths surface gravity of 9.81m/s², giving m/s/(m/s²)=s. For a unit that is pretty much never used on the surface of the earth. And whenever you use it, you need to multiply by 9.81 again.

19:00 Hol' up. you can rewrite the pressure as force/area, which cancels with the other area in the denominator. Mol, can be replaced with 1, if you scale everything down by the avogadro number. You end up with cm/(second*force). Now, Force is just mass×distance/timesquared. So it is distance/(time×(mass×distance/timesquared)). It simplifies to mass/time. In the end it really just tells how much stuff get's trough over time.

3:18 I think a reason as to why torque has the same unit as joules is that torque is the cross product between force and length while work is the dot product, so they're still describing different things

One great thing about Planck units is that a velocity is always expressed as a proportion of the speed of light, which is basically β, making the Lorentz factor an elegant 1 / √(1 - v²).

From the Torr article on Wikipedia: "Historically, one torr was intended to be the same as one "millimeter of mercury", but subsequent redefinitions of the two units made them slightly different (by less than 0.000015%)." Why.