# Talk:2520: Symbols

Great work by whomever did this, but is it possible R_e is something else? I agree that the numerical aspect makes it seem like a fluid mechanics problem, but I've never seen the Reynolds number with a subscripted e... only a regular size e, such that it is Re, not R_e. 108.162.237.93 20:36, 24 September 2021 (UTC)

- R sub e (not Re) is Effective Reproduction Number. This is related to infection rates. I'm pretty sure it's R sub e, not Re given that infection rates are very much on his mind right now.
- It would be out of place relative to all the other entries, though, which are all physics related. IMO it's more likely this was an error.

- Earth's radius is abbreviated "R sub e" 162.158.107.4 21:30, 24 September 2021 (UTC)
- Could be the remainder of a series (i.e. the error when using the first terms of the series as an approximation). Determining upper bounds on this error is usually very tedious.
- R sub e is tire effective rolling radius (or effective radius)--a radius based on the distance traveled by one rotation of a pneumatic tire. Re is similar to the unloaded radius (for radial tires) and normally larger than the loaded radius (distance from axle to ground).
- My first thought was that this referred to the "real part" operator, although that's typically represented by a plain Re (no subscript).

Re seems to be related to number theory, like in those papers where's they tediously prove that there are infinities of different sizes.

Extra vote for number theory theory, I've seen R_e most when referring to Real part of a function, which does often bring in tedious calculations

Re is almost definitely not meant to have any electronic structure meaning here. The subscript alpha in R_alpha is indexing over x,y,z (cartesian coordinates) as a transition dipole moment term.

T to the fourth power looks like blackbody radiation, any ideas what specifically that formula represents? 162.158.203.22 20:40, 24 September 2021 (UTC)

- There's an equation for what reflects off a spherical object that is a quartic equation (although I'd expect concave reflectors, not convex ones, to risk skin-burn. Or, more likely something to do with UV (non-)absorbtion or generation, but I imagine someone knows
*exactly*what it is, without someone like me just guessing wildly. ;) 141.101.99.82 21:05, 24 September 2021 (UTC)

This wiki does not seem to have a consistent formatting structure for lists

The *N _{A}* could also soon become NAN (not a number) thus being only a step away from the dangerous arthmeric error. --162.158.88.43 21:38, 24 September 2021 (UTC)

**Bold Title**

- Content starting with a tab

**Bold title**content continues on same line

- Regular title

Content on a new line, but not starting with a tab

As well as tables and mixes of these formats. Maybe someone should pick one and apply it to all the explanations. I just noticed it because of the inconsistencies as people are quickly throwing something together for this new comic. 162.158.107.4 21:02, 24 September 2021 (UTC)

I read the penultimate line as "Mg" and was trying to imagine a meaning for "megagrams per kilogram". Sloppy Greek letter there, Randall. Nitpicking (talk) 03:17, 25 September 2021 (UTC)

- I find this criticism very unreasonable. Randall's "m" is written very differently, there are plenty of examples of it in this very cartoon to avoid confusion, and micrograms are far more commonly used than megagrams. I had no problem whatsoever recognizing the letter mu, and I don't see how this could be a problem for anyone already familiar with that letter. 162.158.90.85 11:11, 26 September 2021 (UTC)

Why are partial derivatives considered graduate-level? They're typically covered in first level undergraduate science courses, along with gradients and such. FPSCanarussia (talk) 03:34, 25 September 2021 (UTC)

The reference to "micrometer" links to the Wikipedia page for the measuring device, but it should link to the page for the unit of length: https://en.wikipedia.org/wiki/Micrometre Professor Frink (talk) 15:58, 25 September 2021 (UTC)

Adding to “Micrometer/Micrometre” above: this “any” is not really correct:

- Of course, micrometers are used as a measurement of distance in other contexts, but any distance-measuring device capable of accurately measuring micrometer distances would also be expensive.

The “Micrometers” as seen in the Wikipedia article can measure distances of some micrometers accurately, but are not really expensive. Probably even cheaper than any equipment which can *not* measure distances. --162.158.88.239 18:19, 25 September 2021 (UTC)

In certain circles (or, perhaps, between them as they roll), the typical Reynolds number is just three digits... ;) 162.158.159.95 20:04, 25 September 2021 (UTC)

"When radiative transfer is large enough to be the most important form of heat interchange, it is normally also large enough to sear the skin with thermal or ultraviolet burns." Radiative transfer is the dominant heat transfer from a (idle) human body in a 20C room. There is no risk of seared skin in this situation. As an aside if people understood the role of radiative heat transfer we'd have more comfortable and cheaper HVAC systems (and more underfloor heating).172.70.34.91 20:08, 25 September 2021 (UTC)

I cannot recall ever using Avogadro's constant in a stochiometric calculation. You do everything in mole or gram mole. N_{A} implicitly cancels and never even appears.172.70.34.91 20:08, 25 September 2021 (UTC)

mSV (millisievert) is also likely to show up in other internet debates as well, usually related to Chernobyl, Fukushima, Three Mile Island, or [other such nuclear accidents|https://www.ucsusa.org/resources/brief-history-nuclear-accidents-worldwide] Also likely to show up in any discussion on nuclear energy to alleviate global warming, especially given modern reactor designs to reduce such incidents.Seebert (talk) 20:15, 27 September 2021 (UTC)

d⁄dx is not the symbol for a single variable derivative, but the symbol for a total derivative. Partial derivatives and total derivatives happen to be equal when the function depends on only one variable, but in general both partial and total derivatives are used in multivariate calculus 198.41.231.172 05:56, 29 September 2021 (UTC)

I know arguments on the Internet often aren't logical, but the mSV really wouldn't make any sense in the context of arguing about 5G as that is non-ionizing radiation. Ullallulloo (talk) 14:37, 7 October 2021 (UTC)

eV may more specifically be a reference to https://en.wikipedia.org/wiki/Anatoli_Bugorski --172.70.35.70 03:59, 8 October 2021 (UTC)

R_e could also refer to the elastic limit in solid mechanics, where it is the lowest stress at which permanent deformation will occur. At least my university (in Germany) uses that symbol. Interestingly, stress analysis can also involve a lot of numerical work, at least outside of simplified examples. 172.70.250.185 (talk) *(please sign your comments with ~~~~)*

- No comment about your experience, but in response to your edit-comment of "(sorry if I'm editing wrong)", just remember to sign with four tildes ( ~~~~ ) here in the Talk page, to make any discussion easier to read and timestamp things a bit (it was written just now, so I haven't bothered to add that detail, above, future readers can correctly assume just a few minutes have passed from then until now and my own signature addition). 172.69.79.173 19:58, 22 July 2022 (UTC)