Comments on: Dimensional Analysis

By: Casey Kasem

Casey Kasem — Wed, 30 Nov 2011 19:14:11 +0000

Well that is wrong. What it is saying regarding the relationship between the MPG of a Prius and the width of the English Channel is that if the MPG of a Prius rose (build better Prius) then the width of the English Channel would therefore increase (England drifting to the sea).

By: Kos

Kos — Wed, 29 Dec 2010 15:51:14 +0000

You forgot Pol— uh.

The last line: “But what if they build a better Prius? – Then England will drift out to the sea” is a reference to all the negative rumour around Toyota Prious (and it being actually less economic than regular gas gugglers). The phraseme about England drifting to the sea suggests the unlikeness of a new Prius being any better.

I still love its design, though.

By: laola1

laola1 — Fri, 15 Jan 2010 10:10:17 +0000

The comic is a response to http://scienceblogs.com/pharyngula/2009/12/the_god_equation.php?utm_source=mostactive

By: Michael

Michael — Fri, 15 Jan 2010 08:23:33 +0000

And of course the comic is making fun of the way some physicists derive the general form of a formula by looking at the units of the quantities involved. Also, the teacher’s first remark references the experimentalist’s habit to use “to within numerical precision” (depending on the numbers you use you get something between 3 and 4, which is equal to pi “up to numerical precision”) and it also makes reference to a typical crackpot argument, which tries to assign a fundamental meaning to a co-incidental combination of quantities or a co-incidental numerical result.

By: K

Wed, 13 Jan 2010 20:39:32 +0000

one planck energy = 543.3 kWh (so sayeth wikipedia)
((543.3 kWh) / (3.5 million atm)) * ((48 mpg) / (21 miles)) = 3.33016968
(so sayeth google calculator)

By: Olie

Olie — Wed, 13 Jan 2010 17:48:05 +0000

The units are verified and it is evaluated here:

http://jaxwebster.wordpress.com/2010/01/13/xkcd-dimension-analysis/

The overview of it is that it does indeed work. The units cancel out and the values, when input, come to between 3 and 3.5 depending on the exact values you use. I wonder how long it took him to find that.