3047: Rotary Tool

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720 Ollie

|< < Prev #3264 (June 26, 2026)

Title text: This discovery was key to his demonstration of regular/goofy symmetry violation, which won him gold in the theory portion of the X Games.

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Explanation

This is one of 38 incomplete explanations: This page was created by a spin-½ boson. Don't remove this notice too soon. If you can fix this issue, edit the page!

Tony Hawk tells Cueball that doing a single 360° spin causes him to land backward rather than forward. This is unexpected, since a 360° turn in the xy plane is a full revolution, meaning that it should normally return Tony Hawk to his original position rather than perform a half-rotation (normally the result of a 180° spin). As repeating this would reverse his reverse, doubling this to a 720° spin is what finally allows him to land forward. Normally, revolving 360*n degrees, for any whole number (n=0, n=±1, n=±2, etc) should leave him pointing the same range as before, but for him he returns to the same orientation if n is even, but he lands with the opposite orientation if n is odd.

The caption reveals that this is because Tony Hawk is a spin-½ fermion. Spin-½ fermions have the unusual property that they must be rotated through two full turns before returning to their original configuration. This explains the paradox, but is unusual because spin-½ particles are normally very small, only occurring in quantum physics rather than Newtonian physics. Since Tony Hawk is not a subatomic particle,^{[citation needed]} it is unclear how his skateboard tricks could be described only by quantum physics.

A fermion is a classification of particles (or groups of particles) whose intrinsic angular momentum (aka "spin") is half-integer multiple of the reduced Planck constant; the behavior of these objects' spin is described via spinors, a type of complex vector. This is in contrast to bosons, whose spin is an integer multiple of the reduced Planck constant, and described by the normal Euclidean vectors you know and love.^{[citation needed]}

Tony Hawk is an American skateboarder credited with inventing the 720, a trick (under normal circumstances) involving two full mid-air rotations. Since Hawk invented it in 1985, larger mid-air rotations have been invented (up to 1260, three and a half rotations), and according to the comic they can have even stranger quantum properties.

The title text is a riff on the Nobel Prize-winning discovery of CP violation, (something that may have been on Randall's mind, recently, due to the prior comic's subject matter/anti-matter). The regular/goofy styles of riding a skateboard could be considered as a physical quality of the "skateboarder particle", as values of charge and parity are of subatomic ones. The X Games are a prestigious 'street-sport' event that includes competitions in skateboarding as well as other related board- and bike-disciplines. The parallel is made between being able to win a gold medal for impressive skateboarding skills (and demonstrating new tricks, in the process, as Tony Hawk has been known to do) and earning the gold Nobel Prize medal for a scientific achievements in Physics or one of the other established prize categories. So far, nobody has done both of these. But, if this comic is entirely true, perhaps Tony Hawk could be the first to do so.

"Goofy matter", and Tony Hawk's involvement in physics, is also the subject of 2967: Matter. Skateboarding is also the subject of 296: Tony Hawk.

Transcript

This is one of 29 incomplete transcripts: Don't remove this notice too soon. If you can fix this issue, edit the page!

[Tony Hawk and Cueball are talking. Tony Hawk is holding his skateboard. An image, above the heads of Tony Hawk and Cueball, depicts Tony Hawk doing two 360-degree turns on a skateboard]

Tony Hawk: Something weird I've noticed is that if I do a 360 ollie, I land backward. I have to do a 720 to land going forward.

Caption: Tony Hawk discovers that he's a spin-½ fermion.

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Discussion

How come it's at 0.017 RPM for a minute?? and yet 1 RPM for a second? pls fix this randall Midnightvortigaunt (talk) 18:01, 5 February 2025 (UTC)

Its 0.017 RPM for the minute hand. The minute hand revolves once per hour or at 1/60 RPM ≈ 0,017 RPM --172.71.148.59 18:14, 5 February 2025 (UTC)

Ohhh that makes sense I didn't think about it like that Midnightvortigaunt (talk) 19:27, 5 February 2025 (UTC)

Mr.Dude (talk) 17:20, 7 February 2025 (UTC) I wonder what torque is needed to launch the average backyard telescope worthy of a tracking mount at Mach 8 given standard state pressures and temperatures of perhaps average conditions found in Randall’s back yard.

How come the comment above is invisible to me? 172.68.245.229 18:03, 5 February 2025 (UTC)

Possibly because people indented with spaces rather than with colons? 162.158.79.77 19:40, 5 February 2025 (UTC)

72 RPM for a record player...? 162.158.74.25 18:08, 5 February 2025 (UTC)

I could only find 78 RPM disks in the german wikipedia. 172.70.114.56 18:41, 5 February 2025 (UTC)

I came here to make the same comment: 72 is most probably a typo. The old records (at this date, very old, since the transition to vinyl records was 1948 to 1958 (in the US)) were 78 rpm, not 72 rpm https://en.wikipedia.org/wiki/Phonograph_record Rps (talk) 19:30, 5 February 2025 (UTC)

72 is (for example) relevent to font sizes (size 1 = 1/72 of an inch, size 72 = 1 inch), which might therefore have envaigled Randall's head for numbers by a different route, and got him confused. Conceivably he has had to deal with playing old 78s, but probably not for a long time... even the retro-revival of vinyl, recently, has probably not had quite so many old old records released to fill such nostalgic needs. So an easy brain-fudge/thinko to trip over on. 162.158.74.48 00:54, 6 February 2025 (UTC)

There used to be a record label call 72RPM records. 172.69.229.146 (talk) 19:07, 5 February 2025 (UTC) (please sign your comments with ~~~~)

We need one of those tables in here. DollarStoreBa'al (talk) 18:37, 5 February 2025 (UTC)

I made a change to the explanation that all of these numbers are realistic because, I checked out the speed of dental drills and they really do rotate that fast. I haven't checked out all of the other tools, but I suspect that they are also accurate. If you find that any of them are misstated, please correct my correction. Rtanenbaum (talk) 22:38, 5 February 2025 (UTC)

TABLE REQUEST When someone uploads a table, I'd like to recommend a second column for the frequency / reciprocal of the speed. "0.000000000073 minutes" is one every 13.7 billion minutes, or ~26,000 years. Thanks! 172.70.46.107 20:20, 5 February 2025 (UTC)

Me again. Should the column header "revolution time" be "rotation time"? In every instance, the axis of motion is within the object itself; even the second/minute/hour hands go around the axis. 141.101.76.73 16:41, 6 February 2025 (UTC)

TRIVIA 16 2/3 RPM phonographs were used for some voice-recorings back in the day. 172.68.26.24 21:01, 5 February 2025 (UTC)

My parent's old record player (60's, probably) had 4 possible speeds: 16, 33, 45, 78. By the early 80's the current ones only had 33 and 45. Rps (talk) 16:59, 7 February 2025 (UTC)

Album goes back to stacks of 78s. A symphony or opera would be 2, 3, 4 or more disks. They were bound like a photo-album with a leaf for each disk. "78" wasn't "standardized" until the format was fading. 3600-rpm motor and 46-tooth gear is incomplete (one tooth gear??) Early discs were from 60 to 130 rpm. Users would adjust speed by ear (also to ease pitch-matching for karaoke). Only as LPs arrived did someone invent the number "78.26 rpm" (no recordplayer and few lathes of the period were near that accurate). --PRR (talk) 02:34, 6 February 2025 (UTC)

Indeed, my parents had a large collection of old records and at least one had a speed marking of 80rpm.--172.68.186.43 09:17, 6 February 2025 (UTC)

With wind-up players, a lot of them started off playing at one speed and ended playing at a completely different one anyway...172.68.186.50 09:43, 6 February 2025 (UTC)

I suspect there's not many consumers needing a Uranium Enrichment Centrifuge... at least outside of a few countries in the Middle East. --172.70.58.6 08:50, 6 February 2025 (UTC)

Might face some regulatory / export license issues too.172.70.86.129 11:34, 6 February 2025 (UTC)

I feel like there was a lost opportunity to have Dr. Who's Sonic Screwdriver on the list. Maybe the rpms are unknown.162.158.159.107 13:05, 6 February 2025 (UTC)

The table says that 0.00070 "seems off; a sidereal day is 23.93 hours". That's just because (like all of the other settings) 0.00070 is quoted with only 2 significant digits. Every period between 23.64 and 23.98 hours would round to 0.00070 RPM. 162.158.134.199 13:58, 6 February 2025 (UTC)

The question I have is: why are dental drill speeds so high? 172.70.247.92 17:21, 6 February 2025 (UTC)

"why are dental drill speeds so high?" It hurts less. (Are you old enough to remember routine use of belt-driven dental drills?) You can cut a given amount of material (wood, steel, tooth) quickly with heavy force or high speed. Neither is really fun, but hi-speed is generally preferred. --PRR (talk) 19:08, 6 February 2025 (UTC)

Although some materials behave badly to heat (either work-hardening, for some alloys, or melting/burning, like plastics) and that's why variable-speed hand-drills/etc usefully have low speeds (for essentially the same force, when that's done via reostat rather than an actual gearbox). On the few occasions I've had my teeth drilled, I'm pretty sure I've detected the pungent smell of fried tooth-fragments, but it was nothing like as strong as smelling my own nose-flesh being burnt one of the times I had it cauterised to try (and fail) to prevent excessive nosebleeds. 172.69.79.139 21:15, 6 February 2025 (UTC)

The latest NMR CPMAS probes send their rotors to go at 9.6 Mrpm, M=mega. [1] --172.69.109.172 21:56, 7 February 2025 (UTC)

Should we list the rotor diameters to achieve the mach 8 speed mentioned in the title text in the table? I don't think that we should. guess who (if you desire conversing | what i have done) 06:01, 24 February 2025 (UTC)

I (obviously since I worked it all out) think it is in the spirit of the ridiculous idea of the comic and XKCD generally to do these calculations. That said, I'm getting different numbers than your update to make it Mach 8. Denver87 (talk) 16:21, 24 February 2025 (UTC)

I get the following: 4,799au, 74,866km, 37,733km, 3,144km, 52.4km, 1,588m, 1,165m, 728m, 175m, 34.9m, 21.0m, 149.7cm, 87.3cm, 174.7mm. Denver87 (talk) 16:21, 24 February 2025 (UTC)

Happy to share calculation notes, but here's the example for the dental drill: 300,000rpm = 5,000 rps; diameter of: 174.7mm --> circumference of: pi * 174.7mm = 548.8mm; 548.8mm * 5000rps = 2,744,000mm/sec = 2744m/sec; Mach 8 = 8 * 343m/sec = 2744m/sec. Denver87 (talk) 16:21, 24 February 2025 (UTC)

If you agree with the calculations, one of us can at least update it. Denver87 (talk) 16:21, 24 February 2025 (UTC)
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