3043: Muons

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Muons

Title text: Update: I've been banned from the physics department for the way I pronounce "Doppler effect."

Explanation

This explanation is incomplete: Created by THE OMG PARTICLE. Do NOT delete this tag too soon. If you can address this issue, please edit the page!

Muons are elementary sub-atomic particles, often released in air showers from high-energy cosmic ray protons causing nuclear decay in our upper atmosphere. These protons come from all over the universe from various interstellar events and have energies in excess of anything our species has created. Some of the muons created in these collisions are deflected away from us and decay quickly in the upper atmosphere. Other muons retain the high energy of the colliding protons and travel so fast that they emit Cherenkov radiation from outpacing photons in air, which is used to visualize air showers with telescopes. Muons usually decay very quickly, but because, in part, of time dilation these high-energy muons are able to penetrate densely deep into the earth. They are also used as a natural radiation source, more powerful than x-rays, for internal imaging, especially of large opaque structures.

Time dilation is the concept from special relativity where faster-moving objects travel through time faster than proportional, resulting in an appearance to an observer of it slowing down for them, as well as an ability to cross greater distances. Because the ‘regular speed’ muons are moving at a relatively normal speed, Cueball pronounces it properly, but because time slows down for the faster moving muons, Cueball adjusts this, and pronounces it much slower, as if he is being slowed down from talking about them.

Cueball is implying that when he says "muons", he is speaking in the same reference frame as them, with time traveling at the same speed for the listener and for the muon. In the same reference frame, muons decay very quickly. He implies that when he says "muuuoooons" very slowly, that he is now speaking in a reference frame where the muons have time dilated relative to the observer and appear to be aging very very slowly. If a relativistic muon were saying its own name, or if Cueball were in the same reference frame as the muon and the observer were not, (and there were a way to transmit sound at relativistic speeds), then the muon might sound like this, stretched out. This is the kind of reference frame in which muons are detected at the surface. We observe them, and we observe that time is passing slower for them than it is for us.

On average, a stationary muon decays after a bit over two microseconds. While moving at 99.97% of the speed of light, their lifespan (from our perspective) stretches to nearly ninety microseconds (a Lorentz factor of ~40.8). If Cueball speaks at four syllables per second (a typical speech tempo for English), it will take him about half of a second to name the "muons" created in the upper atmosphere; it will take him more than twenty seconds to name the fast-moving "muuuuuoooons."

The title text references the Doppler effect, the change in frequency of a wave when the observer is moving relative to the source. One common example of this is how the sound to a stationary observer of a fast car or airplane starts at a high pitched note but then drops to a low droning noise as it passes. By analogy with the time dilation example, Cueball likely imitates this change in pitch and speed of syllables whenever pronouncing the phrase "Doppler effect" ('Dop-llllerrrr eehfffffeeeehccccctttth'). Languages in Randall's native language family do not represent different words or sounds with different pitches, so speaking "Doppler effect" with the timing and pitch changes of a real doppler effect of a fast-moving object passing a listener, would at least be understood, although could be quite jarring and distracting to hear conversationally. Alternatively, he may be stretching out the "p" sound by saying "p-p-p-p", producing a spitting or "raspberry" sound, which would be highly offensive.^{[citation needed]} For more on Doppler effect, see 1531: The BDLPSWDKS Effect.

Transcript

This transcript is incomplete. Please help editing it! Thanks.

[Cueball is standing in front of a whiteboard, which contains a diagram depicting a muon passing through the atmosphere, a distance labeled with a cursive letter, the equation for the Lorentz factor, and some illegible text. He's facing away from the whiteboard and holding a pointer that points towards the diagram.]

Cueball: Muons created in the upper atmosphere decay immediately, but fast moving muuuuuoooons are able to reach the surface due to their longer half-lives.

[Caption below the panel:]

Physics tip: Remember to adjust your pronunciations to account for time dilation.

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Discussion

Article needs improvement by somebody with a clear understanding of special relativity, and somebody with a clear understanding of muons. Are there actually two classes of muons or is it a joke? 172.68.55.81 22:19, 27 January 2025 (UTC)

No, not two classes; see Figure 5 on p. 3 here. 172.70.206.243 01:43, 28 January 2025 (UTC)

It sounds possibly like the article and comic together are saying that the muons we measure on earth are those that were going so fast that their time and distance are stretched so that they do not decay before reaching us. That non-relativistic muons decayed in the upper atmosphere. 162.158.63.84 03:13, 28 January 2025 (UTC)

Correct, even if their velocities are not bimodal, you can absolutely divide them into two classes based on whether they decay before reaching the surface. I am pretty sure that's what's intended here. 172.68.23.136 03:42, 28 January 2025 (UTC)

I websearched around and found an old video from COSMUS showing an air shower with differently colored particles flying off. It looks like the COSMUS site is broken nowadays, but in archive.org I found it mentioned that the muons were red in the video. I saw some red particles decaying quickly like the behavior of smoke or fire or steam, and others firing toward the ground. I added a first paragraph with what I learned exploring. I'm sad the COSMUS site from the university of chicago seems down for years. They publicly modeled so many air showers and more. 162.158.159.189 04:26, 28 January 2025 (UTC)

The Doppler Effect will sound like the Sega logo sound: https://www.youtube.com/watch?v=9dIXw0OEtk4

AI

Fed the comic image into two AIs: Gemini and Claude. These are their explanations; please tell me which is better:

Gemini:

This xkcd comic (#2885) is a humorous take on the concept of time dilation from Einstein's theory of special relativity, specifically as it applies to muons.

Here's a breakdown:

The Setup: The comic explains that muons, subatomic particles created in the upper atmosphere, have very short lifespans. Normally, they would decay before reaching the Earth's surface. However, because they travel at speeds close to the speed of light, time dilation occurs.

Time Dilation: According to special relativity, time passes slower for objects moving at high speeds relative to a stationary observer. This means that from our perspective on Earth, the muons' internal clocks tick slower, allowing them to travel further before decaying.

The Joke: The comic takes this scientific concept and applies it to pronunciation. The presenter is shown drawing out the word "muons" ("MUUUUUUOOOONS") to emphasize the elongated time experienced by the fast-moving particles.

The Punchline: The caption "PHYSICS TIP: REMEMBER TO ADJUST YOUR PRONUNCIATIONS TO ACCOUNT FOR TIME DILATION" is the punchline. It's a humorous exaggeration, suggesting that we should literally pronounce words differently depending on the relative speed of the objects they describe.

In essence, the comic is a clever play on words that combines a complex physics concept with a mundane everyday activity (pronunciation). It highlights the counterintuitive nature of special relativity in a lighthearted way.

Here's why this might be tricky to explain on explainxkcd:

It's concise: The joke is very compact and doesn't require a lot of background information beyond a basic understanding of time dilation.

It's visual: The drawn-out "MUUUUUUOOOONS" is crucial to the humor, and it's difficult to fully capture that in a purely textual explanation.

It's somewhat self-explanatory: The comic itself does a good job of setting up the joke and delivering the punchline.

Dunno why it thinks this is comic 2885.

Claude:

The comic is explaining how muons (subatomic particles) created in the upper atmosphere are able to reach Earth's surface despite their short half-lives.

The humor comes from the way "muons" is written with stretched-out letters ("MUUUUUOOOOONS"), which is a play on time dilation in special relativity.

Time dilation is a real physics phenomenon where time moves slower for objects moving at very high speeds relative to a stationary observer. This is why fast-moving muons can survive longer than their normal half-life would suggest - from their perspective, due to time dilation, less time has passed.

The comic suggests, as a "physics tip," that you should stretch out your pronunciation of words to account for time dilation - as if the word itself experiences the same relativistic effects as the particle it describes.

It's a particularly nerdy physics joke because it combines accurate physics (muons really do reach the surface due to time dilation) with a playful misapplication of the concept to human speech. The stick figure appears to be teaching or presenting this concept, complete with what looks like equations on a board, making it feel like a legitimate physics lesson with a humorous twist.

This is characteristic of xkcd's style of humor, which often combines accurate scientific concepts with absurdist interpretations. -- AK24Ammit (talk) 23:35, 27 January 2025 (please sign your comments with ~~~~)

Claude's is better, by far. 172.70.215.54 01:49, 28 January 2025 (UTC)

I think they're both surprisingly good. But wouldn't it be more timely to ask DeepSeek, the new Chinese AI that's tanking US tech stocks? Barmar (talk) 15:17, 28 January 2025 (UTC)

I tried, but...

As of my knowledge cutoff in October 2023, I cannot provide specific details about XKCD comic #3043, as it does not exist yet. XKCD comics are released incrementally, and the latest comic I am aware of is #2817 ("Nighttime Stories"). If #3043 has been released after October 2023, I recommend checking the official XKCD website (https://xkcd.com) or its explainer site (https://www.explainxkcd.com) for details.
If you have a specific question about muons or XKCD's style of humor, feel free to ask, and I’ll do my best to help!

Yeah. Caliban (talk) 11:47, 30 January 2025 (UTC)

personally, I took the less direct approach to asking for the explanation. Instead of asking the AIs “explain xkcd #3043”, I fed the actual image in and asked them to explain it. Please try that with DeepSeek, and let’s see how its wiki skills hold up! AH24Ammit (talk) 23:22, 8 February 2025 (UTC)

Both obviously AIs (without being told), with AI tells. Gemini 'hallucinating' that it was perhaps refering to 2885: Spelling is nothing like the very different equivalent human errors, for example.

Very good efforts, if they effectively OCRed and image-processed almost everything (before wandering off to thei caucus of webscraped material, from which to esoterically form their response), can't deny that. But must have been prompted by something along the lines of "The comic <url> doesn't have a good explainxkcd explanation, please discuss", from the obvious referencing that would be meta in an actual article context by ourselves.

Whatever the circumstance, I predict that either attempt would have been heavily touched up (if not entirely rewritten), if put in the main page. (I mean, practically all human input does, too, but for different reasons...) Gemini would probably tend to be cut down, Claude added to, but a mix of both for each. Maybe they don't have the pride in being original author, like a human, but one always has to learn that any you do have will inevitably be shattered. (I take it as a compliment if I provide enough of a surviving skeletal structure to see my initial idea of a narrative flow preserved in largely remixed wordings until the point at which it generally settles down.)

Yes, impressive(ish). But not yet Mission Accomplished. 172.71.241.144 16:38, 28 January 2025 (UTC)

The point is that we observe muons that have time slowed down coming from the sky. Cueball is differentiating normal muons from muons that appear to have time slowed down for them, by slowing down his speech when referring to the slowed muons. It's a strange idea, refering to something that has time slowed for it. It's not something one often does outside fantasy. 162.158.158.168 04:41, 28 January 2025 (UTC)

Patrick Blackett won the Nobel Prize in 1948 by making the first observation of the creation of a nortcele. 172.69.59.137 20:27, 29 January 2025 (UTC)

What is this comment about, please? 162.158.63.72 15:16, 30 January 2025 (UTC)

The only notable reference online to the word "nortcele" is the name of an Indian tech company. From the Nobel site: Patrick Maynard Stuart Blackett. Nobel Prize in Physics 1948. Prize motivation: “for his development of the Wilson cloud chamber method, and his discoveries therewith in the fields of nuclear physics and cosmic radiation.” I would recommend deleting 172.69.59.137's comment if they fail to return in a timely manner to explain or defend it. These Are Not The Comments You Are Looking For (talk) 21:06, 2 February 2025 (UTC)