explain xkcd - User contributions [en]

Talk:3249: Neutrino Project

2026-05-22T20:31:12Z

2A04:6EC0:271:E850:F420:9A86:97FE:2FB7:

Never been this early to a new comic before. Good way to get some editing practice [[User:Black Hat's Hat|Black Hat's Hat]] ([[User talk:Black Hat's Hat|talk]]) 19:14, 22 May 2026 (UTC)
:You just beat me, I was writing a transcript at the same time. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 19:25, 22 May 2026 (UTC)
::Booyah. I was editing transcripts already when it popped it, so I was already primed at the gunshot [[User:Black Hat's Hat|Black Hat's Hat]] ([[User talk:Black Hat's Hat|talk]]) 19:30, 22 May 2026 (UTC)

Is that really Ponytail and Danish at the top? They're hard to distinguish because they're so tiny, but I thought they might be Blondie and Megan. [[User:Barmar|Barmar]] ([[User talk:Barmar|talk]]) 19:16, 22 May 2026 (UTC)
::I'm pretty sure its Ponytail, but it could either be Danish or a wet-haired Megan. Feel free to change it, it's not like the fate of the world hangs on this transcript. [[User:Black Hat's Hat|Black Hat's Hat]] ([[User talk:Black Hat's Hat|talk]]) 19:24, 22 May 2026 (UTC)

Particle physics-compatable swimwear needs to be thoroughly rinsed and air-dried after swimming to protect the sensitive elastane fibers from developing gaps.[[User:BorQhue del Sol|BorQhue del Sol]] ([[User talk:BorQhue del Sol|talk]]) 19:21, 22 May 2026 (UTC)

Added some size estimations for the pool. My math says it should be about 1.5km deep to match S-K’s volume; please re-check that. Not very certain on the diameter estimation, maybe someone wants to pixel-count the stick figures in the background against the visible arc of the pool and correct for perspective? — [[Special:Contributions/2A04:6EC0:271:E850:F420:9A86:97FE:2FB7|2A04:6EC0:271:E850:F420:9A86:97FE:2FB7]] 20:31, 22 May 2026 (UTC) (kleines Filmröllchen)

3249: Neutrino Project

2026-05-22T20:27:47Z

2A04:6EC0:271:E850:F420:9A86:97FE:2FB7: Add character info

{{comic
| number = 3249
| date = May 22, 2026
| title = Neutrino Project
| image = neutrino_project_2x.png
| imagesize = 324x471px
| noexpand = true
| titletext = We definitely put the pool in a mine for shielding. It was absolutely not to hide it from the funding people.
}}

==Explanation==
{{incomplete|This page was created recently by a solar neutrino. Don't remove this notice too soon.}}

A {{w|neutrino}} is a type of subatomic particle that extremely rarely interacts with matter. In nearly all cases, neutrinos pass through objects, regardless of density or composition, with no effects whatsoever. For instance, about [https://icecube.wisc.edu/news/press-releases/2017/11/first-look-at-how-earth-stops-high-energy-neutrinos-in-their-tracks/ 100 trillion neutrinos pass through your body every second] to no noticeable effect.

However, there is a very small chance that a neutrino will collide with any material, including water. Neutrinos can thus be detected by constructing a large pool of water, shielded from all other particles, and carefully monitoring it for the small flashes of light that occur when a neutrino does interact with one of the many water molecules within the pool. {{w|Photomultiplier tubes}} are used to assist in detecting these very faint flashes.

The comic jokes that these detectors were not constructed with this purpose in mind. Instead, [[Cueball]] and [[Ponytail]], the organizers of this project, obtained funding for a “neutrino project” and then embezzled these funds for a pool party, likely primarily to buy the large swimming pool seen in the panel. They supposedly only then realize that the pool could be repurposed as an actual neutrino detector. (It is unclear what, exactly, they had claimed to be building with the funding they somehow obtained.)

It is unclear how large the pool in the comic really is. The {{w|Super-Kamiokande}} detector in Japan, one of the world’s largest and most well-known neutrino detectors, holds over 50,000 tons of water. This is approximately 20 times the water capacity of {{w|Olympic-size swimming pool}}s. The only statement made about the water capacity in the swimming pool is “huge”, which is not an accurate measurement of volume or mass.{{Citation needed}} The pool appears to be between 10 and 20 meters in diameter. While the surface of the pool seems to be at most half as large as that of an olympic-sized pool, its depth could be approximately the same, since it seems to safely allow jumps from an approximately 1m high platform. Therefore, a regular pool of this appearance would be expected to hold less water than an olympic-sized one, and certainly much less than would be required for an effective neutrino detector. However, since the bottom of the pool is not visible, the physicists ''might'' just have built a pool with an appropriate volume by making it extremely deep. Assuming a diameter of 20m and therefore a surface area of approximately 314m², the pool would need to be approximately 1582m deep. Constructing such a pool would be even more expensive than building a neutrino detector{{Citation needed}}, thanks to the large depth.

The title text elaborates on why the pool was suitable for a neutrino detector. In real life, these detectors must be heavily shielded from all other particle interactions that might drown out neutrino interactions. This generally requires them to be deep underground (like {{w|Deep Underground Neutrino Experiment|this}} and {{w|Sudbury Neutrino Observatory|this}} and {{w|Super-Kamiokande|this}}), so a surface-level pool would obviously be unsuitable for that purpose. Randall implies that the pool was built in a deep mine in order to prevent it from being noticed by the people responsible for funding the project, which could fulfill the shielding requirement but is a humorously excessive strategy for hiding a swimming pool from a small group of people.

==Transcript==
{{incomplete transcript| This transcript was written by a pool party attendee. Don't remove this notice too soon.}}

:[There is a large circular pool at the bottom of the panel, with a diving board and several stickfigures in and around it. [[Ponytail]] and [[Cueball]] are talking in the pool, two hairy [[Kidball|Kidballs]] are passing a ball, a Kidball is jumping of the diving board, and a Ponytail with a drink and a [[Danish]] are walking along the outside of the pool.]

: Ponytail in pool: How much trouble do you think we'll be in when they find out we used the grant money to throw a huge pool party instead?
: Cueball: We could argue that we '''''did''''' build a neutrino detector.
: Cueball: There's a lot of water here. A solar neutrino will probably interact with it at '''''some''''' point.
: Ponytail: ...Wait. Actually, if we got some photomultiplier tubes...

:[Caption below comic:]
:How the neutrino detector was invented

{{comic discussion}}<noinclude>
[[Category:Physics]]

3249: Neutrino Project

2026-05-22T20:19:11Z

2A04:6EC0:271:E850:F420:9A86:97FE:2FB7: Added explanation on pool size, with calculations for expected depth and relationship to real neutrino detectors

{{comic
| number = 3249
| date = May 22, 2026
| title = Neutrino Project
| image = neutrino_project_2x.png
| imagesize = 324x471px
| noexpand = true
| titletext = We definitely put the pool in a mine for shielding. It was absolutely not to hide it from the funding people.
}}

==Explanation==
{{incomplete|This page was created recently by a solar neutrino. Don't remove this notice too soon.}}

A {{w|neutrino}} is a type of cosmic particle that very rarely interacts with matter. In nearly all cases, neutrinos pass through objects, regardless of density or composition, with no effects whatsoever. For instance, about [https://icecube.wisc.edu/news/press-releases/2017/11/first-look-at-how-earth-stops-high-energy-neutrinos-in-their-tracks/ 100 trillion neutrinos pass through your body every second] to no noticeable effect.

However, there is a very small chance that a neutrino will collide with any material, including water. Neutrinos can thus be detected by constructing a large pool of water, shielded from all other particles, and carefully monitoring it for the small flashes of light that occur when a neutrino does interact with one of the many water molecules within the pool. {{w|Photomultiplier tubes}} are used to assist in detecting these very faint flashes.

The comic jokes that these detectors were not constructed with this purpose in mind, and were instead created via financial embezzlement from a "neutrino project" that was created solely to obtain funding for a pool party. The organizers of this project supposedly only then realized that the pool could be repurposed as an actual neutrino detector. (It is unclear what, exactly, they had claimed to be building with the funding they somehow obtained.)

It is unclear how large the pool in the comic really is. The {{w|Super-Kamiokande}} detector in Japan, one of the world’s largest and most well-known neutrino detectors, holds over 50,000 tons of water. This is approximately 20 times the water capacity of {{w|Olympic-size swimming pool}}s. The only statement made about the water capacity in the swimming pool is “huge”, which is not an accurate measurement of volume or mass.{{Citation needed}} The pool appears to be between 10 and 20 meters in diameter. While the surface of the pool seems to be at most half as large as that of an olympic-sized pool, its depth could be approximately the same, since it seems to safely allow jumps from an approximately 1m high platform. Therefore, a regular pool of this appearance would be expected to hold less water than an olympic-sized one, and certainly much less than would be required for an effective neutrino detector. However, since the bottom of the pool is not visible, the physicists ''might'' just have built a pool with an appropriate volume by making it extremely deep. Assuming a diameter of 20m and therefore a surface area of approximately 314m², the pool would need to be approximately 1582m deep. Constructing such a pool would be even more expensive than building a neutrino detector{{Citation needed}}, thanks to the large depth.

The title text elaborates on why the pool was suitable for a neutrino detector. In real life, these detectors must be heavily shielded from all other particle interactions that might drown out neutrino interactions, generally requiring them to be deep underground (like {{w|Deep Underground Neutrino Experiment|this}} and {{w|Sudbury Neutrino Observatory|this}} and {{w|Super-Kamiokande|this}}), so a surface-level pool would obviously be unsuitable for that purpose. Randall implies that the pool was built in a deep mine in order to prevent it from being noticed by the people responsible for funding the project, which could fulfill the shielding requirement but is a humorously excessive strategy for hiding a swimming pool from a small group of people.

==Transcript==
{{incomplete transcript| This transcript was written by a pool party attendee. Don't remove this notice too soon.}}

:[There is a large circular pool at the bottom of the panel, with a diving board and several stickfigures in and around it. [[Ponytail]] and [[Cueball]] are talking in the pool, two hairy [[Kidball|Kidballs]] are passing a ball, a Kidball is jumping of the diving board, and a Ponytail with a drink and a [[Danish]] are walking along the outside of the pool.]

: Ponytail in pool: How much trouble do you think we'll be in when they find out we used the grant money to throw a huge pool party instead?
: Cueball: We could argue that we '''''did''''' build a neutrino detector.
: Cueball: There's a lot of water here. A solar neutrino will probably interact with it at '''''some''''' point.
: Ponytail: ...Wait. Actually, if we got some photomultiplier tubes...

:[Caption below comic:]
:How the neutrino detector was invented

{{comic discussion}}<noinclude>
[[Category:Physics]]