3257: Beam Pipe

Beam Pipe

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Title text: 'If you keep trying to spray your collaborators with the beam when they're not looking, I'm turning off the ion source and NO one will get to play with the beam!' --Physics's mom

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Explanation

This is one of 44 incomplete explanations: This page was found with a Physics Nobel Prize. Don't remove this notice too soon. If you can fix this issue, edit the page!

When a liquid is flowing within a tube, the pressure at any point is determined by an equilibrium between the supply pressure and the forces that restrict flow, such as friction with the walls and hydrodynamic effects in the liquid. If the tube is short and the outflow opening is large, the pressure within the tube is close to the exterior pressure (air pressure, in the case of a liquid flowing into air). If the outflow opening is negligible, the pressure within the tube is essentially equal to the pressure of the liquid's supply. If the tube is constructed of an elastic material, it will expand until an equilibrium is reached between the internal pressure and the elastic stretch of the tube... unless the pressure is enough to rupture the tube.

In the case of a hose carrying water, if the exit is fully open, the water pressure near the exit will be moderate: greater than atmospheric pressure, but less than the full pressure of the water supply. The more the exit is restricted, such as by part covering it with a thumb, decreasing the water flow, the closer the pressure near the exit will come to the full pressure of the water supply. (In the limiting case where the exit is fully blocked, the hose will essentially be an extension of the plumbing, and its internal pressure will be that of the water supply, as modified by the gravitational effects of raising or lowering the hose, and the weight of the water). If the hose is elastic (e.g. the usual garden-hose reinforced rubber), it's possible to see it stretch as the nozzle is restricted. Covering it with a thumb, while reducing the water flow, allows the water that does come out to do so at relatively high pressure.

As the LHC can be considered a sort of "pipe" (a beam pipe, as pointed out in the comic title), this comic makes the ridiculous assumption that the same logic applies there — that its beam can be concentrated and redirected by partially covering the end of the beam with a thumb. This wouldn't work in real life: water molecules are moving at low speed and thus do not have sufficient energy to overcome the electrostatic repulsion between their electrons and those of the thumb, forcing them to change path. In contrast the kinetic energy of the particles in the LHC (14 TeV) is far far larger than the repulsion of the thumb. Most particles will pass through unaffected, while those hitting thumb nuclei directly will produce a cascade of new particles similar to those the LHC is intended to produce.

While there is no recorded case of a human getting struck by the particle beam at LHC, Anatoli Petrovich Bugorski did accidentally hold his head into the proton beam of a 76 GeV (about 180 times less than the energies at the LHC) particle accelerator while trying to repair a faulty part. This had severe but not lethal consequences: the resulting acute radiation sickness caused the affected parts of his face to swell and the skin to flake off, The affected nerves never recovered, leaving the left side of his face paralysed and his left ear deaf. The damage to his brain resulted in several epileptic seizures, but did not affect him otherwise, allowing him to continue his work as a physicist, and at time of publication he was still alive at the age of 82.

Thus while pointless, holding the thumb into the LHC beam is unlikely to significantly harm anyone trying it. At any rate, this wouldn't work in real life: the relativistic particles would not behave as a liquid. Also, because the LHC's beam operates in an extremely high vacuum, and the LHC doesn't have any structure to let the beam exit the main accelerator ring, it would be impossible even to test the concept.

The title text expands the joke, once more treating the LHC as if it were a hosepipe. Applying the effect above to a hosepipe is a common thing for children to do — often to spray family and friends with the pressurized water. This applies the same logic to the LHC, imagining the mother of "physics" (the science, as opposed to a person) telling off their presumably adult child for "spraying their colleagues with the beam" — something very incomprehensible in real life.

A variety of devices are marketed to increase the pressure of water supplied to them. The pressure washer is a common example; it uses electrical power to add force to the output water. There are also scams based on devices that supposedly increase the output water pressure without using any externally-provided power, but this is a physical impossibility. The force of the water coming out can't be greater than the force of the water coming in, or a perpetual-motion device could be constructed with the water running in a loop and the added force being tapped to power a generator. At most, the output pressure will be the same as that of the water supply, in the limiting case of zero flow, less any frictional losses within the device.

Transcript

This is one of 26 incomplete transcripts: Don't remove this notice too soon. If you can fix this issue, edit the page!

[A picture shows a (partly obscured by the panel) particle accelerator (namely this one being the Large Hadron Collider at CERN). Megan is shown on a stepladder, covering the beam pipe with her thumb. Cueball is shown standing behind the ladder, watching.]

[Caption below the panel:]

This year's physics Nobel will go to the scientists who figured out that you could make the Large Hadron Collider more powerful by covering part of the beam pipe with your thumb.

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Discussion

Ok why did this take so long to be created? GSLikesCats307 (talk) 12:58, 11 June 2026 (UTC)

I think it was because explainxkcd was down when this comic was published (agian :/) --Clarkexckd8 (talk) 13:01, 11 June 2026 (UTC)

It was like that with the last comic as well. What's causing these outages? GSLikesCats307 (talk) 13:03, 11 June 2026 (UTC)

Maybe it's something with the servers. I have no clue why it took until 12:00 (UTC) to upload though.--Clarkexckd8 (talk) 13:15, 11 June 2026 (UTC)

I'm going to theorise that some third party, out there, is running something that hammers our servers. From the little information the change-logs gives, they're starting it around 22:00 (server time) and it only ends (or people, including the comic-update-BOT, only realise it has ended) at around 12:00 (server time, again).

While this inconsiderate thing is happening, everyone else (and probably themselves, if they're running their hammering massivelg in parallel) is finding it almost impossible to connect, as the back-end is too busy serving the site-database results to the hammerer. (Some edits were made ~05:00ish, the other day. Might have been lucky/persistent to do that. Or hit a rare pause by the bad-actor's efforts.)

Probably not a deliberate DDOS, as these other periods of sanity wouldn't be in such a plan by someone. I suggest it's either someone/something doing (or trying to do) a lot of webscraping, without any though to throttling it down to a less disruptive level, or even an intended auto-spammer (getting thwarted by the initial hurdles that protect this site, but their spamming algorithm just keeps trying).

And the inconvenience to us mere mortals is as applicable to the comic-upload-BOT. The only difference being that it can (in a way programmed specifically not to self-defeatingly DDOS the site) just try again, perhaps every half an hour or so, so is more likely to be the first contributor to the site (when there's a new comic still to post, in its backlog) once the data-pummelling has stopped for the day.

What can we do about it? Not much. Curse the person who (intentionally or otherwise) did this? But it seems to not involve any traces of activity that aren't purely server-log level, or maybe on the prody servers that we also don't control. With any luck, they'll realise their (unintended) mistake and rethink it. Or just have no more reason to do so. Not very comforting, but the best outcome I can imagine happening easily. 82.132.236.149 12:53, 12 June 2026 (UTC)

This is probably nitpicking, but covering the opening of a hose doesn't increase the pressure of the stream, it increases flow rate instead, and with it the nozzle velocity. The pressure at the end of a hose is equal to ambient pressure, and the flow rate adjusts itself to achieve this. (At least in sub-sonic conditions that you would normally encounter, though this may not apply to the LHC...) 2A02:590:1404:9301:2CAC:E347:73BF:C11 14:30, 11 June 2026 (UTC)

Yeah, I noticed that... decreasing the diameter should actually decrease the pressure by bernoulli's law, right? 12.159.97.176 14:31, 11 June 2026 (UTC)

Yeah I was about to mention that too GreaterDog6065 (talk) 14:55, 11 June 2026 (UTC)GreaterDog6065 09:54, 11 June 2026 (CDT)

What if you put your hand in a particle accelerator: https://www.youtube.com/watch?v=8UgKki1tCKI Also, LHC actually has two adjacent parallel beamlines (or beam pipes) each containing a beam, which travel in opposite directions. Cf. https://en.wikipedia.org/wiki/Large_Hadron_Collider#Design --134.102.219.31 12:40, 12 June 2026 (UTC)

Wasn't there a guy who accidentally stuck his head in a similar collider a while ago? Or was it actually the LHC? RG (talk) 02:20, 15 June 2026 (UTC)

If you mean Anatoli Petrovich Bugorski, he was already mentioned in the article. 82.132.238.93 11:38, 15 June 2026 (UTC)
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