Editing 3247: Particle Census

{{comic
| number    = 3247
| date      = May 18, 2026
| title     = Particle Census
| image     = particle_census_2x.png
| imagesize = 651x272px
| noexpand  = true
| titletext = Remember, your answers to the physics census are confidential; we will not be issuing Pauli exclusion principle citations.
}}

==Explanation==
This comic references the {{w|Heisenberg uncertainty principle}} of quantum mechanics. Put simply, it states that there's a limit to how precisely we can know both the position and momentum of a particle — the more precisely we know one, the less we know the other. [[Megan]] says that 'physicists' are taking a {{w|census}} of the positions of all particles in the universe, so they'll be known precisely; therefore, all their momenta will be unknowable. By the time we use the census results, we won't know where any of the particles are — we'll just know where they were at the instant their positions were recorded by the census.

In the United States, the constitution mandates that a population census of people living in all the states be taken every ten years. This is primarily for the purpose of apportioning representatives to Congress, but it has come to be used for many other demographic purposes. There's no law (human or physical) requiring a decennial physics census; if physicists want to do this, it's their own decision.

[https://www.quora.com/How-many-particles-are-there-in-the-universe There are estimated] to be approximately 10<sup>80</sup> protons, neutrons, neutrinos and electrons in the observable universe, which would make even the task of simply enumerating them difficult. Proton and neutron 'particles' are in turn composed of three quarks (numbers of which which also form other so-called-particles/hadrons), which may easily multiply the the number of separately surveyable particles. If photons are to be included in the census, that increases the number of particles to about 10<sup>89</sup>... with a further problem that detecting them would involve processes that generate more photons than are being surveyed. If dark matter is to be included, we don't even know what it ''is'', let alone have a method of detecting and recording its particles (if any). We don't know the size of the universe as a whole, and many physicists theorise it is infinite, in which case, covering all the particles in that would be an infinite task. If any meaningful and usable information about each particle is to be recorded, storing that information would require many particles for each particle in the universe, which would be a logical contradiction unless all of the extra particles were coming from some other space (such as an alternate universe).

Many particles, even within the observable universe, are at vast distances from Earth, where they will be difficult to detect. Some particles, particularly neutrinos, are extremely difficult to detect at all, because of their limited interaction with other forms of matter. Simultaneity is impossible, because of relativity, so it would be meaningless to try to catalog them at a specific time. Furthermore, some of those particles will be in the equipment used to measure, and the people doing the measuring, which will further complicate matters.

In the third panel, someone speaks up and is worried about what will happen to particles during the potential “disruption”. Randomly taking someone’s particles and relocating them would be considered unpleasant,{{Citation needed}} even if you ''could'' tell them where the particles are going, which you can't in this instance.

If all particles' locations were determined (as exactly as possible) it would have to be done using very high energy particles (which would, themselves, have to have their locations determined), leaving all the measured particles moving very fast (less than the speed of light, of course, but close to it), destroying everything and everyone. Given that, the concern voiced is very fair, but unnecessary, as it would not be possible to perform the task that Megan claims will happen.

The apparent need to conduct a thorough particle census, and the (perhaps legitimate) worry about the disruption that is caused bears some resemblence to the impact of an audit (either regularly scheduled or possibly imposed to answer some questions about the target of the audit). While there may be legitimate business/regulatory need to uncover the exact nature of the audit's focus, those people who are still trying to work within the auditable environment may (even if they have nothing personal to hide from it) find the involvement of the auditing team to be disruptive and interfering with their expected workflow (such as key documents being unavailable, as they are being scrutinised by the auditors and unavailable to be suitably updated with work currently in progress, without sparking off further auditing actions in response). In some cases, an 'audit' can even be threatened as a response to some nominal non-compliance with (perhaps unreasonable) demands, the implication being that all normally filed documents are heavy-handedly gone through leaving the target of the audit with an actual mess, the object not necessarily to discover desired information but to cause trouble and inconvenience to those that don't provide satisfactory complience to prior 'requests'. In the comic's instance, it is seemingly more a regular chore than an ''ad hoc'' pressure technique, but at least some of those who are more subject to the audit than they are net beneficiaries of its outcome seem to know that they will be significantly inconvenienced by it.

The title text refers to the {{w|Pauli exclusion principle}}, which states that no two {{w|fermions}} — types of particles that include all ordinary matter — can occupy the same quantum state. As the data recorded by the census is confidential, physics officials will not use it to determine whether to issue citations for particles that violate the exclusion principle. This confuses physical laws, which describe how the universe works and by their nature cannot be violated, with societal laws, which declare what is allowed or required by the government.

==Transcript==
:[Megan is standing behind a lectern, addressing an unseen audience.]
:Megan: Remember, Tuesday is the decennial particle census.
:Megan: Physicists will be recording the location of all particles in the universe.

:[Zoom out to show Megan is on a podium behind the lectern. She holds one hand, palm up, out towards the still unseen audience]
:Megan: Of course, this will cause their momenta to become indeterminite, so please plan for some disruption.

:[The same scene with Megan's hands held down. A voice comes from off-panel at the left through a star burst at the edge of the panel.]
:Audience member [off-panel]: Wait, disruption? Where will my particles go?
:Megan: No one can say, but you'll know ''exactly'' where they were.

==Trivia==
*When this comic was uploaded the normal sized image [https://web.archive.org/web/20260518185623/https://xkcd.com/3247/ was incorrectly 2x size]. It kept showing up at 2x size on [[unixkcd]] for awhile.
*"Indeterminate" is spelt "indeterminite" in the second panel text.

{{comic discussion}}<noinclude>

[[Category:Comics featuring Megan]]
[[Category:Physics]]
[[Category:Public speaking]]