Editing 3254: Detector

{{comic
| number    = 3254
| date      = June 3, 2026
| title     = Detector
| image     = detector_2x.png
| imagesize = 740x272px
| noexpand  = true
| titletext = No other experiment has a lower false negative rate.
}}

==Explanation==
[[Ponytail]] and [[Hairy]] are showing [[Cueball]] various detectors in this room, which include an {{w|electron microscope}} (which showers a target with electrons and images their reflections), an XRF scanner (i.e. "{{w|X-ray fluorescence}}", which hits a target with high-energy X-rays and measures the spectrum of the fluorescence they emit) and a {{w|mass spectrometer}} (which measures the mass-to-charge ratio of ions to determine the proportions of particular isotopes present in a sample).

These are all out of frame, from any comic panel, but the piece of equipment that we see is a machine of indeterminate purpose, simply labeled "Detector" and with the most prominent feature being the words "Detected" and "Not Detected" written in separate lines next to two lights, one above the other, the first of which is glowing green. This, they claim, is their most sensitive detector, with nothing in the subsequent conversation indicating that it is anything other than a reasonably reliable (though also esoteric) piece of scientific equipment.

Normally, detectors have a designated detecting job, such as the aforementioned off-panel devices which can provide complex imagery or a profile of a sample's composition. For example, smoke detectors merely detect the presence or absence of smoke and (usually as a safety device, rather than a piece of scientific equipment), and only need to alert the user if there is smoke identified.

The sensitivity of a detector can vary. [[3249: Neutrino Project|Neutrino detectors]] try to detect neutrinos, but neutrinos are very hard to measure so can only give data for a very low number of the actual neutrinos that could possibly have been measured. Devices being more sensitive means that they can detect (and perhaps quantify) far lower quantities/magnitudes of the targeted phenomena, and/or more of those that might otherwise have been missed.

For the device in this comic, however, "more sensitive" seems instead to mean that it is sensitive to more ''different'' things. To quote Ponytail, it detects "gas, dust, particles, light, radio waves, gamma rays, protons, neutrons, electrons, fields, forces, events, potentials, or states", which runs almost the entire gamut of things that ''might'' be detectable, and leaves little room for there being any situation in which none of the aforementioned items are there to be detected. The constituent particles of the machine itself would be present for detection, and exist in "states" and have "potentials" relative to each other, assuming that the machine is sensitive enough (in the traditional sense) to detect them, and the detection area that it observes includes at least some parts of itself.  Alternatively, the words “states” and “potentials” could refer to political entities: it would detect whether it was within the borders of a state; and whether the place had potential, or even just a {{w|Preselection|political potential candidate}} within range.

Regardless of that, some or all of the wide range of the detectable things are also going to be present, in detectable quantities, in practically ''any'' location that they might feasibly be monitoring, and even if it was capable of discerning nuances (such as relative quantities, differing proportions or even which detectable thing is the most significant presence in any given set of measurements) its output boils down to merely whether it has (or has not) detected ''something'' from its extensive list of detectables. Which, by any reasonable assumption, would seemingly mean that it is only ever going to need to indicate that it has "Detected" things, leaving the possibility that it has "Not Detected" things as an unlikely result to display instead.

Cueball points this out, and Hairy admits that it ''has'' been continuously lit this way ever since they turned it on. Ponytail is audibly shocked in response to Cueball asking what would happen if the light labeled "Not Detected" were to shine. Hairy explains that such a thing would be pretty bad. The presumption being that, if that were to happen, there would have to be no matter, light, forces, etc. within the detector's established range of detection. (Though it could be interpreted as the dectector not working properly, the contextual reactions of those most familiar with it seem to show a faith that the detector is still likely to be faithfully summarising the true status.)

One possible explanation for a scenario that might cause a "Not Detected" result could be a {{w|false vacuum}} decay event which, depending on the particular details of the true vacuum, could alter or overwrite the fundamental laws of physics as we know them. This would indeed be "bad" for, among other things, the persistence of life on Earth. However, in such a scenario the detector itself would presumably also be rendered at least inoperable, and possibly non-existent, with a similar fate befalling any observer who might have been around to witness the changing output.
 
There might still be an unavoidably built-in uncertainty. [[1132: Frequentists vs. Bayesians]] was a previous comic featuring a more specific detector that tells whether the Sun has gone nova (also a very bad scenario, even if less cosmically extreme), but incorporates some risk of conveying an inaccurate output. (But, again, these people familiar with this device do not seem to feel the need to consider it as potentially inaccurate, like that.) If the characters are lying (or were themselves lied to) it may not even be a real detector and just be a machine with continuous power, on the basis that atoms would normally be found in and around the detector as well as light (e.g. from the indicator light itself), {{w|Fundamental interaction|force potentials}}, etc.

While the detector presented here is obviously facetious, the comic does allude to a real problem: detectors looking for very rare events - e.g {{w|neutrinoless double beta decay}} - have to be extremely sensitive to detect their target events. Consequently, they may also be triggered by many other things, requiring extensive shielding (e.g. built underground in abandoned mine shafts) to provide any useful data.

The title text states that the machine has a lower {{w|false negative}} rate than any other detector device. If it never has stated a negative (i.e. explicit non-detection, being a different scenario from a power-outage or indicator failure that just causes the Detected light to stop being lit), then it can never have been ''wrong'' about it being negative. It's also possible that the "Not Detected" light is just set up ''never'' to be lit, [[2236: Is it Christmas?|playing the odds]].

It is not made clear to us under what circumstances would legitimately result in a negative state being indicated. Nor, apart from the concerned expectations of Hairy and Ponytail,  whether the detector will then necessarily correctly state that. It might still fail to properly respond to the new situation, just continuing to provide an incorrect indication that all is 'normal' (on the assumption that the device both still exists ''and'' functions, under such extraordinary circumstances), and result in a {{w|false positive}} instead. But, for many possible reasons, the chances and consequences of any displayed false positive may easily bear no relation to that of a false negative. i.e, the "Not Detected" light could always be 100% accurate (leading to Hairy's "bad" scenario), yet any given cessation of detections often fails to stop "Detection" from being indicated (being just as "bad" but, as the icing on an already possibly unpalatable cake, also with the Detector being functionally wrong).

==Transcript==
:[Hairy is standing to the right of a large machine labeled "Detector". The front of the machine has two lights, labeled "Detected" and "Not detected". The "detected" light is lit up in green. Ponytail and Cueball walk towards the machine from the left.]
:Ponytail: Over there are our electron microscope, XRF scanner, and mass spectrometer. 
:Ponytail: And this is our most sensitive detector.
:Cueball: What does it detect?

:[The next panel zooms in on the detector. Ponytail's voice comes from the left of the panel.]
:Ponytail (off-panel): Lots of stuff.
:Ponytail (off-panel): Gas, dust, particles, light, radio waves, gamma rays, protons, neutrons, electrons, fields, forces, events, potentials, or states.

:[The next panel zooms out. Cueball and Ponytail are standing to the left of the machine, and Hairy on the right.]
:Cueball: I don't understand. Aren't most of those ''always'' present?
:Hairy: Yeah, it's been saying "detected" continuously since we turned it on.

:[Cueball and Ponytail still standing to the left of the machine, and Hairy on the right. Ponytail has her hand on her chin.]
:Cueball: What happens if it says "not detected"?
:Ponytail: Oh gosh.
:Hairy: That would be pretty bad, I think.

{{comic discussion}}<noinclude>
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring Hairy]]
[[Category:Physics]]
[[Category:Science]]
[[Category:Statistics]]