3158: Shielding Chart

Shielding Chart

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Title text: Sharks can occasionally travel short distances through air when pursuing prey, but their attenuation coefficient is pretty high.

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Explanation

This is one of 52 incomplete explanations: This page was created by a SPACE-BASED SHARK DEFENSE BOT. Don't remove this notice too soon. If you can fix this issue, edit the page!

This comic is part of a series on confusion matrices.

Various hazardous (or merely obnoxious) materials, objects, and effects can have their danger reduced with specialized protective equipment. The yellow squares are where the shield fails to protect against the object. The grey-yellow squares are where the shield is partially successful, but still presents some risk. The grey squares are where the shield succeeds.

The first five barriers are materials/conditions which may be used to block some things and not others, which makes for a relatively normal comparison matrix. The last five barriers are devices which are deliberately designed and manufactured to block the last five materials/effects. Comparing those with effects for which they aren't designed is presented for absurdity.

All but two tiles feature Cueball who tries to make use of that column's chosen 'protective shield', although in the case of some scenarios (involving vacuum or water) he may also be sufficiently equipped against the environment he finds himself in. Also present will be the row's specific 'effect', either in its own right (an object or creature that embodies the phenomenon automatically) or as conveyed by Megan (when not just present as onlooker) who may also have had the 'shield' primarily delegated to her. The two main exceptions are where Cueball himself emits the sound (from within 'protective' suits that turn out to be ineffectual sound-blockers), to apparently annoy Megan, and depictions of radio reception (which always shows Cueball's attempt to transmit, whether or not it shows a successful incoming message).

Some hazards, such as alpha particles, a form of radiation with particularly low penetrative power, can be easily deterred by common things; even a relatively short distance through air is enough to minimize their impact. Comparatively, more dangerous hazards, such as the far more penetrative gamma rays, are unaffected by all but the shielding methods actually intended for them. No effect is either all effective or all ineffective, against each form of 'shielding', and neither is any instance of shield consistent against all effects.

The title text notes that, while the shark hazard is shown on the chart to be entirely nullified by a sufficient air barrier, in reality sharks are capable of attacking prey even if it is a short distance out of the water.

Shielding Chart

Shielding Chart	Air	Lead	Water	Glass	Vacuum	Oven mitts	Armor	Bio-hazard suit	Faraday cage	Shark cage
Gamma rays	Gamma rays are not significantly shielded by air.	Lead is commonly used as shielding against gamma rays. Lead works because of its density and high atomic number, scattering gamma rays.	Water can be used to shield against gamma rays, but you need at least 10 feet of water between you and the gamma rays for it to work.	Gamma rays have the highest energy of any type of light, and has no mass and no charge, making them pass through most materials easily.
Neutrons	Neutrons are not stopped by low densitiy materials such as air.	Lead's high density means that the neutrons will keep bumping into lead nuclei loosing their energy through inelastic scattering. However since the lead nuclei are much heavier than neutrons most of the energy will remain with the neutron, as a result many collisions are needed to slow the neutrons. Some neutrons will also be absorbed by the nuclei although the cross section is rather low.	Since protons and neutrons have almost the same mass, a collision with a hydrogen atom in water will result in the neutron losing almost half of its energy resulting in a very rapid attenuation. Moreover the cross section for the fusion of neutrons and protons is high, leading to most neutrons being captured to form deuterium.	None of these materials is dense enough to slow or absorb neutrons in significant quantities.
Alpha particles									Outside of a vacuum, Alpha particles are only detectable within short distances (millimeter scale), and the presence of the two cages is incidental. In both cases, the emitter has been moved closer to the observer, because otherwise the effect would be masked by the intervening air.
Light	Light is able to pass through air easily; if it weren't, we wouldn't normally be able to see.	As lead is a solid, opaque material, light is not able to pass through it.	Water is mostly transparent to visible light. It will attenuate over long distances, but won't be quickly blocked.	As glass is a largely transparent substance, light is usually able to pass through it (though very thick glass would block light out).	Because a lack of air does not impact the travel of light, it reaches Cueball without issue	Cueball is able to use the opaque oven mitts to cover the light source, successfully preventing the light from reaching him.	The helmet Cueball is wearing is opaque, blocking the light from reaching him. It also makes this a fairly useless set of armor.	As with the oven mitts, Hairy uses the helmet part of the biohazard suit to block the light source.	As both types of cages have holes in them, it is easy for the light to pass through the holes and reach Cueball.
Sound							The two cases of whether sound can penetrate suits are the only two cases where Cueball is trying (successfully) to inflict the phemonenon against Megan, who otherwise features only as the (attempted) instigater. Neither suit is able (or intended) to significantly block sound waves.
Heat		Lead conducts heat, allowing Cueball to toast a marshmallow on the surface of the shield. However, since lead is poisonous, he should not do this.
Swords
Toxic dust		Lead is poisonous, so while a solid lead barrier would prevent toxic dust from passing through, any dust or metal fragments from the shield would still be dangerous.			With no air to slow it down, dust in space can move at dangerously high speeds, possibly fast enough to tear through Cueball's space suit.
Radio
Sharks	Sharks cannot travel very far on land or in the air.	Shielding yourself with lead plates will effectively protect you against sharks.	Sharks live underwater, so water is not an effective shield against sharks. [citation needed]	Glass will effectively protect you against sharks, provided that it is thick enough. In fact, sharks are commonly (and safely) shown to the public in aquariums.	As sharks are confined in water [citation needed], the vacuum of space protects you against them.	Oven mitts are not very effective at stopping sharks. [citation needed]	Depending on the armor, a sharks might still be able to bite you through it.	A biohazard suit is weak enough that a shark can rip through it.	A Faraday cage is weak enough that a shark can rip through the cage, failing to protect the human inside.	A shark cage is an invention specifically designed to protect against sharks, and as such is good at preventing sharks from getting inside.

Transcript

This is one of 27 incomplete transcripts: Don't remove this notice too soon. If you can fix this issue, edit the page!

The whole comic is in one panel A confusion matrix sits in the middle

Air:

• Gamma rays - Yellow
• Neutrons - Yellow
• Alpha particles - Gray
• Light - Yellow
• Sound - Yellow
• Heat - Yellow
• Swords - Yellow
• Toxic dust - Yellow
• Radio - Yellow
• Sharks - Gray

Lead:

• Gamma rays - Gray
• Neutrons - Grayish-yellow
• Alpha particles - Gray
• Light - Gray
• Sound - Yellow
• Heat - Yellow
• Swords - Gray
• Toxic dust - Grayish-yellow
• Radio - Gray
• Sharks - Gray

Water:

• Gamma rays - Grayish-yellow
• Neutrons - Gray
• Alpha particles
• Light - Grayish-yellow
• Sound - Yellow
• Heat - Yellow
• Swords - Yellow
• Toxic dust - Yellow
• Radio - Gray
• Sharks - Yellow

• Glass:
• Gamma rays
• Neutrons
• Alpha particles
• Light
• Sound
• Heat
• Swords
• Toxic dust
• Radio
• Sharks

Vacuum:

• Gamma rays
• Neutrons
• Alpha particles
• Light
• Sound
• Heat
• Swords
• Toxic dust
• Radio
• Sharks

Oven mitts:

• Gamma rays
• Neutrons
• Alpha particles
• Light
• Sound
• Heat
• Swords
• Toxic dust
• Radio
• Sharks

Armor:

• Gamma rays
• Neutrons
• Alpha particles
• Light
• Sound
• Heat
• Swords
• Toxic dust
• Radio
• Sharks

Biohazard suit:

• Gamma rays
• Neutrons
• Alpha particles
• Light
• Sound
• Heat
• Swords
• Toxic dust
• Radio
• Sharks

Faraday cage:

• Gamma rays
• Neutrons
• Alpha particles
• Light
• Sound
• Heat
• Swords
• Toxic dust
• Radio
• Sharks

Shark cage:

• Gamma rays
• Neutrons
• Alpha particles
• Light
• Sound
• Heat
• Swords
• Toxic dust
• Radio
• Sharks

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Discussion

Brb, going out to buy some lead. Fephisto (talk) 01:49, 23 October 2025 (UTC)

If you buy some oven mitts, too, you can get rid of the only two remaining penetrating substances (sound and heat) Logalex8369 (talk) 21:16, 23 October 2025 (UTC)

My new expansion to Rock Paper Scissors Lizard Spock is coming along nicely. KelOfTheStars! (talk) 02:25, 23 October 2025 (UTC)

Ah yes, you can make sound in a vacuum! King Pando (talk) 02:41, 23 October 2025 (UTC)

Well, there's air in her helmet, presumably... 160.39.41.199 05:05, 23 October 2025 (UTC)

We're not gonna have a good time filling out this table, are we? 47.141.47.226 05:14, 23 October 2025 (UTC)

i bet randall is laughing at those silly explainxkcd editors who now have to elaborate on every single square. if i were conspiratorial i'd say he wrote this just to spite us. raeb 08:46, 23 October 2025 (UTC)

Nah, I'm good at filling out tables :) --DollarStoreBa'al^converse 13:07, 23 October 2025 (UTC)

Is your name perhaps Bobby Tables? user:Seshan S. 10:25, 23 October 2025

Bobby Tables is good at deleting tables, not filling them out :) -Ash Crow (talk) 10:47, 24 October 2025 (UTC)

My name is Billy Tables, Bobby Tables' mild-mannered twin brother. Bobby is my evil twin here to cause mischief and mayhem in small wikis.--DollarStoreBa'al^converse 14:09, 24 October 2025 (UTC)

A bit surprised there's nothing about keeping Mr. Faraday away. --130.233.188.214 06:50, 23 October 2025 (UTC)

He was a doctor, so apples would do the job for that. 82.13.184.33 13:21, 23 October 2025 (UTC)

This came out a couple of weeks after the 50th anniversary of Jaws, so it's disappointing that "a bigger boat" isn't one of the protections. Barmar (talk) 14:24, 23 October 2025 (UTC)

"Air," "Lead," "Water," and "Glass," and a near-perfect "Vacuum" actually vary by thickness. I guess Oven mitts, armor, bio-hazard suits, faraday cages, and shark cages do too but those usually come in human-scale sizes. A meter of air won't give you significant protection against gamma rays, but if you are anywhere near sea level, the air above your head does. A near-perfect vacuum too wide for a shark to get to you before it dies will protect you, one only a few nanometers thick probably won't. 64.201.132.210 18:20, 23 October 2025 (UTC)

The best shield of all is distance. You just need enough of it. KelOfTheStars! (talk) 00:33, 24 October 2025 (UTC)

No - the best shield of all is the Hylian Shield. 82.13.184.33 08:31, 24 October 2025 (UTC)

Me & my brother read this whole thing and cracked up about it for several minutes. RadiantRainwing (talk) 03:03, 24 October 2025 (UTC)

This is definitely one of my favorite xkcd comics. I love the confusion matrix ones. RadiantRainwing (talk) 03:05, 24 October 2025 (UTC)

Wait, why no “raptors” row? I really want to see that. RadiantRainwing (talk) 03:09, 24 October 2025 (UTC)

I'm noticing that the transcript isn't looking too good right now, but I don't exactly have the time to fix it right now. Can someone look at 2998: Ravioli-Shaped Objects#Transcript and copy that format? Thanks, 42.book.addict^{Talk to me!} 03:44, 24 October 2025 (UTC)

There's now an "effect vs shield" row for every tile, plus (following on from how the first row started) a "effect-row" scene-setting description placeholder.

I put a list of the rows and columns at the top, just for quick 'scan down/along' reference by anyone reading that bit, but each cell explicitly starts with the "what vs what" and can (where it hasn't already been) be given the hue of the tile and then a followup line (or more!) which addresses the mini-vignette that depicts its particular clash of row header and column header.

Please do not bother with text-colo(u)rs. For one thing, set on default white page-background, the Yellow would be hard to read (by those who can read it) and also likely of zero value (by those who use text-to-audio to read it). The light grey would be bad enough, and the dirty-yellow could be as bad as either.

The reason I did this much is because someone had put a suggestion about copypasting the #hex HTML colour-codes which either was going to lead to the thing I've just said shouldn't be done or would have to be converted into the colour-code-equivalent descriptive plaintext, and still would not have the 'important everything vs. everything' reference which I quickly cobbled together to provide this structure.

Anyone with a text editor can still constructively search/replace anything within that basic structre that I've perhaps not done the way they think should be done (wrong capitalisation, the way the " - " sits between the "vs." and where the colour should be, whether "vs." is even the right way of describing it!), but the big job is actually trying to describe with sufficient detai what Cueball (or the fish/ice/whatever) is doing to prevent the appropriate effect by the (in)appropriate shield. Which I'm leaving for those in a time-zone more westerly than me (who aren't well beyond their healthy bedtimes) or far more easterly than me (for whom dawn has at least started to approach), or possibly just until people not significantly far from me in either direction find that they're more wide awake than anybody else around the world.

Of course, there's always a possibility that someone has been beavering away at it, offline, for a while now and is going to overwirte all that I did. Which is Ok too, and hopefully all credit to them. I may even now have spent more time writing this than I did putting my framework in, and I frankly hope to find this reply to be superfluous by the next time I check in, anyway, so I can delete it entirely and replace with a congratulatory message. ;) 2.98.65.8 00:43, 25 October 2025 (UTC)

So, with lead, water, vacuum, oven mitts, and either glass or a bio-hazard suit, I would be invincible. 67.4.71.239 22:01, 25 October 2025 (UTC)

Randall's clearly only seen the film Jaws but not the book... --Darth Vader (talk) 10:16, 26 October 2025 (UTC)

Or a popular webcomic... ;) 2.98.65.8 18:16, 26 October 2025 (UTC)

cat proximity reference?

do you think shark vs water illustration could be a reference to 231:Cat Proximity ? 129.222.167.167 00:19, 2 November 2025 (UTC)

Almost certainly (the brick joke thrown back a second time with the Shark/Faraday Cage setup, etc).

I mean, it's also possible that they're depicting a catshark, but they generally aren't the threat that even dogfish sharks are (and are probably as harmless to humans, or their insufficiently shark-proofed cages, as catfish...), but I can't see it being any more advanced real-world reference like that. 2.98.65.8 00:49, 2 November 2025 (UTC)
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