explain xkcd - User contributions [en]

3158: Shielding Chart

2025-10-23T17:48:14Z

2A02:1210:5A17:D400:F4BB:A32C:2D8D:4251: /* Shielding Chart */

{{comic
| number = 3158
| date = October 22, 2025
| title = Shielding Chart
| image = shielding_chart_2x.png
| imagesize = 740x720px
| noexpand = true
| titletext = Sharks can occasionally travel short distances through air when pursuing prey, but their attenuation coefficient is pretty high.
}}

==Explanation==
{{incomplete|This page was created by a SPACE-BASED SHARK DEFENSE BOT. Don't remove this notice too soon.}}

This comic is part of a series on [[:Category:Confusion matrices|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.

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 {{w|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 {{w|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===
{| class="wikitable" | style="background:#E6C3C3;"
! Shielding Chart
! scope="col"| {{w|Air}}
! scope="col"| {{w|Lead}}
! scope="col"| {{w|Water}}
! scope="col"| {{w|Glass}}
! scope="col"| {{w|Vacuum}}
! scope="col"| {{w|Oven mitts}}
! scope="col"| {{w|Armor}}
! scope="col"| {{w|Hazmat suit|Bio-hazard suit}}
! scope="col"| {{w|Faraday cage}}
! scope="col"| {{w|Shark cage}}
|-
! scope="row"| {{w|Gamma rays}}
| style="background:#FBF8CE;"|Gamma rays are not significantly shielded by air.
| style="background:#C4C5C7;"|Lead is commonly used as {{w|Lead shielding|shielding}} against gamma rays. Lead works because of its density and high atomic number, scattering gamma rays.
| style="background:#D5C58A;"|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.
|colspan=7; style="background:#FBF8CE;"|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.

|-
! scope="row"| {{w|Neutrons}}
| style="background:#FBF8CE;"|Neutrons are not stopped by low densitiy materials such as air.
| style="background:#D5C58A;"|Leads 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.
| style="background:#C4C5C7;"|Since protons an 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.
|colspan=7; style="background:#FBF8CE;"|None of these materials is dense enough to slow or absorb neutrons in significant quantities.

|-
! scope="row"| {{w|Alpha particles}}
| style="background:#C4C5C7;"|
| style="background:#C4C5C7;"|
| style="background:#C4C5C7;"|
| style="background:#C4C5C7;"|
| style="background:#FBF8CE;"|
| style="background:#C4C5C7;"|
| style="background:#C4C5C7;"|
| style="background:#C4C5C7;"|
|colspan=2; style="background:#FBF8CE;"|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.

|-
! scope="row"| {{w|Light}}
| style="background:#FBF8CE;"|Light is able to pass through air easily; if it weren't, we wouldn't normally be able to see.
| style="background:#C4C5C7;"|As lead is a solid, opaque material, light is not able to pass through it.
| style="background:#D5C58A;"|Light is able to pass through water without many issues. As such, the light would have easy access to Cueball.
| style="background:#FBF8CE;"|As glass is a largely transparent substance, light is usually able to pass through it (though very thick glass would block light out).
| style="background:#FBF8CE;"|Because a lack of air does not impact the travel of light, it reaches Cueball without issue
| style="background:#C4C5C7;"|Cueball is able to use the opaque oven mitts to cover the light source, successfully preventing the light from reaching him.
| style="background:#C4C5C7;"|The helmet Cueball is wearing is opaque, blocking the light from reaching him. It also makes this a fairly useless set of armor.
| style="background:#C4C5C7;"|As with the oven mitts, Hairy uses the helmet part of the biohazard suit to block the light source.
|colspan=2; style="background:#FBF8CE;"|As both types of cages have holes in them, it is easy for the light to pass through the holes and reach Cueball.

|-
! scope="row"| {{w|Sound}}
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#C4C5C7;"|
| style="background:#D5C58A;"|
| colspan=2; style="background:#FBF8CE;"| 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.
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|

|-
! scope="row"| {{w|Heat}}
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|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.
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#D5C58A;"|
| style="background:#C4C5C7;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|

|-
! scope="row"| {{w|Swords}}
| style="background:#FBF8CE;"|
| style="background:#C4C5C7;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#C4C5C7;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|

|-
! scope="row"| {{w|Particulate matter#Health problems|Toxic dust}}
| style="background:#FBF8CE;"|
| style="background:#D5C58A;"|{{w|Lead poisoning|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.
| style="background:#FBF8CE;"|
| style="background:#C4C5C7;"|
| style="background:#FBF8CE;"|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.
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#C4C5C7;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|

|-
! scope="row"| {{w|Radio}}
| style="background:#FBF8CE;"|
| style="background:#C4C5C7;"|
| style="background:#C4C5C7;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#C4C5C7;"|
| style="background:#FBF8CE;"|
| style="background:#C4C5C7;"|
| style="background:#FBF8CE;"|

|-
! scope="row"| {{w|Sharks}}
| style="background:#C4C5C7;"|Sharks cannot travel very far on land or in the air.
| style="background:#C4C5C7;"|Shielding yourself with lead plates will effectively protect you against sharks.
| style="background:#FBF8CE;"|Sharks live underwater, so water is not an effective shield against sharks. {{Citation needed}}
| style="background:#C4C5C7;"|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.
| style="background:#C4C5C7;"|As sharks are confined in water {{Citation needed}}, the vacuum of space protects you against them.
| style="background:#FBF8CE;"|Oven mitts are not very effective at stopping sharks. {{Citation needed}}
| style="background:#D5C58A;"|Depending on the armor, a sharks might still be able to bite you through it.
| style="background:#FBF8CE;"|A biohazard suit is weak enough that a shark can rip through it.
| style="background:#FBF8CE;"|A Faraday cage is weak enough that a shark can rip through the cage, failing to protect the human inside.
| style="background:#C4C5C7;"|A shark cage is an invention specifically designed to protect against sharks, and as such is good at preventing sharks from getting inside.
|}

==Transcript==
{{incomplete transcript|Don't remove this notice too soon.}}
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

{{comic discussion}}<noinclude>
[[Category:Confusion matrices]]
[[Category:Sharks]]
[[Category:Multiple Cueballs]]
[[Category:Comics featuring Megan]]

3158: Shielding Chart

2025-10-23T17:44:59Z

2A02:1210:5A17:D400:F4BB:A32C:2D8D:4251: /* Shielding Chart */

{{comic
| number = 3158
| date = October 22, 2025
| title = Shielding Chart
| image = shielding_chart_2x.png
| imagesize = 740x720px
| noexpand = true
| titletext = Sharks can occasionally travel short distances through air when pursuing prey, but their attenuation coefficient is pretty high.
}}

==Explanation==
{{incomplete|This page was created by a SPACE-BASED SHARK DEFENSE BOT. Don't remove this notice too soon.}}

This comic is part of a series on [[:Category:Confusion matrices|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.

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 {{w|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 {{w|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===
{| class="wikitable" | style="background:#E6C3C3;"
! Shielding Chart
! scope="col"| {{w|Air}}
! scope="col"| {{w|Lead}}
! scope="col"| {{w|Water}}
! scope="col"| {{w|Glass}}
! scope="col"| {{w|Vacuum}}
! scope="col"| {{w|Oven mitts}}
! scope="col"| {{w|Armor}}
! scope="col"| {{w|Hazmat suit|Bio-hazard suit}}
! scope="col"| {{w|Faraday cage}}
! scope="col"| {{w|Shark cage}}
|-
! scope="row"| {{w|Gamma rays}}
| style="background:#FBF8CE;"|Gamma rays are not significantly shielded by air.
| style="background:#C4C5C7;"|Lead is commonly used as {{w|Lead shielding|shielding}} against gamma rays. Lead works because of its density and high atomic number, scattering gamma rays.
| style="background:#D5C58A;"|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.
|colspan=7; style="background:#FBF8CE;"|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.

|-
! scope="row"| {{w|Neutrons}}
| style="background:#FBF8CE;"|Neutrons are not stopped by low densitiy materials such as air.
| style="background:#D5C58A;"|Leads 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.
| style="background:#C4C5C7;"|Since protons an 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.
|colspan=7; style="background:#FBF8CE;"|None of these materials is dense enough to slow or absorb neutrons in significant quantities.

|-
! scope="row"| {{w|Alpha particles}}
| style="background:#C4C5C7;"|
| style="background:#C4C5C7;"|
| style="background:#C4C5C7;"|
| style="background:#C4C5C7;"|
| style="background:#FBF8CE;"|
| style="background:#C4C5C7;"|
| style="background:#C4C5C7;"|
| style="background:#C4C5C7;"|
|colspan=2; style="background:#FBF8CE;"|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.

|-
! scope="row"| {{w|Light}}
| style="background:#FBF8CE;"|Light is able to pass through air easily; if it weren't, we wouldn't normally be able to see.
| style="background:#C4C5C7;"|As lead is a solid, opaque material, light is not able to pass through it.
| style="background:#D5C58A;"|Light is able to pass through water without many issues. As such, the light would have easy access to Cueball.
| style="background:#FBF8CE;"|As glass is a largely transparent substance, light is usually able to pass through it (though very thick glass would block light out).
| style="background:#FBF8CE;"|Because a lack of air does not impact the travel of light, it reaches Cueball without issue
| style="background:#C4C5C7;"|Cueball is able to use the opaque oven mitts to cover the light source, successfully preventing the light from reaching him.
| style="background:#C4C5C7;"|The helmet Cueball is wearing is opaque, blocking the light from reaching him. It also makes this a fairly useless set of armor.
| style="background:#C4C5C7;"|As with the oven mitts, Hairy uses the helmet part of the biohazard suit to block the light source.
|colspan=2; style="background:#FBF8CE;"|As both types of cages have holes in them, it is easy for the light to pass through the holes and reach Cueball.

|-
! scope="row"| {{w|Sound}}
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#C4C5C7;"|
| style="background:#D5C58A;"|
| colspan=2; style="background:#FBF8CE;"| 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.
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|

|-
! scope="row"| {{w|Heat}}
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|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.
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#D5C58A;"|
| style="background:#C4C5C7;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|

|-
! scope="row"| {{w|Swords}}
| style="background:#FBF8CE;"|
| style="background:#C4C5C7;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#C4C5C7;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|

|-
! scope="row"| {{w|Particulate matter#Health problems|Toxic dust}}
| style="background:#FBF8CE;"|
| style="background:#D5C58A;"|{{w|Lead poisoning|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.
| style="background:#FBF8CE;"|
| style="background:#C4C5C7;"|
| style="background:#FBF8CE;"|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.
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#C4C5C7;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|

|-
! scope="row"| {{w|Radio}}
| style="background:#FBF8CE;"|
| style="background:#C4C5C7;"|
| style="background:#C4C5C7;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|
| style="background:#C4C5C7;"|
| style="background:#FBF8CE;"|
| style="background:#C4C5C7;"|
| style="background:#FBF8CE;"|

|-
! scope="row"| {{w|Sharks}}
| style="background:#C4C5C7;"|Sharks cannot travel very far on land or in the air.
| style="background:#C4C5C7;"|Shielding yourself with lead plates will effectively protect you against sharks.
| style="background:#FBF8CE;"|Sharks live underwater, so water is not an effective shield against sharks. {{Citation needed}}
| style="background:#C4C5C7;"|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.
| style="background:#C4C5C7;"|
| style="background:#FBF8CE;"|Oven mitts are not very effective at stopping sharks.
| style="background:#D5C58A;"|
| style="background:#FBF8CE;"|
| style="background:#FBF8CE;"|A faraday cage is weak enough that a shark can rip through the cage, failing to protect the human inside.
| style="background:#C4C5C7;"|A shark cage is an invention specifically designed to protect against sharks, and as such is good at preventing sharks from getting inside.
|}

==Transcript==
{{incomplete transcript|Don't remove this notice too soon.}}
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

{{comic discussion}}<noinclude>
[[Category:Confusion matrices]]
[[Category:Sharks]]
[[Category:Multiple Cueballs]]
[[Category:Comics featuring Megan]]