Memo Spike Connector

Explanation:
This is the third installment in the series of Cursed Connectors and presents Cursed Connectors #102: The Memo Spike. It follows 2495: Universal Seat Belt (#65) and was followed 9 days later by 2507: USV-C (#280).
The comic depicts a large metal spike with a wire coming from the base. The spike stabs through two other wires, thus creating an electrical connection between the three. As the name suggests, the spike resembles a stationery spindle , colloquially known as a spike, called a Memo Spike here by Randall. However, unlike normal spindles, this one has a cable of some kind coming out of it, suggesting this is a hub of some sort.
Spindles are used to temporarily hold paper by "spindling" or impaling the paper onto the spike (as depicted in the comic). They're most known for their use in restaurants as a way to hold bills that have been paid, or traditionally in offices that work with many bits of paper, e.g. with invoices in a finance department or hardcopy in newspaper editing, to prevent accidental disturbance/shuffling, at the expense of a small puncture mark in each sheet so impaled. (This could cause errors in papers with punch-holes that are meant to be read by machines, hence the admonition against " folding, spindling, and mutilating ".) In the latter context, the editor might put all the rejected stories onto a spike (rather than into a wastebasket) to prevent them going astray, and this might be the source of the term ' spiked '.
The joke of the comic is while any number of non-destructive connection standards exist, a large spike can provide much of the same results: a conductive object that retains a connection of multiple wires in a way that allows electricity to pass through. Indeed, in the early days of Ethernet, vampire taps were used, essentially spikes that bit into a cable to establish a new branch in the network.  Another type of connection which involves piercing the wire is a punch-down block , a type of insulation-displacement connector , where one or more wires are pushed into a cutting channel instead of onto a spike.
Depending on the type of cable it is also likely to create a short circuit, e.g. by connecting both strands of a twisted pair of strands in a typical Ethernet cable, or the central wire and the sheath of a coaxial cable. In an enterprise environment, this could even happen on a PoE-Connection , which actually carry more noticeable amounts of power (up to 25.5W). Even if this is avoided, the single spike may be large enough to mechanically sever a random subset of the finer strands that exist within a multicore cable such as is commonly in use today.
The title text takes this a bit further. It says that it is backwards compatible with many existing cables. This means any cable large enough to be impaled by the spike could be used. Needless to say it will likely not work anyway. It also continues by saying that phones and tablets can also be connected using this method if you press them down hard enough over the spike. Thus if you actually manage to make the spike penetrate the device's coverings to reach the electrical parts, then there is a connection. The implication is that any device or cable can be connected to any other device or cable as a form of universal adapter/splitter/combiner across arbitrary hardware and communications/power standards. In reality, this could be even more dangerous and will surely destroy the phone/tablet either directly or by overloading their cable connection. [ citation needed ] Also be careful not to impale your hand while trying to push the spike through your tablet's screen.
[A memo spike is shown (a device also called a Spindle). It is a long spike standing up from a round base plate. A wire is coming in from the left and appears to be hardwired into the spike's base element. Two other wires comes in from the right. Both are firmly impaled down upon the spike, penetrated completely through shortly before their apparently unterminated ends. The end of the impaled wire closest to the base faces out and the details appear to show it to be of some variety of multicore (rather than co-axial) manufacture. The other cable's end is a bit higher and points into the image. Above is a title and below is a label.] Cursed Connectors #102 The Memo Spike


Fissile Raspberry Isotopes

Explanation:
Ponytail is admiring her raspberry fields telling Cueball she expects a good harvest... That is if they do not get too many fissile raspberry isotopes! To which Cueball has to ask Too many whats?
The comic is thus a joking analogy to nuclear chain reactions , in which the fission (splitting in two) of one atomic nucleus releases neutrons , which then strike other nuclei and cause them in turn to fission, releasing more neutrons. This chain reaction releases a great deal of energy and is what makes possible both nuclear power and nuclear bombs .
A fissile isotope , such as uranium-235 , is one that is sufficiently large and unstable to undergo such a chain reaction, as opposed to the more common and less unstable uranium-238 . Ponytail fear that her raspberries have too many unstable isotopes so that her fields risk undergoing a similar fission-driven chain reaction. This chain reaction is depicted in the second panel, and she explains that if this happens the entire crop may be gone in seconds. It sounds like this is only dangerous for her economy, i.e. all the berries destroyed, but not a runaway explosion that destroys her field and any living thing nearby.
In real life, raspberries don't undergo such chain reactions. [ citation needed ] As an aggregate fruit , raspberries (as well as blackberries mentioned in the title text) resemble common depictions of atomic nuclei , with each drupelet corresponding to a nucleon (proton or neutron), which is probably why they are the subject of the comic.  (The actual "appearance" of atomic nuclei, in contrast to the common depictions, is complicated by Heisenbergian uncertainty, quantum effects, and strong nuclear force interactions.)  Perhaps these raspberries are byproducts of the experiments depicted in 1949: Fruit Collider .
This comic is also a pun on "pi mesons" or pions , subatomic particles that transmit the strong nuclear force , and the similarity in name to a pie , the food type, as in a raspberry pie . The transmission of the strong nuclear force happens most importantly in the atomic nucleus and is responsible for keeping the nucleus intact, i.e. , preventing it from undergoing fission despite the strong repulsive electromagnetic force present from all the positively-charged protons .
Raspberry pies (and pie mesons of such) are not to be confused with Raspberry Pi , a very popular microcontroller widely used for hobbyist or educational projects.
Ponytail claims that her berries are protected (bound) by fresh raspberry pie mesons. Cueball states he hopes they hold, but Ponytail is confident as these pies are made from her grandma's recipe, i.e. , it is actually a fresh pie made from the berries. The faith in the pie recipe being able to impede the danger references the convention of "Just like Grandma used to make", nostalgia for an infallible cookery ancestor, in this case a hallowed family recipe that acts to mitigate any budding 'berry' chain-reaction. Grandma's baking is not always so fondly remembered and, in this case, it could be some (in)famous inertness and solidity to the product that is reassuring, not any form of culinary excellence.
The title text mentions that the grandma's "blackberry pie meson" recipe was a huge seller, but that then the farm was shut down by a joint FDA/NRC investigation. This refers to the Food and Drug Administration (FDA) and the Nuclear Regulatory Commission (NRC). The FDA is responsible for the regulation and inspection of food in the U.S., and the NRC for the regulation and inspection of nuclear facilities and materials. A hypothetical "blackberry pie meson" might well run afoul of both, being both nuclear and therefore subject to NRC regulations and permitting requirements, and unhealthy to eat and thus violating FDA rules. This could in addition also violate the FDA's rules on radiation emitting products. One might be able to imagine the FDA discovering that the blackberry pies are functioning to contain a nuclear chain reaction, and calling in the NRC to consult. The FDA took a similarly incongruous interest in physics in the title text of 2216: Percent Milkfat .
It is mentioned that the pies were shelf stable , which means it can last a long time without being in a refrigerator. This may be because of its innate radioactivity keeping it free from germs. This may also explain why they were shut down by both the above-mentioned agencies.  The word "stable" also describes atoms , and therefore substances, that do not spontaneously undergo nuclear decay, though a stable isotope may (eventually) result directly from the decay of an unstable one.
[Ponytail and Cueball are standing in a field, looking at rows of crops disappearing in the distance over rolling hills.] Ponytail: I reckon it'll be a good harvest. Ponytail: So long as we don't get too many fissile raspberry isotopes. Cueball: Too many whats ?
[In a half height panel is shown a picture of a raspberry with an arrow to a situation where it is splitting in to two equal parts. From the split there also comes two small drupelets flying out as shown with arrows. Below these two situations is a smaller sketch of how one of these two drupelets will eventually hit another raspberry, which will send out three drupelets when splitting, two of those hitting other berries, that each send out two drupelets. The lower of these are not depicted hitting any, but the upper split hits two again, which each send out two, in an ongoing chain reaction. The depiction stops there. Above this panel is what Ponytail tells Cueball:] Ponytail (narrating): If a raspberry breaks in half, it releases fragments which can cause more splits. Within seconds you've lost the whole crop.
[Ponytail and Cueball are standing in an empty panel talking.] Ponytail: Luckily the berries are bound by fresh raspberry pie mesons. Cueball: I hope they hold. Ponytail: It's my grandma's recipe. They'll hold.


News Story Reaction

Explanation:
In this comic, Cueball is at his computer, likely typing a comment after reading a shocking news story where the Mona Lisa has been attacked and shredded by a pack of wild dogs. The Mona Lisa is one of the most famous paintings in human history. At the time of this comic, the Mona Lisa has not been attacked and is unlikely to be shredded in this circumstance at least by dogs as it is painted on wood, rather than canvas. [1]
At the beginning of his comment, Cueball describes his reaction and disappointment about the event, describing the event as "a loss for humanity." Cueball is then reminded of his first kiss, which occurred inside of a JCPenney , where a picture of the Mona Lisa hung on one of its walls. He adds this to his comment, explaining that this is why the news hits him hard. However, his story has almost no relation to the Mona Lisa , other than that the picture was at the scene as well as being unnecessary.
After posting the comment, Cueball reflects on this and mentions that not every news story is, or needs to be, about himself.
The title text describes an exception to this, where his experience IS directly related to the affected painting, as his ex seemingly planned to get revenge on the painting itself. The title text suggests that the dogs destroyed the painting before Cueball's ex could do so. (But perhaps it could be that she let the dogs in, and so this extra information could lead to the police finding the person who was responsible.)
[Cueball is sitting at a desk, typing on his laptop. What he types is shown above Cueball, as indicated by the line going from his hands to the text.] Cueball: Devastated to hear that a pack of wild dogs got into the Louvre and shredded the Mona Lisa. Cueball: What a loss for humanity. Cueball: My first kiss was in the aisle of a J.C. Penny [ sic ] that had a poster of the Mona Lisa on the wall, so this is hitting me especially hard.
[Caption below the panel] Sometimes I have to remind myself not to make every news story about me.


Projecting

Explanation:
In this comic, Cueball expresses his difficulty with psychological projection . Projection is taking qualities of the self and attributing these qualities to others.
Cueball actually admits he has a real problem with projecting, but while doing so, he is seemingly oblivious to the fact, that he is stating this in a way that projects his self-identified difficulty upon his friends: Ponytail , Megan and White Hat . Of course, this could also just be a joke made by Cueball, as it is the joke in the comic. On the other hand, Cueball and Randall have serious issues with social interactions , and this could just be another example of such a problem.
In the title text, Cueball continues his projections, stating that this is something we all need to work on . So he continues to believe that all the others have the same problem, not just a lot of them as in his original statement, which left the possibility that not all of them had this issue. In the end, he also tops it by saying but especially you all indicating that he imagines his own case is a less serious issue of projection than that he actually projects the others as having.
Alternately, the phrase having a real problem with projection usually means the person speaks quietly, their voice doesn't carry very far, particularly in acting and public speaking environments. Someone with difficulty projecting wouldn't be heard by people in the back row, or perhaps even halfway into the audience (depending how much difficulty they have). This comic is notably smaller than the average xkcd comic, making it the visual / comic equivalent to not projecting. Just as a non-projecting voice cannot be heard very far away, this comic cannot be seen very far away (in either case, not as far as usual). Under this interpretation, the title text is referencing that his audience is also not projecting, they're just as small as he is.
Alternatively, Cueball expresses his difficulty with complex numbers .  There exists a common projection between the complex and reals, but it may not be clear to him about which method to use or how to do it.  If he is projecting onto the real part of the complex line, then his issue is a many-to-one problem, which explains why it is everyone else's problem as well.
An alternative perspective might be that the characters, as stick figures, are represented as two dimensional projections of three dimensional objects, and this projection has an issue that depth information is not preserved, so for example, it isn't clear whether cueball is facing towards us or away from us. As his arms are not foreshortened by the projection, this indicates that he is standing in an unnatural pose, so the fact that he says that especially the other characters have a problem with projection would be a good example of psychological projection.
A further alternative read could be that Cueball is acting as the Randall surrogate, noting that the other characters are projections of Randall's conscious and subconscious self.  The title text could then be read as either directed to those aspects as expressed as characters within the comic, or directed to the reader, who also has things to work on.
A different meaning of the term "Projecting" is seen in the fields of public speaking and drama, being the way that a person clearly uses their voice to address an audience.  If Cueball is not projecting well, then the characters listening to him may ignore him.
Projection is an ongoing issue.  People from disparate communities can experience this all the time, where one person assumes out of habit that the other person has the traits of their community.  On the end of the spectrum, projection can be completely delusional, as the comic hints at.  It would make sense for that be more common for people who attend less to where others are at, such as introverted or powerful people, two groups that experienced engineers can land in.
It is also possible that Cueball is addressing the portion of readers who feel the need to project onto Randall their own desire (and meticulousness in analytical searching) for layers upon layers of hidden meaning in xkcd comics. The assumption that he has stuffed several different obscure punchlines into the one sentence of a single-panel comic is, despite the layered punchlines in some other comics, quite a stretch. Randall may be suggesting that such projections from readers onto him are problematic because they cause comic explanation pages to be filled with rambling speculation that can make the explanation of the actual joke harder to understand.
[Ponytail, Cueball, Megan, and White Hat are standing. Cueball is talking, with arms outstretched, palms up, while the other three are looking at him.] Cueball: Like a lot of you, I have a real problem with projection.


USV-C

Explanation:
This is the fourth installment in the series of Cursed Connectors and presents Cursed Connectors #280: USB-C to UV-C. It follows 2503: Memo Spike Connector (#102) and was first followed just a bit more than half a year later by 2589: Outlet Denier (#78).
This comic depicts a cable that converts from USB-C (at the top of the picture) to UV-C (at the bottom).
USB-C is a rotationally symmetrical Universal Serial Bus (USB) connector. UV-C is a range of ultraviolet light with wavelengths between 100 and 280 nm.  This is often used as a germicide, so this comic may also be related to the COVID-19 pandemic. The U.S. Food and Drug Administration (FDA) has an infosheet with information about these devices and COVID-19. And the connector number (280) is likely chosen because it is the boundary between UV-C and UV-B in nanometres.
Similar cables actually exist, with a USB port at one end to power a small (usually visible light) lamp at the other. A cable with a UV-C lamp could, as noted above, be useful for disinfecting surfaces; however, the depicted design would be problematic because it would expose the user's skin and eyes to harmful ultraviolet radiation.
Unless there is more to the UV-C end than indicated, the cable seems not to have use in bidirectional communication (even to confirm that it is plugged in or shone upon some suitable optical transceiver) so in any data transfer situation it could be a limited-range broadcast-only system at best - which has its uses in certain niche cases.
The title text mentions that the UV-C is unpolarized . This is a pun with two uses of the term polarized. When referring to a connector 'polarization', or absence of it, it means that USB-C does not force you to use a single correct orientation when using it, i.e. you don't have to turn it "right-side-up" like USB-A or USB-micro.
It also refers to the use of a polarizing filter which takes unpolarized light waves and blocks out the waves that are not oriented in the same direction. These are used in sunglasses and photography to eliminate glare and enhance the image. These filters do need to be oriented in a specific direction in order to have the desired effect of passing/blocking a given polarization, perhaps to separate two perpendicularly orientated 'channels' that need to be unmixed exactly knowing the respective orientation of the two signals ( or exactly 180° out, which is what USB-C effectively allows for at present).
The light could also have been circularly polarized , which allows 'left' and 'right' rotating polarizations to simultaneously carry separate signals, but not require the same strict orientation to operate properly, at all, so long as arbitrary mirrors are not involved at any stage of the optical path. Regardless, the implication here is that there is no deliberate rationalization of the light to contend with, anyway, which seems to be just making a positive point out of a potentially lost opportunity to double any intended signal bandwidth. The name "Ultra-Serial Violet..." could be read as consciously eschewing all attempts at parallelism, including talkback.
[A cable with a curled wire displays the end of both of its connectors. The top end has a USB-C connector and the bottom end has a UV-C LED. The UV light is shown coming out of this end with a hazy blue circle around a white middle. The lamp is also bluish. Above is a title and below is a label.] Cursed Connectors #280 USB-C to UV-C


Circumappendiceal Somectomy

Explanation:
In normal medicine, appendectomy is the surgical removal of an appendix . The purpose of the appendix is not fully understood, believed to be a reservoir for a human's gut microbiome. However if an appendix is swelling, it comes with risk of bursting and causing massive damage through internal bleeding and septic bacterial infection. In such cases the appendix may be partially removed through surgery.
Breaking down the comic's title: circum- means "around," -appendiceal means "the appendix," som(a)- means "the body," and -ectomy means "removal." Therefore, a circumappendiceal somectomy would be "a removal of the body from around the appendix." This appears to be the procedure that the doctor in the comic is describing.
The joke is that such a procedure is functionally identical to a typical appendectomy, the removal of the appendix from the body - just viewed from a different perspective. It humorously implies that the entire body of the patient is the problematic part to be removed, leaving the appendix behind.  It should be noted, though, that the procedure is identical only if it's done without disrupting the integrity of the body. There are situations in which an essential part is removed from a damaged or unimportant system by dismantling the system, piece by piece, leaving the part behind.  Obviously, this would not be an advisable method for treating appendicitis . [ citation needed ]
The title text provides personal insight into the comic. It appears Randall has gotten appendicitis before, which may have been the inspiration of 2147: Appendicitis and was treated using antibiotics instead of surgery. However, his appendix became inflamed again, and this time it was removed. Randall's experience is not uncommon, as a 2020 study found that nearly 40% of patients treated with antibiotics for appendicitis required an appendectomy for recurrent appendicitis within 7 years. However, this should be the final time, as it is unlikely to get appendicitis without an appendix. [ citation needed ] However, he does not rule out the possibility that something "extremely unexpected" happened during the surgery which could cause him to suffer from appendicitis again. Possible candidates for such an extremely unexpected event could include the surgeon faking the removal of Randall's appendix and leaving it intact, or removing only part of it, removing Randall's appendix but transplanting someone else's appendix into him instead, or even the appendix's spontaneous regeneration .  While most of these possibilities are absurd, stump appendicitis, in which appendicitis occurs in remnant of the appendix that remains after surgery really does occur in 1 in 50,000 cases according to the article Appendicitis after appendicectomy - NCBI .
[Cueball is sitting with legs out over the edge of an examination table, hugging his stomach, likely because of stomach pains. A doctor in lab coat and a surgical head cap is standing next to the table speaking to Cueball, one arm stretched out towards him.] Doctor: Normally we would remove your appendix from your body. Doctor: But thanks to new surgical techniques, we're now able to remove your entire body from around your appendix!


Useful Geometry Formulas

Explanation:
This comic showcases area formulas for the areas of four two-dimensional geometric shapes which each have extra dotted and/or solid lines making them look like illustrations for 3-dimensional objects. The first, a simple equation for the area of a circle, the second an equation for the area of a triangle with a semi-elliptic base, the third an equation for the area of a rectangle with an elliptical base and top, and the fourth an equation for the area of a hexagon consisting of two opposing right-angled corners and two parallel diagonal lines connecting their sides. In each case, only the area formed by the outline of each shape is calculated.
Similar illustrations are commonly found in geometry textbooks, which are used to depict three-dimensional figures on a two-dimensional page. They commonly make use of slanted lines to indicate edges receding into the distance and dashed lines to indicate an edge occluded by nearer parts of the solid. The joke is that the formulae given here are for the area of each two-dimensional shape within its outer solid lines, not for the surface area or volume of the illustrated 3D object (as would be shown in the geometry textbook). The title text continues the joke by claiming that the dotted lines are simply decorative.
The illustrations depict the following plane or solid figures, depending on the interpretation.
Top Left - Circle with an inscribed ellipse, or Sphere
This illustration is commonly used to depict a three-dimensional sphere, with the ellipse representing a "horizontal" or axial cross-section through the center; the solid lower half of the ellipse represents the "front" of the circumference of this cross-section, while the dotted upper half represents the "back" of the same section, which would be occluded from view if this were a solid shape.
The radius of the circle, from the center to the right edge where it meets the ellipse, is labeled 'r'. In a textbook diagram of a sphere, the radius might be instead labeled with a diagonal line from the center to a different point on the ellipse, implying the generality that all points on that cross-section, and indeed on the whole spherical surface, are at the same radius from the center. However, this line would be shorter on the page than the actual radius, making it useless for the formula of the area of the 2D outer shape.
The area of the 2D shape on the page is the area of the circle, which is A = πr 2 .  This is captioned below the figure.
Coincidentally the area of the horizontal cross-section of the 3D sphere, as depicted by the ellipse, is also πr 2 , and a reader familiar with such diagrams might initially assume that this is what was meant.  However, this does not extend to the other figures.
The 3D sphere commonly depicted by this drawing would have a volume of 4 / 3 πr 3 and a surface area of 4πr 2 .
Top Right - Ellipse with symmetrical diagonal lines, or Cone
This illustration is commonly used to depict a three-dimensional right circular cone, with the lower half of the ellipse representing the "front edge" of the bottom surface, and the upper half representing the occluded "back edge".  However such drawings would usually not use both 'a' and 'b' to describe the radius of the base of the cone, which is drawn as an ellipse due to foreshortening.  Alternatively, the drawing could depict a right elliptical cone.
Randall approximates the area of the 2D shape on the page as the sum of the area of the triangle formed by the major axis of the ellipse and the two lines, and half of the area of the ellipse ( π / 2 ab) since most of the upper half of the ellipse overlaps the triangle.  The equation for this area is A = 1/2 πab + bh.  This is captioned below the figure.
The actual area of a picture of a cone is not Randall's approximation, because the sides connect at the points on the ellipse where they can spread widest and form tangents to the ellipse, and such points are a little higher than those which define the major axis. This is most obvious in cases when h is only a little larger than a. The area can be computed to be exactly A = b (a arccos(-a/h)) + √(h 2 -a 2 )).
The 3D right circular cone commonly depicted by this drawing would have a volume of πr 2 h/3 where r=a=b.  The area of the "lower" surface would be πr 2 , while the surface area of the upper conical surface would be πr√(h 2 + r 2 ).  Neither of these areas can correspond with the caption in the comic, nor does the total surface area (the sum of these two).
If we do not assume that a = b, this drawing could also depict a right elliptic cone.  The volume of the elliptic cone would be π / 3 abh.  The area of the lower surface would be πab and the area of the curved upper surface would be 2a√(b 2 + h 2 ) 0 ∫ 1 √( a²h²(t²-1) - b²(a²+h²t²) / a²(t²-1)(b²+h²) ) dt.
Bottom Left - Two ellipses joined vertically, or Cylinder
This illustration is commonly used to depict a 3D cylinder or right circular prism.  In this case, the upper ellipse represents the "visible" part of the top circular surface, with its "depth" shorter than its "width" due to foreshortening, and the lower part of the lower ellipse represents the "front" edge of the lower surface; the dotted half of the lower ellipse represents the occluded "back" edge of the lower surface.
To add to the confusion, the upper ellipse has its major axis labeled 'd' which usually denotes the diameter of a circular surface, while the lower ellipse has its semimajor axis labeled 'r' which similarly denotes a radius, even though the ellipses drawn have neither diameter nor radius.  The 'h' denoting height is also used for both rectangles and solid objects.  While 'd' in this case is required for the area calculation of the 2D shape, in textbooks only 'r' may be marked and the arrow may be offset at a diagonal rather than in line with any figurative axis, to imply its applicability to any angle of radius.
The non-overlapping parts of the 2D shape are composed of the rectangle formed by the major axes of the two ellipses and the vertical lines, plus half of the top ellipse and half of the bottom ellipse.  The area of the rectangle is dh, and the area of an ellipse with semimajor axis d/2 and semiminor axis r is πrd/2.  The total area is A = d(πr/2 + h), which is captioned below the figure.
A 3D right circular prism (cylinder) would have a volume of πr 2 h and a surface area of 2πr 2 + πdh, or 2πr(r + h) since in this case d = 2r.  The area of each flat surface would be πr 2 .  If we do not assume d = 2r, then the lateral surface area of the right elliptic cylinder is 4h 0 ∫ 1 √( 1 - t²(1-4r²/d²) / 1 - t² ) dt. The volume is π / 2 rdh.
Bottom Right - Parallel Hexagon, or Prism
This illustration is commonly used to depict a rectangular prism, with 'b' denoting the 'breadth', 'd' the 'depth' and 'h' the 'height'.  However, the labeled angle θ, which is necessary for the area calculation of the 2D shape, would not normally be used in a diagram of a rectangular prism, as all angles are assumed to be right angles.  A rhomboidal prism could be accurately described by this diagram with the assumption that the 'base' parallelogram is perpendicular to the 'front' and that the only non-right angle is θ.  In that case 'd' would not accurately describe the depth of the solid, which would be d sin θ.
The area of the 2D shape is comprised of the rectangle at the lower left, the parallelogram above it, and the parallelogram on the right.  The area of the rectangle representing the front face of the prism is bh. The area of the upper parallelogram is db sin θ. The area of the right parallelogram is dh cos θ.  The equation for this area is  A = bh + d(b sinθ + h cosθ) as is given below the figure.
The surface area of the prism would be 2bh + 2db sin θ + 2dh. The volume is bdh sin θ. Assuming a 3D shape, θ can be artificially altered by the projection; the assumption could be made that θ is 90 degrees, and sin θ is 1 (and therefore can be eliminated from the formulas), but since θ is marked, such an assumption might not be valid.
In the history of the development of computer-generated 3D graphics, calculations of the apparent visual area taken up by the projection of a volume may have been useful in occlusion-like optimizations, where each drawn pixel may be passed through many fragment shaders.
[Four figures in two rows of two, each being a common two-dimensional representation of a three-dimensional object, with solid lines in front and dotted lines behind. Each figure has some labeled dimensions represented with arrows and a formula underneath indicating its area. Above the four figures is a header:] Useful geometry formulas
[Top left; A circle with an inscribed concentric ellipse sharing its horizontal diameter. The edge of the ellipse above the major axis is drawn with a dotted line, while the lower edge is drawn with a solid line, similar to textbook depictions of a 3D sphere. The shared radius/semi-major axis to the right of the center is drawn as an arrow and labeled 'r'.  ] A = πr²
[Top right; An ellipse with horizontal major axis, plus two straight lines: one from each end of the major axis, up to a point vertical to the center of the ellipse, so that the major axis of the ellipse (not drawn) and the two lines would form an isosceles triangle with a vertical axis of symmetry. The upper edge of the ellipse above the major axis is drawn with a dotted line, while the lower edge is drawn with a solid line, similar to textbook depictions of a right elliptical cone, or more commonly a right circular cone. The semi-minor axis of the ellipse is drawn with an arrow down from the center and labeled 'a' and the semi-major axis is similarly drawn to the right of the center and labeled 'b'.  To the right of the shape, the height of the isosceles triangle is drawn using arrows, and labeled 'h'.] A = 1/2 πab + bh
[Bottom left; Two ellipses of the same dimensions, with major axes horizontal, drawn vertically one above the other, with vertical lines connecting each end of the major axis of the top ellipse to the corresponding points on the bottom ellipse.  The upper edge of the bottom ellipse above the major axis is drawn with a dotted line, while the lower edge is drawn with a solid line, similar to textbook depictions of a right elliptical prism or, more commonly, a right cylinder (circular prism). Inside the shape, the major axis of the upper ellipse is drawn as a double-ended arrow and labeled 'd'.  The semi-minor axis of the lower ellipse is drawn as an arrow down from the center and labeled 'r'. To the right of the shape, the length of the vertical lines is replicated using arrows and labeled 'h'. ] A = d(πr/2 + h)
[Bottom right; Two rectangles of the same vertical and horizontal dimensions, drawn with one offset diagonally to the upper right of the other, with diagonal lines connecting the corresponding vertices, forming a hexagon with opposite sides parallel.  The upper right rectangle has its left and bottom sides drawn with dotted lines, and a similar dotted line is used connecting the bottom left corner of the two rectangles, similar to textbook depictions of rhomboid-based right prisms, or more commonly rectangular prisms.  Outside the shape, the bottom edge of the lower rectangle is redrawn below the shape with arrows and labeled 'b'. The length of the left edge is similarly redrawn to the left and labeled 'h'. The length of the diagonal line connecting the upper left corners of the two rectangles is similarly redrawn on the top left using arrows and labeled 'd'. The acute angle between the bottom edge of the lower rectangle, and the dotted diagonal connecting the two lower left corners, is labeled 'θ'] A = bh + d(b sinθ + h cosθ)


Modern Tools

Explanation:
Cueball tells White Hat how he has trained a neural net to generate mostly valid Makefiles .
This is the file type that Make searches for. In software development, Make is a build automation tool that automatically builds executable programs and libraries from source code by reading files called Makefiles which specify how to derive the target program. (See 2173: Trained a Neural Net ). Make is a very old tool, having first appeared in 1976.
Then Cueball continues to tell that he next will train it to distinguish between Bash and Zsh.
Bash and Zsh are two command line interfaces for Unix-like OSes. The way to execute commands is almost identical, making detecting a script that contains a mixed syntax nearly impossible. This was previously referenced in 1678: Recent Searches . Bash and Zsh are also old tools, having come out in 1989 and 1990 respectively.
A human-designed 'random Makefile'-maker might have been written with this explicit choice amongst the earlier decisions in the generation process, but an AI might be assumed to have started (many, many generations ago) with something close to utter nonsense and painstakingly reached the stage of (mostly!) valid files along the way. Some might say that the differentiation training would have been better added at another point in the lengthy process.
On top of that, the current (mostly valid) results may even be polyglot and/or shell-agnostic . Dependant upon the fitness tests in use, many other $SHELL -choices and Makefile styles may have been coevolved as valid (if rarer) subgenus of outputs, such as a command.com -based makefile.
In the caption it states that Cueball is using modern tools to make ancient technology, as opposed to other people who use ancient tools and UIs ( User interface ) to develop Modern Tools.
In the title text Randall states that he tried to train an AI ( Artificial intelligence ) to repair his horribly broken Python environment . But the AI kept giving up and deleting itself. The joke partly relates to when it or is not appropriate to personify goal-driven processes.  In the study of alignment of artificial intelligence, it is common to consider AIs finding ways to meet the tasks they are given that are highly unexpected, and then developing into an apocalypse .  A common unexpected solution encountered in research is that the agent finds a way to disable itself as more efficient to meet its reward parameters than anything else it discovers, and then learns to repeatedly do so. The AI might be so intelligent that it had developed critical 'personal' opinions that led it to be so intellectually appalled by the task, or else just found it impossible to fix the python environment and therefore justify its own existence, that it had no other recourse but to commit a form of suicide because Cueball's code was that bad ( which is a recurring theme for Cueball ). Python has been a recurring subject as has Programming and Artificial Intelligence .
The main joke is that Cueball is using cutting-edge tools to develop very old technologies, which is perhaps only useful if one is pursuing hobbies in conflict with a differing AI addiction. As the caption implies, it is much more common for people to use fundamental and well-established tools as the toolchain or building blocks of modern technology. A concrete example of this is writing scripts using decades-old Bash to automatically set up a significantly newer (2014) technology called Kubernetes .
[Cueball is sitting on an office chair at his desk typing on his laptop. White Hat is standing behind the desk looking at Cueball.] Cueball: Okay, I've got this neural net generating mostly valid makefiles. Cueball: Next I'm going to train it to distinguish between Bash and Zsh...
[Caption below the panel:] People often use ancient tools and UIs to develop modern cutting-edge technology, but I do it the other way around.


Recreate the Conditions

Explanation:
Scientists recreate conditions of things to gain scientific knowledge on a topic to better be able to observe why or how things happen. This could be done by making miniature versions of events and simulating events using safe methods.
In this comic, Megan 's lab discovered that the conditions during the seconds after the Big Bang were extremely hot and unpleasant.  They have thus decided to attempt to recreate the conditions of a tropical beach in 2014 instead (7 years prior to when this comic was released). Here, the joke is that instead of recreating a condition  for scientific study purposes, Megan and her crew were simply trying to create a pleasant environment for recreation, in the sense of personal enjoyment.
The title text is a reference to 1949: Fruit Collider a pun of piña colada (Spanish for "strained Pineapple") and a particle collider : the Spanish word "colada" is pronounced similarly to the English word "collider". Taken literally, "piña collider" would be a pineapple collider, which may be interpreted as a fruit juicing machine for making piña coladas.
[Megan is standing, pointing a stick at a poster of a particle collision, (as it looks when measured in a particle collider), where many other particles emerge from the central collision, a black spot, with many thin curved lines going away from it, and two larger beams going straight in. Above the upper part of these lines there are three lines of unreadable text, three unreadable labels are written over three of the lines, and there are two unreadable lines of text at the bottom one at each side of the poster.] Megan: Our lab was trying to recreate the conditions that occurred seconds after the Big Bang.
[Megan is standing with arms lifted to each side, stick in hand, looking straight out, in an otherwise empty panel.] Megan: But it turns out they were extremely hot and unpleasant.
[Megan points at another poster with the stick. The poster shows a picture of a beach, with the sun over the ocean, a palm tree bending in over a parasol stuck in the sand. At the front there is a small table with two drinks on it.] Megan: So now we're trying to recreate the conditions that occurred on this tropical beach in early 2014. Megan: Honestly don't know why we were doing that other thing.


Revelation

Explanation:
A user with a profile picture of a stick figure with hair, who could be on an island and is called John, posts the Bible text from Revelation 6:12 on a social media website. The author(s) of the book of Revelation refer to themselves as John; some religious scholars identify the author as John of Patmos or as John the Apostle . Thus it is likely that the user has the identity of the said John, either as this biblical-era person themselves (online communities existing in their time, or vice-versa) or adopting the historic character name for interpretive or parodic reasons. The comic places a Biblical event in the modern day to portray what it would be like for apocalyptic miracles to happen nowadays. It also depicts how even the epically largest of our most meaningful and moving moments can end up being treated online.
A news channel's official social-media monitor understands this to be an actual (natural) disaster in progress and asks for permission to use the posted information in a broadcast. This could be what would have happened if John had been using Twitter in his own time, in which case his Revelation might have received this response from that time's similarly-connected reporters, perhaps not comprehending the observations to be 'prophetic visions of the future', with potentially a different level of significance altogether, rather than reports of events just happened.
If the monitor has just found some form of dislocated account (a very old message, a modern echo for proselytizing purposes or a jape of some kind) then they appear to have been drawn in, having not recognized it as historic text from the Bible.
Whichever way, the response is typical of a 'foot in the door' approach probably used for any and all candidate 'breaking news' citizen-reports, identified by trawling and searching the media-feeds for newsworthy content by either reporters or an 'algorithm'. As well as trying to ask for republishing permission, as per the duty of care reporters should grant to their sources, it is couched behind a typically bland statement of concern.
The reply may seem underwhelming, given the Revelation-level nature of the scenario, but this early in the reporting cycle the researcher may not have enough facts from which to respond more empathetically. Without any 'empathy' the channel and its staff may look entirely uncaring, but anything too effusive would also look unprofessional. Whether the news-organization and/or its staff could be truly concerned, or simply going through the motions, would highly depend upon their established reputation in the eyes of one viewing this exchange. Cynicism might be involved, all round.
The title text modifies verse 14 from "And the heaven departed as a scroll when it is rolled together; and every mountain and island were moved out of their places" to instead reference the infinite scrolling of a news ticker . Thus this news story would just be one on an infinite scroll page of ever-new stories.
Alternatively, a Biblical-level disaster actually IS occurring, in which case the newscaster's response is underwhelming, to say the least.
Each of the described events happens at times. The sun is black during an eclipse, the moon is red when it sits at the horizon and/or in eclipse, and earthquakes happen on a frequent basis across the planet. When events happen together, it can have great import, and people may become more disconnected from what is real or common nature as lives become digitized. Many people are so used to sunrises and sunsets while seeing the moon high in the sky that they do not realise that the moon also turns red when it rises and sets.
In 2014, a series of four total lunar eclipses were identified by some Christian preachers as being the " blood moon " mentioned in Revelation 6:12, but the world did not proceed to end. [ citation needed ]
[A Twitter-like page is displayed with a post and a comment nested beneath it. The top poster's profile image is of a man with wild hair, standing on hill near a coast looking out over the ocean. The beach is visible below him. His name is revealed in the comment as John. The poster of the comment's profile image is of a man with flat hair. There is a logo "9 News" at the bottom right. Beneath both pictures are unreadable text. There are also four icons with unreadable text beneath both posts. A line divides the original post and the comment.] John: And I beheld when he had opened the sixth seal, and lo, there was a great earthquake; and the sun became black as sackcloth of hair, and the moon became as blood.
Channel 9 News: Hi John, incredible story, hope you and your family are safe. Can Channel 9 News share your account in broadcast and print?


Saturn Hexagon

Explanation:
Saturn's Hexagon is a cloud formation on Saturn centered on its north pole. Similar to Jupiter's Great Red Spot , Saturn's Hexagon has proven a persistent feature observed by multiple space probes. The cause was not known until recently, when data from the 2006-2009 Cassini–Huygens probe could be analyzed in depth. This finding was widely publicized in popular science media (see for example [1] ) and is related to how currents flow deep within Saturn's atmosphere.
Randall proposes an alternate explanation: it is the top of a soccer ball . Soccer balls are made in the shape of a truncated icosahedron , where faces alternate between regular hexagons and regular pentagons to achieve a more uniform roll. This design was introduced in 1968 as the Adidas Telstar , and is now considered the "traditional" soccer ball. The article is shown to refer to this as the "BSBIT model", a technical-sounding acronym from "Big Soccer Ball In There".
"Soccer" is the name used in the United States for association football , a game called simply "football" in much of the world. Similarly, the US makes wide use of customary units of measurement (inches, feet, miles, pounds, etc.) where much of the world uses the SI or metric system (centimetres, metres, kilometres, kilograms, etc.), so "football" is jokingly referred to in the title text as the SI name for "soccer". As much of the Web panders to a significantly US-based audience [ citation needed ] , many sites use only American customary measurements and omit metric equivalents, which might annoy non-US users; Randall parodies this by sarcastically and non-seriously apologizing. [ citation needed ] . Just as the American customary units derive from British Imperial units , the term "soccer" originated in the UK, originally to distinguish it from rugby football (sometimes "rugger"), before soccer became the most common form of football there.
This comic may also reference something often quoted to students decades ago that Saturn would float if there were a large enough pool of water to hold it, often having been stated as "Saturn is a giant beach ball".  This refers to the property that Saturn is the planet with the lowest average density .  This, of course, is a lot more complicated in reality.
Incidentally, the presentation of the truncated-icosahedral 'football', pressing one clear polygonal face up along the upper limit of the planetary sphere, has much in common with the (non-truncated) icosahedron that floats within a Magic 8-Ball , arranged to display just one random triangular face whenever its viewing window is upwards. This may be coincidence, without any obvious attempt to directly reference any of the popular memes relating to this. Randall has previously parodied the magic 8-ball in 1525: Emojic 8 Ball .
[Cueball is presenting in front of a poster, which he is pointing at with a stick.]
Cueball: We're proud to announce that our team has finally determined the origin and nature of Saturn's polar hexagon.
[The poster represents Saturn and its ring-system. There is a massive football/soccer ball drawn as if inside the semi-transparent planet, taking up slightly less than half of it by volume.
One of the ball's hexagons coincides with Saturn's polar hexagon, and is labelled "Hexagon". Other labels are illegible. The poster's title is "There's a Big Soccer Ball In There". The rest of the poster is illegible, except for a section heading that reads "BSBIT Model".]


Lab Equipment

Explanation:
This comic claims that in every science lab, there exists some piece of equipment that sticks around less for being useful, and more because the scientists and technicians just think the device is really cool.
The comic presents a laboratory containing equipment for analysis of substances. While giving Cueball a tour of the lab equipment, Ponytail shows a spectrometer — a device that examines light emitted from or passed through samples to fingerprint emission or absorption lines in the mix of light. Next she shows the "Nd:YAG" lasers. It is unknown if the multiple lasers are for redundancy or if they have different specifications and are for different tests. "Nd:YAG" stands for neodymium-doped yttrium aluminum garnet ; it is a lasing medium commonly used in lasers. Lastly she shows off a decommissioned laser not used in experiments, but rather for toasting marshmallows.
The claim that such things are almost universal is, in fact, very realistic. When doing any research, especially cutting-edge research, it's often difficult to predict what equipment will be useful or not, so it's inevitable those some things will be purchased, and not turn out to be very effective in their experiments.  Some of these things will end up being sold, put into storage, repurposed, or even thrown away, but some equipment is enjoyed by the researchers, despite a lack of official uses, and so will end up being kept around.  Researchers, being human [ citation needed ] , are going to do some things in the lab for their own amusement, rather than because it's part of a formal experiment, and if equipment has already been purchased, keeping it because it's enjoyable is usually overlooked.  Additionally, just playing around with high-end equipment can occasionally lead to useful discoveries. Basic research is difficult to plan out, and sometimes just letting scientists play around with powerful equipment can produce unexpected results, which can lead to new scientific understanding.
The title-text mentions that she's using "annealing techniques" to make the perfect s'more.  A s'more is a popular treat in the United States and Canada, consisting of one or more toasted marshmallows and a layer of chocolate sandwiched between two pieces of graham cracker. Annealing is more commonly a heat-treatment technique used to influence the nature of the crystals in metals for structural reasons.  This is done when jewelry is molded from molten metal, but more likely Randall means a use of annealing in scientific research. Annealing is also used in glass production .  This suggests that Ponytail is trying to use lasers and/or other specialized heating equipment to control the melting process of the chocolate, in conjuction with precision toasted marshmallows, to perfect this treat.  She points out that this shouldn't be mentioned on the grant application. When labs apply for grants to purchase or upgrade equipment, or to fund research projects, they emphasize the scientific principles that could be advanced (and potential useful products that might be produced) as a result of their research.  The idea that researchers might be using the equipment to amuse themselves and work on whimsical side projects would be unlikely to impress the groups offering the grant, [ citation needed ] even though, as Randall points out, such things are pretty much ubiquitous.
[Ponytail and Cueball are talking to each other. They are standing between two tables with equipment scattered on them, including lens-stands and eye-protection. Ponytail is pointing away from Cueball towards an unidentified off-panel location.]
Ponytail: The spectrometer is over here, the Nd:YAG lasers are over here, Ponytail: and in the corner is a laser that turned out not to be useful for us, but we keep it because it's fun to toast marshmallows with it.
[Caption below the panel] Every lab in every field has some piece of equipment like this.


Vaccine Research

Explanation:
This comic is another entry in a series of comics related to the COVID-19 pandemic , specifically regarding the COVID-19 vaccine .
The comic starts with White Hat using a common conversational tactic used by vaccine skeptics, and conspiracy theorists, in order to try to persuade others, typically claiming that they did their own research. The phrase "done my own research" is often taken to mean that the speaker is skeptical of the topic, and has done only cursory fact-checking, typically consulting only nonscientific sources that confirm and validate their prior beliefs. However, subverting expectations, it seems that White Hat genuinely had researched the subject deeply, consulting a large number of primary sources, and coming to a conclusion matching the overwhelming scientific consensus that vaccination against COVID-19 is safe and effective. The conclusion he expresses is humorously simple, but entirely in keeping with every expert analysis: "These vaccines are pretty good... Seems like it would be great if lots of people got them."
In the last panel, White Hat asks if there are any efforts to distribute the vaccine, to which Cueball responds with understated irony. Anyone genuinely informed about the vaccines would have to be aware of the huge scale of vaccine rollout efforts, or of the resistance to them. It strains credulity that someone could read "hundreds of studies" on the topic and not be aware of how many people had been vaccinated. Cueball, however, doesn't mock White Hat's incongruous ignorance, but simply responds that there's been "some effort", which satisfies White Hat.
At the time this strip was posted, only about 42.3% of the world population had been vaccinated against COVID-19. In low income countries, however, distribution has been negligible, and the rate is below 1.9% .
In the title text, Randall comments that he feels a little sheepish that he has spent way too much time and effort confirming the statement "yes, the vaccine helps protect people from getting sick and dying". This has been known for a long time despite the anti-vaxxers' efforts. But, as he states, this could be seen as a hobby . Anti-vaxxers often refer to people who get vaccinated as "sheep".
This comic may be a sort of spiritual successor to 2281: Coronavirus Research .
[White Hat is talking to Cueball.] White Hat: I've been hearing about vaccines. White Hat: But I decided to do my own research.
[In a frame-less panel White Hat continues to talk to Cueball.] White Hat: So I spent months on the Internet reading hundreds of studies.
[Close up of White Hat as he speaks to Cueball, who replies from off-panel.] White Hat: And wow, I gotta say, White Hat: these vaccines are pretty good. Cueball (off-panel): Oh, really.
[Zoomed back out, to White Hat and Cueball talking.] White Hat: Yeah, seems like it'd be great if lots of people got them. White Hat: Is anyone working on that? Cueball: There's been some effort. White Hat: Okay, cool.


Hubble Tension

Explanation:
Ponytail is telling Cueball about the expansion of the universe telling him that there are three main estimates of the rate of expansion, and that they all disagree. She then tells him of the two well known (and very complicated) methods, and finally the joke is that the third method is performed by a guy named Dave (who replies from off-panel), and he claims to measure the speeds with a radar gun, as if the galaxies were speeding here on Earth.
The fact that most galaxies are receding from us, and that the distance to the galaxy is directly proportional to the speed (as measured by red-shift ) was discovered in the 1920s by Edwin Hubble and others. This constant of proportionality is known as the Hubble Constant .
One way of measuring the Hubble Constant is to measure the distance to (relatively) nearby galaxies. Once distance is obtained, speed can be easily obtained by measuring the red-shift and thus the Hubble Constant calculated. Measuring the distance turns out to be fiendishly difficult because a distant bright star looks the same as a dim star that is closer, and localized movements can influence the speed of recession — though less significantly, for multiple reasons, the further away are the objects that you study.
In practice, astronomers have a number of ways of measuring distance that work at different scales, and they can be built upon to measure distance to far away galaxies. This is known as the Cosmic distance ladder .
The first rung is parallax . As the Earth orbits around the Sun, nearby stars appear to move slightly relative to distant stars; a star that moves by one second of arc is said to have a distance of 1 Parsec — about 3¼ light years or 30 trillion (3x10 13 ) kilometers.
The next rung is Cepheid variables , which periodically brighten and dim. The frequency of variation is related to the absolute brightness of the star, and thus by comparing the absolute to the relative brightness (subject to the Inverse-square law where not otherwise obscured) the distance can be measured.
The final rung is Type Ia supernova , which occur when an accreting white dwarf exceeds 1.4 solar masses. Because the initial mass is always identical, the absolute brightness of the explosion is as well, so the distance can be similarly calculated.
Putting these together, the best measurement of the Hubble Constant is 73 km/s/Mparsec.
This is in conflict with the other main way of measuring the Hubble Constant, analyzing makeup of the Cosmic Microwave Background (CMB) radiation, which yields a value of 68 km/s/Mparsec. The difference is statistically significant, and well outside the error bounds of each measurement.
Since the CMB technique relies on our understanding and assumptions about the early universe, as well as on the cosmological effects of General Relativity on large scales, if this discrepancy proved real it could be the gateway to new discoveries in cosmology and gravity, as well as possibly shed light on the origin of the universe and a ' Theory Of Everything '. Cosmologists got quite excited about this. It might also be that there was a previously unaccounted-for error in any of the rungs of the cosmological distance ladder and, once that is fixed, the two results will be consistent.
The third method introduced in this comic is a guy named Dave who is trying to use a radar speed gun (as used by the police for detecting speeding cars) to try to measure the movement of astronomical bodies.  A radar system works by sending electromagnetic radiation from the gun and then measuring the returned radiation to determine how far away or how fast a moderately distant object is moving.  Because of the transmission and return times required (and the inverse-square law), a radar device will only be able to get information about the very closest objects, such as the Moon (a type of Moon bounce ) and other objects orbiting the Earth (or perhaps the Sun), where the influence of being in orbit utterly dominates over any possible Hubble-shift. Doing that still needs very powerful radar systems like the former Arecibo Telescope to be able to get any useful information from that far away; a hand-held radar gun would not be able to 'lock on' across those distances, let alone distant galaxies.
Going by back-calculating grossly 'idealized' universe models, as suggested by the other two estimates, a receding velocity of 85 miles per hour ('mph'; about 137 kilometers per hour, 'kph' or 'km/h') should be seen at a distance of roughly 1700-1850 light-years, on the order of the thickness of our galactic disc. Much too far to use a radar gun on, also much too close to exclude any significant galactic stellar motions. Much the same is true if the figure is actually 85 kph (1050-1130 ly), as suggested it might be in the title text.
Aside from being practically incorrect, that value of 85 kph relates to around 53 mph, which might be the normally observed traffic speed on certain roads (especially if someone is conspicuously using a radar gun!) if by 'all directions' you effectively mean 'both directions' of traffic flow that Dave could possibly be measuring. Dave may have been referring to the kind of Galaxy that he can more easily find out the velocity of.
The comic is likely making fun of the common internet phenomenon of amateur (wannabe?) scientists seeking to discredit established scientific facts by reporting the results of experiments made using everyday tools.  Dave has probably heard of the fact that there is no agreement in the scientific measurements of the Hubble constant and decided to try to settle the controversy using the tools at his disposal, without remotely realizing that the margin of error required in the measurements is well outside the range of what can be used with conventional objects.
Dave might also lack an understanding of units of measure and dimensions. Ponytail describes the measurements of the rate of universal expansion, a speed that varies with distance, in km/s/Mparsec, having dimension 1/T or 1/time. Dave made his measurements in miles/hour or km/h, which have dimension L/T or length/time. These are not comparable with the official units. Dave does not appear to be aware of this (and Ponytail does not draw Cueball or Dave's attention to it).
[Cueball and Ponytail are walking to the right. Ponytail has her palm raised.] Ponytail: There are three main estimates of the universe's expansion rate and they all disagree.
[They keeping walking to the right.] Ponytail: Measurements of star distances suggest the universe is expanding at 73 km/s/megaparsec.
[They are still walking to the right.] Ponytail: Measurements of the cosmic microwave background suggest it's expanding at 68 km/s/megaparsec.
[They continue walking to the right. Ponytail points towards Dave who replies from off-panel to the right.] Ponytail: And Dave, who has a radar gun, says it's expanding at 85 mph in all directions. Dave (off-panel): Those galaxies are really booking it! Ponytail: Thanks, Dave.


Rover Replies

Explanation:
There is a Twitter account for NASA's Perseverance Mars Rover , which recently collected samples. The Twitter account tweets in the first person like in the comic. Likely a human on earth is playing the role of the rover [ citation needed ] . While the exact post shown does not exist, it has posted a similar tweet.
The first four replies (in order of top-to-bottom) are likely just general compliments to the rover, demonstrating that the replies are indeed wholesome. Reply three in particular references rocks, as the main purpose of most Mars rovers is to perform Martian geology.
Reply five is a mashup of conspiracy theories, including about 5G communications, vaccines , and others. Ponytail then replies "Quiet, we're not doing that here", implying either that she doesn't want it in the replies to this, that she thinks that the rude reply should be posted somewhere else, that she's a NASA employee stating that NASA does not have a 5G vaccine-microchip factory, or that she also is a conspiracy theorist trying to redirect the fellow commenter to other forums with more susceptible audiences.
The next reply references people saying where they're from, then clarifying where that is in brackets, e.g. Wingerworth (England). This commenter expands that to clarify that they are from Earth, joking that the planet may be ambiguous as the Mars rover is not on Earth. In reality, this ambiguity does not exist as humans only live on Earth, [ citation needed ] thus contributing to the humor.
The second-to-last reply is likely a misunderstanding, with the commenter believing that the rover is digging to perform anthropology or paleontology, not geology. The commenter could, however, believe that there is/was complex life on Mars, thus allowing the possibility that there are Martian skeletons for the rover to find.
The final reply is a reference to Ingenuity , a small helicopter which Perseverance took to Mars as a technology demonstrator . It has been very successful and completed many flights, often taking it quite far from Perseverance.
The title text is in the form of another reply. The character posting that reply believes that the rover has taken its phone to Mars, and has used that to take the pictures. This is likely because most photos on social media are taken on phones, and social media sites are often designed for phones. In addition, Perseverance and Curiosity differ from previous rovers in that they have cameras mounted on flexible arms, allowing them to take photographs of themselves - somewhat akin to a smartphone on a selfie-stick. In reality, Mars rovers don't have smartphones, and Perseverance is taking photos with an equipped camera.
While this comic is most likely referencing Perseverance, there is another small possibility that Curiosity is shown here, as Curiosity also has collected samples . This is unlikely though due to the timing of this comic.
[A post of a rocky landscape and a close-up of a rock is next to a profile picture of the camera of a Mars rover.] Just collected a sample!
[Comments below. Each comment has an icon of a person or other image next to it and an illegible name above the comment.] [face of Cueball-like character]: These pictures are great! [curved lines]: I'm so proud of you [Cueball-like stick figure]: Wow you know a lot about rocks [Megan]: Go go go go go! [spiral galaxy-like image]: More propaganda from NASA's 5G vaccine microchip factory [Ponytail]: Quiet, we're not doing that here [unidentified stick figure]: Hello from Missouri (Earth)! [Hairy]: Did you find any skeletons yet [Blondie]: I hope your helicopter comes back!
[Caption below frame:] The most unexpectedly wholesome place on the internet is the replies to NASA's rovers on social media.


Lumpers and Splitters

Explanation:
It is common to separate groups of things — species, people, languages, software models, etc. — into categories , but different people may do this in different ways. "Lumpers" work from the ground up by focusing on similarities among individual things to create larger categories, while "splitters" do the opposite, taking larger categories and trying to find characteristics that are not shared by all members of the group to further divide them into smaller subsets.
The comic points out the meta -ness of categorizing people based on how they categorize. It labels Megan and Cueball as those two types of categorizers. Megan, the lumper, describes herself and Cueball as both being "categorization pedants", lumping the two distinct categories "lumpers" and "splitters" into one. Cueball, the splitter, subcategorizes Megan into a more specific type of lumper: a "meta-lumper"—since the things Megan was lumping includes lumpers themselves—thereby splitting off lumpers from meta-lumpers. If Cueball further categorized himself he would be a meta-splitter.
The title text references the opening line of the novel Anna Karenina by Leo Tolstoy, which reads (as translated into English), "Happy families are all alike; every unhappy family is unhappy in its own way." Randall is drawing a parallel between this line and the lumper/splitter distinction because the line lumps one group of things (happy families) while splitting another group (unhappy families).
Additionally, this may be a reference to the podcast episode "Lingthusiasm Episode 60: That's the kind of episode it's - clitics" [1] , published a few days before the comic, wherein the hosts separate people into lumpers and splitters of clitics.
[Megan and Cueball are standing looking at each other. There are boxes beneath each of them with a label.] Megan: Really, we're both just categorization pedants. Label: Lumper
Cueball: Ahh, so you're a meta -lumper. Label: Splitter


Sloped Border

Explanation:
Every country has land and sea international borders that demarcate the extent of their territory and their legal jurisdiction. These borders are established through law, treaty, or consensus. Establishing an international border is maintained by present-day customs, immigration, and security checks. Some countries (like Cyprus ) have established a buffer zone outside of their international border in order to gain additional protection during a conflict, and most countries have an offshore Exclusive Economic Zone in order to preserve exclusive proprietorship of marine resources such as oilfields and fishing grounds.
In this comic, Cueball and Blondie have established a "sloped" international border through a treaty. Usually borders are perpendicular to the ground [ citation needed ] so that all the air(space) above the ground belongs to the same country. This is called Air sovereignty . Thus it suffices to define the border on the earth surface, as 1D lines across the curved 2D surface. The precise definition is that a line from the center of the Earth through the point of the border is drawn. Sloped terrain is immaterial to the border of the air sovereignty which is still vertical, even if not perpendicular to the terrain.
If the borders were sloped (with respect to the horizontal ground level) an airplane would need to know its precise height to decide if another country's jurisdiction currently applies. With the help of the Global Positioning System this would be in principle possible, although the height information of GPS is less reliable.  (It might be possible to program a computer to use altitude data from the airplane's altimeter along with latitude and longitude data from the GPS and a relevant ground relief database to make an accurate determination.)
Most countries would not agree to a border that cuts into their airspace and shrinks their territory as the altitude increases; most cases of countries losing area have come about as a result of trying to avert, or losing, an armed conflict. It is entirely possible that Cueball's country has compelled Blondie's country to accept its demands, of which the redrawn border is one. Alternatively, Cueball's country may be deliberately reducing its own airspace purely because it will cause problems.
There is at least one famous case of a border being affected by elevation: the Franco-Swiss border bisects the staircase of the Hotel Arbez . Hence, although part of the upper floor is geographically in France, the entire floor is Swiss territory, because it is only accessible through Switzerland.
The mathematical computation for an angled air sovereignty seems relatively straight-forward at low level and could be expressed with a single line of code or a single equation, although the people acting on the information are likely unfamiliar with code and equations and likely use tools with completely no support for sloped borders.  The mention of curvatures in the title text may reveal some emergent problems that need accounting for.
A totally straight line drawn far enough upwards at an angle will find the surface of the Earth curving away beneath it (not even considering terrain undulations) and the angle to the local vertical will reduce as it continues, tending towards vertical as you head towards infinite altitude.
Alternately (although it seems this is not the case) the profile of the sloped border may be assumed to remain at a constant angle to the shifting vertical, in which case it describes a certain form of spiral (which will eventually loop around the earth).
A third option is that it gains altitude at a constant rate, with respect to the passage of land measured on its surface track, to form a different spiral , in which case it will still loop around the Earth but at an angle that increasingly tends towards horizontal.
While the comic doesn't mention this, such a boundary should probably also extend underground, in the opposite direction. (The straight-line version, if implemented, will eventually reach a depth at which it is tangential to the radius and then rise back through the surface an equal distance further around the planet.)  This would then impact, at practical depths for such things, planning rights for property foundations and, at deeper levels, mining rights for minerals.
Practically an upper-limit to a nation's claim (somewhat below satellites, e.g. the Karman Line) and a lower limit (well before reaching the Earth's mantle) will prevent many of these complications, together with intersections with other (probably vertical) 'territorial volume' borders that will supercede in any compound claims to ownership. - However, it is still very important to specify exactly which curve (i.e. with respect to what) the boundary is designed to respecting.
"GIS" refers to geographic information system , a set of tools and methods for capturing, analyzing and presenting spatial and geographic data. While altitude is already an (optional) element in the blocks of information, people developing these systems would be inconvenienced by the additional requirements demanded by the border described in the comic.
It is possible this comic is inspired by such boundary disputes as the Beaufort Sea 'wedge' which, while in this case perpendicular to the surface, suffers from alternative interpretations of how to extend it from the shoreline out towards international waters.
[Cueball and Blondie are standing on a podium. They are holding a document together between them, filled with unreadable text. On either side of the podium are two informational graphics each on a stand. They are placed a bit behind the back side of the podium. The graphic to the left shows a cross-sectional view of a non-vertical border, shown as a dotted line going up between Cueball and Blondie, who both are standing on the ground. The angle is indicated and noted, and the line tilts towards Blondie's side. The graphic on the right shows a skewed perspective of a similar setup of the non vertical border, shaded so what is behind it becomes gray. There are also some lines on this plane to indicate where it is. It almost looks like a window, but people can move through it. There are also two more persons than on the left, Megan, who is on the same side of the border as Cueball, and another Cueball-like guy standing next to Blondie. Megan is entirely on Cueball's side of the plane, but the other three are positioned so they are intersected by the 'shaded plane' of the border, with the effect that some or most of their bodies are beyond the sloped boundary, in the gray area, but not all. Cueball and Blondie are postureed in a mutual greeting across this border, as the others look on.] Cueball: With this treaty, we are proud to announce the creation of the world's first sloped international border! Angle: 74°
[Caption below frame:] If I'm ever put in charge of a country, I'm going to spend all my time trying to think of new ways to make life a nightmare for GIS people.


Symbols

Explanation:
This comic refers to elements of (mostly mathematical or engineering) notation commonly used in various fields of math and science. Each piece of notation is presented as "symbolizing" not what it specifically means, but a typical context in which it might be encountered, see below .
Many of the individual descriptions look like verbiage that might be found on informational or warnings signs or placards, although typically with a silly edge.
The title text refers to two non-SI units of radiation measurement, röntgen and rem . In the mid-20th century when they were in use, the dangers of radiation weren't as well understood as today, so an area with radiation that was noteworthy back then is probably dangerous , hence the no trespassing part.
Later Randall made a similar comic, 2586: Greek Letters , regarding the use of Greek letters in math.
d ⁄ dx : An undergrad is working very hard d/dx is the symbol for a single-variable derivative . This is one of the basic operations in calculus and consequently is ubiquitous in the work of undergraduates in the sciences. A hard-working undergraduate in the relevant fields would churn through exercises using this symbol.
∂ ⁄ ∂x : A grad student is working very hard The replacement of the standard "d" letters with the curly letters "∂" denotes the partial derivative, which generalizes the ordinary derivative to multi-variable calculus.  Problems with partial derivatives, especially partial differential equations, can be extremely challenging. Although PDEs would typically be first taught at an undergraduate level, difficult partial derivatives would be encountered in graduate-level work.
ħ: Oh wow, this is apparently a quantum thing ħ (pronounced "h-bar") is a symbol used for (the reduced) Planck's constant , a universal, fundamental constant in quantum physics. ħ is equal to the energy of a photon divided by its frequency, and angular momentum in quantum mechanical systems is measured in quantized integer or half-integer units of ħ.
Classical physics appears as a limit of quantum physics if all "actions" (quantities of dimension energy * time, momentum * length, or angular momentum) are much larger than ħ. Conversely, you can also formally set ħ=0 to get classical results from quantum formulae. This means that effects that are proportional to some power of ħ cannot be explained classically, and instead are "a quantum thing".
Rₑ: Someone needs to do a lot of tedious numerical work; hopefully it's not you The Reynolds number (which is usually denoted by "Re," not "R e " as it appears in the comic) is the most important dimensionless group in fluid mechanics. Named for Osborne Reynolds, Re characterizes the relative sizes of inertial and viscous effects in a moving fluid. Large values of Re are indicative of turbulent flow, which cannot usually be retrieved analytically, and so numerical modeling is necessary. Accurate numerical studies of high-Reynolds-number flows are notoriously difficult to create and program.
Alternatively, Rₑ could stand for electronic transition dipole moment in a molecule. This appears in quantum-mechanical calculations of transition probabilities and also includes a lot of unpleasant numerical work. Rₑ is also a term used for the radius of the Earth at mean sea level, though this is not necessarily a complex term in and of itself.
Another alternative is that Rₑ could refer to Relative Error, a measurement of precision or accuracy.  Used often in the analysis of scientific data and numerical analysis.
(T a ⁴ - T b ⁴): You are at risk of skin burns The Stefan-Boltzmann law says that a perfectly absorbing ("black body") source emits electromagnetic radiation with a power per unit area of σT 4 , where σ is a known constant and T is the absolute temperature. The quantity (T a 4 – T b 4 ) thus appears in any calculation of purely radiative energy transfer between two bodies, one at temperature T a and the other at T b . When the radiative transfer is large enough to be the most important form of heat interchange, it is normally also large enough to sear the skin with thermal or ultraviolet burns.
N A : You are probably about to make an incredibly dangerous arithmetic error N A , or Avogadro's number , is the number of molecules in a mole of a substance, approximately the number of carbon atoms in exactly 12 grams of carbon-12. This is an enormous number, exactly 6.022 140 76 × 10²³, or 602 214 076 000 000 000 000 000. Working with N A , it is easy to accidentally divide by it instead of multiplying or vice versa, leading to erroneous and nonsensical answers such as ~10 -23 molecules (even though you can't have less than 1 whole molecule) or ~10 46 moles (>10 43 to to 10 45 kilograms, depending on the chemical) of a substance.
µm: Careful, that equipment is expensive Micrometers are a very small unit of distance. Micrometers are commonly used to measure wavelengths in the infrared, and infrared detectors are very expensive, compared with visible wavelength counterparts. Of course, micrometers are used as a measurement of distance in other contexts, but any distance-measuring device capable of accurately measuring micrometer distances would also be expensive. Similarly, tools used to create or calibrate items within micrometer tolerances can also be expensive.
mK: Careful, that equipment is very expensive Kelvin is a temperature scale roughly speaking similar to Celsius, but taking absolute zero as its zero point instead of the freezing point of water (rigorously speaking, its definition is now based on the Boltzmann constant ). Millikelvins (1/1000 of a Kelvin) are used for high precision temperature work.  Frequently this is used in processes of cooling temperatures to nearly absolute zero - such as superconductors or other quantum effects that occur when atoms are almost still.  This is suggesting that the symbol appears on a sensitive experimental system probing quantum mechanical behavior that would likely only exist in an advanced laboratory. Any equipment that works down at mK temperatures, or at least to mK precision and accuracy, is likely to be very expensive.
nm: Don't shine that in your eye Nanometers are frequently seen in the listed wavelengths for lasers. Pointing a visible or infrared laser at someone's eye is notoriously dangerous; the tightly-focused coherent light can cause permanent damage very quickly.
eV: Definitely don't shine that in your eye Electron volt energies are typical of moderate-energy particle beams, produced by accelerating electrons (or protons) over macroscopic voltages. These particle beams can be even more damaging (and are probably a direct reference to Anatoli Bugorski) to soft tissues than optical-wavelength lasers.
mSv: You're about to get into an Internet argument The millisievert is a unit of radiation dose absorbed. It is a very small dosage, but the joke refers to Internet trolls debating the effects of low-dose radiation sources, such as 5G wireless networks. Randall's comment may also be referring to this chart .
mg/kg: Go wash your hands This unit measures the dose of a drug or other chemical in milligrams per kilogram of body mass. If the appropriate dose - or worse, the lethal dose - is measured in mg/kg (parts per million), then the substance may be quite toxic.
µg/kg: Go get in the chemical shower A unit 1/1000 times the size of mg/kg. If a dosage is measured in micrograms per kilogram (parts per billion), any accident probably requires whole-body decontamination procedures.
π or τ: Whatever answer you get will be wrong by a factor of exactly two π is defined as the ratio of a circle's circumference to its diameter, while τ is defined as the ratio of a circle's circumference to its radius (and is therefore equal to 2π). π has been used as the primary constant for describing the circumference and area of circles millennia ago, but proponents of τ claim that τ is more natural in most contexts since it makes working in radians more straightforward. The joke here is that whichever constant you use, it will probably be the wrong one (off by a factor of two, one way or the other) for the formula you are trying to use. The debate over Tau vs Pi was solved by Randall in this compromise: 1292: Pi vs. Tau .
[A list with 14 different scientific constants/symbols are shown. Next to each symbol is a description. Above the list is a heading and beneath that a subheading.] Symbols And what they mean
d ⁄ dx An undergrad is working very hard ∂ ⁄ ∂x A grad student is working very hard ħ       Oh wow, this is apparently a quantum thing Rₑ     Someone needs to do a lot of tedious numerical work; hopefully it's not you (T a ⁴ - T b ⁴)    You are at risk of skin burns N A You are probably about to make an incredibly dangerous arithmetic error µm    Careful, that equipment is expensive mK    Careful, that equipment is very expensive nm    Don't shine that in your eye eV Definitely don't shine that in your eye mSv  You're about to get into an internet argument mg/kg      Go wash your hands µg/kg      Go get in the chemical shower π or τ      Whatever answer you get will be wrong by a factor of exactly two


Toothpaste

Explanation:
Cueball is telling Megan about his friend. He indicates that she said something shocking and probably hurtful. He then states that even though she tried to apologize it was too late, the words had been said and it cannot be taken back.
He uses a phrase to underline this: You can't put the toothpaste back in the tube.
Putting toothpaste back in its tube is often used as an analogy for something irreversible, such as how you can't undo speaking. Megan, however, rejects this assertion and says that you actually can put toothpaste back in its tube, which is certainly possible in some cases. There are many ways to do this, and none of them are recommendable if the toothpaste has come into contact with something non-sterile.  But she chooses a particular nasty one where she would blow the paste in her mouth back into the tube. This is obviously much more unsanitary than simply returning unused toothpaste to the tube, which someone might reasonably want to do after squeezing out more than they wanted.
Cueball is so disgusted by this suggestion that he states that Megan's suggestion is the worst thing she has ever said.
The joke then comes when Megan assumes that Cueball's original analogy still holds, that taking words back is like putting toothpaste back in to the tube. So therefore she can actually unsay something. She starts to say exactly what Cueball's other friend did "Sorry, I can take it back". But then she says, "It's just like--", and was presumably about to continue,  "--putting toothpaste back in the tube" (or perhaps, since it's Megan, was going to give a new analogy that was even worse). However, Cueball forcefully interrupts her, because the idea of putting toothpaste back in the tube now evokes the distasteful mental image of Megan blowing used toothpaste back into the tube.
Toothpaste is normally loaded into the tube from the back, before it is crimped shut. However, it should technically be possible to push an extruded amount of paste back in from the front by wrapping one's lips around the whole front of the tube and blowing the paste you have in your mouth back in. This positive pressure can re-inflate the tube the same way one blows up a balloon. However, blowing the toothpaste back into the tube would be highly unsanitary, and as the main purpose of toothpaste is to clean teeth, the end result is both counterproductive and disgusting. [ citation needed ] In some cases paste coming out of a tube will be sucked back in if the pressure is released. Such containers would probably be able to suck toothpaste back in, if it was still lying on the toothbrush in one blob (or on the table/in the sink if dropped). As above mentioned this would be unsanitary as germs etc. could get back inside the tube, where the paste is supposed to be clean.
The title text spoofs a common line found in toothpaste commercials: "9 out of 10 dentists recommend using our brand." This statement is very easily manipulated through any number of basic marketing tactics (such as only asking 9 dentists, whom are all paid handsomely), and its ubiquity lends it to spoofing. In this case, it's spoofed by saying that nine out of ten dentists are dis satisfied with Megan's approach (or with Randall and his ideas, as it is usually he who speaks in the title text; if it refers to Randall himself it is reminiscent of all the conferences he has been banned from ) and have banned the toothpaste spitter from their offices.
It may actually say more about any dental establishment that does not disapprove of what Megan apparently is not just theorizing about doing - but maybe they are disapproving too, just not considering it bad enough to ban her from office.
[Cueball, holding his arms out, is talking to Megan.] Cueball: I can't believe she said that. Cueball: She apologized, but you can't put the toothpaste back in the tube.
[Megan holds a hand, palm up, out towards Cueball as she replies.] Megan: Sure you can; it's easy. You just put your mouth over the opening.
[Finally they stand straight talking.] Cueball: Well, that's the worst thing you've ever said. Megan: Sorry, I can take it back. It's just like- Cueball: No!


Two-Factor Security Key

Explanation:
Two factor security authentication (also see #Trivia ) is something that Ponytail has clearly been talking to Cueball about. In this strip, Cueball is telling her that he has finally buckled down and gotten the two factor security key that she has pestered him to get.
He recites the trials that he endured in "installing" the key, all of which seem plausible configuration issues for setting up a proper two-factor authentication from scratch.  However it is then revealed that all this work was just the task of attaching the 'key' (which looks like it could be a common brand of physical two-factor key fob or dongle) onto his metal keyring.
Metal keyrings are reliably secure as far as keeping a key attached, but this is in part because of how notoriously difficult it is to add a key to or remove a key from them. The rings must be forced apart and held apart while the key traverses however many layers the ring has (usually two or three, though keyrings with more layers are not unheard of). Cueball confidently asserts (to off-screen Ponytail, who probably was expecting something more practical) that his key is not coming off, indicating both a (well-founded) faith in the keyring's ability to keep his key, and a desire to not go through the same process in reverse.  Presumably all his effort was in "installing" the key onto the keychain, and he probably hasn't actually set it up for any of his accounts, leaving them just as insecure as they were.
The title text has a similar double meaning.  Cueball would of course use it to the "proof" of his efforts installing the key--though difficult, metal keyrings can be forced apart physically by human hands, at least if the human in question has fingernails sturdy enough to slip between the rings, at which point the insertion of a finger would be enough to keep it apart until the key is inserted. However, keeping the rings apart can be strenuous on the fingers, and can result in bruising, which Cueball is all too familiar with. Proof of work alludes to the cryptographic concept, which ties (sideways, as proof of work is a security term for a concept intended to deter denial of service and similar volume-based attacks but not directly related) back into the two-factor authentication.
Additionally a third meaning could be that while he spent a lot of time setting up 2FA he totally overlooked the possibility of him losing his whole keychain thus locking him out of all the services that requires 2FA if he didn't set up yet another layer of backup.
[Cueball and Ponytail stand facing each other.] Cueball: I got one of those two-factor security keys you've been bugging me about. Ponytail: Great!
[Cueball and Ponytail continue facing each other.] Cueball: It took a lot of work, fiddling with configurations, annoying setbacks, and general pain,
[Closeup on Cueball holding a keychain.] Cueball: ... but I finally got it onto the metal ring of my keychain. Ponytail [off-panel]: At least now it's secure. Cueball: Yeah, this thing is not coming off.
An authenticaion 'factor' is a distinct method of proving your legitimate use of a service or product. They can be broadly be grouped into three main groups.
One-Factor Authentication now may trying to avoid the shortcomings of the Password system (including the intervention of a 'remembered' password) by developing passwordless authentication techniques based upon "have/are" factors only.
Two-Factor Authentication was usually the addition of a physical/biometric authentication method to augment each use of a known password/PIN (e.g. the 'rolling token' number).
Conversely, the physical authentication of a bank-card has required backing up by its remembered PIN when used in cash-machines/ATMs. (In shops, checking against the signature written on the same card was for a long time the verification of valid ownership, this recently progressed to Chip-And-Pin, but then in many cases has been superceded by Contactless (NFC) versions, making it a Single-Factor solution in sufficiently low-value transactions.)
Many people may be more familiar with an occasional Second-Factor Re Authentication, when (for one reason or another) they are no longer able to provide a valid password for some login or other, and activate the "Forgot my password" request which sends a link to their backup email account. Where one is set up, is still active and and you have not also lost the ability to access that. (This is not the situation that Cueball is in, or may be in.) This has largely replaced the infamous "Challenge Question" (though may still be combined with it)  probably to defeat replay-attacks or the more clever phishing attacks.
Three-Factor Authentication should really be a "know" and "have" and "are" combination. Imagine the cinematic scene of the 'President' granting authority for a nuclear attack by inserting a physical key into the required device, typing in their code and then presenting their eye to a retinal scanner.
Anything that is (seriously) quoted as Four-Factor, or above, is going to either duplicate the number of required verifications of a similar scope (towards diminishing returns) or is describing a setup of a number of optional methods from which a lesser number would be considered sufficiently valid to provide. e.g. registering all ten finger/thumb-prints in case of some random future digital injury.