1249: Meteor Showers
Title text: Remember, meteors always hit the tallest object around.
This comic spoofs the way that astronomical events are often reported in the mass media — events are often tagged with undeserved superlatives or described as being more dramatic than they actually are. In some cases, outright misinformation is spread. This phenomenon occurs in part by the result of over-eager scientists, but mostly because of journalists with no deeper knowledge on the subject they write about.
Meteor showers typically occur regularly each year. It always happens at the same days because the Earth is crossing the dust path of a particular comet. Sometimes meteor showers are in fact likely to be relatively spectacular when the peak of the shower occurs while your part of the world is in darkness and there is little moonlight. However, even in these cases it must be understood that there is nothing unusual about the meteor shower itself. The shower consists of small particles about one millimeter in diameter. Only their high speed lets them produce enough light to be visible from Earth's surface. The names of the showers refer to the constellation from which they appear to radiate.
Most of the meteor showers listed in the comic are real, but some are made up (and indicated as such below).
|Bring pets inside during peak activity
|While keeping pets inside may be reasonable on days when fireworks are let off in the beginning of a new year, no regular meteor shower poses much danger to pets.
|Not viewable in region 2 countries
|Apparently a play on the tricuspid valve in mammalian hearts, or possibly on bicuspid teeth. The mention of "Region 2" is a reference to region locking, a digital rights management (DRM) scheme intended to restrict media to certain areas. DRM of course does not apply to natural events. However, meteor showers are also geographically restricted, and the visible area might roughly coincide with a DRM region. Region 2 covers a large and scattered area, including Europe, the Middle East, South Africa, and Japan: it is a meaningless geographical "region" for the purpose of astronomy.
|(Alpha / Theta) Centaurids
|Too faint to see without going outside
|Since indoor lights and window glass make them harder to see, it would take a very bright meteor (like the Chelyabids two entries below) to be visible without going outside.
|Inverted shower converges toward Aquarius instead of radiating away
|This fictional shower would collect shooting stars into the origin to prepare for the real Eta Aquariids meteor shower associated with Halley's comet and diverging from Eta Aquarii in Aquarius; the real shower peaks around May 6th. Due to perspective, meteor showers appear to radiate outwards from a certain point in the sky. Meteor showers may be seen to converge on a point on the opposite side of the sky, but with the earth in the way there would only be a few visible going past the edge, seen as nearly parallel streaks overhead, so the convergence point would hardly be notable.
|Only one meteor per shower, but it's big.
|A reference to the February 15, 2013, Chelyabinsk meteor whose explosion shattered windows within a large radius.
|Meteors sometimes scream
|A meteor large enough to reach the lower atmosphere could produce sound audible to observers on the ground, but this is very unusual.
|Daytime Zeta Perseids
|Likely a NASA hoax
|This shower is mostly observed via its effects on radio and TV signals, and therefore a good target for conspiracy theorists responding to June's Invisible Meteors - NASA Science.
|50/50 mix of meteors and shooting stars
|The "50/50 mix of meteors and shooting stars" is a joke, as "meteor" and "shooting star" are synonymous.
|Southern Delta Aquariids
|Meteors very bright, but stationary
|This is saying that they are indistinguishable from stars, or that the stars themselves are actually meteors.
|Fast, highly intelligent, can open doors
|Dromaeosaurids are a family of dinosaurs containing the genus Velociraptor, well-known from the movie Jurassic Park in which they are presented as a deadly menace, fast and especially intelligent to the point of understanding how to open a door; this representation of Velociraptors is a recurrent topic in xkcd. It seems, however, that Randall may have finally gotten over his fear of them; as of February 2024 (current newest comic: 2900: Call My Cell), this comic is the most recent mention of Velociraptors on xkcd. Velociraptors being able to open a door is also mentionned in 135: Substitute.
|Instead of falling from sky, meteors erupt from ground
|Erupting from the ground is the funny inverse of falling from the sky, what meteors always do.
|Visible even when eyes are closed
|Probably a reference to Pyramidal cells, a type of neuron. The "tau" reference has two possibilities. The "visible even when eyes are closed" could refer to the Tau particle, a heavy sibling of the electron. When they traveled outside of Earth's magnetosphere on their way to the Moon, Apollo astronauts saw flashes of light about every three minutes even with their eyes closed; these were caused by high energy particles (cosmic rays) penetrating their eyes and brain. The other possibility is that it refers to Tau protein, a normal structural protein within brain neurons. In Alzheimer's Disease, abnormal Tau proteins can aggregate within pyramidal cells to form insoluble skeins. The number of these "neurofibrillary tangles" roughly correlate with the severity of cognitive impairment.
|Very slow, but follow you if you run
|This may have something to do with the fact that "draconids" etymologically means "of the dragon", which could make for a fearsome meteor shower. And if you run it will track you down, albeit slowly. This may also be a reference to Boo, a character in the Mario series of video games that is slow but follows you if you turn your back on them. In the game Terraria, meteors (or rather, "meteor heads") follow this exact behavior.
|Entire shower happens at once
|Rather than taking place over the course of a week, all the meteors in the shower happen at the same time. This would involve about 3000 meteors appearing simultaneously, which would be quite an impressive sight.
|In 1966, unusually active Leonid shower killed God
|There was a very active Leonid shower (a "meteor storm") in 1966, and a precursor to it in 1965. The article Is God Dead? was published in Time Magazine on April 8 of 1966. Perhaps this suggests that the meteors killed God earlier in the year when they and He were further out in the solar system?
|Can be deflected with tennis rackets
|Meteors usually don't reach the surface of the Earth, being destroyed in the atmosphere. If they do approach the surface, deflecting them with tennis racquets would probably not be the most effective strategy, unless Randall is implying that the Geminid swarm is composed of tennis balls.
The title text refers to the folk wisdom that lightning strikes the tallest thing around, but this has never been applied to meteors, where it is basically the size (area) that determines the likelihood of an impact with a given object. Randall expressed frustration over how "maddeningly inexact" the lightning statement is, and elaborated on the problem mathematically, in the what if? Today's topic: Lightning.
- [A list of 16 meteor showers, with a caption above, labels on the three columns and then every other row in gray, beginning with a gray row beneath the line below the column labels.]
The xkcd guide to meteor showers Name Peak Notes Quadrantids January 4th Bring pets inside during peak activity Tricuspids January 21st Not viewable in region 2 countries Centaurids February 6th Too faint to see without going outside Beta Aquariids February 10th Inverted shower converges toward Aquarius instead of radiating away Chelyabids February 15th Only one meteor per shower, but it's big. Lyrids April 22nd Meteors sometimes scream Daytime Zeta Perseids June 9th Likely a NASA hoax June Boötids June 27th 50/50 mix of meteors and shooting stars Southern Delta Aquariids July 19th Meteors very bright, but stationary Dromaeosaurids July 22nd Fast, highly intelligent, can open doors Perseids August 12th Instead of falling from sky, meteors erupt from ground Tau Pyramids August 15th Visible even when eyes are closed Draconids October 8th Very slow, but follow you if you run Orionids October 21st Entire shower happens at once Leonids November 17th In 1966, unusually active Leonid shower killed God Geminids December 13th Can be deflected with tennis rackets
- In the original version of this comic the date beneath the Dromaeosaurids shower was June 12th, the date of the velociraptor attacks in the Jurassic Park movie. To get the order of the dates correct it was probably easier to change just the date rather than move the Dromaeosaurids to the entry below June 9th.
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