1880: Eclipse Review
Title text: I watched from a beautiful nature reserve in central Missouri, and it was--without exaggeration--the coolest thing I've ever seen.
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This comic is the fifth consecutive comic with a solar eclipse as the topic. On August 21, 2017, a total solar eclipse was visible within a band across the contiguous United States from west to east. The other comics are 1876: Eclipse Searches, 1877: Eclipse Science, 1878: Earth Orbital Diagram and 1879: Eclipse Birds. As the first XKCD written since the total solar eclipse, Randal is ready to provide his "review."
The comic is another comparison graph, like 1775: Things You Learn or 1701: Speed and Danger. It contrasts how cool something sounds and how cool it actually is. It has five points on it, planetary conjunction, supermoon, lunar eclipse, partial solar eclipse, and total solar eclipse.
While the four other things than total solar eclipse are relatively close to each other on the "how cool to see" scale, the graph is not even high enough to plot the total solar eclipse point as indicated by the dotted arrow showing that this point should be way higher up. This is as opposed to leaving the point out, as Randall did with the coconut in 388: Fuck Grapefruit, where it is only mentioned in the title text. This could be an indication that if the scale had been high enough to fit the total solar eclipse point, then the rest of the points would be on the x-axis without any indication of which would be cooler.
A total solar eclipse correctly sounds like it is the coolest of the five, but it is vastly cooler to see it in person by a wide margin. It seems like Randall is trying to convice those who missed the eclipse this time to go watch in seven years when another total solar eclipse is visible in the USA.
- Planetary Conjunction
In a planetary conjunction two or more planets are visible close together in the night sky. This happens relatively often because all planets lie in roughly the same plane around the sun (the
Sagittal ecliptic). This looks like two big stars close to each other, and isn't particularly exciting.
A supermoon is a full moon or a new moon that approximately coincides with the Moon's closest approach in its elliptic orbit around the Earth. This results in a larger-than-usual apparent size of the lunar disk, but a typical human doesn't recognize the difference. Nevertheless, in recent years the press has often announced supermoons as important astronomical events. The opposite of a supermoon is called a micromoon. A "supermoon" sounds very cool, but like a planetary conjunction it's almost indistinguishable in the average night sky (see 1394: Superm*n).
- Lunar Eclipse
A lunar eclipse occurs during the full moon and, like at a solar eclipse, happens only when the Moon is in the region where the orbital planes of the Moon and the Earth intersect. The Earth's shadow falls on the Moon, causing it to appear dark red. The moon doesn't generally darken completely due to some light still reaching the Moon through the outer layers of the Earth's atmosphere. As with solar eclipses, lunar eclipses occur on average once every six months, but they can be viewed by anyone who is on the night-time side of Earth during the eclipse, as opposed to only being visible from a small strip of the Earth's surface. A lunar eclipse looks noticeably different from a usual full moon, making it fairly cool.
- Partial Solar Eclipse
There are three types of non-total solar eclipses. A partial eclipse occurs when the Sun and Moon are not exactly in line with an observer on Earth, and thus the Moon doesn't fully obscure the Sun. An annular eclipse occurs when the Sun and Moon do line up with an observer on Earth, but the Moon is too far away from earth to block the entire Sun. The Sun appears as a very bright ring, which is also called an annulus. A hybrid eclipse is an eclipse which is total when viewed from some parts of the earth, but is annular when viewed from others. These mixed eclipses are comparatively rare, even when compared with total eclipses. A large percentage of the continental United States experienced a partial eclipse along with the total solar eclipse on August 21st. A partial solar eclipse is quite cool, but nowhere near as dramatic as a sky-darkening total solar eclipse.
- Total Solar Eclipse
The total solar eclipse is the topic of this and the four preceding comics. It occurs during the new moon, and happens only when the Sun and Moon are exactly in line with an observer on Earth and when the Moon appears large enough to fully obscure the Sun. Unlike a lunar eclipse, only a small portion of the Earth lies within the Moon's shadow at any given time, roughly a disc with a diameter of approx. 100 km. The disc moves very fast over the Earth's surface, meaning that at any given location eclipses can't last longer than a few minutes. At locations outside of this shadow-disc, in a region over a few thousand kilometers, the eclipse is partial.
In the title text, Randall remarks that, without any exaggeration or hyperbole, the total solar eclipse was the coolest thing he has ever seen in his life.
- [A scatter plot with five labeled dots is drawn. The x-axis reads "How cool it sounds like it would be" and the y-axis is labeled with "How cool it is to see in person".]
- [Bottom left] Planetary conjunction
- [Bottom middle] Supermoon
- [Low left-center] Lunar eclipse
- [Low-center middle] Partial solar eclipse
- [Upper right, with a dotted arrow above it pointing up] Total solar eclipse
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