2792: Summer Solstice

2023-06-22T19:46:13Z

Indigo: Correction to wiki link.

{{comic
| number = 2792
| date = June 21, 2023
| title = Summer Solstice
| image = summer_solstice_2x.png
| imagesize = 238x373px
| noexpand = true
| titletext = Then I'll start work on my lunar engines to line the Moon up with the ecliptic so we can have a solar eclipse every month (with a little wobble so they're not always on the equator.)
}}

==Explanation==
{{incomplete|Created by a TOTAL SOLAR ECLIPSE ENJOYER- Please change this comment when editing this page. Do NOT look directly at the sun, unless there's a total solar eclipse.}}
[[Cueball]] celebrates the the {{w|summer solstice}}m which occurred on the Day of this comics release. [[Megan]] then comments on this by saying that there will be six day to the latest sunset of the year, to which a confused [[White Hat]] exclaims ''Wait, what?''

The summer solstice occurs when one of Earth's poles has its maximum tilt toward the Sun. Although the summer solstice is the longest day of the year for that hemisphere, the dates of earliest sunrise and latest sunset differ by a few days. This is because of two different effects. First, Earth's axial tilt means that at some points in the year, the Earth is slightly ahead in its total rotation, whereas at other parts it is behind. Second, Earth orbits the Sun in an ellipse, and its orbital speed varies slightly during the year. These two effects combine to give the {{w|Equation of Time}}, which relates variable solar time to steady clock time. Near the summer solstice, the two have competing effects, with the axial tilt making the days later and the orbit making days earlier. The axial tilt is the faster changing of the two at the summer solstice, so it wins out, meaning that sunsets are still getting later for a few days after the solstice, despite the days getting shorter. White Hat, a laymen not aware of this correction, assumed that the latest sunset would occur on the summer solstice. Similarly the earliest sunrise already happened before the solstice. This is given since the day (time the sun is over the Horizon) was longest on the solstice, but the Sun will set later for then ext six days, meaning the sun will rise even later during those six days to make the day shorter.

The caption says that [[Randall]] is working on a giant machine capable of adjusting the Earth's orbit. And once finished the first thing he will use it for, is to fix this discrepancy so the longest day will also have the latest sunset (and thus earliest sunrise). This could be accomplished by either making Earth's orbit circular and removing the axial tilt (which would eliminate the solstices), or trying to balance the {{w|orbital eccentricity}} with the axial tilt, making the solstices match the days of closest or furthest distance from the Sun (perihelion or aphelion). This "fix" would avoid people like White Hat getting confused.

The title text discusses his next plans for increasing the number of {{w|solar eclipses}} from 0-1 each year to one each month. Solar eclipses occur when the {{w|Moon}} is directly between the Sun and Earth. Because of the tilt of the Moon's orbit to the {{w|ecliptic}} (the plane of the Earth's orbit, as ''sort of'' [[1878: Earth Orbital Diagram|demonstrated here]]), most of the times when the moon is between the Sun and the Earth they're not in direct alignment, so the Moon's shadow misses the Earth and we don't get an eclipse. Randall's engine will shift the Moon's orbit so it's not tilted so far and we get eclipses every month. But if it were exactly aligned with the ecliptic, eclipses would always be near the equator, so he'll leave a little wobbling so other areas will get eclipses too. Randall thinks solar eclipses are extremely cool, as noted in [[1880: Eclipse Review]], and would prefer that some of the eclipses will be visible from where he lives. He just had one six years ago (2017), and will soon get another (2024), but after that there will not be any eclipses over mainland USA for many years.

==Transcript==

:[Cueball, Megan and White Hat are standing. Cueball and Megan have their arms raised.]
:Cueball: Happy summer solstice!
:Megan: Only six days until the latest sunset of the year!
:White Hat: ...Wait, what?

:[Caption below the panel:]
:When I finally finish building my giant engine capable of shifting the Earth's orbit, this is the first thing I'm fixing.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring White Hat]]
[[Category:Astronomy]]
[[Category:Time]]

2792: Summer Solstice

2023-06-22T19:44:41Z

Indigo: Modification to explanation (the orbit alone would account for the opposite effect, making the latest sunset happen before the solstice! The axial tilt is needed to explain why it come later.)

{{comic
| number = 2792
| date = June 21, 2023
| title = Summer Solstice
| image = summer_solstice_2x.png
| imagesize = 238x373px
| noexpand = true
| titletext = Then I'll start work on my lunar engines to line the Moon up with the ecliptic so we can have a solar eclipse every month (with a little wobble so they're not always on the equator.)
}}

==Explanation==
{{incomplete|Created by a TOTAL SOLAR ECLIPSE ENJOYER- Please change this comment when editing this page. Do NOT look directly at the sun, unless there's a total solar eclipse.}}
[[Cueball]] celebrates the the {{w|summer solstice}}m which occured on the Day of this comics release. [[Megan]] then comments on this by saying that there will be six day to the latest sunset of the year, to which a confused [[White Hat]] exclaims ''Wait, what?''

The summer solstice occurs when one of Earth's poles has its maximum tilt toward the Sun. Although the summer solstice is the longest day of the year for that hemisphere, the dates of earliest sunrise and latest sunset differ by a few days. This is because of two different effects. First, Earth's axial tilt means that at some points in the year, the Earth is slightly ahead in its total rotation, whereas at other parts it is behind. Second, Earth orbits the Sun in an ellipse, and its orbital speed varies slightly during the year. These two effects combine to give the {{w|Equation of Time}}, which relates variable solar time to steady clock time. Near the summer solstice, the two have competing effects, with the axial tilt making the days later and the orbit making days earlier. The axial tilt is the faster changing of the two at the summer solstice, so it wins out, meaning that sunsets are still getting later for a few days after the solstice, despite the days getting shorter. White Hat, a laymen not aware of this correction, assumed that the latest sunset would occur on the summer solstice. Similarly the earliest sunrise already happened before the solstice. This is given since the day (time the sun is over the Horizon) was longest on the solstice, but the Sun will set later for then ext six days, meaning the sun will rise even later during those six days to make the day shorter.

The caption says that [[Randall]] is working on a giant machine capable of adjusting the Earth's orbit. And once finished the first thing he will use it for, is to fix this discrepancy so the longest day will also have the latest sunset (and thus earliest sunrise). This could be accomplished by either making Earth's orbit circular and removing the axial tilt (which would eliminate the solstices), or trying to balance the {{w|eccentricity}} with the axial tilt, making the solstices match the days of closest or furthest distance from the Sun (perihelion or aphelion). This "fix" would avoid people like White Hat getting confused.

The title text discusses his next plans for increasing the number of {{w|solar eclipses}} from 0-1 each year to one each month. Solar eclipses occur when the {{w|Moon}} is directly between the Sun and Earth. Because of the tilt of the Moon's orbit to the {{w|ecliptic}} (the plane of the Earth's orbit, as ''sort of'' [[1878: Earth Orbital Diagram|demonstrated here]]), most of the times when the moon is between the Sun and the Earth they're not in direct alignment, so the Moon's shadow misses the Earth and we don't get an eclipse. Randall's engine will shift the Moon's orbit so it's not tilted so far and we get eclipses every month. But if it were exactly aligned with the ecliptic, eclipses would always be near the equator, so he'll leave a little wobbling so other areas will get eclipses too. Randall thinks solar eclipses are extremely cool, as noted in [[1880: Eclipse Review]], and would prefer that some of the eclipses will be visible from where he lives. He just had one six years ago (2017), and will soon get another (2024), but after that there will not be any eclipses over mainland USA for many years.

==Transcript==

:[Cueball, Megan and White Hat are standing. Cueball and Megan have their arms raised.]
:Cueball: Happy summer solstice!
:Megan: Only six days until the latest sunset of the year!
:White Hat: ...Wait, what?

:[Caption below the panel:]
:When I finally finish building my giant engine capable of shifting the Earth's orbit, this is the first thing I'm fixing.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring White Hat]]
[[Category:Astronomy]]
[[Category:Time]]

explain xkcd - User contributions [en]

2792: Summer Solstice

2792: Summer Solstice