Editing 1825: 7 Eleven
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==Explanation== | ==Explanation== | ||
| − | This comic pokes fun at the idiosyncrasies of time keeping. Since units of time are intimately tied to a planet's rotation, and planets rotate at different rates, time keeping doesn't always follow a simple pattern. | + | {{incomplete|Basic Explanation. Needs more. Solar day vs. sidereal day? Do NOT delete this tag too soon.}} |
| + | This comic pokes fun at the idiosyncrasies of time keeping. Since units of time are intimately tied to a planet's rotation, and planets rotate at different, inconsistent rates, time keeping doesn't always follow a simple pattern. | ||
| − | Many stores advertise being open 24/7, which means that they're open all day, every day. Many locations of the convenience store chain {{w|7-Eleven}} are now "open 24 hours", again meaning they are always open (despite historically being open only from 7 AM | + | Many stores advertise being open 24/7, which means that they're open all day, every day. Many locations of the convenience store chain {{w|7-Eleven}} are now "open 24 hours", again meaning they are always open (despite historically being open only from 7 AM and 11 PM local time, hence its name). |
| − | The main joke in the comic refers to the fact that a {{w|Timekeeping_on_Mars#Time_of_day|day on Mars}} (the time it takes for Mars to make a full | + | The main joke in the comic refers to the fact that a {{w|Timekeeping_on_Mars#Time_of_day|day on Mars}} (the time it takes for Mars to make a full revolution on its own axis) is about 24 hours and 37 minutes of Earth time. If a 7-11 store is open for literally 24 Earth hours per Mars day, then it would actually be closed for around 37 minutes each day. Of course, this is only an issue if Earth and Mars time units are mixed. Had the sign implicitly referred to 24 Mars-hours (where one Mars-hour is defined as 1/24 of a Mars day), then the store would be open for the entire Mars day. |
The duration for the Martian day used by [[Randall]] is the Martian {{w|sidereal day}} (how long it takes the non-Sun stars to get to the same position in the sky) of 24 hours, 37 minutes, and 22.663 seconds. However, Mars exploration missions use the Martian {{w|solar day}} (how long it takes the Sun to get to the same position in the sky) or {{w|Timekeeping_on_Mars#Sols|''sol''}} of 24 hours, 39 minutes, and 35.244 seconds. Thus in practice, the 7-11 store would be closed for 39 minutes daily instead of 37 minutes. Likewise, Earth time usually refers to solar days; a typical (mean) sidereal Earth day is 23 hours, 56 minutes, 4.0916 seconds long. | The duration for the Martian day used by [[Randall]] is the Martian {{w|sidereal day}} (how long it takes the non-Sun stars to get to the same position in the sky) of 24 hours, 37 minutes, and 22.663 seconds. However, Mars exploration missions use the Martian {{w|solar day}} (how long it takes the Sun to get to the same position in the sky) or {{w|Timekeeping_on_Mars#Sols|''sol''}} of 24 hours, 39 minutes, and 35.244 seconds. Thus in practice, the 7-11 store would be closed for 39 minutes daily instead of 37 minutes. Likewise, Earth time usually refers to solar days; a typical (mean) sidereal Earth day is 23 hours, 56 minutes, 4.0916 seconds long. | ||
| − | The first part of the title text refers to {{w|Daylight_saving_time|daylight saving time}} (DST), where | + | The first part of the title text refers to {{w|Daylight_saving_time|daylight saving time}} (DST), where days can be shortened or lengthened on predefined days of the year in order to maximize use of available sunlight. In the United States, most places set clocks forward by one hour on the second Sunday of March, resulting in a 23-hour day, and back again on the first Sunday of November, resulting in a 25-hour day. Thus technically, even a 7-11 in the US would not truly be open "24 hours" every day. Arizona and Hawaii are called out as exceptions because they do not observe daylight saving time (except on the Navajo reservation in Arizona). Randall has made fun of DST [[:Category:Daylight saving time|several times before]], and once again he shows his disdain for DST by saying only the two states not using DST are honest. This comic came out over a month after DST began in the US. |
| − | The second part of the title text refers to {{w|leap seconds}}, which | + | The second part of the title text refers to {{w|leap seconds}}, which are sometimes added to the end of a month in order to synchronize time with Earth's actual rotation. Months with a leap second will see its last day being one second longer than 24 hours. Since leap seconds apply to all Earth-based clocks, any store on Earth would not technically be open for exactly 24 hours on such days. Alternatively, a negative leap second would result in a day one second shorter than 24 hours. So far, all leap seconds have been positive, and given the slowing of the Earth's rotation it is unlikely that a negative leap second will ever occur. Leap seconds have been referred to before in the title text of [[1514: PermaCal]]. |
==Transcript== | ==Transcript== | ||
