Why are some countries a day behind/ahead others if time moves at the same rate everywhere?
In: Earth Science
Because of timezones.
Yes (for the purposes of normal life and this question, so I’m choosing to ignore time dilation due to gravity) time moves at the same rate everywhere.
Historically, midnight, or 12am, has been in the middle of the night, and noon, or 12pm, has been in the middle of the day (roughly speaking).
This worked for the majority of human history because one person only really cared about what the time was where they were, so if its the middle of the day it must be noon.
but as people and information started traveling further, faster, this didnt work as well. say youre in america in the late 1800s, and youre taking a train from point A, and traveling West to point B. You leave at noon point A time, and ride the train for 3 hours.
You might expect to arrive there at 3pm, but when you get off the train, the clock on the townhall only says 2:30. How is this possible?
Well, each town had set their clock relative to the sun, hitting noon when the sun is the highest, but since youve traveled west, the town you arrived in has a sunrise at a different instance than the town you came from in the east, since the earth is a spinning ball.
This confused people, and needed a solution for scheduling trains and communications and stuff. Hypothetically, everyone could pick one time and just use that, but that would make times very weird for some people
say you picked NYC as your base point, and said noon, 12pm, when the sun is highest in NYC will be noon everywhere. People who lived on los angelos, california would go “wtf thats weird, the sun has barely risen here that doesnt make any sense.”
So instead they came up with timezones, so they could somewhat standardize time by knowing the timezone difference in two locations, while also allowing people to keep their normal schedule of having noon in the middle of the day (roughly).
this more accurately represents how say at noon in NYC, the sun is already setting in Moscow Russia, and it is already around the middle of the night in Australia. and then how at 6pm in NYC, it is already the early morning in Australia with the sun starting to rise soon.
Time zones. Only part of the Earth is facing the sun at any point in time. When the sun is rising in one part of the world, it is setting in another.
If you start in New Zealand at sunrise and call it Monday, and follow that sunrise all throughout the world, all the way to Hawaii, you will have Monday throughout the world, but then only a few hours later it will be sunrise again in New Zealand, so it must now be Tuesday, but it’s still Monday morning in Hawaii.
It is down to the relative position of the Sun so where you are on the globe the Sun would rise at a different time, so to keep everything relatively balanced and no one having sun rise at midnight, there are time zones around the planet where the time changes by an hour as you cross the imaginary line between time zones. However when you go completely round the planet the time zones meet up again at the same time, but the problem is that each time zone was adding an hour to the time the final zone is now 24 hours ahead of the next one so you have the international date line as the final time zone moving from one day to the next.
Time zones. There are 24 since it takes the earth about 24 hours to spin 1 complete rotation, so depending on where you’re at, it could be day/night. The difference is how we mark what part of that 24 hour cycle your zone is in, which is why some happen to be “the next day” ahead. That’s only because their daylight began before the next one west of them. They’re not actually in the future, they’re just ahead on the rotation of the earth, or at least where we chose to draw the line.
Time moves at the same rate everywhere on Earth (barring things like relativity), but our concept of time isn’t based on an absolute truth, it’s based on things like “when the sun first comes up” or “when the sun is directly overhead in the sky” or “when it’s dark.
For most of human history, this wasn’t a huge deal, and we didn’t have a reason to go more formal than that. This slightly changed with the Industrial Revolution, as we now had artificial electric lights and factory work, but it was only local time that mattered for the most part, and if you traveled you would just readjust based on that, since traveling still took up a lot more time.
This started to change once we got trains, and then really needed a bit of formalization once flying across the oceans was common. It really hit a peak more recently with the internet and the ability to communicate near-instantly with any arbitrary part of the world at any time.
So, the concept of timezones was born somewhere in there. The idea being that each country would set its time according to when noon was, and that this would solve things. As part of this, we needed *somewhere* for the day to switch over, since if we didn’t we’d all be switching days at different times and it wouldn’t be super intuitive for anyone but the people who were in Greenwitch England (where the “standard time” is set for global timezones; you take GMT, Greenwitch Mean Time, and either add hours if you’re east of Greenwitch, or subtract hours if you’re west of Greenwitch), until you get to the International Date Line, which is (more or less) right on the other side of Greenwitch’s longitude line.
This is still an imperfect system, as [Tom Scott](https://www.youtube.com/watch?v=-5wpm-gesOY) will tell you, as there are all sorts of exceptions to the standard things. Part of it being that we’ve had to refine our concept of time as our scientific knowledge grew (for instance: we added in leap years because someone at some point realized that we kept having the season changes shift around, so that the start of each season would be a day later once every 4 years, and this is because the world goes around the sun not once every 365 days, but once every 365.25 days. And then we had to change it *again* because we’re actually something like 365.247 days per year, and the hack for this is that a year is a leap year if it’s divisible by 4 *and not* divisible by 100, but if it’s divisible by 100 *and* is divisible by 400, then it *is* a leap year again.)
And this is before you have to talk about leap seconds.
It has to do with telling time based on the visible position of the sun. We tell our time relatively based on daylight hours; no matter where you go in the world (aside from the far North or I think south) you know it’ll always be day time at noon, sun coming up around 6, and going down around 7, obviously this changes based on where you are, and the the season, but you get the idea.
Because of that, we have to set somewhere as the 0 point, that we base all other time off of. Back when this was decided, they chose Greenwich, England. Now, we need to set times ahead of Greenwich, and behind it, because it’s our middle point, so there’s 24 hours in a day, we’ll extend the times zones 12 hours back, and 12 hours forward. This means that just as someone in GMT -12 is finishing their day, someone in GMT +12 is starting a new one, since they’re now 24 hours ahead. If it’s 1200, 06 October 2020 in greenwood, it’s 0000, 06 October 2020 in GMT -12, and it’s 0000, 07 October 2020 in GMT +12, because they’re 12 hours closer to facing the sun
[Relevant Johnny Harris](https://youtu.be/aBppb2quqkE)
You’re confused about what time is. And what it means to be a day behind/ahead.
Time moves at the same rate around the world. Countries that are “behind/ahead” aren’t in the past/future they’ve just measured time from a different starting point.
The way we measure time is a human construct that we can adjust for our convenience. And it’s based on the rotation of the earth on its axis and it’s orbit around the sun. Because the earth is round, when the sun comes into view on one side of the planet, the other side is no longer able to see it.
Since we’re talking about measurement, let’s relate it to distance. If two people, 50m apart, run 100m in the same direction, they both travelled the same distance, but they’re still 50m apart.
Likewise if one side of the world has their sun rise 12 hours before the other, they both travel through time at the same rate but will measure their days from a different starting point.
There is the internationational date line in the Pacific. Once it is 12:00am there, it’s the next day while all time zones behind it are still the previous day. They are less than a day apart it’s just that some are in one day ahead and others are still the day behind.
Timezones are just a measure of where the sun is in relation to the person that lives there. 12pm est is when the sun is above New York/ Florida. 12pm Pacific is when the sun is above California. Since the sun rises over New York first, their ‘day’ starts 4 hours earlier than California. But ‘time’ is the same. It just the way we measure their local time zone that is different.
Latest Answers