Since this is I’m gonna explain my question the same way.
Imagine there is a time-hating wizard who magically removes all time-keeping instruments like atomic clocks, phones and watches, so there is no way of knowing the time right now. If then we were asked to ‘bring back’ the old time that we used (e.g. so that we start again measuring 12:00 in London exactly when it was 12:00 in London before the wizard) could this be done? Is there something physical constant (like kg or meter) that determines what time of day it is? Or, did someone just say “we start measuring time from now, and I say that it is exactly 14:32…”?
Also, if there is this constant that allows us to know exactly when a certain time is, doesn’t that mean we don’t need atomic clocks and can just compare ourselves to this constant? Idk what this would be but perhaps when the sun is absolutely highest in the sky somewhere?
In: 40
In olden days they used to set the time based on the position of the sun, like a sun dial, a clock tower in the nearest town would hold the official time everyone would set their clocks after, because the earth is curved, the time would be different in one place to another, this wasn’t a problem until railways needed to be precise so they decided a standard time, precise time was also important for naval navigation. Anyways, the speed of light is a constant we know the velocity of, therefore we could set our time based on that.
What determines what time of day it is was originally when the sun is directly overhead, at noon.
Originally eyeballing it like “Yeah, it’s about noon here now” was good enough. As trains began to connect more distant places faster, and we needed more accurate time tables, we came up with concepts like timezones so that we’d have an agreed-upon time. We now measure time zones by how many hours off they are from Coordinated Universal Time (or UTC, which comes from the French name). UTC is descended from Greenwich Mean Time, which is basically the time according to the sun at the Greenwich Royal Observatory in London.
Before there were clocks or timezones and stuff.
There were the things in the sky.
Everyone can track the sun and note at what time it’s at its highest.
This became noon.
that’s where measuring hours started.
For a long time everyone would set their clocks to be 12 pm at their local noon, but as trains were invented, this mess of time was hard to work with so they made a particular observatory in Greenwich be the 0 point and divided the world from there.
The movements of the planet affects the seasons, specifically you can track how long the day lasts, and figure out how long it takes for the earth to go around the sun by how the length of the day changes.
You can also do some equivalent things like counting how many times the moon changed phases, or seeing what stars were where at certain times.
Or what big planets were doing.
You see stuff like that for determining the year/months still in many cultures.
Basically none of them agree on when the year starts, that date is pretty arbitrary. The current start date involves some convoluted and largely irrelevant curiosities regarding a Roman God called Janus.
Perhaps not with the same accuracy, but close enough to say when 14:32 is.
Our time was originally based on the sunset/sunrise at Greenwich London. We know where that is and we can see where the sun is from there (weather permitting).
We would have to adjust everything for time zones and daylight savings time.
But getting things back accurate to the minute seems doable.
nope, that aspect is all relative.
we can measure the seasons just fine, so the calendar could be the same. but it might be out by six months if this time Wizard makes the southern hemisphere dominant. we’d still have noon and midnight in each specific location and probably allocate a local time for that. it means a lot to say “i was up until 3am last night”, but only if you have local times. if we all use the same timezone, i now also need to know your location and then use math to work out if that’s a sensible bedtime or not.
we couldn’t recreate the month names now, so they’d be different, and probably just numbers.
there’s nothing special about utc, it was just agreed before America became dominant. the dateline being largely in the ocean is useful, although we could maybe fine tune that so it’s not half covering an island. that said there’s 2 main ways to cut the land masses to fit onto a 2d map: America on the left or Europe on the left. it doesn’t really make sense on paper otherwise, so it’s unlikely that a central time zone that was internationally agreed would go through America. maybe europe would keep the utc noon line, probably not London tho, although i might try to put it just to the east of Africa. eastern Australia might get it if we draw Europe on the left of the map.
that said, America might just start using a standard that goes through Washington dc and the rest of the world might follow. that might happen anyway.
so could we recreate utc? not really. the calendar? kind of. month names? no. 24 hours in a day? I’d say unlikely: we tend towards metric now and would probably have 10 or 100 main units in a day. but it’s possible, since 12 is actually a useful number to divide and having two halves to the day does make some sense. i doubt we’d have 12 hour repeating clocks tho, that’s just weird. am and pm … what?
we’d still have/recreate the same lattitude and longitude lines, and timezones would broadly follow longitude, as now.
So there are 3 things to consider.
Time and time measurement. There is no objective time. There is a difference between time and measures of time. Think of it this way, it is possible to measure the height of a person. To do so, there needs to be a measure of height – meters, centimeters, feet and inches etc. But does “height” exist? It is merely a measure assigned to a person.
Time measurement. In modern times, the standard for time measurement is the count of the vibrations of a certain atom. A second in time is defined (by humans). This measure is universal so, as long as the right atom is measured and a counter available, it is possible to figure out what one “second” is.
Reference time. This is the division of passing time into things like days, weeks, months, dates. This is also human created and the nearly universally agreed upon major division is the day because there is a very obvious noon (sun overhead, short shadow) that is common to anyone on earth. It is very easy to measure the difference between one noon and the next. Other things like the period of a year are also observable, if we use telescopes. But the other references like month, day, year (2022AD, lunar etc) are not. If this knowledge were erased from everyone, there would be no way to recover it. It would be guesswork.
We’d use the sun like we used to. Other commenters have pointed out that noon is the easiest point of the day to measure. That’s because the sun reaching it’s highest point in the sky is not subtle and easy to measure.
You wouldn’t even need anything complicated. Jab a stick in the ground, and you can trace the shadow throughout the day. Noon is when it’s the shortest and points straight towards the nearest pole. if you’re not in the tropics. From there, you mark the arc into hours. Now you have a reference to build your mechanical clock around.
That’s how clocks began in the first place. They were mechanical sundials with the hour hand simulating the shadow of a sundial. In the Northern Hemisphere where they were invented, a sundial’s shadow starts in the west, swings north, and then to the east. The same direction we now call clockwise (and used to call sunwise).
It would be some astronomical way, using the sun or other stars passing in front of some optical device. You’d also have to align that device somehow, probably using gravity. Hard to tell how precise you could get like that, but for one second resolution it would have to be able to differentiate angles as small as a “cake” devided into 86400 pieces. Maybe even the gravity of a mountain near you could distort your measurement, because the device would be misaligned(?)
We would probably come up with a lot of the same stuff that the ancient Babylonians did, just with a higher degree of specificity.
~360 days in a year because the position of the sun changes ~1 degree in the sky every day, months being ~28 days long (probably 4 weeks of 7 days and a catch-up period at the end for ease of accounting going forward) we would probably define the hour/minute/second out of a base 10 system as opposed to a base 60 system, so it would probably be 100 seconds to a minute 100 seconds to an hour (like it was 10 seconds to a minute 10 minutes to an hour for the Babylonians)
Time, both present and future, is all about synchronization and coordination of efforts.
Time, past, is all about cateloguing those previous efforts.
So as long as we have a system capable of cateloguing the synchronization of our efforts, your question will remain irrelivent.
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