After reading the post about the Earth’s rotation slowing down, that makes me think, will time a long way in the future eventually become innacurate?
It already is inaccurate. There are not 24 hrs in a day. It’s 23 hrs and IIRC 59 min and like some odd seconds. That is way we have Leap Years every four years, to correct the calender. There are not 365 days either. 364 and some fraction. I’d have to Google it to be accurate.
Time is pretty much a man-made concept and setup for “ease of use”.
If all months had 28 days, for instance, they would be the same with 13 months in a year 52 weeks/4weeks per month= 13. 365 days/28days per month=~13.0357. It’s pretty much all made up and inaccurate by it’s nature.
The measurement of time intervals will become more and more accurate.
That’s not why we have leap years. There are three astronomical phenomena that are used for clocks and calendars.
[ol]
[li]Rotation of the Earth.[/li][li]Moon orbiting the Earth.[/li][li]Earth orbiting the Sun.[/li][/ol]
Leap seconds are used to compensate for the difference between the actual rotation of the Earth and the standard day composed of 86,400 atomic seconds.
Leap years are used to compensate for the difference between the Earth’s orbit around the Sun and the standard year composed of 365 days.
Some calendars use leap months to compensate for the fact that there are not an integral number of lunar months in a solar year.
Well, the concept of linear time is a human invention. It basically does not exist. Time behaves more in a circular fashion. So time as it is now could not become inaccurate, as our concept of it isn’t accurate to begin with.
Cite?
What I’m asking is e.g. that will someday, today the 1st, would actually be the 2nd and we wouldn’t know it. Could that happen?
No, because there’s absolutely no natural reason to consider one day the 1st. The calendar and the clock are both man-made inventions, and are only meaningful because we agree that they are meaningful–really, they’re convenient fictions.
We’ve created measurements of time that are independent of potentially variable things like the Earth’s rotation and the speed of light. The second is, officially, determined by a number of radiation cycles of an atom of Cesium.
Even if the Earth’s rotation slowed down, that would stay the same.
What’s your definition of a day? If it’s based on the apparent motion of the Sun in the Earth’s sky, then I doubt it. Civil time is loosely synchronized to the apparent motion of the Sun. That’s why we have leap seconds.
you are confusing units of time which are abstract with the sidreal day and solar year which are defined by the rotation and revolution of the earth. I have to deal with this all the time as a database programmer when dealing with calender intervals. Dates can be defined in multple ways, as a year month and day in a specified calendar system and all those have anomalies or number of seconds or days from an epoch date. If a programming task needs to add a number of days to a specified date I can do that unambiguously. If a business function requires me to add months it can quite a bit more tricky.
The first could only become the second if someone defined it that way. This happened but it was actually a ten day change. In 1582 April 4 was followed by April 14, at least if you bought your calendar from Papal supply. This correction was done because the previous calendar did not correctly reconcile the number of sidreal days in the solar year.
But that might change:
Not quite. A year contains just under 365 and a quarter days. (365.242199 days, according to Google.) The leap year serves to add a day to the calendar, not subtract.
This may be interesting for you:
What Astronomical Events Form the Basis of Calendars
Thanks to all for the corrections and clarifications. I should not try to quote from my college astronomy class. Too much Time has pasted! Point still stands though, time is a man-made fiction and is inaccurate in it’s nature.
There are 23h 56m 4.10s in the average Earth rotation, and about 23h 59m 59.998s in the average time from noon (sun at highest overhead) to noon. but as mks57 has already said, that is not why we have Leap Years. The latter is why we have leap seconds, the former is a result of the “extra” day we lose going around the Sun–so over the year, about 24x60min/365 per day, which is a little less than four minutes.
The system is now designed so that does not happen, in the fashion that the first day of spring (the vernal equinox) will be at about the same time of year each time. The older calendar allowed that to shift, and that was the reason for the reform four hundred years ago. In order to take care of it, we have to use a tropical year (average time from one vernal equinox to the next) instead of the actual (sidereal) time the earth goes around the sun, which is twenty minutes longer.
So, in another sense, we are already shifting days–the earth is in a different part of its orbit on the same day each year. It shifts by a whole day each 24x60min/(20 min/year), or about 70 years.
Not sidereal days necessarily.
The change took place at different times in different countries too. In most English speaking countries, it took place in 1752–and since it was a couple hundred years later, they had to add eleven days instead of ten. And, while they were at it, they moved the date of the year change from March to January 1. That’s the reason for the discrepancies in George Washington’s birth date and year, since we was born before the change, in a February.
The measurement of time is arbitrary, not inaccurate. As mentioned in post #9, the second is a defined and standard unit, and we can measure with great accuracy and precision how many seconds pass between events. If not, the computer that you’re using to read this would not be possible.
In 1582, people when to bed on Thursday, October 4th and woke up on Friday, October 15th. Pope Gregory made this change to the Julian calender, and now we have the Gregorian Calender. So whether Emperor or Pope, temporal decisions are essentially decided by the powers that be.