Time
Created Saturday 29 June 2024
What is Time?
- Time is a measurement sometimes referred to as the 4th Dimension.
- It is the period between two events.
- It is the relative part of the day with reference to Midnight.
- The International standard for time is the Second.
- Time always progresses forwards.
History
Early humans experienced the passage of time with simple definitions:
Day: Progressed from Night > Sunrise > High Noon > Sunset > Night
Months (Moon): The changing phases of the moon, New > First Quarter > Full > Last Quarter > New
Year: The passing of the seasons, Winter > Spring > Summer > Autumn > Winter
Early Humans had no need to measure time to any great accuracy as they were Hunter gatherers and later settled to become Farmers and everything revolved around the natural rhythms of animals and plants.
When humans started to organise their days for the purpose of commerce or religion, it became necessary to divide the days and years into a more formal arrangement, so the first calendars and clocks were devised.
The first clocks were based on the position of the sun in the sky and used its shadow to indicate the 'Time' of day, this was the sundial, at night the positions in the sky of known stars were observed.
It was the ancient Sumerians who first divided the day and night into 12 periods each, the length of each period varied depending on the season, in summer there is around 14 (modern) hours of daylight and in winter only 10 hours.
This problem got even more exaggerated the further you were away from the equator, inside the arctic circle you can experience up-to 24 hours of daylight in the summer and zero in the winter.
Early Egyptian scholars discovered that at the equinoxes when day and night are of equal length, the sun moves by 15 degrees in 1/12 of the day, so sundials were marked with 'Hours' at 15 degree intervals so each hour became a fixed duration.
Epoch
An epoch is the starting reference point for the measurement of time or date.
Notable Epochs:
Clock time: Midnight 00:00
Julian Day: started in 4713 BCE, a date at which three multi-year cycles started (which are: Indiction, Solar, and Lunar cycles) and which preceded any dates in recorded history and ends in 3268CE.
Unix time: 1st Jan 1970 @ 00:00
Rata Die: 1st Jan year 1, Count of days of the Common Era
Lilian date day 1 = October 15, 1582, The start of the Gregorian Calendar.
Anno Mundi, AM: started on 6 Oct 3761 BCE - Year of the world as devised through creation myths
Holocene Era, HE also known as Human Era, Add 10,000 to CE year number ie. 2024 CE = 12024 HE, HE uses the "beginning of human era" as its epoch, arbitrarily defined as 10,000 BC and denoted year 1 HE
Julian Calendar
The Julian calendar was proposed in 46 BCE by (and takes its name from) Julius Caesar
This was a calendar with 365 days in a normal year and introduced an extra 'leap' day every 4 years to correct for the earths orbit of 365 1/4 days, However this proved to be an over simplification of the actual 365.2422 days.
So by 1545 the calendar was out of sync with the solar year due to adding more than required leap days, so Pope Gregory XIII commissioned a revised calendar to correct the error.
The motivation for the adjustment was to bring the date for the celebration of Easter to the time of year in which it was celebrated when it was introduced by the early Church.
Not all country's adopted the new calendar immediately, some as late as 2016, England adopted the Gregorian calendar on 3 September 1752 when 11 days were removed and the calendar went from 2nd Sep (Julian) to 14th Sep (Gregorian)
Apparently this caused some rioting amongst the population demanding the return of the 11 days.
Hour
originally, 1/12th of the time between sunrise and sunset.
The time it takes the sun to traverse 15 degrees of Longitude.
Minute
adjective:
meaning very small
noun:
60th part of an Hour (1st Minute - Small part)
60th part of a Minute ( Second Minute)
Why 12 & 60?
duodecimal, base 12, traces it's origines back to counting in multiples of 12 as can be counted on one hand using the thumb to count the number of segments on each finger.
Sexagesimal, also known as base 60, is a numeral system with sixty as its base.
It originated with the ancient Sumerians in the 3rd millennium BC, was passed down to the ancient Babylonians, and is still used—in a modified form—for measuring time, angles, and geographic coordinates.
It can be counted using two hands, 0-12 on one hand and 5 x 12 on the other (12, 24, 36, 48, 60)
Different time standards
In ancient times when sundial's were the common method of telling the time, Noon or 12 O'Clock was when the sun was at it's highest point (High Noon) when it crossed the local meridian, this of course was dependant on where on earth you lived, This is referred to as 'Local Solar Time' (LST) and as people did not travel great distances this was not a problem.
After the invention of mechanical clocks, which were only affordable to the rich, or public clocks on churches Etc. it was found that LST and the time shown in the clock can be different by as much as -14/+16 minutes depending on the time of year.
This is because the clock measures time at a constant rate and the sun's position in the sky is dependant on the tilt of the Earths axis and the non circular orbit around the sun, due to the length of a day, the time between to successive solar noon's is not exactly 24 hours and can vary between 23:59:40 and 24:00:30, the clock measures the Local MEAN Solar Time, or LMT. This difference can be calculated using the Equation of Time.
Most places in England used Local Mean time to set the clocks, this was fine as long as you didn't go far from home, However after the building of the railways, people started travelling more and using railway timetables to catch the trains, this proved to be problematic as different towns were all on different times, so if you travelled from London to Penzance the local times were 22 minutes apart!!
To combat this in 1847 the railways adopted London time as the standard and was shown on all railway station clocks, initially the clocks were set from the train guard's watch from London time, but after the invention of the Telegraph the railways would set the clocks from time signals sent via telegraph from London, This became known as 'Railway Time'. By 1855 most of the UK had adopted GMT (Greenwich Mean Time) as the standard, this was not legally recognised until The Interpretation Act 1978
Time Zones
Each country has decided to adopt one of the 26 time zones around the world, this is so the the local Civil time is closely matched to Local Solar Time which helps the population synchronise to the natural circadian rhythms, some country's are so large that different parts of the country are on different time zones, others use one time zone for the whole country (China). Each timezone is separated by approximately 15 degrees Longitude and are mostly set at 1 hour intervals.
This allows the population of a single country to synchronise there daily activities, but if you travel to another country or communicate via telephone or email then you have to allow for the different time zones.
UTC
If you are trying to co-ordinate activities across different time zones then some confusion can occur, so, organisations such as airlines, military, space travel and astronomy use a global timezone known as UTC or Coordinated Universal Time, this is independent of timezones or daylight saving time, it is the same time as GMT. Prior to the adoption of UTC, GMT was the standard world time but is now a timezone identifier just as CET, EDT Etc.
Daylight Saving Time
As if it is not confusing enough to deal with different timezones, some country's in the world (North America & Europe) change their clocks by +1hour during the summer months, this gives the impression of an extra hour of daylight for outdoor activities in the summer, this of course is not true as it does not increase the number of daylight hours but simply fools people into getting up an hour earlier so they see more of the available daylight. To add even more confusion the dates on which the change occurs is different for each country.
There are many arguments for and against daylight saving time, but it just adds more confusion, for instance, some states in the US have different rules for different parts of the same state!!
In the future as the people become more globalised i can see more people adopting UTC as an everyday timezone, this will make coordinating events across the globe less confusing, the only down side is that people will need to retrain their minds to work with different times, High noon will no longer be at 12:00 in most of the world and people won't get up at 07:00 and go to bed at 23:00.
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