EARTH TIME
Created | Updated Oct 20, 2010
Time seems a simple system to keep track of the days, bedtimes and dates, but once you start thinking about it it's a rather complex concept.There are different calenders, like the Jewish and Chinese, but this is the one used worldwide.
First the two points the calender was based on:
Circulation period around the Sun: 365.256 days
Circulation period of Moon around Earth: 27.32 days
Based on the circulation period of Earth around the Sun a year is 365 days, the approximate time it takes earth to travel around the Sun. There is, since Earth actually takes 365 days and a quarter, a leap year once in four years. This means that the year has 366 days instead of 365, the extra day is February 29th and is the result of four times a quarter day extra at the end of each non-leapyear.
A year is divided in four seasons; winter, spring, summer and autumn. Every season lasts about 3 months. The seasons are mostly based on the changing of the weather.
North of the equator:
Winter : December 21st - March 21st
Spring : March 21st - June 21st
Summer : June 21st - September 21st
Autumn : September 21st - December 21st
South of the equator:
Winter : June 21st - September 21st
Spring : September 21st - December 21st
Summer : December 21st - March 21st
Autumn : March 21st - June 21st
Generally it's cold in the winter and warm in the summer. However this depends on the climate in the area. Close to the equator there will hardly be any difference.
A year is also divided in 12 months. Each month has their own name; January, February, March, April, May, June, July, August, September, October, November and December. A month is either 30 or 31 days long, February being the only exception of 28 (or 29 in a leap year) days.
Then there's weeks, there are 52 weeks in a year. A week is 7 days long. The days are: Monday, Tuesday, Wednesday, Thursday, Friday, Saturday and Sunday. Saturday and Sunday (and usually Friday evening too) are know as "the weekend"
There are 24 hours in a day. Often divided in morning, afternoon, evening and night. There are no determined time periods for these, and it may vary from place to place. This division of the day is just used in greetings (i.e. Good morning).
Telling time can be done by either using a.m and p.m. for respectively the first and the second half of the day (after the first half of the day you start counting at one again, earth clocks are designed this way), or using the hour of the day.<BR/>
Example: For 6 hours in the second half of the day you can use 6 p.m. or 18.00.
An hour is divided in 60 minutes, and a minute is divided in 60 seconds.
In short:
A (normal) year has....
.... 4 seasons
.... 12 months
.... 52 weeks
.... 365 days
.... 8,760 hours
.... 525,600 minutes
.... 31,536,000 seconds
TIMEZONES
On November 1, 1884, the International Meridian Conference in Washington, D. C., the timezones were designed. The 24 standard meridians, every 15 east and west of 0 at Greenwich, England, were designated the centers of the zones. The international dateline was drawn to generally follow the 180 meridian in the Pacific Ocean. Because some countries, islands and states do not want to be divided into several zones, the zones' boundaries tend to wander considerably from straight north-south lines.
SUMMER AND WINTER TIME
This system is also known as Daylight Saving Time, which, as the name says, was designed to save daylight. When summer starts you set your clock one hour forward and when the winter starts you set your clock one hour back to avoid having to get up when it's still dark in the winter (of course in some places it's dark all day during the wintertime). Unfortunately there's no international date for the resetting of the clock, so do US does it one week later than Europe.
HISTORY OF EARTH TIME
- 3761 BC - Start of Jewish calender based on the moon positions
- Approx. 2000 BC - Egyptians make shadow-clocks
- Approx. 1500 BC - UK. Stonehenge built, possibly meant as an enormous calender
- Approx. 1360 BC - Egypt. The first waterclocks where the time is indicated by changing waterlevel
- Approx. 800 BC - Egypt. The oldest existing sundial
- 45 BC - Start of Julian calender on January 1st. Roman ruler Gaius Caesar changes the original Roman calender year from 120 to 365 days
- 1 DC - Start of christian calender based on Julian
- 500 - China. Invention of incense-clock. Incense burns evenly along a maze-like pattern
- 622 - July 16th. Start of Muslim-calender, the day that Mohammed fled from Mekka to Medina
- Approx. 800 - Invention of candle-clock. Lines on the candle indicate the amount of burning hours
- Approx. 1290 - First European mechanical clocks
- Approx. 1300 - ..... in Europe
- Approx. 1400 - First portable clocks
- 1504 - Germany. First pocket-watch
- 1582 - Introduction of the Gregorian calender
- 1657 - Netherlands. Huygens invents pendulum
- 1675 - Netherlands. Huygens invents spring-watch
- 1790 - First wristwatches
- 1840 - Scotland. First electrical clock
- 1884 - US. International meridian-conference. Time-zone system established to abolish small local time differences and to make 12 o'clock the middle of the day in all countries
- 1922 - US. First automatic wristwatch
- 1929 - First quartz clock
- 1948 - US. First atomic clock. The most precise time meter
- 1955 - First cesium-atomic clock
- 1967 - First quartz wristwatch
- 1967 - Re-gauging of the second
- 1991 - The most precise atomic clock ever invented
http://physics.nist.gov/GenInt/Time/time.html - More history of time.
First the two points the calender was based on:
Circulation period around the Sun: 365.256 days
Circulation period of Moon around Earth: 27.32 days
Based on the circulation period of Earth around the Sun a year is 365 days, the approximate time it takes earth to travel around the Sun. There is, since Earth actually takes 365 days and a quarter, a leap year once in four years. This means that the year has 366 days instead of 365, the extra day is February 29th and is the result of four times a quarter day extra at the end of each non-leapyear.
A year is divided in four seasons; winter, spring, summer and autumn. Every season lasts about 3 months. The seasons are mostly based on the changing of the weather.
North of the equator:
Winter : December 21st - March 21st
Spring : March 21st - June 21st
Summer : June 21st - September 21st
Autumn : September 21st - December 21st
South of the equator:
Winter : June 21st - September 21st
Spring : September 21st - December 21st
Summer : December 21st - March 21st
Autumn : March 21st - June 21st
Generally it's cold in the winter and warm in the summer. However this depends on the climate in the area. Close to the equator there will hardly be any difference.
A year is also divided in 12 months. Each month has their own name; January, February, March, April, May, June, July, August, September, October, November and December. A month is either 30 or 31 days long, February being the only exception of 28 (or 29 in a leap year) days.
Then there's weeks, there are 52 weeks in a year. A week is 7 days long. The days are: Monday, Tuesday, Wednesday, Thursday, Friday, Saturday and Sunday. Saturday and Sunday (and usually Friday evening too) are know as "the weekend"
There are 24 hours in a day. Often divided in morning, afternoon, evening and night. There are no determined time periods for these, and it may vary from place to place. This division of the day is just used in greetings (i.e. Good morning).
Telling time can be done by either using a.m and p.m. for respectively the first and the second half of the day (after the first half of the day you start counting at one again, earth clocks are designed this way), or using the hour of the day.<BR/>
Example: For 6 hours in the second half of the day you can use 6 p.m. or 18.00.
An hour is divided in 60 minutes, and a minute is divided in 60 seconds.
In short:
A (normal) year has....
.... 4 seasons
.... 12 months
.... 52 weeks
.... 365 days
.... 8,760 hours
.... 525,600 minutes
.... 31,536,000 seconds
TIMEZONES
On November 1, 1884, the International Meridian Conference in Washington, D. C., the timezones were designed. The 24 standard meridians, every 15 east and west of 0 at Greenwich, England, were designated the centers of the zones. The international dateline was drawn to generally follow the 180 meridian in the Pacific Ocean. Because some countries, islands and states do not want to be divided into several zones, the zones' boundaries tend to wander considerably from straight north-south lines.
SUMMER AND WINTER TIME
This system is also known as Daylight Saving Time, which, as the name says, was designed to save daylight. When summer starts you set your clock one hour forward and when the winter starts you set your clock one hour back to avoid having to get up when it's still dark in the winter (of course in some places it's dark all day during the wintertime). Unfortunately there's no international date for the resetting of the clock, so do US does it one week later than Europe.
HISTORY OF EARTH TIME
- 3761 BC - Start of Jewish calender based on the moon positions
- Approx. 2000 BC - Egyptians make shadow-clocks
- Approx. 1500 BC - UK. Stonehenge built, possibly meant as an enormous calender
- Approx. 1360 BC - Egypt. The first waterclocks where the time is indicated by changing waterlevel
- Approx. 800 BC - Egypt. The oldest existing sundial
- 45 BC - Start of Julian calender on January 1st. Roman ruler Gaius Caesar changes the original Roman calender year from 120 to 365 days
- 1 DC - Start of christian calender based on Julian
- 500 - China. Invention of incense-clock. Incense burns evenly along a maze-like pattern
- 622 - July 16th. Start of Muslim-calender, the day that Mohammed fled from Mekka to Medina
- Approx. 800 - Invention of candle-clock. Lines on the candle indicate the amount of burning hours
- Approx. 1290 - First European mechanical clocks
- Approx. 1300 - ..... in Europe
- Approx. 1400 - First portable clocks
- 1504 - Germany. First pocket-watch
- 1582 - Introduction of the Gregorian calender
- 1657 - Netherlands. Huygens invents pendulum
- 1675 - Netherlands. Huygens invents spring-watch
- 1790 - First wristwatches
- 1840 - Scotland. First electrical clock
- 1884 - US. International meridian-conference. Time-zone system established to abolish small local time differences and to make 12 o'clock the middle of the day in all countries
- 1922 - US. First automatic wristwatch
- 1929 - First quartz clock
- 1948 - US. First atomic clock. The most precise time meter
- 1955 - First cesium-atomic clock
- 1967 - First quartz wristwatch
- 1967 - Re-gauging of the second
- 1991 - The most precise atomic clock ever invented
http://physics.nist.gov/GenInt/Time/time.html - More history of time.
