History of the measurement of time

1. time measurement method

1.1. The ancients used sundials in numerous forms for crude time measurement

1.2. The Egyptians invented an advanced Water Clock

1.3. the clock first appeared in Europe

1.4. The hourglass uses the flow of sand to measure the flow of time

2. calender

2.1. Lunar calender: using moon to caculate the time

2.2. Lunisolar calender:

3. World time

3.1. Greenwich Mean Time (GMT)

3.1.1. Older standard

3.1.2. Using telescopes instead of atomic clocks

3.2. Universal time(UT)

3.2.1. the modern term for the international telescope-based system

4. Definition

4.1. It is a one-dimensional quantity

4.2. using to quantify the durations of events and the intervals between them

5. meaning of time

5.1. It is a fundamental structure of the universe

5.2. Time is often viewed as a continuum: from past to present to future

6. time travel (fiction)

6.1. concept of moving backwards and/or forwards to different points in time