The History of Time Measuring Methods

Project realized by : Crisan Laurentiu ,Ungureanu Dorin ,Rareș Sabou ,Vladimir Rus ,Tatar Beatrice and Gherman Natan

Coordinating teacher : Alina Popescu

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Calendars

• An easy method for keeping track of the earths position around the sun is the calendar. over the course of time there were multiple versions of it , nowadays the most common one is the Gregorian consisting of 365 days a year and 366 days every 4 years.

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• The Gregorian calendar was introduced in 1582 as a replacement for the Julian calendar.
• The big difference between them was to space leap years differently.

Egyptian Calendar

• The egyptian year was 365 days long. It consisted of 12 months, each having 30 days. At some point, during the First Dynasty, five additional days were added (sometime around 3000 BC).
• Because this calendrical year was nearly a quarter of a day shorter than the solar year, the Egyptian calendar lost about one day every four years relative to the Gregorian calendar.

The Mayan Calendar

• The Mayans had 3 different calendars, but in day to day life they used the Haab' calendar. First it was a 360-day calendar, later, five days were added after the last month, "Cumhu", in order to make the year 365 days long. Those five days, called "Uayeb," were considered to be unlucky.

The Roman Calendar

• The Roman year started on 1 March and had only 304 days or 10 months (March, April, May, June, Quintilis, Sextilis, September, October, November and December). These 304 days were followed by an unnamed 50-day period. The

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• Roman king Pompilius introduced February and January (in that order) between December and March, increasing the length of the year to 354 or 355 days. In 450 BC, February was moved to its current position between January and March.

The Arabic Calendar

• The Arabic calendar, also known as the Islamic, Muslim or Lunar Hijri calendar, is a lunar calendar consisting of 12 lunar months, in a year of 354 or 355 days.

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• It is used to determine the proper days of Islamic holidays and rituals, such as the annual period of fasting and the proper time for the Hajj.

The History of Time Measurement/Keeping

The Moon and Stars

• The synodic month, or complete cycle of phases of the Moon as seen from Earth, averages 29.530588 mean solar days in length (i.e., 29 days 12 hours 44 minutes 3 seconds).

The Solar Clock

• The sundial is the earliest type of timekeeping device, which indicates the time of day by the position of the shadow of some object exposed to the sun's rays. As the day progresses, the sun moves across the sky, causing the shadow of the object to move and indicating the passage of time.
• The oldest known sundial was made in Egypt in 1500 BC

Water Clock

• An Egyptian sundial from about 1,500 BCE is the earliest evidence of the division of the day into equal parts, but the sundial was no use at night.

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• The passage of time was extremely important for astronomers and priests who were responsible for determining the exact hour for the daily rituals and for the important religious festivals, so a water clock was invented.

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The Oil Lamps

• There is archaeological evidence of oil lamps about 4,000 BCE, and the Chinese were using oil for heating and lighting by 2,000 BCE. Oil lamps are still significant in religious practices, symbolic of the journey from darkness and ignorance to light and knowledge.

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• The shape of the lamp gradually evolved into the typical pottery style shown. It was possible to devise a way of measuring the level in the oil reservoir to measure the passing of time.

The Mechanical Clock

• Mechanical clocks replaced the old water clocks, and the first clock escapement mechanism appears to have been invented in 1275.

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• The first drawing of an escapement was given by Jacopo di Dondi in 1364. In the early-to-mid-14th century, large mechanical clocks began to appear in the towers of several cities.

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• All had the same basic problem: the period of oscillation of the mechanism depended heavily on the driving force of the weights and the friction in the drive.�

The Quartz Clock

• The battery sends electricity to the quartz crystal through an electronic circuit. The quartz oscillator vibrates quickly and with precise frequency (32,768 times/second) in response to the electronic charge.

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• The circuit counts the vibrations and generates regular electric pulses of one per second.

Bibliography :

• https://www.youtube.com/watch?v=URK9Z2G71j8&t=145s
• https://nrich.maths.org/6070

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