- Scientific thinking
- The oldest science
- Egyptians and time
- Solar and lunar calendars


[SLIDE 1]

Scientific thinking is based on everyday observations and trial and error experiments. Science in its modern form requires painstaking attention to detail, testing each piece of information to ensure that it is reliable, having a willingness to discard beliefs that are not consistent with observable facts about the physical world.


[SLIDE 2]

Astronomy is considered the oldest science.  While it was not practiced the same way in ancient times, there were still amazing achievements in astronomy.

Ancient people used observations of the sky to keep track of time, seasons and to aid in navigation. The length of our day is the time it takes the Sun to orbit the sky once. Ancient peoples used to tell time by observing the Sun's path through the sky. Some cultures used sundials. The Egyptians used obelisks, which functioned as simple clocks. At night time, ancient people also estimated time from the position and phase of the Moon or by analyzing constellations that were visible.

The seven days of the week are named after the seven major astronomical objects that were known in ancient times, including the Sun, Moon, and the five planets easily visible to the naked eye - Mercury, Venus, Mars, Jupiter, and Saturn.


[SLIDE 3]

The first known clocks can be traced back to the Egyptians some 4,000 years ago.

The Egyptians were also responsible for creating our framework for hours that we use every day. They divided daytime and nighttime each into 12 equal parts, which came to be 12 hours for a.m. and 12 hours for p.m.

The word 'a.m.' stands for ante meridian which is Latin for "before the middle of the day." The word 'p.m.' stands for post meridian which is Latin for "after the middle of the day."


[SLIDE 4]

Many cultures built structures such as the Temple Mayor in modern day Mexico City (formerly the Aztec city called Tenochtitlan) and aligned city buildings with cardinal directions of north, south, east and west to keep track of the rising and setting positions of the Sun. This also helped in tracking seasons.

The first written calendars were based on the Moon. The lunar calendar has the same moon phase on the first day of each month. A lunar calendar has 12 months, with roughly 29 to 30 days per month. A full 12-month lunar calendar has 354 or 355 days, or about 11 days less in a year than a solar calendar. This calendar is still in use in some parts of the world and in the Muslim religion.

Today, we use a solar calendar - one that is synchronized with seasons so that solstices and equinoxes fall approximately on the same days every year. Lunar and solar calendars can be synchronized by using a timing coincidence: the lunar phases repeat on the same solar dates every 19 years. If there is a full moon on Feb 11, 2018, there will be a full moon 19 years later on February 11, 2036. To take advantage of this fact, the Jewish calendar adds a thirteenth month to certain years in order to keep the lunar calendar roughly synchronized to the seasons.