Summary of Chad Orzel's A Brief History of Timekeeping

By IRB Media

Please note: This is a companion version & not the original book. Book Preview:

#1 The Glorious Revolution in England in the late 1600s saw the deposition of the Catholic king of England and Scotland, James Stuart, and his replacement by his daughter, Mary, and her husband, William of Orange. This triggered a number of uprisings in the British Isles, including the Williamite War in Ireland.

#2 The solstice marker at Newgrange, Ireland, is a physical cycle that repeats at regular intervals. It is the appearance of sunlight in the central chamber that provides a clear readout for a physical cycle that repeats at regular intervals.

#3 The sun moves across the sky from left to right, and the earth rotates counterclockwise. From a vantage point above the north pole, the earth rotates counterclockwise, so a day looks like the image on the next page.

#4 The sun follows a different path in the two hemispheres. At northern latitudes, the rising sun moves up and to the right, while at southern latitudes, it moves up and to the left. Only on the equator does the sun go straight up from the eastern horizon.

• Language: English
• Publisher: IRB Media
• Release date: Jun 4, 2022
• ISBN: 9798822530096

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Insights on Chad Orzel's A Brief History of Timekeeping

Contents

Insights from Chapter 1

Insights from Chapter 2

Insights from Chapter 3

Insights from Chapter 4

Insights from Chapter 5

Insights from Chapter 6

Insights from Chapter 7

Insights from Chapter 8

Insights from Chapter 9

Insights from Chapter 10

Insights from Chapter 11

Insights from Chapter 12

Insights from Chapter 13

Insights from Chapter 14

Insights from Chapter 15

Insights from Chapter 16

Insights from Chapter 1

#1

The Glorious Revolution in England in the late 1600s saw the deposition of the Catholic king of England and Scotland, James Stuart, and his replacement by his daughter, Mary, and her husband, William of Orange. This triggered a number of uprisings in the British Isles, including the Williamite War in Ireland.

#2

The solstice marker at Newgrange, Ireland, is a physical cycle that repeats at regular intervals. It is the appearance of sunlight in the central chamber that provides a clear readout for a physical cycle that repeats at regular intervals.

#3

The sun moves across the sky from left to right, and the earth rotates counterclockwise. From a vantage point above the north pole, the earth rotates counterclockwise, so a day looks like the image on the next page.

#4

The sun follows a different path in the two hemispheres. At northern latitudes, the rising sun moves up and to the right, while at southern latitudes, it moves up and to the left. Only on the equator does the sun go straight up from the eastern horizon.

#5

The shadow-measuring trick determines the angle between straight up at your location and straight up at the spot where the sun is directly overhead, which is almost the latitude of your location. It’s only exactly your longitude on two days a year, the equinoxes in March and September.

#6

There are four special points in the orbital cycle, two of which are obvious: the June and December solstices when the north pole is inclined toward or away from the sun. The other two are March and September dates when the angle between the axis and the earth-to-sun line is 90 degrees.

#7

The effect of the earth’s axial tilt is to change the latitude where the sun is directly overhead at midday. Between March and September, this point is north of the equator, and between September and March, it is south of the equator.

#8

The builders of Newgrange were trying to capture the motion of the sun, which they did by building a passage tomb that was aligned with the shortest day of the year. The tomb is still functioning perfectly today, more than 5,000 years after its construction.

#9

The monument of Stonehenge was built around 2500 BCE, and was completed with five enormous trilithons, two uprights with a lintel across the top, in a horseshoe pattern. The open end faced northeast.

#10

The builders of Stonehenge were neopagans who gathered at sunrise on the summer solstice to see the sun rise next to the Heel Stone, but the trilithon would just as impressively frame sunset on the winter solstice.

#11

The use of solar effects in monumental architecture is not unique to the prehistoric cultures of Britain. Similar markers are found in a wide range of cultures around the world, and many have become famous seasonal tourist attractions.

#12

The idea of a spherical Earth was accepted in classical times, and the first good measurement of its size dates back over 2,200 years, to the Greek scholar Eratosthenes.

#13

Eratosthenes, the Greek mathematician, measured the minimum length of a shadow on the solstice in Alexandria, from which it was easy to calculate