History of Time

This article discusses time, space and historical views of them and how societies of understood and measured them

Historical Cosmologies

how socieites have understood the earth

• Egyptian Cosmology

>> here for a list of historical cosmology

Earth, Sun, & Moon

• cyles of sun, moon, and the stars observed by earliest mankind
• early time measured by movement of the heavenly bodies

Seasons

• Summer and Winter EQUINOX >> largest tilt
• Spring/ Autumn SOLSTACE >> at the equator

Latitude

• the parallels : they stay parallel to each other across the earth
• easily measured by figuring out the date and the daily apex of the sun...mark sun’s height against the tilt of the earth...

Longitude

• not easiliy measured
• where Latitude is fixed by nature, Longitude is arbitrary, man-made measurement
• Columbus “sailed the parallel” but was totally unaware of his longitude

>> todo: organize the below notes: They way to measure longitude is to know how many hours from a fixed point... Earth spins in 24 hours 1 hour = 1/24th the spin of the earth, or 15 degrees >> or: 1 hour difference = fifteen degrees of longitude each hour away from the home clock = 15 degrees of longitude >>measurement taken at high noon >>15 degrees = 1,000 miles at the equator >> the time difference is always regular, but the no. of miles depends upon the latitude

Admiral Clowdisley: 1707 - five warships going north after victorious fights in Gibaltrer - fog for twelve days - hit islands, lost 4 ships, 2000 men - Clowdisley washed ashore, woman stole his emerald ring and killed him >>sailor warned they wree on the wrong path... put to death for insubordination

Longitude Act of 1714: £20,000 for a solution

1741: Centurion - sailed around Cape Horn (S. America) (Good Hope = S Africa) - 58 days of wind, sleet, rain, and snow - scurvy - Capt. figured he’d gone 200 miles westward of Tierra del Fuego - 1st clear night, he steered north to a known island with fresh water - hit land, and it was EAST, Cape Noir... on edge of Tierra del Fuego >>currents had turned him around>>.sailed backwards - headed west - finally hit a latitude he wanted.. but didn’t know longitude >>go east or west? - went west, then turned around>> wrong way -- hit wall of coast along Chile >>turned around again, and finally hit the right island - 250/500 sailors died, meanwhile � Longitude solutions: Dead reckoning >.throw log over and see how long it takes to drift away bark of the dog buoys sounding the hour across the ocean compasses ... problems with true north vs. magnetic north ..inconsistent ... not relative

Stars: problems = cloud cover waves mapping accurately

Moon = best bet Measure it’s locaion against het sun... but it’s gone several days / month hard to see several days / month due to daytime trajectory

Star/Moon measurements were okay on land... stable, time, wait out weather, etc. Galileo’s solution >> re-worked maps... older maps underestimated distances and exaggerated outlines of nations >> Louis XIV: “complained that he was losing more territory to his astronomers than to his enemies”

Clocks: problems = - waves - temperature changes - accuracy

Harrison clocks >>get web photos

Calendars

• measurement of time based upon social need by measuring heavenly bodies

Paleolithic calendars

• • • 13,000 BC cave painting depicting cycles of the moon
• Neolithic
  • emphasis upon growing seasons
    • see Stone Henge as solar calendar

Babylonian Calendar

• • divided the sky into 360 degrees based on the circular path of the sun divided by the days in the year
    • 1 degree = 1 hour
    • created the Zodiac

Egyptian calendar

• • based on star Sirius (they recognized some planets)
  • 1st of the year = day of the Nile flooding
  • 360 days x 12 months x @ 10 days
  • 12 month solar year
  • adopted by the Romans, used by Copernicus

Greek Calendar

• Hipparchus:
  • applied Greek astronomy (sun, moon, stars, planets and their motions) and mathematics
    • earlier Greek astronomers and mathematicians, such as Eudoxus of Cnidus, established these concepts
    • that the solar year was 365.24 days was already understood by them
    • Hipparchus measured the year more exactly to 365.24667 days or 365 days, 5 hours, 55 minutes, 12 seconds
  • he also identified the "procession of the equinoxes"
    • = he understood that earth is not an exact sphere
    • and that the earth changes its rotation angle slightly, estimating it at 1 degree change per century
    • thus he identified the difference between:
      • "solar" or "tropical" year = the time for the earth to rotate around the sun as measured by equinoxes or solstices (i.e. in relation to the sun)
      • "sidereal" year = the time for the earth to rotate around the sun as measured against the stars, which is impacted by the "procession of the equinoxes"

Roman calendar

• 10 lunar months: from Spring moon in March to late December... 300 days
  • 2 (modern) months ignored because it was without meaning to them
    • Romans ignored them
  • but this system caused confusion
  • so it was adjusted by Julius Caesar, Caesar Augustus, and others to bring regularity
    • February was shortened to 28 days, with an additional day added every 4 years (29 days)
      • the 29th day was called "Bissectus"
    • Caesar Augustus added month names for Julius Caesar (July) and himself (August) thus using the calendar for propaganda and authority

Gregorian calendar

• 1582

Clocks

• measurement of time based upon dailiy position of sun
• >> todo

Early clocks

• Sundial
  • Clepsydra: drips of water during the night... measuring the flow of water from one container to another
  • Hour glass/ Sand glass
  • 1st accurate clock (pendulum) by Christian Huygens in 17th century
  • Han from island off China: had 12 day months...

• European time
  • hours & seconds
    • per "Brunelleschi's Dome" p. 51,
    • "hora" latin for prayer
    • liturgical hour was divided in four parts of ten minutes, with each minute divided into forty "moments"
  • by 1400 hours were divided into 60 minutes
    • 60-minute hours used to measure work times, such as on construction of Duomo in Florence
    • more precise measurement reflected that "pace of life was increasing"
      • source: "Bruneleschi's Dome" p. 51

Time, Distance, Movement & Communication

• see main article Movement
• time measure by distance
• defined by geography & distances
• technological advance is to overcome barriers to movement of geography and distance

Forms of Human Movement

• walking / running
• water
  • sail
• animal propulsion
  • domestication of animals for transport
• mechanized propulsion
• communication across distance was a function of movement
  • writing
  • transportation revolutions speed communciation
• modern communications revoluation
• speed of correspondences measured by distance (letter-writing)
• telegraph revolutionizes abiltity to send messagaes over distance instaneously