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Time
I'm Bruce and this is a talk about time.
Time Is a Social Construct
I'm gonna be talking about years and hours and minutes and days and stuff.
Turns out time is pretty weird, and not a real thing that exists in the universe.
Mostly this is just gonna be a bunch of fun facts about the history of time.
In the Beginning
Since the dawn of time, time was dawn.
People used day/night cycles and seasonal variations to keep track of the passage of time.
Hours
In ancient Egypt, they thought the constellation Sirius was cool because it could be used to predict the flooding of the Nile (very important).
Sirius has 12 stars, so the Egyptians thought it was a cool timey number and divided the night into 12 intervals.
Everyone else in the wider region copied them (Babylonians, Greeks, Romans, etc.)
Unequal Hours
Originally, there were 12 hours of daytime and 12 hours of nighttime.
If you lived near the equator, this works pretty well.
If you don't, it means that a winter daytime hour is shorter than a summer daytime hour.
Where I grew up (Seattle), this means that an hour would be:
- 42 minutes long on December 21 during the day
- 80 minutes long on June 21 during the day
Unequal Hours
Downsides
- The same thing takes a different number of hours in different seasons.
- Need to think about what season it is.
Upsides
- Easy to measure with a sundial.
- Kinda useful to talk about fractions of available daylight time.
- No one wants to do anything during winter, so the hours are correspondingly wimpy.
- Very human.
Minutes and Seconds
- Invented in the Islamic golden age
- First minute division of an hour
- Second minute division of an hour
- 60 is a cool number (thanks Sumerians)
- Is divisible by 2, 3, 4, 5, 6, 10, 12, 15, 20, 30
Calendars Are Hard
People historically kept track of the seasons using an awkward combination of lunar cycles and solar cycles, which was complicated and kept drifting out of sync (not an even number of moon cycles in a year).
- Julius Caesar was a pontifex
- Good for electoral shenanigans
- But had to perform a religious ceremony to adjust the calendar
- Too busy doing imperialism to bother adjusting the calendar
- Got way out of sync
- Invented the Julian Calendar to get out of the job
- Solar calendar, so no drift
- Later Pope Gregory adjusted the calendar
- The "Gregorian Calendar"
Weeks
- 7 days because, uh, 7 celestial bodies I guess?
- Sun, moon, 5 other planets
- Days of the week named for the celestial bodies:
- Saturn day
- Sun day
- Moon day
- Then the Norse got involved somehow
- Tyr's day
- Wotan's day (Odin)
- Thor's day
- Frigg's day (gotta get down on Frigg's day)
Astronomy Sucks as a Clock
Very sloppy, filing a bug report now:
- Can't tell time when it's cloudy
- Daylight hours change seasonally
- Latitude and longitude
- Earth wobbles, so latitude and longitude are also bullshit
- Continental drift
- Not an integer number of lunar cycles in a year
- Not an integer number of days in a year
- 365.2422 is a lame number (not easily divisible)
- Drifts over time because we live in a fallen world
We Can Make Better Clocks
I mean, not at first. Old clocks sucked.
- Water clocks
- Dripping in a bucket at constant-ish time
- Candle clocks
- Put nails in the side of the candle to loudly fall out
Imperialism and Capitalism
Two of the main driving forces for making better clocks were imperialism and capitalism (name a more iconic duo)
Imperialism
- How do we keep time across a world-spanning empire?
- How do you know how far you are across the ocean with no landmarks?
Capitalism
- How do you make workers show up on time?
- How do you make workers work longer?
- How do you keep a train schedule between cities?
Time Zones
Once trains got fast enough, you'd actually notice time differences between cities.
Every city ran on local solar time.
Railroads hated it, so they pushed for the adoption of hour-bracketed time zones.
Synced up with Greenwich Observatory as the standard time.
Time Balls
Greenwich Observatory had a time ball that they dropped at exactly 1pm.
Ships saw it drop and set their clocks accordingly.
Some random guy saw one and thought it would be a cool party event for the NYT opening a new HQ in Times Square in 1905.
Clocks and Watches
Invented for navigation and religious purposes, repurposed for industrial factories.
Previously people came in to work when the sun came up, left when the sun went down.
Factory owners introduced clocks to remove all slack from their workers' lives.
Major labor clashes over workers being fired for not arriving at exactly the right time, but also factory owners cheating the clock.
Workers forbidden from having their own watches.
What Is Time?
Once clocks started getting accurate, it raised the question: "what is a second?"
Not: 1/(12 * 60 * 60)th of a day
Earth's rotation changes (tidal deceleration).
The French standardized the definition of a second:
- Originally based on an average day length
- Then based on the year length of 1900 (?!) "ephemeris second"
- Then bombarding ammonia with radiation till it radiates
- Then caesium radiation frequency (atomic clocks)
- In 2022, redefined to use optical clocks
Problems for the Future
Oh god, there's relativity too.
- Synchronizing time across planets is hard
- Time is subjective
- Time dilation
- Your time is not my time.
- Relativity of simultaneity
- What even is "now"?
I give up.
Time's Up
Okay I'm done.