diff --git a/time/in-time.webp b/time/in-time.webp new file mode 100644 index 0000000..65a8992 Binary files /dev/null and b/time/in-time.webp differ diff --git a/time/time-ball.webp b/time/time-ball.webp new file mode 100644 index 0000000..d4ba18f Binary files /dev/null and b/time/time-ball.webp differ diff --git a/time/time.md b/time/time.md new file mode 100755 index 0000000..4668156 --- /dev/null +++ b/time/time.md @@ -0,0 +1,261 @@ +#!/bin/env slides + +# Time + +![sxiv -sf -f](time.webp) + +I'm Bruce and this is a talk about time. + +-------------------------------- + +# Time Is a Social Construct + +![sxiv -sf -f](in-time.webp) + +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 + +![sxiv -sf -f](time-ball.webp) + +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. diff --git a/time/time.webp b/time/time.webp new file mode 100644 index 0000000..b4f8dbe Binary files /dev/null and b/time/time.webp differ