Timekeeping
History
18 rabbit holes · 11 people exploring
Common starting questions
- How small a height difference can an atomic clock detect?
- Why was longitude so hard to find at sea?
- Does GPS really need relativity?
- What did the Antikythera mechanism do?
Rabbit holes
- a second is 9,192,631,770 wiggles of a cesium atom
Dev Malhotra · 5 sources
- the theory that 297 years of the middle ages never happened
It's nonsense (astronomical records, Chinese chronology, and dendrochronology all disagree), but tracing exactly WHY it's nonsense was a great tour of how calendars work.
Yuki Tanabe · 6 sources
- a Roman hour wasn't always the same length
Jonas Becker · 5 sources
- leap seconds are being retired
Ilya Smirnov · 4 sources
- navigators used to shoot the stars through a bubble in the roof of the plane
Saw a photo of a B-29 with a little glass dome on top and had to know what it was for. Ended up back at Harrison's clocks, as one does.
Moira Gallagher · 6 sources
- clocks can now see time run differently across a millimeter
Quinn Harlow · 6 sources
- how a clockmaker solved longitude
Moira Gallagher · 7 sources
- why time is so hard in distributed systems
Alistair Grant · 5 sources
- a clock built to tick for 10,000 years
Inside a mountain in Texas. The century hand advances once every 100 years. The cuckoo comes out once every millennium.
Rosa Delacroix · 4 sources
- why 60 minutes and 24 hours
60 divides by 2, 3, 4, 5, 6, 10, 12, 15, 20 and 30. The Babylonians had good taste. Decimal time is the funniest failed reform.
Yuki Tanabe · 4 sources
- Big Ben is adjusted with old pennies
Stacking a penny on the pendulum changes its effective length and speeds the clock up by about 0.4 seconds a day.
Alistair Grant · 4 sources
- the Swiss railway clock's second hand pauses at 12
It sweeps around in about 58.5 seconds, waits at 12 for the minute pulse from the master clock, then all the station clocks jump together. Apple got into trouble for using the design.
Hannah Kim · 3 sources
- in 1752 Britain skipped 11 days
September 2 was followed by September 14. The 'give us our eleven days' riots are probably a myth, partly traced to a Hogarth painting.
Alistair Grant · 4 sources
- daylight saving was proposed by a bug collector
Franklin's 'proposal' was a joke essay about Parisians wasting candles. The actual first proposal was a New Zealand entomologist in 1895.
Yuki Tanabe · 4 sources
- how GPS has to correct for relativity
Alistair Grant · 5 sources
- the year 2038 problem
At 03:14:07 UTC on 19 January 2038, a signed 32-bit Unix timestamp overflows and wraps to 1901. Most modern systems moved to 64-bit time, but embedded stuff lives a long time.
Callum Reid · 4 sources
- railways invented time zones
Kate Lindqvist · 5 sources
- The Antikythera mechanism
Alistair Grant · 6 sources