I read in a wiki article about clocks, and whenever the article mentioned a new development in clock technology, it would talk about how the new clock "erred by less than 5-10 seconds," etc.
How was there a universal standard for timekeeping before satellites? And how did we come up with a universal standard for "this is how long an hour is, and this is the exact time 2pm is" and so on.
Sorry if this is a confusingly worded question, I wasn't sure exactly how to articulate what I meant here.
There are two questions here :
The division of the day into 24 hours is surprisingly ancient and dates back to Ancient Babylonia. 12 and 24 were chosen because they were easily divisible into 1,2,3,4,6,8 a significant advantage when using a number system that becomes complicated with fractions.
Likewise 60 minutes in an hour was an easier number for astronomers to work with and divide than, for example, 50 or 100 would be.
As the astronomical learning spread west to the Mediterranean and east to India, this way of dividing the day went with it, becoming adopted by Greece and Rome and thereby into all of Europe.
The second question is how a time was agreed on. Well it wasn’t until the invention of the railways and the telegraph made uniform time desirable and possible. Until then everywhere determined their own time by observing local noon, which would be 20 minutes earlier in London than in Exeter, and 35 minutes earlier than in Penzance. Local noon was determined by sundial or meridian line ( there is a fine example of a local meridian line in the historic Bromley House library in Nottingham inlaid in brass on a reading room floor. It is, of course since the standardisation of time consistently 6 minutes slow).
Local noon in cities was often marked by a time marker, a tradition that continues in many British cities - the ball at the Greenwich observatory in London, the noon cannon in Edinburgh, a siren in Sheffield and many others.