Railways and Zones

The History of Timekeeping

Course 2 · Chapter 7 · Railways, Time Zones and the Modern Clock

Until the nineteenth century, noon was where the Sun said it was. Because the Sun reaches its highest point a little later as you go west, local noon in Edinburgh came about twelve and a half minutes after noon in London (check the figure), and every town kept its own time. That was no trouble when the fastest way to travel was a horse. When railways arrived, running a timetable across a country of many local times became a puzzle that only a single shared time could solve. This chapter follows that change, the creation of time zones, and the arrival of the quartz and atomic clocks that now stand behind every phone.

Local Time and the Railway Problem

Under local mean time, a town set its public clock by the Sun, or by a sundial adjusted for the equation of time (Chapter 2). A traveller going from Edinburgh to London would find their watch wrong on arrival by a few minutes, which mattered little before the train.

Timetables

A timetable showing the same departure for every station had to say whose time it used. Some early timetables listed several, which confused passengers.

Safety

Trains on single lines, running to different clocks, risked collision. Accurate shared time was a safety matter and not just a convenience.

Cost

Missed connections and arguments between companies were expensive, which gave the railways a strong reason to agree.

Railway Time in Britain

The Great Western Railway is generally credited with adopting London time along its line from 1840, and other railways followed over the next few years (check the dates). The telegraph, which ran alongside the tracks, allowed a time signal to be sent from Greenwich to stations across the network (check). By the late 1840s most British railways ran on "railway time", which was Greenwich Mean Time, and by 1855 the great majority of public clocks had followed (check).

The law catches up Railway time was convenient but had no legal force at first, and some towns resisted, notably those that had their own tradition of time. In 1880 a law made Greenwich Mean Time the legal time throughout Great Britain (check the date and wording). Edinburgh's clocks therefore moved a few minutes from the Sun's time to London's, and a city that had set its clocks by the Sun for centuries now set them by Greenwich.

Time Zones and the Prime Meridian

Large countries faced the problem on a bigger scale. The United States and Canada had dozens of local railway times in the 1870s, and the railways there agreed on a system of time zones in 1883 (check). The proposal of a worldwide system of zones is often linked to the Canadian railway engineer Sandford Fleming, who campaigned for it (check).

Step	What happened
1884	The International Meridian Conference in Washington chose the meridian through Greenwich as the world's prime meridian (check the vote and the details)
Zone system	The world divided into zones about 15 degrees wide, an hour apart, though real zones follow borders and politics
Adoption	Countries took up standard time over the following decades, at different speeds
Date line	A line roughly opposite Greenwich where the calendar date changes by a day

Daylight saving The summer shift of the clocks was introduced in Britain in 1916 during the First World War to save fuel (check). The idea is often credited to William Willett, a builder, who proposed it in 1907 (check). Scotland's long summer evenings and dark winter mornings have made the topic a recurring argument ever since.

Quartz and Atomic Clocks

The twentieth century changed the foundation of timekeeping. Previously, the Earth's rotation was the standard and clocks were checked against the stars. Two new technologies took over as the reference.

Quartz. A small crystal of quartz vibrates at a very steady frequency when an electric current passes through it. Quartz clocks were developed in the 1920s and 1930s (check), and became cheap enough for wristwatches from the 1960s and 1970s (check). A good quartz watch is accurate to a few seconds a month.
Atomic clocks. Atoms of certain elements, such as caesium, absorb and emit radiation at an extremely precise frequency. The first practical caesium clock was built in England in the 1950s (check), and in 1967 the second was defined by caesium's frequency rather than by the Earth's turning (check). The best modern atomic clocks lose or gain about a second in many millions of years or better (check).

The Earth is not a perfect clock Atomic time proved steadier than the Earth, whose rotation slows slightly and varies from year to year. To keep civil time in step with the Sun, an extra "leap second" is occasionally added to the official time scale. This is the topic of Chapter 8.

Exercises

Exercise 1

Edinburgh is about 3 degrees west of Greenwich. Using 4 minutes of time per degree, work out how far Edinburgh's local solar time was behind Greenwich Mean Time, and explain why this mattered for railways.

→ Solution

Exercise 2

A train leaves London at 09:00 and takes 8 hours to reach a city 30 degrees west. The traveller's watch is still on London time. What does a local clock, running on solar time, read when they arrive?

→ Solution

Exercise 3

List the three main drivers (technology, safety and money) that pushed Britain to a single time, and for each give one sentence on how it applied. Then write one sentence on whether you think a law was necessary.

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Quick Reference

Local time: each town kept the Sun's time; 4 minutes per degree of longitude
Railway time: London time spread along the railways from the 1840s
Law: Greenwich Mean Time made legal in Great Britain in 1880
Zones: 1884 meridian conference; zones about 15 degrees wide
Daylight saving: introduced in 1916
Quartz: a vibrating crystal; cheap and accurate
Atomic: the second defined by caesium in 1967
Check: dates of adoption, the conference details, named campaigners, accuracy claims

Next chapter: Capstone: Time Today, which covers how time is kept now, leap seconds, satellite navigation and the story as a whole.