Every year comes the time when many of us change our clocks from summer or summer to winter time. And the usual confusion sets in, is it an hour before or back? Why do we have to change the time? In fact, the EU member states were asked if they would simply skip summer time.
The sun used to tell us the time – but we always had to make corrections to our readings to be effective.
The reason why we have summer time is, for example, that the daylight time is not constant throughout the year – it differs in winter from that in summer ̵
As the year progresses, so does the length of the days, as do the places where the sun rises and sets on the horizon. There are also variations in the position and height of the sun during a day, with the peak height indicating noon.
The knowledge of these markers helped people to create the first sundials that determine the time (by tracking shadows on the dial) thousands of hours from years ago.
But time comes in many definitions. With a sundial you can determine the local solar time at your geographical location. This is very different, considering that the earth is a sphere.
When lunch is in London, the sun is highest in the sky, but much farther east in New York. As a result, longitude becomes important when comparing such times.
Even in the UK, this difference is 40 minutes when comparing the farthest locations from east to west.
The politics of the time
The change in length in the sun The time was used for navigation, but caused a variety of problems in the construction of a rail network in the United Kingdom in the 19th century.
To make sure you know when to expect a train, timetables must be obtained once. At that time, a uniform time was created to ensure that the entire United Kingdom used Greenwich Mean Time (GMT). This idea has been further developed to create the now established time zones.
However, the time zones seem to have been created randomly in some parts of the world. This results mainly from the idea of standardizing times in common commercial and political regions.
For example, most European countries use Central European time, although they easily cover three theoretical time zones. Spain took over the Central European period during the Second World War under Franco's regime to bring the country closer to Germany. This remains true to this day, although the country is exactly the same length as the United Kingdom.
The sun was also long time to set clocks. But only one time had to be marked in time: the middle of the day. This was achieved by Meridian sundials, which have a small opening and a north-south aligned line. If the line is crossed, this is local noon time.
However, this ingenious method had to be corrected as well. The sun does not seem to move across the sky at a constant speed.
Both the elliptical orbit of the earth around the sun and the inclination of the earth's axis against the orbital plane cause the sun to lie above or below its average position all year.
The time that we actually use for our watches assumes a smooth and medium position of the sun, which is why we call it "medium solar time". The offset between these two times is captured by the so-called time equation.
Later we began to adjust our clocks with visual cues, signals via telegraph and later sending time signals via radio. Today we can use GPS.
Having recognized all the complexity of deriving the correct time from the sun's position, the definition of time on atomic clocks (International Atomic Time – IAT) seems perfect.
These are based on the nearly perfectly repeated signal that electrons emit in atoms as they change the energy level, so we do not have to rely on the variable position of the sun.
As a result, we should have solved our problems with what's right. Right time is – we could use an atomic clock instead of Greenwich Mean Time and just add the time zones.
Since 1972, however, we have included the so-called "second second" to maximize sunlight by taking into account small imperfections. Earth rotation, when we measure the solar time in Greenwich. This represents a slow discrepancy between the time measured by atomic clocks and the mean solar time in Greenwich.
Jump seconds are introduced either at the end of June or December when needed. This watch review is carried out by the International Earth Rotation and Reference Systems Service.
The agency uses radio telescopes that are interconnected over extremely long distances, observing very distant objects, called quasars, to measure the exact position and orientation of the earth.
Since 1972 we have added a total of 37 seconds at irregular intervals, which is pretty much. This means that the mere use of atomic clocks is not sustainable. We would end up wrong for half an hour in 700-800 years – eventually we will influence when the darkness sets in.
After all our efforts to find the right time to test the sun and create atomic clocks, we still rely on the sky. Instead of using the sun, we use distant radio sources in our universe observed by astronomers to tell us how much our time is different from the perfect construct measured by atomic clocks.
In the end, we still have time to make sure We define coincidences with our daily experience of day and night and the rhythms defined by the Sun on Earth.
And maybe it's good to keep time as relative. If we want to live on Mars and beyond, we need to create a time when the days and years are different.
This article was published in the conversation by Daniel Brown, Lecturer in Astronomy, Nottingham, Trent University under a Creative Commons license. Read the original article.