Probably, the most familiar question is “What time is it?” Well today, there are clocks everywhere that will tell you about the exact time. But, have you ever wondered how you can tell time without using a clock or watch and by just relying on the sun? Some of you might find it hilarious, yet did you know that in the past, people only rely on the sun to tell the time?
The first kind of clock was actually sundial where you will see the shadow of the object moves as the sun moved. The object, which casts a shadow in sundial is known as Gnomon. The shadows that are made by the sun move as hours go by.
What You Should Know about Sundial?
Sundial is considered as the oldest known device for measuring time. This is based on the fact that the object’s shadow will move from the object’s one side to the other as sun moves from the direction of east to the west during the day.
Sundial basically consists of plane and gnomon. The face of the dial is divided into hours and there are times quarter and half hours. Gnomon is the flat metal piece that’s set in the dial’s corner. This points toward North Pole in Northern Hemisphere and towards the Southern Hemisphere’s South Pole. The Gnomon’s upper edge should slant upward from dial face at the angle that’s equal to the latitude of sundial’s location.
The sundial is an hour off during daylight in the summer when the clocks are reset. Aside from that, standard time or clock time will vary from the time provided by the sundial since it’s kept uniform across the time zones. Every time zone varies from its neighbors by a full hour more in Alaska and China. In every zone, the sundial time matches the clock time at a geographical longitude. However, correction should be added and must be proportional to the difference in the longitude from locations where the time of sundial is exact.
Sundial time and local time were the same up to the 2nd half of the nineteenth century and every city kept its local time and it is still the case when it comes to Saudi Arabia. In the standard time of the US, it was introduced by railroads to set up uniform timetables.
Video by John Shiltz on how a Sundial Works
There is also a small periodic variation that exists, which is known as equation of time, which amounts to most to about fifteen minutes and contributed by 2 factors. The first factor is that the motion of the Earth as it revolves around the sun is an ellipse with slightly variable speed according to the Second Law of Kepler’s. The second factor is ecliptic, which is inclined by about 23.5 degrees to the Earth’s equator that means the projection of apparent motion of the sun is reduced near these two’s crossing points.
Creating a sundial is easy. If you want to keep track of time during your outdoor adventure and you don’t want to use a watch or clock to know the time, a sundial may come in handy. But, there are also some tricks that you could do instead of bringing a sundial with you.
3 Simple Tricks to Use the Sun to Tell the Time
- Use Fingers to Calculate the Remaining Sunlight
If your smartphone fails to give you the time, there are some digits you may use to tell the current time and that is your fingers. Start by standing under the sun, extend your arm in front of you and rotate your wrist so that your palm will face horizontally. You should close your fingers together. Then, align your little finger with the horizon.
To reach the sun, count the finger widths. Depending on the time of the day and season, you might have to continue stacking your hand over the other hand to keep count. 4 finger width show an hour of sunlight.
- Tell Time Through Tracking the Position of the Sun
You do not have to be a Boy Scout or Girl Guide to know that when sun is sitting at the center of the sky, it is around noon and when the sun rises from the east and always sets in the west. These are the basic things that most of you know, yet typically these are not enough to tell time with any level of precision. For you to get an accurate reading from the sun, you will need to have some ideas about the daylight hours in your location, provided the season. For instance, if you are in Winnipeg, the usual June day casts sixteen daylight hours. With that in mind, you may divide the sky using an imaginary arc in the direction of east to west, which consists of equal sixteen segments to represent the best possible time. In this case, sunrise could be due about 5:30 am from the east and sunset will be 9:30 pm from the west.
- Follow Your Shadow
The last thing to be afraid of when you’re wandering in a remote place is your shadow. As some of you might have noticed, one’s body casts different shadows as the day passed by. The sun’s position in the sky overhead causes the shadows to be shortest at noon time and the longest during late evening and early morning. What is more is that they move and once you can manage to find the north, you may use your body as your makeshift sundial, reading the length and direction of your shadow for you to estimate the time of the day.
Telling time with the sun isn’t hard. If you know how to do it properly and by following those tricks above, you can be assured that your outdoor experience will surely be more exciting than you expected without the need for you to watch on the clock or any timepiece each time you wander around.
Have you learn on how to use Sun to tell the time? Comments below if you want to share some experiences using Sun to tell the time.