In the absence of modern timekeeping devices, humans have relied on celestial bodies for millennia to tell the time. The sun, with its predictable diurnal cycle, has been an indispensable guide for navigation and timekeeping. Determining the time by the sun, also known as solar timekeeping, is a skill that transcends cultures and time periods, and it continues to fascinate adventurers, historians, and nature enthusiasts alike. Embark on a journey to unravel the ancient art of telling the time by the sun, a timeless skill that connects us to our ancestors and the natural world.
The fundamental principle behind solar timekeeping lies in the earth’s rotation on its axis. As the earth rotates, different parts of the planet face the sun, resulting in the cycle of day and night. The position of the sun in the sky, therefore, changes throughout the day, providing a reference point for timekeeping. To determine the time, one must observe the sun’s position relative to the horizon or other fixed landmarks. Various methods have been devised to interpret the sun’s position, including using sundials, shadow sticks, and even the human body as a timekeeping tool.
Understanding the concept of solar noon is crucial for accurate timekeeping. Solar noon occurs when the sun reaches its highest point in the sky, which varies depending on one’s latitude and the time of year. By observing the sun’s position relative to solar noon, one can estimate the time of day. For instance, if the sun is halfway between the horizon and solar noon, it is approximately 9 a.m. or 3 p.m. By further dividing the time between solar noon and sunrise or sunset into equal intervals, one can refine the time estimate. While it may not provide the precision of modern timekeeping methods, solar timekeeping offers a profound connection to the natural rhythms of the earth and the sun.
The Sun’s Daily Path
To understand how to tell the time by the sun, we must first understand the sun’s daily path. The sun’s daily path is the apparent path that the sun takes across the sky each day. As the earth rotates on its axis, the sun appears to move from east to west. The sun’s daily path is affected by its declination, which is the angle between the sun’s rays and the equator. The sun’s declination changes throughout the year, reaching its maximum in the summer and its minimum in the winter.
When daylight saving is in effect, the clock is advanced one hour, which means that the sun will appear to rise and set one hour later than it would at standard time. Therefore, to determine the time using the sun when daylight saving is in effect, you will need to adjust the time you read from the sun by one hour.
The sun’s daily path can be divided into four main periods:
| Period | Time | Sun’s Position |
|---|---|---|
| Sunrise | 6:00 AM | Rising in the east |
| Noon | 12:00 PM | Highest point in the sky (directly overhead) |
| Sunset | 6:00 PM | Setting in the west |
| Midnight | 12:00 AM | Below the horizon |
The sun’s position in the sky can be used to estimate the time of day. For example, if the sun is halfway between the horizon and the zenith, then it is approximately 9:00 AM or 3:00 PM.
Determining the Cardinal Directions
To determine the cardinal directions using the sun, you’ll need to know the following:
- The sun rises in the east and sets in the west.
- At noon, the sun is directly overhead in the northern hemisphere (south of the equator) and directly below in the southern hemisphere (north of the equator).
- The shadow of an object points away from the sun.
Knowing these basic facts, you can follow these steps to find the cardinal directions:
- Place a stick or other straight object in the ground.
- Mark the tip of the stick’s shadow on the ground.
- Wait for a few minutes and mark the new tip of the shadow.
- Draw a line between the two marks. This line represents an east-west line, with the first mark representing west and the second mark representing east.
- Stand with your feet on the east-west line, facing east (towards the first mark). Your left hand will be pointing north, and your right hand will be pointing south.
| Time of Day | Shadow Direction |
|---|---|
| Morning | West |
| Noon | Straight down |
| Afternoon | East |
Using a Stick or Shadow to Track Time
This is perhaps the most straightforward method of telling time with the sun. By placing a stick or other object vertically in the ground, you can observe the length and direction of its shadow throughout the day. The sun’s movement from east to west causes the shadow to change in length and rotate around the stick.
Morning: As the sun rises in the east, the shadow cast by the stick will be long and point towards the west. The shadow will gradually shorten and rotate clockwise as the sun moves higher in the sky.
Noon: When the sun is directly overhead (around noon), the shadow will be at its shortest and will point directly down. This is the moment when the sun is highest in the sky and can be used as a reference point for determining midday.
Afternoon: After noon, the sun continues to move west, and the shadow of the stick will begin to lengthen and rotate counterclockwise. The length of the shadow will continue to increase as the sun sets.
To estimate the time of day using this method, observe the following general guidelines:
| Shadow Length | Approximate Time |
|---|---|
| Short and pointing directly down | Noon |
| Short and pointing slightly away from the sun | Late morning or early afternoon |
| Long and pointing away from the sun | Early morning or late afternoon |
| Long and pointing towards the sun | Evening or early morning |
Note that these guidelines are approximations and may vary slightly depending on your location and the time of year.
Creating a Sun Dial
A sun dial is a simple device that can be used to tell the time by the sun. It consists of a flat surface, called a face, with a pointed stick, called a gnomon, sticking out of it. The gnomon casts a shadow on the face, and the position of the shadow indicates the time of day.
To create a sun dial, you will need the following materials:
- A flat piece of wood or cardboard
- A pointed stick
- A protractor
- A compass
- A marker
Once you have gathered your materials, follow these steps to create your sun dial:
- Draw a circle on the flat piece of wood or cardboard. This circle will represent the face of the sun dial.
- Mark the center of the circle. This point will be the center of the gnomon.
- Use the protractor to measure and mark the following angles on the circle: 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees, and 90 degrees. These angles will represent the hours of the day.
- Use the compass to draw a line from the center of the circle to the 12 o’clock mark. This line will represent the noon line.
- Insert the pointed stick into the center of the circle, so that it is perpendicular to the face of the sun dial. The stick should be long enough so that it casts a shadow on the face of the sun dial at all times of the day.
Hour Angle 12:00 PM 0° 1:00 PM 15° 2:00 PM 30° 3:00 PM 45° 4:00 PM 60° 5:00 PM 75° 6:00 PM 90°
The Equation of Time
The equation of time, related to the Earth’s elliptical orbit around the Sun and the tilt of its axis, complicates the relationship between solar time and standard time. The true solar day (the time it takes for the Sun to return to the same spot in the sky) varies slightly from the mean solar day (the average length of a day throughout the year). This variation is known as the equation of time, which can be either positive or negative.
The table below shows the equation of time for various days throughout the year:
| Date | Equation of Time |
|---|---|
| January 1 | +7 minutes |
| March 1 | -14 minutes |
| May 1 | +3 minutes |
| July 1 | -6 minutes |
| September 1 | +10 minutes |
| November 1 | -16 minutes |
To determine the correct solar time, the equation of time must be added or subtracted from the standard time depending on the time of year. For example, on January 1, when the equation of time is +7 minutes, the solar time will be 7 minutes ahead of the standard time. Conversely, on July 1, when the equation of time is -6 minutes, the solar time will be 6 minutes behind the standard time.
Seasonal Variations in Sun Position
The sun’s position in the sky varies throughout the year due to the tilt of the Earth’s axis. As a result, the length of the day and the time of sunrise and sunset change depending on the season.
In the Northern Hemisphere, the sun reaches its highest point in the sky during the summer solstice (around June 21st). During this time, the days are longest and the sun rises and sets at a higher angle.
In contrast, during the winter solstice (around December 21st), the sun reaches its lowest point in the sky. The days are shortest during this time, and the sun rises and sets at a lower angle.
In addition to the solstices, the equinoxes (around March 20th and September 22nd) mark the days when the sun crosses the celestial equator. On these days, the day and night are equal in length all over the world.
The following table summarizes the seasonal variations in the sun’s position for different latitudes in the Northern Hemisphere:
| Latitude | Summer Solstice | Winter Solstice | Equinoxes |
|---|---|---|---|
| 0° (Equator) | Sun overhead | Sun overhead | Sun directly east and west |
| 30° | Sun 78° above horizon | Sun 22° above horizon | Sun 63° above horizon |
| 60° | Sun 47° above horizon | Sun 13° above horizon | Sun 37° above horizon |
| 90° (North Pole) | Sun 24 hours above horizon | Sun 24 hours below horizon | Sun 12 hours above and 12 hours below horizon |
Atmospheric Refraction
Atmospheric refraction is the bending of light as it passes through the atmosphere. This is because the atmosphere is made up of layers of air with different densities, and light travels faster through less dense air. As a result, light from the sun is bent towards the earth, which makes the sun appear higher in the sky than it actually is. This effect is most noticeable at sunrise and sunset, when the sun is near the horizon. Atmospheric refraction also causes the stars to appear to twinkle.
Sunset
Sunset is the time of day when the sun disappears below the horizon. This occurs because the earth is rotating on its axis, and the sun is moving in the opposite direction. As the sun sets, it appears to move closer and closer to the horizon until it finally disappears. The time of sunset varies depending on the time of year and the latitude of the observer.
Determining the Time by the Sun (Steps 9)
- Find a clear area with a good view of the horizon.
- Identify a vertical object, such as a tree or a building.
- Mark the shadow cast by the object.
- Wait 15 minutes and mark the shadow again.
- Measure the distance between the two marks.
- Divide the distance by the length of the shadow at sunset.
- Multiply the result by 12 to get the number of hours before sunset.
- Subtract the number of hours from 12 to get the time of sunset.
- Add 1 hour for daylight saving time (if applicable).
For example, if the distance between the two marks is 10 feet and the length of the shadow at sunset is 5 feet, then the number of hours before sunset is 10 / 5 = 2. Multiplying this by 12 gives 24, which is the number of hours before sunset. Subtracting this from 12 gives 12 pm, which is the time of sunset. Adding 1 hour for daylight saving time (if applicable) gives 1 pm as the time of sunset.
Practical Application in Outdoor Activities
The skill of telling time by the sun can be incredibly useful in various outdoor activities, especially when a watch or other timekeeping device is unavailable. Here’s how you can apply this knowledge in different scenarios:
Camping and Hiking
When camping or hiking, knowing the time can help you plan your activities, set up camp before nightfall, and manage your energy levels more efficiently.
Hunting and Fishing
For hunters and fishermen, timing is crucial. Determining the time by the sun can help you locate game, predict feeding patterns, and maximize your chances of success.
Boating
When boating, it is essential to be aware of the time for safety reasons. It can help you avoid potential hazards such as sunset and darkness, ensuring a safe return to shore.
Land Navigation
Telling time by the sun can complement land navigation techniques. By knowing the time, you can estimate your distance traveled and maintain your bearings more accurately.
General Outdoor Activities
For any outdoor adventure, knowing the time can help you plan your activities, regulate breaks, and adjust to the changing conditions of sunlight.
How to Tell the Time By the Sun
You do not always need a watch or mobile phone to tell the time. If you have a clear view of the sun, you can use its position in the sky to estimate the time of day. Remember to adjust the results to take into account whether your country uses daylight saving time.
To tell the time of day with the sun, you need a stick and a flat surface. On the flat surface, mark the position of the shadow from your stick every hour starting from sunrise until sunset. Label each position with the corresponding time. Once you have a sun clock, you can use it to tell time throughout the day.
People Also Ask
How accurate is telling the time by the Sun?
The accuracy of your sundial depends on the precision of your measurements and the time of year. Generally, you can expect accuracy to within 15 minutes, but this can vary.
Can I tell the time by the Sun at night?
No, you cannot tell the time by the Sun at night. The Sun is below the horizon, so you cannot see its shadow or position.
How does a sundial work?
A sundial works because the Earth rotates on its axis. As the Earth rotates, different parts of the planet are exposed to the Sun. The Sun’s position in the sky changes throughout the day, causing shadows to move. By measuring the length and direction of the shadow, you can determine the time of day.
