Time is an elusive concept, a construct we humans have created to measure the passage of days and nights. But what if you were stranded without a watch or any other timekeeping device? Fret not, for nature provides an ancient and reliable clock: the sun.
The sun’s apparent journey across the sky, from east to west and back again, has guided humans for millennia. By observing the sun’s position, we can estimate the time with surprising accuracy. This technique, known as solar timekeeping, relies on the interplay between the sun’s movement and the Earth’s rotation.
To tell the time by the sun, find an unobstructed view of the horizon and observe the sun’s position. If the sun is just above the eastern horizon, it’s likely around 6 or 7 AM. As the sun rises higher in the sky, the time advances. By noon, the sun will be at its highest point, directly overhead. From noon onwards, the sun will gradually descend towards the western horizon. When the sun meets the horizon, it’s approximately 6 or 7 PM.
The Height of the Sun
The height of the sun in the sky is one of the most obvious ways to tell what time it is. As the Earth rotates on its axis, the sun appears to move from east to west. The higher the sun is in the sky, the closer it is to noon, and the lower it is, the closer it is to sunrise or sunset.
The angle of the sun can be measured using a protractor or a sundial. A protractor is a tool that measures angles, and it can be used to measure the angle between the horizon and the sun. A sundial is a device that uses the shadow of a stick to tell the time. The length of the shadow changes throughout the day, and it can be used to determine the angle of the sun.
The following table shows the approximate height of the sun in the sky at different times of day:
| Time of Day | Angle of the Sun |
|---|---|
| Sunrise | 0 degrees |
| 9:00 AM | 45 degrees |
| Noon | 90 degrees |
| 3:00 PM | 45 degrees |
| Sunset | 0 degrees |
The Position of the Sun
The position of the sun in the sky can give you a good indication of the time of day. In the Northern Hemisphere, the sun rises in the east and sets in the west. At noon, the sun is at its highest point in the sky, directly overhead.
The sun’s position changes throughout the day as the Earth rotates on its axis. The following table shows the approximate position of the sun in the sky at different times of the day:
| Time of Day | Sun’s Position |
|---|---|
| Sunrise | East |
| 10:00 AM | Southeast |
| Noon | Overhead |
| 2:00 PM | Southwest |
| Sunset | West |
The sun’s position can also vary depending on your latitude. For example, the sun is higher in the sky at the equator than it is at the poles.
Shadows and Their Length
The length of a shadow can indicate the time of day, provided it’s a sunny day. However, the relationship between shadow length and time of day is not linear. The angle of the sun relative to Earth’s surface changes throughout the day, which affects the length of a shadow. Generally, shadows are:
- Shortest around noon
- Longest at sunrise and sunset
If you know the time of sunrise and sunset, you can estimate the time of day based on the length of a shadow. However, it’s essential to note that this method is only an approximation and can vary depending on factors such as the latitude and topography of your location.
Noontime Shadow
The shortest shadow of the day occurs around noon. This is because the sun is directly overhead at noon, casting a shadow that is directly beneath the object. The time at which the shadow is shortest can vary slightly from noon, depending on your location and time of year.
The following table shows the typical length of a noontime shadow for different latitudes:
| Latitude | Noontime Shadow Length |
|---|---|
| 0° (Equator) | 0 feet |
| 30° | 1/2 the height of the object |
| 45° | 3/4 the height of the object |
| 60° | Equal to the height of the object |
The Analog Clock Method
The analog clock method is a simple way to tell time using the sun. It works by comparing the position of the sun in the sky to the hands of an analog clock. To use this method, you will need to know the time of sunrise and sunset for your location. You can find this information online or in a local almanac.
Once you know the time of sunrise and sunset, you can use the following steps to tell time using the sun:
- Face the sun.
- Imagine an analog clock in the sky, with the sun at the center.
- Divide the sky into 12 equal parts, with the sun at the 12 o’clock position.
- The hour hand of the imaginary clock will point to the hour that it is. For example, if the sun is at the 3 o’clock position, it is 3 o’clock.
There are a few things to keep in mind when using the analog clock method.
- This method is only accurate within about 15 minutes.
- It does not work well in cloudy weather.
- It is not as accurate in the winter as it is in the summer.
Despite its limitations, the analog clock method is a simple and easy way to tell time using the sun. It is a useful skill for anyone who spends time outdoors.
Determining the Time Using the Hour Hand
To determine the time using the hour hand, you need to know the following:
- The time of sunrise for your location.
- The time of sunset for your location.
Once you have this information, you can use the following table to determine the time:
| Sun’s Position | Time |
|---|---|
| Sunrise | 6:00 AM |
| 9:00 AM | 9:00 AM |
| 12:00 PM | 12:00 PM |
| 3:00 PM | 3:00 PM |
| Sunset | 6:00 PM |
For example, if the sun is at the 9:00 AM position, it is 9:00 AM. If the sun is between the 9:00 AM and 12:00 PM positions, it is somewhere between 9:00 AM and 12:00 PM.
The Digital Clock Method
Another helpful method is the digital clock method. This method is best used when the sun is low in the sky, such as during sunrise or sunset. To use the digital clock method, you will need:
- A digital clock
- A piece of paper
- A pencil
Instructions
- Place the digital clock on the paper.
- Mark the time on the clock when the sun is at the horizon.
3.Wait 15 minutes and mark the new time on the clock.
4.Draw a line between the two marks.
5.Divide the line into 12 equal parts. Each part will represent one hour.
Example
If the sun is at the horizon at 6:00 AM and 15 minutes later it is 6:15 AM, the line will be divided into 12 equal parts, and each part will represent one hour:
Time Hour 6:00 AM 12 6:15 AM 1 6:30 AM 2 6:45 AM 3 7:00 AM 4 7:15 AM 5 7:30 AM 6 7:45 AM 7 8:00 AM 8 8:15 AM 9 8:30 AM 10 8:45 AM 11 You can now use the digital clock to tell time by the sun. Simply point the clock at the sun and match the hour mark with the division on the line that is closest to the sun. This will give you the current time.
Using the Sun’s Shadow Ratio
This method is based on the principle that the length of an object’s shadow is proportional to the sine of the angle of elevation of the sun. To use this method, first measure the length of your shadow and the length of a fixed object, such as a tree or a building. Then, use the following formula to calculate the angle of elevation of the sun:
Angle of Elevation = arctan(Shadow Length / Object Height) Once you know the angle of elevation of the sun, you can use a chart or a calculator to determine the time of day. Here is a sample chart that you can use:
Angle of Elevation Time of Day 0° Sunrise/Sunset 15° 7:00 AM/5:00 PM 30° 10:00 AM/2:00 PM 45° 12:00 PM 60° 2:00 PM/10:00 AM 75° 5:00 PM/7:00 AM 90° Solar Noon Please note that this method is only accurate within a few minutes, as the sun’s elevation changes rapidly near sunrise and sunset. Additionally, this method is not as accurate when the sun is low in the sky, as the shadows are longer and more difficult to measure accurately.
Observing the Time of Key Events
Sunrise and Sunset
Sunrise and sunset are the most obvious and easily recognizable time markers during the day. As the Earth rotates, different parts of the planet face the Sun, resulting in the progression from darkness to daylight and back to darkness.
Noon and Midnight
Noon is the time when the Sun is at its highest point in the sky, and midnight is the time when the Sun is at its lowest point below the horizon. These times can be determined using a sundial or by observing the position of the Sun’s shadow.
Dawn and Dusk
Dawn is the period of time just before sunrise when the sky begins to brighten. Dusk is the period of time just after sunset when the sky gradually darkens.
Equinoxes and Solstices
The equinoxes and solstices are specific dates throughout the year when the Sun’s position in the sky changes significantly. The equinoxes occur when the Sun crosses the celestial equator, resulting in equal day and night. The solstices occur when the Sun is at its highest or lowest point in the sky, resulting in the longest or shortest day of the year.
Seasonal Changes
The Sun’s position in the sky varies throughout the year, affecting the length of daylight and darkness. In the Northern Hemisphere, the days are longest during the summer solstice and shortest during the winter solstice.
Latitude
The latitude of a location affects the time of sunrise and sunset. As you move closer to the equator, the days become longer and the nights become shorter. Conversely, as you move towards the poles, the days become shorter and the nights become longer.
The Equation of Time
The equation of time is a correction factor that accounts for the difference between the Earth’s mean solar time and its apparent solar time. Mean solar time is the average time of day over a year, while apparent solar time is the time of day as measured by the sun’s position in the sky. The equation of time is necessary because the Earth’s orbit around the sun is not perfectly circular, and the Earth’s axis of rotation is tilted.
The equation of time can be expressed as a table of values, which shows the difference between mean solar time and apparent solar time for each day of the year. The following table shows the equation of time for the Northern Hemisphere:
Month Equation of Time (minutes) January -14 February -11 March -4 April +6 May +15 June +17 July +15 August +12 September +7 October +1 November -7 December -12 To use the equation of time, simply add or subtract the appropriate number of minutes from the mean solar time to get the apparent solar time. For example, if the mean solar time is 12:00 PM on January 1st, then the apparent solar time is 12:00 PM – 14 minutes = 11:46 AM.
Adjusting for Latitude and Time Zone
The Earth’s rotation on its axis combined with its position in space relative to the sun creates an interesting phenomenon: time zones. Time zones are imaginary lines that encircle the globe, each representing a specific hour of the day. The Earth is divided into 24 time zones, with each zone being one hour ahead of the previous one.
Latitude is another factor that affects the time of day as perceived from a specific location. The Earth’s axis of rotation is not perpendicular to the plane of its orbit around the sun, so different parts of the Earth receive different amounts of sunlight at different times of the year. As a result, the time of day can vary by as much as an hour between two locations at the same longitude but different latitudes.
Calculating Time by the Sun
To calculate the time by the sun, you need to know your latitude and the current time zone. Once you have this information, you can use the following steps:
1. Find the equation of time for your latitude. You can find this information online or in a book on astronomy.
2. Calculate the solar noon by adding the equation of time to the mean noon. Mean noon is the time when the sun is directly overhead, which is not necessarily the same as 12:00 PM.
3. Calculate the local time by subtracting the difference between your time zone and the longitude of the location.
For example, if you are in New York City (longitude -74°), and the current time is 12:00 PM EST, and the equation of time is -4 minutes, the solar noon would be 11:56 AM EST. To calculate the local time, you would subtract the difference between your time zone and the longitude of the location, which is -5 hours, to get 6:56 AM local time.
The following table provides the equation of time for different latitudes:
Latitude Equation of Time (minutes) 0° 0 10° -10 20° -20 30° -30 40° -40 50° -50 60° -60 70° -70 80° -80 90° -90 Advanced Techniques for Precision
To achieve even greater precision, consider the following advanced techniques:
Technique Instructions Gnomon Method Use a vertical stick or pole as a gnomon. Mark the point where the tip of the shadow falls at two different times, such as 10:00 AM and 2:00 PM. The midpoint of the line connecting these points will indicate true noon. Equal Shadows Method Place two sticks vertically at equal distances apart. Measure the lengths of their shadows. When the shadows are equal in length, the time is approximately true noon. Transit Time Method Observe the sun’s movement through a frame or sight tube. Mark the time when the sun is exactly centered or when its center aligns with the top edge of the frame. Average the times of two or three such observations to determine true noon. These techniques require careful measurements and practice to master. However, they can provide highly accurate timekeeping, especially in situations where modern timepieces are not available.
How To Tell What Time It Is By The Sun
The sun’s position in the sky provides a natural clock that can be used to estimate the time of day. This method has been used for centuries by people all over the world. To tell what time it is by the sun, you need to know the following:
- The time of year
- The latitude of your location
- The time of day
Once you have this information, you can use the following steps to tell what time it is by the sun:
- Find the sun’s position in the sky. The sun will be highest in the sky at noon and lowest in the sky at sunrise and sunset.
- Estimate the time of day based on the sun’s position. The sun will be in the east at sunrise, in the south at noon, and in the west at sunset.
- Adjust your estimate based on the time of year and your latitude. The sun will be higher in the sky in the summer and lower in the sky in the winter. The sun will also be higher in the sky at higher latitudes and lower in the sky at lower latitudes.
With a little practice, you can become quite accurate at telling what time it is by the sun.
People Also Ask
How accurate is telling time by the sun?
Telling time by the sun is not as accurate as using a clock or watch, but it can be a good way to estimate the time of day if you don’t have access to a timekeeping device.
Can you tell time by the sun at night?
No, you cannot tell time by the sun at night.
