The day
The Sun's daily path gives the day.
Shadow of a stick
A stick casts a shadow on the ground. The shadow changes length during the day.
When is the shadow shortest?
What this lesson covers
The idea
The Sun's apparent daily motion, due to Earth's rotation, is the basis of the day; the average time from the Sun's highest position one day to the next, shown by the shortest shadow, is 24 hours, the mean solar day.
Shadow of a stick
A stick casts a shadow on the ground. The shadow changes length during the day.
When is the shadow shortest?
- When the Sun is at its highest
- At sunrise
- At sunset
Follow the shadow
Open each tab.
The mean solar day
The Sun appears to rise and set because the Earth rotates on its axis. This natural cycle is the foundation of the day. The average time from the Sun's highest position on one day to its highest position on the next day is 24 hours, called the mean solar day.
The Sun's daily motion is due to the Earth's rotation. The average time from the Sun's highest position one day to the next is 24 hours: the mean solar day. The shortest shadow shows the highest Sun.
Notes
The day comes from Earth's rotation. Mean solar day = 24 hours.
Check yourself
The shadow of an object is shortest when the Sun is …
The mean solar day is how many hours?
Answer: 24 hours
The mean solar day is 24 hours.
The Sun appears to rise and set mainly because of the Earth's …
The natural cycle of the Sun due to the Earth's rotation is the basis of the …
- rising. The shadow is long when the Sun is low.
- setting. The shadow is long when the Sun is low.
- at its highest in the sky — correct. Yes!
- rotation on its axis — correct. Yes!
- revolution around the Moon. The Earth does not revolve around the Moon.
- shadow. It is due to the Earth's rotation.
- month. The month comes from the Moon's phases.
- day — correct. Yes!
- year. The year comes from the seasons.