As the Earth rotates on its axis, it turns through how many degrees of longitude in one hour?

The Earth rotates through 360 degrees in about 24 hours. So, in one hour, it turns through 360 / 24 = 15 degrees of longitude.

Related calculations:

• In 24 hours, the Earth turns 360 degrees.
• In 1 hour, it turns 15 degrees.
• In 4 minutes, it turns 1 degree (because 60 / 15 = 4).

Longitude and time:

• Since the Earth rotates from west to east, places to the east see the Sun rise earlier than places to the west.
• For every 15 degrees of longitude, local time differs by one hour.
• For every 1 degree of longitude, local time differs by 4 minutes.
• Places east of the Prime Meridian (0 degrees, passing through Greenwich, London) are ahead of Greenwich time, and places to the west are behind it.

Example:

• A place at 30 degrees East longitude is 30 x 4 = 120 minutes, or 2 hours, ahead of Greenwich.
• A place at 45 degrees West longitude is 45 x 4 = 180 minutes, or 3 hours, behind Greenwich.

Local time and standard time:

Local time is based on the position of the Sun at a particular place; it is noon when the Sun is highest in the sky.

Since local time changes continuously with longitude, countries adopt a standard meridian, and all places in a time zone follow the time of that meridian. This is called standard time.

Sidereal day and solar day:

The Earth completes one rotation relative to the stars in 23 hours 56 minutes 4 seconds. This is called a sidereal day.

A solar day, measured from noon to noon, is 24 hours, because the Earth also moves along its orbit and must turn a little extra to bring the Sun back to the same position.

Why not the other options?

• ✗1 degree takes 4 minutes, not one hour.
• ✗4 degrees and 30 degrees do not match the Earth's rate of rotation.