Motions of the Earth

​Objectives:

​

​1. describe the rotation and revolution of planet Earth;

2. discuss how time is measured on Earth and

discuss how the tilt of Earth’s axis affects the life on the planet

Multiple Choice

What are the primary motions of the earth?

• Rotation

• Revolution

• Axial Precession

• all of the above

How long does it take to make one full rotation?

​Rotation-turning or spinning of a body on it's axis which is tilted 23.5 degrees.

Multiple Choice

Why is the sidereal day shorter than that of the mean solar day?

• The re-occurrence of noon requires an additional minutes with respect to the Sun.

• The measurement of the mean solar day is the re-occurrence of a star.

• The measurement of the sidereal day is the re-occurrence of noon.

• The movement of the Sun with respect to another star takes an additional four minutes.

​it requires an additional of 4 minutes to meet the next noon

Open Ended

Why do we use the mean solar day to measure time rather than the sidereal day?

​In 1884, an international system was established to standardize time measurement

worldwide. This system divides Earth into 24 time zones.

Multiple Choice

Knowing the difference of mean solar day and sidereal day, do stars rises exactly at the same time?

• Yes

• No

Revolution

the motion of a body such as a planet or moon, along a path, around some point in space

Multiple Choice

The Earth’s orbit is NOT perfectly circular.

• True

• False

​Each year, on about January 3/4, our planet is about 147.3

a million kilometres from the Sun, closer than at any other time---a position know as

perihelion. About 6 months later, on July 4/5, Earth is about 152 million kilometres from the Sun, farther away than at any other time---a position called aphelion.

Multiple Choice

How many solar days does it take to complete one revolution?

• 366

• 365.25

• 365

• 365.75

Open Ended

Why do we have a leap year every 4 years?

(365.25)

Multiple Choice

Does it mean that the main cause of the season is the distance between Earth and Sun?

• No

• Yes

Multiple Choice

How many degrees is the Earth tilted on its axis?

• 0 degree

• 25.3 degrees

• 52.3 degrees

• 23.5 degrees

​The summer solstice occurs on June 21 and marks the beginning of summer.

​The winter solstice occurs on December 21 or 22 and marks the beginning of winter.

Multiple Choice

In the northern hemisphere, what day marks the first summer solstice?

• June 21st

• December 21st

• September 21st

• March 21st

Multiple Choice

In the southern hemisphere, what day marks the first winter solstice?

• June 21st

• December 21st

• September 21st

• March 21st

Multiple Choice

Why do poles experience 6 months of daylight and 6 months of night time?

• due to the earth's tilt

• due to the earth's rotation

• due to the earth's revolution

• due to the earth's axial precession

Multiple Select

When does the sun exactly rises on the east and sets on the west?

• spring equinoxes

• fall equinoxes

• summer solstices

• winter solstices

​Axial Precession

​the axis traces a circle on the sky "wobble effect"

​

​The period of precession is 26 000 years.

Multiple Choice

Will Polaris always be the earth's north star?

• Yes

• No

Poll

Is it possible that the sun is also in motion?

• Yes

• No