Types of Motion of the Earth

Types of motion of the earth is a very common topic in general geography. This is very frequently asked in competitive exams which makes this topic very important from an exam perspective. In this article, we are going to discuss the types of motion of the earth and its effect on living beings. Students need to revise this topic on regular basis and consolidate their exam preparation.

Types of Motion of the Earth

1. Rotation:

• The rotation of the earth on its axis in the anti-clockwise direction.
  
• The earth takes around 24 hours to complete one rotation.
  
• The rotation of the earth is responsible for the occurrence of days and nights.
  
• The circle that separates day and night on Earth is called the circle of illumination.
  
• The earth rotates around its tilted axis. The Earth’s rotation axis forms an angle of 23.5° with the normal. That is, it forms an angle of 66.5° concerning the raceway plane. The orbital plane refers to the plane of the Earth’s orbit around the Sun.

Why is a day always longer than a night at the equator?

• Without an atmosphere, there would be no refraction, and at the equator day and night would be roughly equal, at least between the equinoxes.
  
• But because of the atmosphere, the sun’s rays are refracted (light refraction). Especially in the morning and evening when the sun’s rays hit diagonally, the refraction of light becomes strong.
  
• The actual sun is below the horizon, but its apparent image appears above the horizon due to refraction. As a result, the day is longer than the night at the equator.
  

Why does temperature decrease with increasing latitude (moving from the equator to the poles)?

• This is because of the spherical shape of the Earth (the geoid) and the position of the Sun. This is because the energy absorbed per unit area decreases from the equator to the poles. This is because the equator receives direct sunlight and the poles receive oblique or oblique rays of the sun.

2. Revolution

• The movement of the Earth around the Sun in its orbit is called Revolution. It takes 365¼ days (1 year) to go around the sun.
  
• The six hours remaining each year become 1 day (24 hours) in 4 years. This remainder day is added to February. 
  
• February has 29 days instead of 28 every fourth year. A year with 366 days will be considered a leap year.
  

A. Solstice

• On June 21st, the Northern Hemisphere tilts toward the Sun. Sunlight falls directly on the Tropic of Cancer. As a result of this, these areas experience more heating effects.
  
• Areas near the poles receive less heat because the sun’s rays hit them obliquely. The North Pole is tilted toward the Sun, and beyond the Arctic Circle, there is continuous sunlight for about six months.
  
• Areas north of the equator are summer because most of the northern hemisphere is lit by the sun. The longest day and shortest night in these places are on June 21st.
  
• At this point in the Southern Hemisphere, all of these conditions are reversed. It’s the winter season. The night is longer than a day. This position of the earth concerning the sun is called the summer solstice.
  
• On December 22nd, as the South Pole tilts toward the Tropic of Capricorn, it receives direct sunlight from the Sun. As the sun’s rays fall perpendicularly at the Tropic of Capricorn (23½° s), much of the southern hemisphere will be brighter, and the southern hemisphere will experience summer with longer days and shorter nights.  In the northern hemisphere, the opposite is true. This position of the earth concerning the sun is called the winter solstice.

B. Equinox

• Direct sunlight hits the equator on March 21st and September 23rd. In this position, none of the poles are tilted toward the Sun. Therefore, the whole earth experiences the same day and the same night. This is called an equinox.
  
• September 23 is the autumn season [summer to pre-winter] in the northern hemisphere and spring [post-winter to pre-summer] in the southern hemisphere. 
  
• On March 21st, it’s the opposite: Spring in the Northern Hemisphere and autumn in the Southern Hemisphere. In this way, we can see that there are changes in day and night and seasons due to the rotation and revolution of the earth.
  

Why do regions outside the Arctic Circle receive sunlight throughout the day in summer?

• This is due to the tilt of the earth.
  
• The Earth’s axis in the Arctic is tilted towards the summer Sun.
  
• Thus, the entire Arctic Circle is in an ‘illumination zone’ all day long during the summer.

What is Daylight saving time in some temperate regions?

• Daylight Saving Time (DST) or daylight saving time is the practice of moving clocks forward one hour during the summer months.
  
• In summer, evening hours are extended at the expense of morning hours.
  
• Typically, users in areas with daylight saving time (some northern and southern countries) will advance their clocks by one hour just before spring begins and return to standard time in the fall. 
  
• Benefits: Advances in watches are useful for retail, sports, and other activities that use daylight after hours. It reduces the nighttime consumption of incandescent lamps, which are used to consume electricity.