Motions of the Earth Flashcards
Name the two primary motions of the Earth.
Rotation & Revolution
Define Rotation
Rotation is the turning around of the Earth on its axis.
Define Revolution
Revolution is the movement of the Earth around the Sun.
Define Axis
Axis is the imaginary line passing through the center of the Earth on which the Earth Rotates.
How does the tilted axis of the Earth affect the length of days and night of the Earth?
If it was not tilted, All places would experience 12 hours of day & 12 hrs of night.
Define Circle of Illumination
It is the imaginary line which demarcates area of light from area of darkness
Days and nights vary the least at the ___________ and most at the ___________.
Equator, Poles
Speed of Earth’s Rotation at equator
1667 kmph
Speed of Earth’s Rotation at the Pole
0
Speed of Earth’s Rotation at 40 degrees north
1275kmph
Effects of speed of rotation on Earth
- Affects the shape. A phenomena called the equatorial bulge takes place due to the centrifugal force exerted by rotation of Earth.
- Affects general circulation of the atmosphere. Moving air is deflected to right in northern hemisphere and to the left in the Southern atmosphere.
Effects of Earth’s Rotation
- Equatorial Bulge
- East-West movement of the sun and all heavenly bodies
- Day and night
- Circulation of air and water: Rotation causes consistent change
- Tides: Rotation of the Earth results in every meridian coming into the positions of two high tides and two low tides almost every 24 hours
Define Coriolis effect
The moving air is deflected to the right in the Northern Hemisphere and left in the Southern Hemisphere.
Define Perihelion
On about January 3rd the Earth is closest to the sun. (147 M km)
Define Aphelion
On about July 4th the Earth is farthest from the sun. (152 M km)
Define Solstice
The time when the midday sun is directly overhead at one of the tropics.
Define Equinox
The time when the midday sun is overhead at the Equator.
Define Northward apparent migration (Uttarayan)
For six months of the year, the sun appears to be moving north. It begins after 22nd Dec and is completed on June 21st.
Define Southward apparent migration (Dakshinayan)
For six months of the year, the sun appears to be moving south. It begins after 21st June and is completed on 22nd Dec.
Differentiate between Rotation and Revolution
Rotation
- It is the movement of the Earth around its axis.
- The Earth takes 24 hours to complete one rotation.
Revolution
- It is the movement of the earth around the sun
- The Earth takes 365.25 days to complete one revolution.
Differentiate between Aphelion and Perihelion
Perihelion
- On about 3rd January, the Earth is closest to the sun.
- The distance between the earth and the sun is 147.5 million km
Aphelion
- On 4th July the Earth is farthest from the sun
- The distance between the earth and the sun is 152.5 million km
Difference between Solstice and Equinox.
Solstice
- The time when the mid-day sun is directly overhead at one of the tropics.
- It takes place on 21st January and 22nd December.
Equinox
- The time when the mid-day sun crosses over the equator.
- It takes place on 21st March and 21st September.
GR: We always see the sun rising in the East.
As the Earth rotates from West to East, the eastern part gets lighted first and hence we see the sunrise in the East.
GR: The length of day and night equal at all places on the earth on March 21st.
The rays of the sun fall vertical on the equator, so the distribution of light is equal all over the world resulting in duration of day and night equal from pole to pole.
GR: Vertical rays are hotter than slanting rays.
Vertical rays are concentrated over a smaller area so they heat up the earth more.
GR: Norway is called the land of the Midnight Sun.
A good part of Norway is situated North of the Arctic Circle where the duration of daylight goes on increasing from 24 hrs. to six months poleward.
When is
a. Summer Solstice
b. Winter Solstice
c. Spring Equinox
d. Autumn Equinox
e. Aphelion
f. Perihelion
a. 21 June
b. 22 December
c. 21 March
d. 23 September
e. 4 July
f. 3 Jan
Effects of Earth’s Revolution
- Cycle of Seasons
- Apparent Migration of the Sun resulting in change in altitude of midday sun.
- Temperature or Heat Zones
