A geostationary satellite revolves around the earth from west to east once in 24 hours. How does the the satellite appear to a person in earth's surface ?

Question

a) Stationary in the sky.

b) Moving east to west.

c) Moving south to north.

d) getting smaller with time.

 

Thank you for your time. 

 

Answer 1

This question requires you to know (1) how the Earth rotates. both direction and time, and (2) the definition of "geostationary."

 

(1) the Earth revolves around our Sun once per year, but it rotates on its axis once per day (that is, every 24 hours, roughly).  When you consider that from the location of our Sun, this would mean the Earth goes around the Sun is a wide orbit while spinning like a top 365 (roughly) times in each rotation.  Spinning in which direction?  Well, from the view of a person on Earth, the Sun comes up in the East and sets in the West (because we define a "North star." and a "North pole" to establish an orientation).  There is a nice world map showing the pattern of light and darkness on time.gov.  Now, how does the Earth rotate so that the light from the Sun moves from East to West?  Well, the Earth rotates from West to East -- remember that.

 

(2) "geostationary" means that the satellite is always above the same geological spot on the Earth.

 

O.K., this problem states that the geostationary [remember the definition in (2)?] satellite rotates "from West to East" [remember how the Earth revolves?] "once in 24 hours" [that is, the same time as it takes the Earth to rotate once. or one day]. so a person on the Earth is travelling in the same direction at the same rotational speed as the satellite.  "a person on the Earth's surface" would see the satellite as "stationary in the sky" (obviously using some sort of telescope because this satellite must be at a bigger distance from the Earth than many satellites).

 

Now, to be check that you understand this concept, PLZ answer this: "Our Moon revolves roughly once for each orbit around the Earth (so a Moon year and a moon day around the Earth are both about 27 Earth days).  From a position on the Earth, the Moon appears to go from East to West (like the Sun appears to do).  BUT -- from a position on the Moon, does the Earth move much in the sky (note the title of the famous picture "Earthrise" taken by the Apollo astronauts)?