Question

The earth-moon distance is about 60
earth
radius what will be the diameter of the earth
(approximately in degree) as seen from the moon.​

Answer 1

AnswEr :

The radius of the Earth can be treated as an Arc as the distance between the Moon & Earth is greater than that of the radius of the Earth.

Let us assume that the radius of the Earth is Re(forming an Arc).

Given that, distance between them Earth & Moon is 60Re.

Hence, angle subtended by the distance r at an Arc of length l is given by,

⇒ θ = l/r

where l is the length & r is the given distance between them Earth & Moon

Substituting the values :

⇛ θ = 2 Re/60Re

⇛ θ = 1/30

⇛ θ = 1/30 × 180/π [Conversion into degree]

⇛ θ = 6/3.14

⇛ θ = 2° (Approx.)

∴ The overall Diameter of the earth if seen from the moon is about 2°.