Question

how to prove that earth is sphere in shape

Answer 1

without looking it from space
we can also say it is sphere
because as we know that those object which has terminates radius are always round in figure


hope it will helps you

Answer 2

Since the earth is rotating (see the “Foucault Pendulum” experiment for a definite proof, if you are doubtful), the consistent oval-shadow it produces in each and every lunar eclipse proves that the earth is not only round but spherical—absolutely, utterly, beyond a shadow of a doubt not flat.