Muslim astronomers measured earth and realized

The Muslim astronomers measured the Earth and realized that it was round.

Explanation:

It has lately come to light that the Muslims were the first to discover that the Earth was round. The device named astrolabe that was initially developed by the Greeks was further modified by the Muslims and used to measure Earth during their voyages. From the angular readings that they got of the distances from one place to another and the differences that they found out in the lengths of latitudes, they concluded that the Earth is round.