(I)The early telescopes used lenses, familiar at the time from lenses in spectacles, to gather light and focus it. (II) Later in the 17th century, scientists realized that curved mirrors could also gather and focus light. (III)Since the light did not need to pass through the mirror, mirrors proved to be more efficient than lenses for large telescopes. (IV) Consequently, in 16Isaac Newton built the first telescope lo use mirror to collect light, rather than lens. (V)But it is through satellites and probes rather than telescopes that our knowledge of space has increased.