Question

the main, or central, idea of the passage is a powerful dual microscope called the blink comparator enabled clyde tombaugh to discover pluto. how does the detail in bold develop the main idea? in the early 1900s, astronomer percival lowell theorized the existence of a planet beyond neptune; however, he was never able to find \planet x.\ after lowells death, clyde tombaugh took up the search, using a telescopic camera to photograph areas where he thought planet x might be found. tombaugh used an amazing tool called a blink comparator to analyze these photos. equipped with two powerful microscopes, the device allowed the user to examine two different photographic images taken at different times, using a dial to switch rapidly between them. tombaugh knew that planets, unlike stars, move in orbits—so he looked for minute differences that could signify a moving body. in february 1930, tombaugh found two images, taken six days apart, that were very slightly different: an object had changed locations. thanks to the blink comparator, he had found the elusive planet x, now known as the dwarf planet pluto. it explains the difference between a microscopic view and a telescopic view. it explains how the blink comparator helped tombaugh compare photos. it instructs the reader how to use a blink comparator to examine photos.

Explanation:

The bold - faced detail describes the blink comparator's features (two microscopes, ability to switch between images) and how it was used by Tombaugh to compare photos and find Pluto, thus developing the main idea of how the blink comparator enabled the discovery.

Answer:

It explains how the blink comparator helped Tombaugh compare photos.