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 Lowell's 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.
Smart
out of 1
2
What is the main idea of the passage?
-The blink comparator enabled Clyde Tombaugh to compare photographs taken
at different times.
-A powerful dual microscope called the blink comparator enabled Clyde
Tombaugh to discover Pluto.

new york state wildlife expert richard thomas found that a woodchuck could   chuck around 35 feet of dirt in the course of digging a burrow. thomas reasoned that if a woodchuck could chuck wood, he would chuck an amount equivalent to the weight of the dirt, or 700 pounds.

word count 168

serve the people! ,” smoothly translated by julia lovell, offers an initial sample of yan lianke’s writing to an english-speaking audience. a bluntly drawn, mildly erotic fable, it teases mao zedong by poking fun at a true believer who obeys the chairman’s precepts too literally. to a western sensibility, the broad strokes of yan lianke’s humor would seem to pose little risk of inciting rebellion, whether of the flesh or of the body politic. but then, part of the book’s attraction is that it doesn’t have a western sensibility. it lets the reader see — or rather, intuit — what jokes chinese officials don’t consider funny, and how very little it takes for a writer to be branded an incendiary in 21st-century china, more than three decades after the death of mao, a decade after the death of deng xiaoping and seven years since china entered the world trade organization, a move that would seem to signal a willingness (however wary) to mingle with the rest of the world.