Directions:
You will be taking the Grade 6 English Language Arts/Literacy Post-test.
You will be asked to read a passage. Read the passage and all the questions carefully. Some questions will ask you to choose one correct answer, while others will ask you to choose more than one correct answer. You may look back at the passage when needed.
To answer a question, click on the circle or circles of the correct answer.
Read the passage Mapping the Invisible. Then answer the questions.
Mapping the Invisible
by Stephen Ornes
1 Most maps show places you can visit and how to get there. Most maps, however, were not made by astronomers—physicists who study stars and galaxies far, far, far away. At a recent meeting in Texas, three teams of these scientists presented new maps unlike any atlas, globe or street guide. These maps show where dark matter, giant globs of invisible stuff, lurks.
2 One of the most mysterious—and common—materials in the cosmos, dark matter forms in giant clusters and long strings. This matter hides all throughout the universe, although you’ll never see it no matter how hard you look.
3 Dark matter is literally the darkest stuff imaginable. It neither produces nor reflects light, which means it’s invisible to human eyes and to most scientific instruments. That makes it a challenge to measure and study. What makes the matter more frustrating: Scientific measurements show that the universe holds about five times as much dark matter as ordinary matter. Making up the known (and knowable) part of the universe, ordinary matter includes you, your dog, Earth, the sun, stars and planets.
4 Scientists find dark matter in the same way they detect other things we can’t see—by observing how the invisible stuff affects things we can see. We can’t see wind, for example, but we can feel a breeze or watch a windmill spinning on a hill. Dark matter doesn’t spin windmills, but it does have gravity. Like ordinary matter, dark matter pulls on everything around it with gravity. Dark matter’s gravity holds galaxies together and bends rays of light as they stream past—in much the same way light bends as it travels through water or glass.
5 To make the new maps, astronomers trained powerful telescopes on large patches of sky to watch for distorted light arriving from distant galaxies. One group used a telescope perched 14,000 feet above sea level atop a dormant Hawaiian volcano. It recorded light from stars and other celestial bodies. Two other groups used a telescope on top of a mountain in New Mexico, which watched the sky for nine years.
6 These telescopes recorded light that came from galaxies billions of light-years away. (A light-year is the distance traveled by light in one year, about 25 million times the distance from Earth to the moon.) By studying how the light changed as it traveled through space, the astronomers could estimate the rough location and shape of dark matter clumps.
7 The scientists’ work is like figuring out how big and thick a pair of eyeglasses is by looking through them and measuring how differently the world appears.
8 “You can imagine that dark matter is leaving its signature on the images of very distant galaxies,” said Catherine Heymans of the University of Edinburgh in Scotland. She worked on the project that used data from the Hawaiian telescope.
9 Her team’s map shows that giant blobs of dark matter reside with giant blobs of ordinary matter, such as big galaxies or galactic groups. Even though scientists already suspected that dark matter and ordinary matter show up in much the same places, it was reassuring to see the same connection in the maps.
10 “We are very happy that this is very similar to what we’ve been expecting,” Ludovic Van Waerbeke of the University of British Columbia in Vancouver told Science News.
11 One of the new maps shows dark matter in a swath of sky that to the naked eye is more than 600 times as large as a full moon. The other covers an area more than a thousand times as large. But that’s just the beginning: The astronomers want to conduct further studies to better understand those invisible lumps and hope to survey the whole sky within10 years or so.
“Mapping the Invisible” by Stephen Ornes, from February 1, 2012 Science News for Kids, copyright © 2011 by Society for Science & the Public. Used by permission.
