by Kathi Wagner
Observing Other Worlds
Do you like to take trips? Everyone likes to see what’s beyond the curve in the road, over the top of the hill, or like Christopher Columbus, over the next horizon. Although you can’t really visit them, now that you know about all these interesting planets, moons, and galaxies, wouldn’t it be fun to take a closer look at them? Many cities have observatories that magnify what you can see with your eyes or binoculars and they welcome visitors. Maybe you have a smaller version of one of them in your hometown. If you can’t do either of these things, look at a calendar, one that shows the full and little crescent moons. See when the moon will be dark; it’s also called the new moon, because this is the best time to look at the stars and the galaxies. Make sure there are few clouds. Try to find a place where there aren’t any streetlights. Then gather up some of these things you may want for your own sky-watching kit:
• A blanket, so that you can sit or lie down
• A set of binoculars, but try using only your eyes at first
• A compass to help you to find the North Star
• A pen and paper, so you can write down the stars you find
• Some snacks
See if you can borrow a star map from a grownup, so that you know where to begin to look for the stars. If you use a flashlight, the bright light may make it hard for you to see the stars after you turn it off, so be sure to cover the lens with red plastic wrap. Invite some friends and your family to go along, so they can enjoy the fun!
Which One?
Sir Isaac Newton first discovered the mystery of gravity when I almost fell on his head while he was sitting under a tree. Which one am I?
A. Orange
B. Acorn
C. Walnut
What Goes Up…
Have you heard the story about Isaac Newton and the apple that almost struck him as it fell to the ground? He wondered why it didn’t remain in the air or even go up into the sky! Newton called the force that pulled the apple to the ground gravity.
After someone told you that the world was spinning, didn’t it make you wonder why you weren’t dizzy or why you didn’t fly out into space when you jumped up in the air? Have you ever ridden on the flying swings at an amusement park? Before the ride starts, the swings hang down, but as soon the machine starts spinning, the swings move upward. The rider feels as though she is flying off into space; scientists call this centrifugal force. As the ride stops, gravity pulls the swings back down to the ground. How many other rides can you name that use centrifugal force and gravity to make you feel like you’re in another world?
Try This
Going for a Spin
Ask an adult to tie a knot in a string and then thread it though a tennis ball. In an open area, hold on to the string and start spinning around; because of centrifugal force, the ball seems to pull more, the faster that you spin. When you get dizzy and stop, gravity will make the ball fall to the ground and probably you will, too.
Balancing Act
Newton believed that gravity was also what held the moon close to the earth and the earth close to the sun. Like the swing on the ride, the moon is slowly moving out and away from our planet. The earth’s rotation is gradually slowing, its gravitational pull is less, and the moon’s spinning motion is moving it further out from the earth. Over time this has made our days longer. Scientists believe that, long ago, a day lasted several hours less than it does now. Gravity affects everything we do each day. Turning a corner too fast on your bicycle and landing on the ground afterwards is just one example of centrifugal force and gravity at work. Can you think of others?
A Real Balancing Act
Can you balance a ball on the palm of your hand? How about spinning it on the tip of your finger? It might be easier if you try twirling a coin on a tabletop. Balance is very important to all things in the world and in space. There needs to be just enough rain and sunshine for crops to grow, and there must also be a balance between the day and night. The universe seems to be based on a balance between push and pull. If gravity was too strong here on Earth, you could barely lift your feet to walk, which would be like walking through water. If we didn’t have enough gravity, you might have to wear weights to keep you on the ground. Ask your family if you can wear a pair of their big boots or heavy shoes around for a few minutes to see how it would feel to have more weight pulling down on you. Having balance, especially balance in our gravity, is a wonderful thing.
WORDS to KNOW
GRAVITY: Gravity is the force that pulls things toward the earth. There is also a gravitational force in many other areas throughout the universe that seems to hold things together.
One in a Billion
With billions of stars in the sky, it’s not easy to find one star in particular! Can you find the five-pointed star that is hiding in this corner of the galaxy?
Try This
Taking the Long Way Around
Many galaxies are elliptical, shaped more like a racetrack than a circle. If you want to see if the stars on the inside edge of a galaxy would go around faster than the stars on the outside edge, challenge one of your friends at a nearby racetrack! Go around once and see if the one on the inside track wins. Then trade places to see if the one on the inside track still wins.
You’ll Get a “Bang” Out of This
Have you ever placed a drop of water on one of those capsules with a foam sponge inside? Almost immediately, a foam animal appears. Now imagine that the capsule is smaller than a grain of sand and the foam is really made of super hot material that grows thousands, maybe millions or billions of times larger within seconds. Many scientists are uncertain if the creation of the universe was a quiet event like the growth of the sponge or if there was a “Big Bang” like fireworks, only louder, when it happened. Some believe that they know when the Big Bang happened because they have learned how to measure the age of the galaxies and the radiation created by the event that still lingers all around the edge of the universe. Just imagine if we were having a cake for the universe’s birthday party, we would need around 15 billion candles!
Can you name the visible colors in a rainbow? Each color has a frequency wave, just like the numbers on your radio. Many astronomers use special instruments on their telescopes to determine which one of these colors or frequencies a star or a galaxy sends out. A redshift or low-frequency wave indicates that they are speeding away from the Milky Way Galaxy. If the red-shift amount increases as you observe another galaxy (this means the other galaxy is moving even faster). If you were in another galaxy, it would seem as though our galaxy was speeding away from it. Does this make you wonder where the center of the universe really is? If you want to see an example of this, type in the words “Hubble & center of universe” in your search box on the Internet and see what you think!
Light Years Away
A farmer might think that a light year means that an ear of corn is smaller than last year, and a weatherman might use the words to tell you there wasn’t a lot of rain in the last 365 days. Can you think of other meanings for the word “light”? An astronomer would be describing how many miles light would travel in a vacuum over the length of a year, which is over 5,000,000,000,000 miles! The spacecraft, Voyagers 1 and 2, after making a journey lasting for almost 30 years are just reaching the edge of the system that holds the sun and its planets. Light traveling at 186,000 miles per second would only take minutes to cover the same distance. If you would decide to become an astronomer right now, you might still be able to receive information from these ships for about fifteen more years! Even after we lose contact with these spacecraft, they could travel for many more years.
Sweet Scientists
Start at a letter marked with a dot. Collect every other letter as you spiral into the galaxy. When you get to the center, go back the way you came, collecting the unused letters until you reach the dot again. Write the letters, in order, in the spaces provided. When you are finished, you’ll have three silly answers to the riddle!
Which One?
What goes up must come down—that is my law. Without me you would float through the air like a feather. Which one am I?
A. Centrifugal force
B. Friction
C. Gravity
D. The wind
Just for Fun
It’s in the Bag
Have you ever popped a balloon when it is full of air? Most astronomers think the big bang may have happened in a similar way. To see the force of the big bang at work, blow up a small brown paper bag and punch it until it pops. You might even have a contest to see who can pop their bag first.
Going Out with a Bang
If you have ever mixed baking soda with vinegar, you have seen how something fairly small can instantly become fairly large. It is thought that when the universe was born it started out small like a grain of sand but grew very quickly into the almost endless skies we gaze at today. The universe is constantly moving and spreading to places unknown. What could cause such a large explosion? Scientists have different theories of how the universe was formed, but most of them feel the big bang makes the most sense and explains all the things we are still seeing billions of years later.
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Chapter 7
Space Oddities
Maybe you have seen comets and meteors speed across the sky or have heard that asteroids sometimes reach the earth. But did you know the universe also contains blinking lights called pulsars? These pulsars flash so regularly that you could almost set your watch by them. There are also black holes that can pull stars to their destruction, and a mysterious, dark unseen matter scattered throughout the universe. At the edge of the solar system are what astronomers think are millions of icy objects just waiting to become new comets.
In the Blink of an Eye
Do you like to read mysteries? Astronomy is one of the biggest mysteries of all because it is all about what happened and why. Do you remember what a supernova can do? If it explodes and nothing is left but stardust, someday it may become another star. But what if part of it collapses inward after the explosion? When it does happen, astronomers think a neutron star is instantly created. A neutron star is an object so massive that half of a teaspoonful could weigh as much as a million blue whales, the largest animal on Earth. If you think the magnets on your refrigerator are strong, imagine if you could squeeze that magnet to the size of a pinpoint. Scientists believe this compression is what really increases the magnetic field of the neutron star. Once the neutron star starts spinning, it sends out a radio signal. You probably think of your AM or FM radio as the only radio signals around, but your TV stations also use them as well as many other people like the police, firemen, truckers, and pilots. Have you ever felt the pulse in the inside of your wrist with your finger? Try to find it and count how many times a minute you can feel that beat. It should be regular like the pulse of a spinning neutron star, called a pulsar. Your heart probably beats at a different rate than your friend’s. Each pulsar’s signal also sends out a different rate and so its location can be identified if the radio beam is directed toward Earth. Try taking your pulse and the pulse of your friend each day for a week, and write down your numbers. Did they change?
Try This
Picture This
See if your family has a camera that will take pictures of the night sky, or if they know someone who does. On a clear night try taking a few pictures of the sky right in a row. Later examine the pictures to see if anything changed from picture to picture. You could also start an album of amazing shots.
FUN FACT
Flashing Lights
Lighthouses vary the pulses of their lights to identify their location. Some types of neutron stars are called “lighthouse models” because of the signal they send.
Amazing Quasars
Now that you know that stars can be located by following a radio wave to the star, what would you do if you found a radio wave, but couldn’t find the star? Like the astronomers, you would keep searching until you did! The light from the “star,” although viewers on Earth can barely see it at all, is brighter than almost any other object in the sky and this indicates that it is a source of tremendous energy! How bright is this light? Brighter than a trillion suns! Astronomers have found out that they are actually quasars, quasi-stellar radio sources, and many of them are located at the farthest edge of the universe. By measuring the huge red shift in the spectrum of each quasar, they are able to determine how fast it is speeding away from Earth and how far away it is. Can you guess how far the quasar would have traveled in the time it has taken to read this book, especially since the universe is continually expanding? Scientists also wonder what else might be hiding near these mysterious quasars. Many astronomers believe they may be the centers of galaxies that cannot be seen by any type of telescopes. Are there still quasars in the universe today? No one can be sure due to how rapidly light travels; what we are seeing now may have happened billions of years ago! Do you think those quasars have been replaced by black holes? And do you ever wonder if the universe keeps expanding, will the planets also get farther apart? Although that would seem logical, it doesn’t appear to be the case. At this point in time the objects in our solar system seem to remain the same distance apart just as they always have been.
Try This
Now You See It, Now You Don’t?
Black holes aren’t the only things that can make stuff disappear. Try pouring water in a clear glass and adding a few of the following things to it one at a time like salt, sugar, baking soda, pepper, and flour. What happens? Now try testing a few other things. Which ones disappear?
The Sky Is Falling
Have you ever watched the whirlpool that is made in your bathtub when the water drains out? A black hole is like a whirlpool in space, dragging any stars that pass close enough to their destruction. Do you know what powers a whirlpool? Gravity does! When a supernova collapses a heavy neutron star is formed. If that same star had been bigger, a smaller, heavier black hole with much more gravity would have been created. Astronomers have been able to prove neutron stars or pulsars exist because they send out radio waves, but a black hole’s gravity is so strong it won’t even let light escape from it. To be able to find a black hole, astronomers must look for its effect on other objects in the sky. Although X-ray radiation also cannot escape from a black hole, a star that circles it can have its gas pulled away. The radiation generated from the hot gas is transferred into the empty space beside it and this can be measured. Scientists have found the space is very small, but the gravitational pull is incredibly strong, so they believe they are seeing a black hole at work.
Where would you look for the nearest black hole? Many of the stars in other galaxies appear to be orbiting around a huge, empty space. Maybe this is also what keeps Earth’s Milky Way Galaxy spinning around.
Which One?
I have almost perfect timing. Some people say you could almost set a watch by me because of my flashy ways. Which one am I?
A. Quasar
B. Pulsar
C. Asteroid
D. Planet
Seeing in the Dark
Have you ever walked into a theater after the movie has started? Although you know it is filled with seats and other people, you really can’t see anything but a big, bright, moving screen! Telescopes have revealed that the universe is filled with endless luminou
s galaxies, but most astronomers believe that the galaxies are surrounded by a dark halo or circle filled with dark matter. How did they discover the existence of this substance? Numerous calculations seem to prove there is too much gravity beyond the edge of each galaxy and throughout the universe for the amount of bodies of light that we are able to see! Scientists have come to question their original beliefs that all objects with gravitational pull must be visible. At this point in time astronomers can only guess what form this unseen matter might take. It might be dark galaxies, dwarf stars too faint to be seen, or black holes. Most scientists believe the dark matter formed right after the big bang and that it could be particles that are so tiny that they can’t be seen or aren’t able to send out enough radiation to be measured! Sounds hard to believe, doesn’t it? Even after they have totaled up all the light and dark matter, there is still 70 percent of the gravity they can’t explain in the universe. They believe that dark energy, the driving force for the expanding universe, accounts for the rest of it. One way to think of it is like magnetism or electricity. Just because you can’t see it doesn’t mean it isn’t there. Until astronomers discover a way to measure it, they just have to believe it is there because they see its effect!
Name That Nebula
Over 200 years ago, astronomer Charles Messier was searching for comets. Instead, he found lots of fuzzy objects that looked like comets but were really star clusters, galaxies, and nebulae. Messier described these objects and their positions using numbers, but modern astronomers have given these deep sky objects more descriptive names! Figure out the picture puzzles to learn the names of nine of the nebulae on Messier’s list.
