Table of Contents The Sun and the Seasons 4 The Moon and the Tides 8 Weather Day to Day 12 Predicting the Weather 20 Severe Weather 26 Climate across the World 36 Glossary 46 Index 47 Show What You Know 47 Websites to Visit 47 About the Author 48
In this long photo exposure you can see how the rotation of the Earth makes it appear as though the stars travel in circles around the poles The Sun and the Seasons Stand in one place and look up at the sky It probably feels like you’re not moving at all In reality you’re zooming along with Earth at 18 5 miles 30 kilometers per second around the sun At the same time the Earth itself is spinning at 1,040 miles 1,674 kilometers per hour It’s amazing you aren’t dizzy But just as you cannot feel yourself moving at 60 miles 97 kilometers per hour in the car you cannot feel the movement of the Earth Gravity keeps you grounded and your momentum or speed matches our planet’s But you still experience the effects of all that movement It takes 24 hours for the Earth to complete one complete spin or rotation It’s 4
daylight for those on the side of the Earth facing the sun and night for those on the other side The Earth’s spin gives us day and night but Earth’s year-long journey around the sun gives us the seasons The Earth is not perfectly parallel to the sun The Earth’s axis has a slight tilt of 23 5 degrees because the extra land at the North Pole makes the Earth top-heavy The Northern Hemisphere is tilted away from the sun for part of the year and toward the sun for another part As the tilted Earth travels around the sun the angle of the sun’s rays hitting the planet changes and causes the seasons What’s a Leap Year It takes the Earth a year to revolve around the sun Each revolution lasts 365 25 days Every four years each quarter of a day adds up to a single day In those leap years the year has 366 days with the extra day on February 29 The North Star and the Southern Cross As the Earth travels around the sun its place in the solar system shifts That changes our view of the stars Constellations that are out in summer will dip below the horizon in the winter and vice versa Meanwhile the rotation of the Earth also changes the placement of the stars in the sky But you’ve probably heard that the North Star named Polaris is always in the northern part of the sky How can that be The Earth tilts toward Polaris and the Earth’s tilt never changes so the North Pole always faces the North Star When we look toward the North Pole we’re always looking toward Polaris A similar star signpost is in the south called the Southern Cross or Crux The five stars that make up the Southern Cross guided explorers as they sailed toward Australia and New Zealand in the Southern Hemisphere 5
