Contents CHAPTER 1 What Is Outer Space 4 CHAPTER 2 How Do We Explore Outer Space 8 CHAPTER 3 Deep Exploration CHAPTER 4 Humans in Outer Space CHAPTER 5 Ship Shape CHAPTER 6 What’s Next ACTIVITY Your Space Science Mission Glossary Learning More Index and About the Author 16 24 30 36 44 46 47 48
CHAPTER 1 What Is Outer Space Outer space begins about 60 miles 100 km above the surface of Earth Humans cannot live there There is not enough air to breathe Stars shine in blackness above the atmosphere because there is no air to scatter light and make the sky blue The distances between objects in space are so big that they are not measured in the units of length we use on Earth Distances in outer space are measured in light-years Distance and Light A light-year is the distance that light can travel in one year Light travels at a specific speed of about 186,000 miles 300,000 km per second Doing the math this means that light travels around 5 9 trillion miles 9 5 trillion km in a year The nearest star to Earth is 4 3 light-years away The distances into deep space measure into the billions of light-years atmosphere Outer space begins at the edge of the atmosphere which is the envelope of gases that surrounds Earth 4
Stars and their solar systems group together in space in massive clusters known as galaxies Defining Space Space is full of stars planets asteroids and comets These features are all clumped together in galaxies Our Solar System includes the Sun and the planets that surround it It lies on one of the spiral arms of a galaxy called the Milky Way one of 100 to 200 billion galaxies that exist in the universe The closest galaxy to ours is the Andromeda Galaxy It is 2 3 million light-years away Telescopes are used to help scientists see into space They can see as far as 13 7 billion light-years What lies beyond is a mystery Our universe may not be the only one that exists No one really knows how big space is It is possible that space is much much bigger than we think it is today Future Finds Our understanding of space comes from scientific research and theories As we continue to dig deep into the unknown we find new pieces of information that constantly change challenge and confirm our current body of knowledge The science of outer space is continually evolving Come join the journey 5
