WHY HUMANS EXPLORE SPACE Humans have been interested in exploring or studying space for thousands of years Starting in about 1600 scientists used telescopes to get a better view of the objects in the sky Only in recent decades has it been possible to travel into space to get a closer look at the Moon and other bodies More than 5,000 spacecraft have been An astronaut from the space shuttle Challenger floats in outer space 4
launched into space to gather information since 1957 They include spacecraft with humans onboard space probes and satellites The Soviet Union now Russia and the United States were originally the main countries exploring space Many other countries are now involved including China and the European countries that are part of the European Space Agency Through space exploration humans have learned a great deal about the planets stars and other objects in space NASA’s Hubble Space Telescope captured this image of stars seen in our Milky Way galaxy Without space exploration we wouldn’t have solar panels LED televisions or ear thermometers These are just a few inventions to come from studying space Think About It 5
UNDERSTANDING GRAVITY The biggest challenge of getting objects into space is breaking through Earth’s gravity Gravity is a pulling force that works across space It causes all objects to attract other objects For example the Sun which is millions of miles from Earth pulls on Earth and the other planets and objects in the solar system These objects would move in a straight line but the force of gravity pulls them toward the Sun At the same time the speed of the pull of the Moon and Earth on each other orbit of the Moon around Earth pull of gravity that changes the path of the Moon path the Moon would naturally take Moon Earth Gravity is the force that keeps the Moon orbiting or circling around our planet 6
planets in their orbits keeps them from falling into the Sun On Earth gravity pulls objects toward the center of the planet This is what makes objects fall It is also what keeps objects in place rather than floating around In order for spacecraft to leave Earth they must have enough power to overcome the pull of gravity The force of gravity also pulls the planets including Earth toward the Sun Compare life on Earth to life without gravity What would it be like What might be hard What might be fun Compare and Contrast 7
