Introduction: Defying Gravity
Liftoff, Second Edition — by Diana Larsen, Ainsley Nies (4 / 56)
For ages, humans have watched birds soaring and have wanted to fly. We stayed earthbound until we learned about the effects of gravity and how to overcome them. Now we can defy gravity with a rocket launch, or liftoff. Rockets generate energy at the start of flight, giving humans the force to overcome gravitational pull and boost themselves skyward.