"Science - Can You Explain to Your Children What Keeps Them Up - The Shuttle, Space Station, Moon?"," Everyone living today has been aware of space adventurism: the first flights, then orbits by Russia and the U. S
then onward to the moon (the heart-gripping uncertainly of survival of astronauts on Apollo 13); the first steps of a human on the moon ("A giant leap for mankind"); the Space Shuttle exploits (and fiery disastrous explosions); the astonishing assembly of the complex and gigantic Space Station (cooperation between the U.S and Russia)! Space achievements in the past half-century rank with the history-book adventures of Magellan and Columbus in probing the unknown.
Therefore, the answer to this question: "gravity" is certainly involved (Newton and his apple) - but gravity should actually force all this orbiting hardware (also the moon) to fall to Earth! Why don't they? (If the questioner holds back any further comment until the questionees respond further; probably half will venture uncertainly, "Maybe there is no gravity in space".
Gravity is always pulling everything toward Earth's center, (including humans - measured by our weight on a scale).
The key question is why these items remain in orbit about Earth; why don't they fall onto Earth? The answer is that they do - they are constantly falling to Earth - they are constantly falling to Earth, but are also traveling so fast around Earth, that gravity is pulling them into an orbit about Earth.
To be precise, to put the Space Shuttle or any vehicle into orbit, it must be rocketed with such horizontal speed that the constant pull of gravity forces it into an Earth orbit.
The faster the speed, the higher the orbit.
Therefore, the orbiting vehicle (Mercury, Apollo, Shuttle or moon) will continue to coast along in their orbiting journeys about Earth.
A top technical management team of cognizant Engineering managers of all major systems and subsystems - from both NASA and major subcontractors - has been designated and assembled to witness the launch, purpose: so that immediate technical decisions can be made, should any emergency arise.
We are seated on a rising array of wooden benches as if at a high school athletic field.
Only recently, many had participated in an exhaustive briefing to top NASA officials at the final Flight Readiness Review conference - as to the possibilities, probabilities and consequences of failure in any area.
Three miles away, powerful flood-lights show the Shuttle assembly standing vertically on the launch pad, the Orbiter (astronaut-carrying vehicle), the large center fuel tank and the two solid boosters - all a brilliant white under the concentration of flood-lights, limned against the dark, morning sky.
Slowly, the Shuttle assembly rises; all hold their breaths as fingers of fire emanate from the three powerful engines and the solid rocket boosters.
It then rapidly accelerates, growing smaller and smaller until it is out of sight.