Quote:
Originariamente inviato da zappy
non so se mi convince...
la ISS non è in caduta libera, altrimenti cadrebbe a terra.  |
No, ed è proprio questo il tipico errore.
L’ISS continua a cadere, ma la terra, essendo sferica, diventa costantemente più distante, per cui “non si avvicina mai” (in realtà per vari motivi un minimo di perdita di quota c’è, e viene compensato periodicamente).
Dal
sito NASA:
“
How Can Spacecraft Fall Around Earth?
What does it mean to fall around Earth? Earth's gravity pulls objects downward toward the surface. Gravity pulls on the space station, too. As a result, it is constantly falling toward Earth's surface. It also is moving at a very fast speed - 17,500 miles per hour. It moves at a speed that matches the way Earth's surface curves. If a person throws a baseball, gravity will cause it to curve down. It will hit the ground fairly quickly. An orbiting spacecraft moves at the right speed so the curve of its fall matches the curve of Earth. Because of this, the spacecraft keeps falling toward the ground but never hits it. As a result, they fall around the planet. The moon stays in orbit around Earth for this same reason. The moon also is falling around Earth.”