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Tuesday, April 11, 2017


An object in motion will stay in motion.

An object at rest will stay at rest.

This is Newton's first law of motion or the "law of inertia"

We did not use fuel to propel the Apollo space craft to the moon or from the moon to the Earth. Fuel was used to escape the gravitational field of the Earth and later the Moon. Fuel was used to push the Apollo spacecraft in the direction it needed to go.

But once the Apollo space craft was moving toward the moon or toward the Earth, no fuel was used for propulsion. The Apollo space craft continued to move through empty space. There was no friction of an atmosphere to stop the Apollo space craft. Inertia was the means of Space travel to the moon. The gravitational forces of the Moon and Earth also came into play as the Apollo capsule approached them.

Earth Rise from the Moon    Courtesy of NASA   taken by astronaut Frank Borman


  1. Did they have to swing around the moon to get back or use fuel? Can't remember the details.

    1. Apollo dropped off anything unneccessary in space to reduce weight. The Apollo spacecraft had an orbiter and a landing craft. Fuel was used to lift off from the moon. The gravity is so slight on the moon, that you could jump high enough to be propelled into space.
      After reattaching to the orbiter. Michael Collins stayed in the orbiter to facilite the lander with Buzz Aldrin and Neal Armstrong to reattach.
      The orbiter orbited the moon until the right point in the orbit enabled a trajectory. Rockets were fired to turn the orbiter lander toward Earth. Once again, inertia was used by the Apollo space craft to move toward the Earth. Gravity eventually took over and the lander separated from the orbiter to land in the ocean.

  2. Hi Ann - thanks for this interesting aspect on the 'inertia' ... we so often forget the scientific aspects of words ... Inertia - I'd think of sloth! And when I'm almost out of it ... half-way through the A-Z - but you've reminded us of such an interesting point about 'motion' - cheers Hilary


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