1. Let’s not confuse weight and mass. Mass is an irrelevant concept, but weight depends on the gravitational field of which celestial body the object is in. On Mars, for example, everything weighs about 60% less than on Earth.
2. Isaac Newton was the first scientist who formulated the law of universal gravitation.
3. In the absence of gravity, the bones of the human body lose up to one percent of calcium per month, and after losing a few percent they become brittle.
4. The word “gravity” comes from the Latin “gravitas”, which means “gravity”.
5. After returning from orbit, astronauts are forced to get used to gravity again. During the time spent on the expedition, they often manage to forget that objects have weight, and fall if they are released.