Gravitational interaction between Earth and a human sized object
cease to hold an object, a familiar phenomenon happens: it drops.
This fall is caused by the Earth's attraction because of the
gravitational interaction that exist between all objects with mass.
Gravity is responsible for falling all objects.
The gravity makes objects fall toward the ground but for more accuracy
we can say they are attracted to the center of Earth.
" Interaction " means there are two actions: from Earth upon the object
and also from the object upon Earth. So we could ask " Why Earth
doesn't move whereas general properties of interactions tell that the
two actions have an identical strenght ? ". The answer is quite simple:
The gravity has different effects upon Earth and upon the object
because they have different masses. The bigger a mass is, the less the
object moves. Some actions of identical strenght have more effects on a
light object than on a heavy one: The Earth is really far more massive
than a human sized object therefore an action upon it have no
interaction between two human sized objects
around us ( table, pencil, chair etc ) have a mass and therefore exert
between them gravitationnal interactions but our daily experience tells
us they don't attract each other like two magnets could do it.
The gravity still exist for these objects but their mass is so weak
that gravity has also some very weak effects, so weak that they are not
The effects of gravity between objects at the human scale can therefore
interaction between Earth and Sun
motion of Earth around the Sun is one of gravity effects.
Why gravity doesn't make Earth fall upon the Sun ?
can be compared to a stone that is tied to a string that someone makes
holding the string attracts this one, and the string attracts the
stone: from this attraction combined to a suitable initial speed
results a circular motion.
The Earth is like the stone, gravity like the string and the Sun like
the hand: The Earth have a circular motion around the Sun because of
its initial speed and because of the Sun gravitational action.
other circular motions in the solar system and beyond can be explained
the same way