Why do we always fall down when we jump up? Why does an object fall when we hold it in our hand and then let it go? Why do the oceans have tides? How can we send space shuttles into space? How is it possible that the moon, sun, and other stars are so high above the earth that they are not held down by anything visible?
All of these amazing facts have a common physical explanation, a force that acts on everything in the entire universe. This force is called gravity or the force of attraction [Makam 98].
The force of gravity was discovered by a 17th-century physicist named Isaac Newton.
Not many years later, the renowned physicist Galileo Galilei argued that a heavy object (a stone) would fall faster than a light object (a feather), simply because the friction of the light object in the air slows down the pull of gravity.
In other words: gravity acts on all bodies equally, and the only reason that the feather or the bag, for example, land more slowly, is because the feather has a large surface area relative to its volume, and therefore air resistance is particularly high (since the contact area if air is large), and their friction in the air slows down the fall.
Brian Cox of the BBC decided to repeat Galileo's experiment in a room without air - a vacuum. According to Galileo, both objects would be expected to fall at the same speed, since the air that creates friction is not present, and in the room only the force of gravity acting equally on all objects remains.
What were the results of the experiment? Watch.
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