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What Goes Up...
As the story goes, Sir Isaac Newton
(1642-1727) was sitting under an apple tree and admiring the Moon when an apple fell on his head. (Most historians agree that Newton did see an apple fall -- but not that it actually bopped him.) At that moment Newton had an inspiration: the force pulling the apple down and the force keeping the Moon in its orbit around the Earth were one and the same. The force was gravity, and Newton explained that gravity pulls toward the center, not just down to the ground. In other words, the apple fell towards the center of the Earth, and his head just happened to get in the way.
Original theory: In 1687, Sir Isaac Newton published Principia Mathematica, which explained
the theory of gravitational pull.
Characteristics: the force of attraction between all objects exists throughout the Universe.
Significance: one of four "fundamental forces" of the Universe; keeps our feet on the ground and the planets in orbit
Stars are shaped like spheres because:
gravity pulled them into that shape as they formed
they eroded into round shapes over millions of years
round shapes have less wind resistance
Correct!
Stars are round because gravity pulls their mass towards their centers. That's why you won't see any square or triangular stars.
An object's gravitational pull is affected by:
distance and mass
distance and brightness
mass and speed of light
Correct!
A more massive object has a stronger pull than a less massive one. This strength is also affected by distance -- the closer the objects, the stronger the pull.
The Moon has no gravity.
Fact
OR
Fiction
?
Fiction
The Moon is less massive than the Earth, so its gravity pulls less than on Earth. Astronauts can jump high, but they don't float away.