The earth spins because of how it was created.
Millions of years ago, it was created amidst
lots of gas and dust, which formed a small mass.
As the gas and dust kept collecting and the mass
continued getting bigger, the gravity surrounding
it increased too. The more powerful it got, the
faster it attracted these particles and created
sort of a spinning whirlpool. At one point the
mass, called Earth, couldn't get bigger and the
gas and dust particle whirlpool was at a minimum,
but the Earth kept spinning and will continue
It's not so much that the Earth has to spin,
but it does spin. Spinning mass has what is called
angular momentum, which is a physical quantity
like energy, mass, or linear momentum. Angular
momentum can't be created or destroyed (also like
so many other physical quantities), so the only
way to stop the Earth from spinning is for the
Earth to hand off its angular momentum to
The Earth is slowly doing this, actually: the
tides caused by the moon exert a torque on the
Earth which slows down its rotation, while at the
same time pushing the moon further out in its
orbit from the Earth. During the Silurian period,
about 430 million years ago, the Earth's year was
the same length in terms of number of seconds or
minutes, but had over 400 days, meaning that the
Earth was spinning fast enough to make 400
complete revolutions in the time that it now can
only do about 365.
Click Here to return to the search form.