Earth precesses around its axis every ~26000 years.
But in addition to this precession, there is an extra wobble that was observed by Kustner and later followed up by Seth Carlo Chandler, Jr called the Chandler Wobble that occurs at a much smaller time scale.
In 1888, Kustner found that the latitude of Berlin had changed slightly
during his observations of the night sky.
Therefore in 1891,Chandler. decided to conduct a 14 month study examining this change. The following is a plot of the spiral path taken by the earth’s axis over that 14 month period.
The following plot shows the motion from 1909 – 2001.
Although many theories indicate that this is due to the fact that earth is not a perfect spherical rigid body, it is still not entirely clear on the mechanism that drives earth into this small wobbly motion.
If you took a closer look at the plots you would find that this wobble is of the order of a couple of meters which most certainly does not seem like a lot.
But if you are an astronomer if you do not account for this correction, you might just end up pointing your telescope at the wrong object
is an excellent argument given by Galileo in favor of the rotation of
the Earth and why things would still fall to the same place even if the
Earth were rotating:
In replying to this, those who make the earth movable answer that the canon and the ball which are on the earth share its motion or rather that all of them together have the same motion naturally.
Therefore the ball does not start from rest at all but to its motion about the center joins one of projection upward which neither removes not impedes the former.
will see the same thing by making the experiment on a ship with a ball
thrown perpendicularly upward from a catapult. It will return to the
same place whether the ship is moving or standing still
The profundity of this argument is that, the very same principle that ‘ball does not start from rest at allbut with velocity of the earth’ is used by space shuttles to reach orbital velocity with lesser fuel consumption.
But despite Galileo’s argument, it was still believed for a long time that it were the heavens that moved and not the earth.
God hath established the world which shall not be moved in spite of
contrary reasons because they are clearly not conclusive persuasions.
We have been discussing about the rotation of the Earth in the past couple of posts but lets take a second to understand why the earth is rotating in the first place.
Here is a quick summary:
Our Solar System formed about 4.6 billion years ago when a huge cloud
of gas and dust started to collapse under its own gravity.
As the cloud collapsed, it started to spin. Some of the material
within this cloud gathered into swirling eddies and eventually formed
into planets. As the planets formed, they kept this spinning motion.
As material gathered in more closely to form a planet, like Earth, the
material spun faster. This is similar to what you see when skaters pull in their arms and spin
And as a result since there are no forces are acting on Earth to slow it down, it continues to spin to this day. **