May 31, 2018 Thursday
Bedtime Story
Initial Angular Momentum was Imparted during Its Origins
Last night I had left you with the
accretion process that often takes place in the interstellar dust due to
gravity which is truly a run-away process just like a ball set rolling down the
slope.
Once it starts, there is no stopping it –
initiation of accretion only further accelerates the process as more and more
dust matter get closer to each other significantly increasing the effect of
gravitational force.
Ever increasing mass in the center of the
action eventually leads to the collapse, and as the collapse continues things
get interesting because the law of conservation of angular momentum begins to
display its effect.
This specific conservation law dictates
that the spinning of a body will accelerate as the spinning body collapses
within itself.
There are several real-life events, the most
classical one that you can watch on several YouTube videos is the increase in
the rate of spin of a skater when he or she pulls in his/her arms closer to the
body.
The increase in spin keeps the angular
momentum constant as now the radius (arms) of the body (figure skater) has
decreased from before (when the arms were out stretched).
What holds true for stars also holds true
for planet earth.
Earth rotates today and we have days and
nights because it is the same spin that was imparted to it during its formation
that keeps on going today thanks to the law of conservation of angular momentum.
Because our planet is largely spinning and
revolving in vacuum, there is a very little torque acting on it, at least as
far as our miserable existence is concerned, it can almost be discarded.
Of course, certain amount of external
torques do have acted on our planet over so many billions of years and continue
to do so in the form of collisions from meteorites and asteroids.
In fact, not just meteorites and asteroids
but it is believed that our planet had undergone multiple collisions and
bombardments even with objects that were as large as planets.
In fact, it is believed that one such major
blow that is fancifully known as the “giant-impact” or the “Big Splash” took
place when a protoplanet fancifully named as Theia struck our planet just 0.1
billion years after the solar system had formed; Which amounts to almost 4.4 to
4.45 billion years back.
Our Solar System itself formed 4.6 billion
years ago, once again thanks to the gravity leading to the gravitational
collapse (which is different from accretion) of a small part of a giant
molecular cloud.
Soon after our solar system had formed
something seriously gigantic that is believed to be a protoplanet called Theia
struck our planet at an oblique angle when our planet was nearly fully formed.
It is believed that Theia’s iron core would
have sunk and merged with the young Earth’s iron core and similarly a large
part of its mantle would have got assimilated with our mantle.
We shall continue with the violent journey
of the birth of our planet in the nights to come.
Stay tuned to the voice of an average story storytelling
chimpanzee or login at http://panarrans.blogspot.com
Good night Mon Ami and my fellow cousin ape.
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Another great educator and a teacher that I am aware of is
Professor Subhashish Chattopadhyay in Bangalore, India.
While I narrate stories, Professor Subhashish an electronic
engineer and a former professor at BARC, does and teaches real mathematics and
physics.
He started the participation of Indian students at the
International Physics Olympiad.
Do visit him here:
All his books can be downloaded for free through this link:
For edutainment and English education of your children, I
recommend this large collection of Halloween Songs for Kids:
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