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Ask The Scientist – Why Does The Earth Rotate?
John P. Millis, Ph.D. for redOrbit.com – Your Universe Online
This article is the latest installment in a new series where redOrbit’s in-house experts will answer questions submitted by you, the reader. Got a science or space question that’s stumping you? Each week we’ll select a handful of the wiliest questions you can whip up to tease the brains of our resident gurus (we like call them ‘geeks’).
Question:
“Why does earth rotate? And if it is for conserving angular momentum, then why doesn’t its speed slow down with time?” – Anjum N.
Answer:
This is a common question, one that I get nearly every semester from my astronomy students. And, of course, our everyday experiences tell us that in order to cause something to rotate, a force must be applied – like spinning a nickel on a table. Also, over time – in most cases very quickly – the object slows down and comes to rest.
So, how is it that the Earth began to rotate? And, perhaps more puzzling, why is the Earth still rotating billions of years later?
The simple answer to this quandary, as our question proposer guessed, is a concept in physics known as Conservation of Angular Momentum. Imagine an ice skater spinning on the ice with her arms extended. As she then pulls her arms into her side, the rate of her rotation increases. This is the conservation law in action.
Now, let’s imagine a large interstellar gas cloud. We see these all over our galaxy, some isolated and small. Others extend hundreds of light-years across or more.
For our purposes, we will imagine one a few light-years in diameter, mainly composed of hydrogen and helium and trace amounts of other elements. The individual molecules of gas are moving around in a nearly random fashion. If we add up this motion, we will find that the cloud, overall, has a non-zero momentum and angular momentum. While it is possible that the system is completely at rest, this is highly unlikely in general.
Now, if this cloud is suddenly disturbed – say by a nearby supernova event or passing star – the cloud may start to collapse. As it does the cloud begins to shrink, becoming more dense. Consequently, the cloud begins to rotate more rapidly, just as our ice skater did when she pulled her arms in.
Even if the initial rotation speed of the gas cloud was low, the immense compression as the cloud begins forming into a solar system is enough to install a considerable rotation. Over hundreds of millions of years, the central part of the cloud forms the central star – our Sun – while the rest of the disk supplies the material that will form the planets. And, as one would expect, the co-rotation of the disk is why all of the planets orbit in the same direction around the Sun.
As we focus in on the individual planets, like Earth, we notice that all of the planets orbit to at least some degree. Again, this is due to the overall angular momentum of the system being conserved. Every piece of matter that went into forming the Earth each had its own particular angular momentum, and as they all became joined together they contributed to the “spin” of Earth.
In the early days of formation there were other things that could have added to the rotation we see today: impacts from large planetoids, and even asteroids or comets. Today, the spin of the Earth is more consistent, since there is little to affect its motion.
The reason a spinning top slows down and eventually stops is because of friction and drag, sapping the rotational energy of the top and bringing it to rest. But the Earth does not experience significant drag from the solar system.
Of course, there are things like the Moon’s gravity, the drag of the magnetic field through interstellar space and the solar wind, which can slow the Earth down. But these effects are small in comparison to the rotational energy of Earth.
So there you have it: the reason that the Earth orbits the Sun and spins on its axis is due to conservation of angular momentum. And while there exist natural ways in which this motion can be altered, the Earth won’t stop spinning anytime soon.
Source: http://www.redorbit.com/news/space/1113143960/earth-what-causes-it-to-rotate-051214/
Wow, I’m surprised to see that an “expert”, someone who actually teaches astronomy for a living doesn’t even know the correct answer to his own question. But then that’s not too surprising since counterintelligence has been quite busy suppressing certain pieces of knowledge, certain fundamental principles which are necessary to understand the construction and operation of this universe.
If one needs any any proof of this, one needs look no further than the confiscation of all of Tesla’s notes and research material immediately after his death, and the “loss” of some of Maxwell’s fundamental equations.
In the above cited example of the Conservation of Angular Momentum with the ice skater, he fails to mention that the application of angular momentum was necessary to start the rotation in the first place, which in that example, would be supplied by the skater’s muscles. Then, as the skater pulls her arms in that EXISTING rotation (which was started by her contracting muscles) increases per the Conservation of Angular Momentum.
Now, let’s move to his next example using an interstellar dust cloud. Per his own description:
“The individual molecules of gas are moving around in a nearly random fashion. If we add up this motion, we will find that the cloud, overall, has a non-zero momentum and angular momentum.”
Okay, there’s no angular momentum – no rotation.
He then goes on to describe how this gas cloud begins to condense, and right after that says:
“Consequently, the cloud begins to rotate more rapidly, just as our ice skater did when she pulled her arms in.”
Notice above he says it begins to rotate MORE rapidly, but there is no mention at all of the source of the ORIGINAL rotation. What STARTED that rotation in the first place? And no, it’s not because that gas cloud was disturbed by a nearby supernova which mysteriously caused a massive rotational reaction rather than merely a distortion or dispersal pattern.
Even a dust cloud which is NOT disturbed by a nearby supernova will over time, as it begins to coalesce and condense under it’s own gravitational forces, begin to rotate.
The source of the rotation or spin is the basic underlying physics of matter in this universe involving electromagnetic and gravitational forces, physics which has been intentionally suppressed in order to hinder and control certain technologies and understandings.
Homepage:
http://www.upwardvectorpubs.com
Slight correction on the above wording
Now, let’s move to his next example using an interstellar dust cloud. Per his own description:
“The individual molecules of gas are moving around in a nearly random fashion. If we add up this motion, we will find that the cloud, overall, has a non-zero momentum and angular momentum.”
Note he says “nearly random fashion”. That’s the key. But then right after that says that it has a “non-zero” angular momentum, a big change from nearly random. So where did this angular momentum come from in the first place? And that’s my point here. It’s coming from forces which are being overlooked and not discussed.