There’s an old saying that goes something like this: “Love makes the world go ‘round.” And, while love does its fair share of work trying to keep the planet Earth intact (from human beings), I’m not so sure that it contributes to the rotational force of the planet. But, with the Earth’s “Energizer Bunny”-like stamina, what does make the Earth go ‘round? If you look online, you’ll find a million explanations about the “conservation of angular momentum,” which states that:
“The angular momentum of a system remains constant unless acted on by an external torque.”
And, so, the explanations online all offer the same, redundant argument. Because of constant collisions a billion years ago, the Earth, and apparently every other planet, achieved momentum.
And … voila! Mystery solved. Well … unless you account for the law of conservation of angular momentum whereby external forces acting on the spinning object would slow it down.
I would theorize that the same scientific principal of conservation of angular momentum that explains why the Earth is spinning equally explains why it should not be spinning for several reasons:
First, the sun is an external gravitational force and keeps the Earth locked into an orbit (supposedly), under the principles of centripetal acceleration. In a co-rotating non-inertial reference frame where an object is static, the centripetal force is balanced by the inertial centrifugal force, so the velocity vector is constant (zero). To make that more clear, in an inertial frame, an object has no forces acting on it and travels in a straight line (Newton’s first law). Ergo, there is a force acting on the Earth that is part of its rotation around the sun and that force has a gripping effect that the rotation of the planet has to overcome. It’s no different than being in a “Gravitron”, carnival ride where you can freely stand and move, but there are forces which restrict that movement. Even within a gravitational sphere (such as being a human being on Earth), while we are free to move, gravity impacts and even limits the speed and distances at which we can move. Therefore, the sun should be a form of friction to the Earth’s rotational efforts.
Secondly, the Earth’s gravitational field is not free from obstacles. The moon provides a physical drag on the Earth’s rotation. While it may not be a huge drag, think of how a car slows down when releasing the acceleration pedal. The combination of effects between parts of the engine, the road, the air, and other factors all contribute and the moon … is one of Earth’s factors that would slow it down if a foot was taken off of the gas pedal.
Third, space is not empty. There are objects that collide with the planet Earth and each of those has an effect of force. It’s already well known by the massive craters found on the planet’s surface both above and below the ocean that these impacts have been epic in scale. However, unless the trajectory of impact was in an alignment of greater than 45 degrees perpendicular to the current spinning trajectory of the Earth (and I am doing some pseudo math here … so feel free to correct me), the force of a one million megaton impact focused on a singular point would be an incredibly powerful force against the Earth’s continuing rotation. To further the case, any arguments to the contrary would also contradict the popular notion that Venus and Uranus spin in the opposite direction “due to meteor impacts”. Well, at least if you consider Newton’s laws and the fact that an opposing force with the equivalent power of the rotational torque that started the planet spinning (under the conservation of angular momentum theory), would be like two gears slamming into each other whereby the gear overcoming the force of the other would have to possess not only the full force of the opposite body, but enough force to also start a hundred billion year cycle of rotation in the opposite direction. That’s a lot of force … I mean … a LOT. Like … *boom* … ‘bye, bye’ (whatever planet is impacted by that force)! Of course, there are arguments to this notion where angular momentum will remain constant based on a series of factors such as trajectory of conflicting forces, quantity of force, etc. However, the moon and the sun do impact the Earth’s rotational speed … and that is only by the relationship between gravitational forces. I would estimate that hitting a spinning rock with a series of other, large rocks, as long as the trajectory is opposite the rotational direction of the primary rock … would slow it down. I have yet to see an otherwise working example of infinite perpetual motion.
Finally, there is another factor about rotation which is the fact that the Earth is not a free-spinning sphere in a complete vacuum. It is, in fact, an elliptically shaped object that has a lot of weight (including moving objects like 7 billion people), weather patterns, earthquakes, and other natural occurrences that do have a significant impact on the planet’s gravitational forces.
So … why … is it still spinning?
Under the conservation of angular momentum, depending on the original speed of the Earth that got it rotating in the first place, unless an equal amount of oppositional torque acted upon the planet, the rotation would continue. Yet, it can be worn down over time.
So, for starters, the Earth currently rotates at an estimated 1,040 mph, or 24,901 miles per day (that is miles divided by 23 hours, 56 minutes, and 4 seconds). And, we have evidence that the rotation is slowing over time. Versus 1972, the length of a day is now 1.6e-8 seconds longer. So, let’s imagine that this is a constant (because it’s not a constant, so we have to pretend for the moment). In 44 years, we’ll gain 1.6e-8 seconds on a day due to a slowed rotation. That would mean that in 400 million years, the length of a day would be 0.145 seconds shorter than it is right now. Doesn’t seem like much of a change, does it?
However, there’s a conundrum. Penn State astronomer Kevin Luhman claims that the Earth is slowing at a rate of 1 millisecond (1 thousandth of a second) per year due to the moon alone. Well, 400 million years ago, that would be 400,000 seconds, or 277 hours lost in a year (or 3.16%). Now, if the sun, the moon, one thousand meteors, and the fact the Earth is not in a vacuum all contributed the same equivalency of impact on the Earth’s rotation that would be a loss of 277 thousand hours in a single year from 400 million years ago. The only way for that to work would be for the rotation of the Earth to be much greater than what it is now. How much greater? I don’t have the exact mathematics on this, but on the surface (and someone, please feel free to counter this), it would have to be 30 times greater than an 8,760 hour year. So assuming that a year was somewhere in the same approximation of length, the Earth would have had to be spinning at a rate of 33,000 mph. At that speed, the gravitational force of the planet would have probably been significantly greater than what it is now. Of course, this would also provide an answer as to why dinosaurs were so large, given the physical dimensions of a creature needing to overcome that force (assuming the moon was around that long ago to also be a contributor).
Just remember that all of this is predicated on two principals: that every planet was born spinning and under that pretense (conservation of angular momentum), that the effects of the multitudes of contributing factors to slowing the Earth would have to literally be negligible to justify that the Earth was not spinning faster. But, does it seem reasonable that everything just magically spins, left or right, because they’re born that way?
Given the chaotic principals of nature, it’s highly unlikely that every planet magically forms with a rotational force unless there was some underlying cause that was “universal”. For example, the molecular spin of atoms and molecules. Perhaps it’s the nature of elements in massive quantities with their electromagnetic interaction that gives cause to the rotation? That would be a good justification for “gas” giants like Neptune and Jupiter (if you believe Jupiter is a gas giant, which, I don’t), where there are not enough “collisions” to justify a rotation.
It’s difficult to believe that while the Sun’s gravitational force 92.96 million miles away (Sun to Earth) may be small, at one-third the distance, Mercury would face an exponentially higher level of resistance whereby its rotation should have potentially come to a complete halt, and yet, it hasn’t. After all, when an object is rotating inside the space station, even in a vacuum with limited interference, it doesn’t stay rotating.
Another potential reason for the rotation of just the Earth is its supposedly molten/iron core. The rotational core creates a rotating magnetic field around the planet which keeps it spinning. However, this would eliminate the ‘gas giant’ theory of Neptune or Jupiter (although I’ve already contradicted that as previously noted). Even in the Hadron collider, where particles are accelerated in an extreme vacuum and held at the center of the collider tunnel by large, magnetic fields, they do not keep spinning simply on their own (after all, in a complete vacuum, there is really no other force to act upon them). The surrounding magnetic fields designed to accelerate the particles also offer just the smallest amount of resistance necessary to slow them down (unless additional energy and fluctuation of the magnetic fields is applied causing acceleration).
Another important factor in the model of our planetary system is the North and South poles of our own planet. Anyone who has worked with magnets knows that magnets have a tendency to want to flip around (opposites attract) unless rotated (levitron physics). Thus, the somewhat flat nature of the concentric magnetic rings around the Sun may serve another purpose, which is to balance the planets in place, adding spin, and keeping them from flipping around / staying balanced. This is a little more obscure of an idea and would require a lot of research and investigation, but is nevertheless, on the list of possibilities.
Or, perhaps there is an even more mysterious force at work whereby the spherical nature of the gaseous surface around a planet, like the spherical appearance of the electrons around a nucleus, are part of the same system. And, in this alternate model, the concentric rings around the sun, around Saturn, and around the nucleus of an atom are also all interrelated. This would point to a universal force that also keeps the planets spinning (the micro and macrocosms). Of course, if we’re not careful, this could borderline on Deism and the spinning top theory!
Or, maybe the old adage is correct: love makes the world go ‘round. So … stop hatin’ everybody! Otherwise … we’ll all be thrust into space … and I’m not quite dressed for that!
Whatever the mysterious force may be that creates a universal constant on all celestial bodies, the universe, and even the microcosmic universe of atoms and molecules, one thing is for sure: it’s a great design!
Thanks for reading!
“Simple. Cows fly, but not dogs, so the dogs attacked the cows and the cows ran to the moon or ‘jumped to the moon’ – and the force of their legs pushing off the Earth makes it spin.” – Ozothen, Ozothren (on why does the Earth spin)