Liberal Arts Blog — Absolute and Relative Motion: the Earth, the Airplane, the Car
Liberal Arts Blog — Wednesday is the Joy of Science, Engineering, and Technology Day
Today’s Topic — Absolute and Relative Motion: the Earth, the Airplane, the Car
How come I can’t feel the earth rotate? Can you feel it? I can certainly feel rotational motion when I get on a merry-go-round. In fact, I can’t stand it. I feel dizzy and nauseous and get off. Who was the first guy to figure this out and write about it? What is the most concise way to explain this to a third grader, fifth grader? 8th grader? By analogy with being on an airplane or in a car? Think of this as thinking and writing challenge. In how short a sequence of sentences can you explain this to a child? Has anyone ever written a poem about it? A sonnet? A set of rhyming couplets? Put it to music? Perhaps to a catchy rock tune? Thanks to Leon for inspiring this post. Experts — please chime in. Correct, elaborate, elucidate.
GRAVITY, CONSTANT ROTATION, THE ATMOSPHERE ROTATES WITH THE EARTH
1. “The gasses that make up the atmosphere are attracted to the the solid parts of the earth by gravity. This makes the particles spin with the earth at the same rate.” (Quora, first link below)
2. “You, your friends, the buildings, cars and even the air around you is being held together by Earth’s gravitational pull. Since the Earth rotates at a near-constant speed (that is, it doesn’t speed up or slow down in any way noticeable to us), we simply spin with it and don’t feel a thing.” (Children’s Museum of Indianapolis, second link below) Is that really self-explanatory? It seems explanation by assertion to me.
3. “You can only feel motion if your speed changes. For example, if you are in a car which is moving at a constant speed on a smooth surface, you will not feel much motion. However, when the car accelerates or when the brakes are applied, you do feel motion.” (Cool Cosmos, third link)
NB: The earth is spinning around the sun at 67,000 miles per hour!
THE GREAT IF — WHAT IF THE EARTH STOPPED? WELL, WHAT IF YOU SLAMMED ON THE BRAKES?
1. What would happen to the coffee if you slammed on the brakes of your car?
2. What would happen to the coffee on the trolley of the airplane if the airplane stopped?
3. For reference: a jumbo jet flies at about 500 miles per hour, about half the speed of the earth’s rotation. The Earth travels around the sun at roughly 67,000 miles an hour (earth’s orbit = roughly 584 million miles divided by 365 days = 1.6 million per day divided by 24 hours = roughly 67,000 mph).
NB: Extra credit question How many people would Superman kill if he stopped the earth? Answer: the earth’s entire population. (from Neil deGrasse video, last two links)
THANK GOD FOR THE SPINNING EARTH, THE NIGHT, AND THE HARMONY OF IT ALL
1. Isn’t it a miracle that the damned thing just keeps on spinning? Every day a new dawn. Every day another sunset.
2. Every day a chance to take a break, sleep, re-boot in the soothing darkness under a canopy of planets and stars.
3. Who synched all these systems, astronomical and biological, so finely, so exquisitely, so mathematically precisely?
NB: Nobody or somebody? which is more plausible? was Pascal right after all?
FOOTNOTE — Galileo’s Account from 1632 book, Dialogue Concerning the Two Chief World Systems, via Quora (5th link) — Imagine being in the main cabin below decks on a large ship…
Shut yourself up with some friend in the main cabin below decks on some large ship, and have with you there some flies, butterflies, and other small flying animals. Have a large bowl of water with some fish in it; hang up a bottle that empties drop by drop into a wide vessel beneath it. With the ship standing still, observe carefully how the little animals fly with equal speed to all sides of the cabin. The fish swim indifferently in all directions; the drops fall into the vessel beneath; and, in throwing something to your friend, you need throw it no more strongly in one direction than another, the distances being equal; jumping with your feet together, you pass equal spaces in every direction. When you have observed all these things carefully (though doubtless when the ship is standing still everything must happen in this way), have the ship proceed with any speed you like, so long as the motion is uniform and not fluctuating this way and that. You will discover not the least change in all the effects named, nor could you tell from any of them whether the ship was moving or standing still. In jumping, you will pass on the floor the same spaces as before, nor will you make larger jumps toward the stern than toward the prow even though the ship is moving quite rapidly, despite the fact that during the time that you are in the air the floor under you will be going in a direction opposite to your jump.In throwing something to your companion, you will need no more force to get it to him whether he is in the direction of the bow or the stern, with yourself situated opposite.The droplets will fall as before into the vessel beneath without dropping toward the stern, although while the drops are in the air the ship runs many spans. The fish in their water will swim toward the front of their bowl with no more effort than toward the back, and will go with equal ease to bait placed anywhere around the edges of the bowl. Finally the butterflies and flies will continue their flights indifferently toward every side, nor will it ever happen that they are concentrated toward the stern, as if tired out from keeping up with the course of the ship, from which they will have been separated during long intervals by keeping themselves in the air. And if smoke is made by burning some incense, it will be seen going up in the form of a little cloud, remaining still and moving no more toward one side than the other. The cause of all these correspondences of effects is the fact that the ship’s motion is common to all the things contained in it, and to the air also. That is why I said you should be below decks; for if this took place above in the open air, which would not follow the course of the ship, more or less noticeable differences would be seen in some of the effects noted.
A LINK TO THE LAST FOUR YEARS OF POSTS ORGANIZED BY THEME:
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#2 “39 Songs, Prayers, and Poems: the Keys to the Hearts of Seven Billion People” — Adams House Senior Common Room Presentation, 11/17/20
Please share the coolest thing you learned this week related to science, engineering, or technology. Or, even better, the coolest or most important thing you learned in your life related to science and engineering.
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