The Dzhanibekov effect
An evening pause: This very very strange and somewhat inexplicable rotation effect occurs for real in at least one place, on a very large scale, and could have a significant effect on the Earth at some point. I will elucidate on Monday.
Hat tip Chris McLaughlin.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
An evening pause: This very very strange and somewhat inexplicable rotation effect occurs for real in at least one place, on a very large scale, and could have a significant effect on the Earth at some point. I will elucidate on Monday.
Hat tip Chris McLaughlin.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
If the earth is going to flip over…thank goodness.
I could have sworn I was watching this here a few weeks ago, must really be losing it. :(
I read an apocalyptic fiction book that came out in 1976 about this called The HAB Theory. It was written by Allan W. Eckert, best known for writing for Mutual of Omaha’s Wild Kingdom. It was pretty well trashed by critics, but I found it enjoyable. One of his themes that makes it interesting is the over specialization in physical sciences and how they do not interact with one another. The beginning of the book is, well lets say insane.
Can’t wait till Monday.
Connection with sun spot cycles?
A 2017 Russian movie about salvaging Saljut 7? That’s a must see!
Sir Dr. Roger Penrose
“Twistor theory”
Institute Henri Poincaré, Paris. October 2015
https://youtu.be/kmYfYOW0vSg
1:34:42
This is actually not against my intuition, although it looks funny. I suppose that intuition isn’t universal but individual.
An object that has inertial energy to rotate along one axis, has its perpendicular axes (chaotically?) vulnerable to small changes. So it can easily flip on those axes, but will keep its energy along the axis it is rotating energetically. The ice skating dancer can easily trip and fall over by mistake, but cannot so easily reverse the rotation.
I imagine the object tumbles randomly on all axes, but that this noise is dominated by an initial rotation along one axis. So its orientation is sensitive along all axes except the one that is spinning significantly.
Localfluff–
Good stuff.
“The Biggest Ideas in the Universe”
Dr. Sean Carroll
#1. Conservation
March 2020
https://youtu.be/AeNSMJtKGc0
28:16
So that is why the earth’s equator has a larger circumference than the prime meridian? I was told the equator was larger because it’s spinning momentum stretched the earth outward, like spinning pizza dough. So which came first the chicken or the egg? Was the equator always larger and thus over time spun around its maximum moment of inertia, or was it indeed stretched out like pizza dough?
Did a metor strike get the earth spinning in the first place? I think I recall hearing that theory a long time ago. If so I wonder how long it took for the earth to stabilize and start spinning around its maximum moment of inertia? Absolutely fascinating video. It has really got me thinking. I won’t even get started on the forces acting on an airplane propeller. I think this is somewhat the same thing as gyroscopic precession, but only in zero gravity.
John C,
You asked: “So that is why the earth’s equator has a larger circumference than the prime meridian? I was told the equator was larger because it’s spinning momentum stretched the earth outward, like spinning pizza dough.”
What you were told is correct. The fluid nature of the Earth’s interior is what allows for the bulging to occur, and as the Earth cools the bulge should remain built into the solid Earth. With its fluid interior, its spin will result in the equator bulging.
“Did a metor strike get the earth spinning in the first place?”
The spin of the Sun and the planets, as well as the planetary orbital directions, are largely a result of the net angular momentum of the part of the stellar nursery around the center of mass that formed into our solar system. The Earth’s spin is a result of all the matter that has fallen onto the Earth, and has been somewhat modified by tidal interactions with the Moon. A popular theory is that the Moon was formed after a collision of a large object with the Earth, but there would have been a spin of the Earth before that collision. That collision and the resulting net loss or gain of material would also have affected the Earth’s spin.
The Earth won’t flip, because it is spinning around the Z axis shown in the video, rotating in the plane of the yellow disk.
“I think this is somewhat the same thing as gyroscopic precession, but only in zero gravity.”
The The Dzhanibekov effect (intermediate axis theorem) is so rarely observed on Earth that it was not well known. It is not like gyroscopic precession A propeller also rotates around the Z axis shown in the video, so would not be susceptible to the Dzhanibekov effect.
If you mean a torque-induced precession of the propeller, the tendency for the propeller to want to change direction up or down on the airplane when the airplane turns left or right, then that is also not the Dzhanibekov effect and is another well known phenomenon. This phenomenon is what helps keep a bicycle upright during a turn, but it can put a lot of unwanted forces on the bearings in a hard drive or in the reaction wheels (momentum wheels) of a spacecraft, so it is important to handle your laptop carefully, if it has a hard drive.
Dynamics is a tricky subject and is sometimes counterintuitive. This made it both fun and a real pain in the butt in school. Derek (I think that is the video’s host) is trying to explain a complex phenomenon in simple terms.
Thanks Edward! Very informative. Interesting to think about how forces would present themselves in a zero gravity environment free of aerodynamics as well.
John C,
Review the video from the 7:25 point to the 9:30 point. The discussion changes from centripetal forces to centrifugal forces due to the change in reference frame (from inertial to spinning). Derek (I think that is the video’s host) explains that the spinning reference frame sees centrifugal forces that the inertial observer does not see. The forces on both sides balance out, so there is no X, Y, or Z translational motion of the spinning bolt, but there are two forces that force a flip of the bolt. Then the forces are very small, thus little flipping motion is observed, until the forces build up again.
The tennis racket example shows that it does not just happen in space but on Earth, too. The tennis racket flips as a free-body, unrestrained, in the Earth’s gravitational field as it accelerates toward the ground. Lack of gravity is not the important part, it is being unrestrained in motion.
By the way, about 11 minutes into the video, Derek shows that a bottle with liquid in it will also turn so that it spins around a different axis (a different phenomenon), similar to what happened to Explorer 1. We can perform the same experiment on Earth by throwing an unopened soda can into the air while spinning it around its long axis, like the bottle in the video. By the time the can comes back down, it is tumbling end over end, just like the bottle. When I show this to people, I do in on a lawn so that I can toss the can into the air more than once — and hopefully drink the contents after the demonstration.
Edward-
yes, good stuff!
…going tangential…..
Dr. John Barrow “renowned populariser of science” has died
https://www.theguardian.com/science/2020/oct/27/john-barrow-obituary
and, a nice little backgrounder on Newton….
The World of Isaac Newton
Gresham College Lecture; October 2020
Robin Wilson/Raymond Flood
https://youtu.be/JSzdN7tYVYw
51:45
This effect does not have to be in a zero gravity environment. There are slow mo videos that show the same forces at work here on the ground in a 1G state. A wing nut, spinning off of a bolt about 4/5 feel off the floor, flips several times on its downward trek to the floor.