Talk:Coriolis force

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Eotvos is NOT the vertical (+/-Z) Component of Coriolis

This article presents factually incorrect information about Coriolis. More than nearly any physics phenomenon, Coriolis seems to be shrouded in anecdotal explanations that have nothing at all to do with Coriolis, and this "Eotvos = vertical Coriolis" is one that is repeated constantly. And yet in one minute at a white board, Coriolis and Eotvos are easily shown to be discrete unrelated phenomenon. Just because they both act in the same direction (+Z with an eastward velocity, -Z with a westward velocity, does not mean they are the same or even related.

Imagine I am shooting a bullet to the east at the equator. My intended sightline from Rifle to Target creates a linear vector RT. The eastward rotation of the earth also imposes an inertial vector that is tangential to my location on earth, and thus is ever so slightly inclined upward in relation to vector RT. The net vector that becomes my resulting sightline is the sum of RT and this inertia vector I, or I+RT. THIS is Coriolis and will make my bullet strike about 3.6 inches high on a typical 1,000 yard eastward shot and about 3.6 inches low on a typical 1,000 yard westward shot.

Completely separate and unrelated to this is the Eotvos phenomenon. Eastward or westward velocity will be higher (east) or lower (west) relative to the center of the earth's mass. This increases (east) or reduces (west) the perceived centrifugal force, which is actually just a reduction (east) or increase (west) net gravitational force G. This means my ballistic computation of the correct superelevation that creates a trajectory arc that is subtended by vector RT will be slightly off because it assumes a constant for G. This means my bullet will arrive a tiny bit high firing east and a tiny bit low firing west. In my example above this G error may be +/- a half inch or an inch at these 1,000 yard times of flight. But this is NOT Coriolis and is unrelated in every way to Coriolis.

SkyKing36 (talk) 00:56, 21 November 2020 (UTC)

Gravitational force is constant for a given distance between the center the interacting masses, to calculate the net force, gravity is a centripetal component that keeps our motion circular the faster we spin the smaller the net resulting vertical force, but gravity remains constant. --Crystallizedcarbon (talk) 10:35, 22 November 2020 (UTC)

It's also worth noting that the section on Eotvos (caused by centrifugal force) describes how it is parabolic in nature. While acting downward for low values of west velocity of the hypothetical train, it reverses direction and acts upward for high values of west velocity. But under the section for 'Rotating sphere', the formula for Coriolis acceleration, ${\boldsymbol {a}}_{C}$, will not result in any upward value for any magnitude of west velocity. --Robot42marvin (talk) 02:30, 23 December 2021 (UTC)

"cannon on turntable"

The "cannon on turntable" section is mentioned, but does not exist in the article. Darkman101 (talk) 00:23, 1 April 2021 (UTC)

Seems silly. Removed. Constant314 (talk) 00:40, 1 April 2021 (UTC)

Draining in bathtubs and toilets

I came here to add an article on the subject of this section (which I did) but found this section to be a mess for many reasons. I have attempted to clean it up a bit. RobP (talk) 19:20, 30 April 2021 (UTC)

Thanks for the work. I think that the section needs to be pruned severely. There is a lot of redundancy. Constant314 (talk) 19:38, 30 April 2021 (UTC)

Thanks... but I disagree that mentioning the widespread incorrect beliefs about this subject, covered in RS, is "irrelevant to the subject of the article," particularly that museums on the equator perpetuate the incorrect info. RobP (talk) 22:19, 30 April 2021 (UTC)

Any other opinions on this subject? I added this material which has now been deleted: Also, the importance of one's location relative to the equator regarding the direction water drains, purportedly due to the difference in Coriolis force strength, is a misconception that is purposely reinforced by some equatorial museums. This is in addition to other erroneous claims being made about other forces affecting people and objects differently due to equatorial proximity.[61] RobP (talk) 05:12, 9 May 2021 (UTC)

Verification needed on the true definition of the Coriolis force

The first sentence is "In physics, the Coriolis force is an inertial or fictitious force" In meteorology, the Coriolis force is an inertial term in the expression of the horizontal dynamics. It looks like an inertial force but it has just the formulation of an inertial force.

You wrote "The (inertial) force affecting the motion of air "sliding" over the Earth's surface" which is a well known analogy, yes an analogy. The truth is that air is not sliding, it is constrained by the ambient hydrostatics and Earth sphericity+rotation. The exact statement, without the analogy, is: "The true force affecting an air parcel that is forced to move horizontally over the Earth's surface"

I suppose that only a very very very few people remarked that, but it is pretty evident that the impossibility of cyclones to be filled (geostrophic approximation) can not be due to geometry and inertia, but due to a true opposing force involving ambient hydrostatics and Earth sphericity+rotation. — Preceding unsigned comment added by 2a01:e0a:9d2:3e20:c540:bf51:1a8b:5496 (talk) 10:11, 24 September 2021 (UTC)

Simple cases

The direction of the ball from the point of view of an observer as moving from the thrower is described here as going in the opposite sense of motion to that of the turntable (or carroussel). But when altitude winds move northwards from the equator they go eastwards, pushed by coriolis force (and would tend to go round in a clockwise manner if not diverted and reversed by presure gradients that exist on the borders of depressions when moving north). Wouldn't it then go further than the thrower (like the texan boy tossing a paperplane northwards to Nebraska but which lands in Delaware*) instead of apparently marking a delay relative to the motion of the carroussel like is showed here ? To me the curves represented on this page would only be right if the paperplane of the boy landed in california*.. ??? I might be completely mistaken, thanks in advance for your help.

• =https://education.nationalgeographic.org/resource/coriolis-effect/

Samoth Yallavec'h (talk) 14:31, 21 June 2023 (UTC)

I understand what you’re getting at but, I believe your assumption changes completely when mass is taken into account. The paper airplane could also be affected by the famous butterfly in Brazil flapping its wings. A missile? Not so much. Also, bringing winds at altitude into it, don’t apply to the paper airplane. I mean no disrespect, just discussing. SmokeyShyla (talk) 16:48, 13 July 2023 (UTC)

The ball is a free body, moving under inertia. The wind gets dragged along with the Earth by friction with the ground and fluid friction within itself. They are not equivalent situations. A hurricane is more like a spinning ice skater. She pulls her arms inward, and she spins faster in the direction that she is already going. The atmosphere is spinning with the Earth. Low pressure pulls it inward so that it spins faster in the direction that it was already going. It may not be accurate to call it an example of Coriolus force. Constant314 (talk) 23:03, 13 July 2023 (UTC)

@Samoth Yallavec'h: Which image from the simple cases section do you think is contradictory with altitude winds? In the first image (person throwing ball to the center of the carousel, carousel rotating counter-clockwise as seen from above) is akin to the altitude winds you describe - sort of. The caveat here is that the person actually is throwing the ball "north" and "west"-ward in order to hit the pole. In the rightside image, which shows the path in the rotating frame, the ball is being pushed into a clockwise-like curve ("eastward") but again the person has thrown the ball with a bit of "westward" motion in the rotating frame. Essentially, the texan boy threw the paper airplane at california and it ended up in nebraska. --FyzixFighter (talk) 01:32, 14 July 2023 (UTC)

Hello and thank you all for your answers. @FyzixFighter what I can't buy is the idea that the leftside image is representative of the coriolis force acting on both altitude winds moving northwards and the paperplane tossed by the boy. Indeed : in both of these latter situations, a greater amount of rotating speed is accumulated by the objects than by the reference points on earth surface at higher latitudes, inertia causing then both air and paperplanes to go eastward while moving north. But if inertia worked the same way on the ball tossed aboard the carroussel, shouldn't it be charged with cinetic energy and hence, while moving in a centripetal way, go in the same direction as this of the carroussel but even further, therefore counter-clockwise ? Just to make it clear : I am not saying the figure is wrong or doesn't represent what would happen in reality, but just questioning its representativeness of the coriolis effect, which, to me, doesn't appear to depend on any point of view but just on different distances from a rotation axis. Again thank you in advance ! 90.42.24.253 (talk) 12:47, 15 July 2023 (UTC)

@Samoth Yallavec'h: Again I want to confirm that we are talking about the image with the carousel rotating in the counter-clockwise direction. If that is the case, the left figure represents what a stationary observes and therefore there is no Coriolis force/effect present in that image. In the stationary frame the ball travels in a straight line from the thrower to the pole because there are no forces in that plane acting on the ball once it leaves the thrower's hand. One thing that I think is absent from the description of the image is that the thrower, from their perspective, has to aim to the left of the pole in order for the ball to hit the pole. The initial velocity in the rotating frame is not pointed at the pole, but has a clockwise (eastward) component. This is evident in the right figure in that image. The thrower is not throwing the ball strictly centripetally from their perspective. In the thrower's frame, the ball curves and attributes the change in direction to the Coriolis force. But in the left figure, there is no need to invoke a phantom force as the motion of the ball can be attributed to the initial velocity and other real forces.

If the thrower did launch the ball strictly centripetal from their perspective, the stationary observer would not see the initial velocity as pointing at the pole and would not say it was strictly centripetal. The stationary observer would see the ball still move in a straight line, but would not need to invoke a phantom force to explain why it did not hit the pole - it missed because the initial velocity of the ball had both radially inward and tangential components. --FyzixFighter (talk) 15:11, 15 July 2023 (UTC)

To say it differently.

• The ball-thrower is aware that he is on a rotating carousel and makes the appropriate adjustments when he throws the ball.
• If he were unaware that he was on a rotating platform, and threw the ball directly at the target, he might infer that there was an unknown force acting to deflect the ball.
• If he were aware that he was on a rotating platform, and the rotation speed was low enough, like when standing on the Earth, he might ordinarily ignore the fact that the ground beneath him was rotating and then invoke a fictitious Coriolis force to account for the deviation of long trajectories.

Constant314 (talk) 17:52, 15 July 2023 (UTC)

Excuse my elusiveness, yes I was talking about the counter-clockwise rotating carroussel. Ok then if I'm getting it right, the person represented by the blue dot is, in both figures and the matter of view point set aside, not facing the pole but rather looking slightly on its left, even though we see him from above as a stationary observer and though the tossed ball follows a straight line that cuts the center of the carroussel ? And the coriolis effect can still be invoked in the right picture... The boy aiming at California to reach Nebraska helped me out a lot ^^ but just a last question : how is it that we still see the deviated trajectory of depressions and hurricanes from space, where we stand as stationary observers disconnected from earth rotation ? To me it sounds like the left figure here should also represent a deviated trajectory now ^^ I must be taken aback by the effect of the point of view and its importance in the definition of the force... Thank you again ! 90.42.24.253 (talk) 20:04, 15 July 2023 (UTC)

Revisit Intuitive Explanation section?

(Context: I am a non-mathematician, non-physics major that nonetheless uses Wikipedia to gain better understanding of a wide variety of topics.)

The Intuitive Explanation section should be written such that the explanation is accessible to anyone with a basic knowledge of science, but, to be honest, most people do not have the math to understand the preceding sections and so may get discouraged before they even get this far. The graphic at the beginning of the article is wonderful to show the inertial force. A second animation depicting the effects of the inertial force on a long-range object traveling from the equator towards a pole (or from a middle latitude towards the nearer pole would be great in the introduction. I don’t believe that graphic and the brief explanation would interrupt the introduction too much. That way, the Intuitive Section could be deleted. Comments appreciated. SmokeyShyla (talk) 16:41, 13 July 2023 (UTC)