Talk:Coriolis force

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General Relativity

There is an article on the Coriolis field. I think it should definitely be merged into, or at least referred to in this article because the Theory of General Relativity is designed to deal with these matters without any need for inertial frames or fictitious forces and has been proven correct for a while also. I am sure someone with enough mathematical skills can do this properly. The article about the Coriolis field still has no references or formulas, so it needs some work.Viridiflavus (talk) 18:09, 12 May 2011 (UTC)

Sun and distant stars

A recent edit removed the section The Sun and distant stars from the article on the alleged grounds that it was "erroneous". A subsequent edit restored it on the alleged grounds that it wasn't. I nearly did this myself until I checked the calculations more carefully and found a couple of problems with them.

In the first place, because of the Earth's annual revolution about the Sun, the origin of any coordinate system which is fixed with respect to the Earth must be undergoing an acceleration, which therefore gives rise to a pseudoforce in the opposite direction in the equations of motion in that coordinate system. Although the magnitude of this pseudoforce's action on the Sun is some two orders of magnitude smaller than those of the Coriolis and centrifugal pseudoforces, it is not negligible, because—except at the equinoxes—it has a non-zero component along the Earth's axis, which the other two pseudoforces do not. In the fixed-Earth coordinate system, therefore, it is only the pseudoforce resulting from the acceleration of the coordinate system's origin which can account for the Sun's apparent motion in declination, which can amount to as much as 0.4° per day (at the equinoxes).

Strictly speaking, the same considerations apply to the apparent motions of stars other than the Sun, but even the closest of those is so far away that the effects of the pseudoforce resulting from the acceleration of the coordinate system's origin are effectively negligible (unless one wants to account for the annual parallax of those stars that are sufficiently close to have it).

The second problem is the (to me) confusing and unnecessary distinction between stars with zero declination (i.e. directly above the equator) and those with non-zero declination. Provided the equation Ω ⋅ r = 0 is replaced with the more general Ω · r = |r| Ω sin(δ), where δ is the (fixed) declination, exactly the same equations can be applied to any star, regardless of whether its declination is zero or non-zero. Nor do I understand why the case of stars with non-zero declination should be described as "more complicated", or the explanation of this supposed complication that was given in the previous version of this section. In a coordinate system which is fixed with respect to the Earth all distant stars, regardless of their declination, move around circles centred on, and perpendicular to, the Earth's axis.
David Wilson (talk · cont) 03:05, 29 September 2011 (UTC)

It said the motion of the Sun was dominated by the Coriolis and Centripetal forces, which is correct. The additional gravitational force on the Sun is much smaller than the C&C forces, as evidenced by the fact that the annual (orbital) motion of the Sun is about 365 times smaller than the daily (rotational) one. The section was inserted at a time when there was a vehement discussion whether the C&C forces would apply to static objects and was kept as simple as possible. Why did you remove the section that pointed out the observed curved path of rising, culminating and setting, caused by applying Buys Ballot's law to stars? It is the ultimate consequence. −Woodstone (talk) 09:05, 29 September 2011 (UTC)

"It said the motion of the Sun was dominated by the Coriolis and [centrifugal] forces, which is correct."

The problem with that statement—which, by the way, I neither asserted nor implied was incorrect—is that it was completely irrelevent to the rest of the section (as currently written), in that it talks about the Sun's (and only the Sun's) apparent motion, whereas the rest of the section is devoted entirely to a discussion of the apparent motion of distant stars. When I wrote in the summary of my edit to the article that "it's at least inaccurate for the Sun", the "it" in that statement was referring specifically to the explanation of the effects of the Coriolis and centrifugal forces on the apparent motions of distant stars. That explanation would be inaccurate for the Sun for the reasons I have already explained above.

After opening with the above-mentioned statement about the Sun's apparent motion's being dominated by the Coriolis and centrifugal forces, the previous version of the section under discussion switched, in the very next sentence, to considering the case of a distant star. It then went on to give the very nice explanation of the effects of the Coriolis and centrifugal forces on the apparent motion of such a distant star without ever returning to the case of the Sun or mentioning it again. Now if you're only going to give an explanation which applies to distant stars, but can't be applied without significant modification to the Sun, why on earth mention the Sun at all in the first place? At best it's apt to puzzle readers (as it did me) as to why the Sun was mentioned at all, and at worst it could mislead them into thinking that the given explanation was supposed to apply just as well to the Sun as to distant stars.

I have no particular problem with a statement about the effects of Coriolis and centrifugal forces on the the Sun's apparent motion being included, but if it is, it needs to be accurate. Here is a draft of a possible wording (which I am as yet far from satisfied with):

"The apparent motion of the Sun or a distant star as seen from Earth is dominated by the Coriolis and centrifugal forces. First consider a distant star ... [skip explanation for distant stars] ...

The apparent motion of the Sun is a little more complicated. In the course of a year the Sun moves up to 23.4 degrees north and south of the celestial equator, and since the Coriolis and centrifugal forces are directed perpendicular to the Earth's axis, they cannot account for this motion. It is in fact accounted for by a third fictitious force arising from the Earth's acceleration towards the Sun. Although this fictitious force is very much smaller than the Coriolis and centrifugal forces, it has a component of continuously varying magnitude which acts in a direction parallel to the Earth's axis and thereby accounts for the Sun's apparent motion in that direction."

Personally, I don't believe such an inclusion would at all improve the article, but I'm not going to complain if someone wants to add it.

Answer to question:

"Why did you remove the section that pointed out the observed curved path of rising, culminating and setting, caused by applying Buys Ballot's law to stars?"

Mea culpa. Perhaps it would have been better to tag it with a request for clarification. I removed it because:

1. The vector algebra (as now modified) seems to me to provide perfectly adequate and complete explanation of how the apparent motion of any distant star is accounted for by the Coriolis and centrifugal forces. I couldn't (and still can't) see that any special explanation was needed for stars that are not directly above the equator; and
2. I found it almost completely incomprehensible (as I also do the statement that Buys Ballot's law is applicable to the stars).

Since you appear to understand whatever it is that the final paragraph was trying to say, it would be helpful if you could provide a more detailed explanation (it's quite possible that I'm simply missing something obvious). A detailed explanation of why I find the paragraph confusing is likely to be quite lengthy, so I won't try to give one here. However, if you believe the issue is worth pursuing I will provide such an explanation in a separate section below.

David Wilson (talk · cont) 15:36, 1 October 2011 (UTC)

Article name

As things are now, Coriolis force is a redirect to Coriolis effect. However, usage would suggest it should be the other way around: a Google book search "Coriolis effect" -poem, -poems turns up 93,500 results, while the search "Coriolis force" turns up 334,000 results, almost four times as many, and without the spurious links that "Coriolis effect" turns up when used without restrictions. Brews ohare (talk) 16:15, 10 December 2011 (UTC)

"Left and Right"

Where the article currently says "veer to the left" and "veer to the right", I would argue that the terms "Left" and "Right" are too ambiguous, as they assume (without even mentioning) the observer is facing in a particular direction. Left and Right do not even have specific meanings in this context, unless one expects readers to remember something like the Right Hand Rule, which is anything but intuitive.

Rather, I propose that the article state that it "veers to the West" in both cases. This is completely unambiguous, and does not assume that the observer is facing any particular direction. -- Jane Q. Public (talk) 03:07, 7 January 2012 (UTC)

Right and left are relative to the movement of the particle. It's like saying that a car turns right. Nothing ambiguous there. On the contrary, saying West or any other direction is wrong most of the time. For example, a particle moving East will veer South on the Northern hemisphere. Only particles moving towards the equator would veer West (in both hemispheres). −Woodstone (talk) 09:01, 7 January 2012 (UTC)

Left and right are not ambigous in this case. To be sure that left and right are properly defined, we need two perpendicular directions, one that is "forward" and one that is "up". Forward is of course the direction of movement, and up is easy as long as there's gravity or some "ground surface" to use as reference. If we were talking about stationary objects, we would have a problem. If we were talking about objects in outer space, we might have a problem. But we're not, so there's no problem. 131.116.254.198 (talk) 09:56, 14 January 2012 (UTC)

Vandalism

Blatant vandalism inn the section on Bathtubs/Toilets. "Big floppy donkey dick"

173.79.117.146 (talk) 19:45, 20 February 2012 (UTC)

It was reverted by a bot within a minute, you're seeing a cached page. Materialscientist (talk) 00:00, 21 February 2012 (UTC)

Question=

What does this mean from the article: Perhaps the most important instance of the Coriolis effect is in the large-scale dynamics of the oceans and the atmosphere. In meteorology and oceanography, it is convenient to postulate a rotating frame of reference wherein the Earth is stationary. In accommodation of that provisional postulation, the otherwise fictitious centrifugal and Coriolis forces are introduced.

Why are the otherwise fictirious forces now real due to a purely abstract analytical formulation (fixed earth and rotating frame). There must be something missing in this explanation such as the motion constraints introduced through the atmospheric friction cause a real force that is like coriolis. the example I can think of is the merry go round. You are constrained to follow a curved path and to do so the seat pushes on you with a real force of opposite sign but equal magnitude as the centrifugal force (i.e. the centripetal acceleratoin required to make you follow th edge of the merry go round) Skimaniac (talk) 04:56, 3 March 2012 (UTC)