# Coriolis effect in artillery debunks Flat Earth?

Um, no....that cannot be 'the' reason because one would then be negating the answer to one of the other favourite flat earther misperceptions. After all, a common claim by flat earthers is that if the Earth is rotating then why doesn't the ground zoom under us at 1000mph if we jump up in the air. We respond that our momentum is what prevents that scenario happening.

Coriolis is actually caused by the difference in angular momentum across latitude. Conservation of mass/energy and all that. It is a vector thing, rather than the ground moving 'under' the object. If Coriolis was caused by the ground moving under an object then the effect would be largest at the equator....when in fact the reverse is the case.

I wish it were that simple, but it isn't. Far from it.

To prove that, I could prefix this following sentence with a description of a scenario which would make the sentence undeniably one hundred percent true:
The coriolis effect is maximal at the equator.

The coriolis effect is caused by having a rotating reference frame. The apparently paradoxical scenario I (don't) describe above would be just as true on the surface of a cylinder rotating about its own axis, and yet the angular momentum is identical everywhere.

(For those who read MB without JS enabled, there's a spoiler block below - either enable javascript, or view html source.)

Bringing the cylinder into things makes the lattitude irrelevant. Another situation where lattitude is irrelevant is the one where there is no lattitude, such as the turntable. And that was mentioned as being an analoge to the poles. Where the coriolis effect is maximised. And for the same reason.
The coriolis effect is proportional to the cross product of the velocity and the frame rotation vector. At the equator, or anywhere on my cylinder world, if you make the velocity straight down (or straight up), the cross product will be directly forwards (or directly back). At the poles of globe earth, if the velocity's straight up or straight down, the cross product is zero. So the description to prefix the sentence above to make it true is:
I will drop a ballbearing from a tall perfectly vertical tower.
At the equator, the ballbearing will be deviated towards the eastern wall (*NOT* the western one, it doesn't lag because the ground's moving under it, it *leads* because the top of the tower's moving faster, and that's the velocity vector it was given at launch). At the pole, nothing happens.

You are permitted to imagine "mind blown" animated gifs here. It's not intuitive. I have terrible visualisation skills, and I can barely get my head around it, I just understand the cold characterless sterile mathematical equations. For me the ballbearing in a tower at the equator scenario might be the simplest one to visualise, and of course it's essentially the same as missing the igloo to the right in the earlier posts.

Ah maybe I understood what you mean: if you shoot at the pole then you don't need any correction, because the pole only rotates, it does not translate. But if you shoot at a point on the equator then the needed correction is maximal because the tangential speed at the equator is the highest. This looks correct, as I think is correct that a missile launched straight north from the equator to hit the pole will be seen (in the Earth reference frame, say from the launch point) to loop around before hitting (and this is the Coriolis force), while in the missile reference frame it just follows a straight trajectory due north.
a ballistic missile launched straight north from the equator to hit the pole will be seen to deviate to the right, miss the pole altogether, and cross the equator again

If you correct for that east-moving feature of your rotation, and do start the projectile on a path directly towards the axis of rotation, by aiming west of it, then you will indeed see the bullet swing left, then right, and then hit the target
the bullet will not "swing left", it'll fly left initially because you aimed in that direction, and then deviate ("swing") to the right.

Coriolis is actually caused by the difference in angular momentum across latitude.
angular velocity, not angular momentum

angular momentum increases with the radius, coriolis force decreases

a ballistic missile launched straight north from the equator to hit the pole will be seen to deviate to the right, miss the pole altogether, and cross the equator again

the bullet will not "swing left", it'll fly left initially because you aimed in that direction, and then deviate ("swing") to the right.
Yes you are right, I should have thought better before writing.

the bullet will not "swing left", it'll fly left initially because you aimed in that direction, and then deviate ("swing") to the right.
Are you attempting to distinguish between the verb "swing" and the verb "fly" in this context? I can happily replace my verb with "go", are you prepared to replace your verb with "go" too? If so, what are you disagreeing about?

Aside - did you solve my puzzle without the spoilers?

Are you attempting to distinguish between the verb "swing" and the verb "fly" in this context? I can happily replace my verb with "go", are you prepared to replace your verb with "go" too? If so, what are you disagreeing about?
You originally wrote, "you will indeed see the bullet swing left, then right". This describes e.g. the behaviour of some balls in the video I posted, due to friction.

My issue with this statement is that the bullet will "go left" because you aimed left, i.e. it actually goes straight as expected, and then seems to deviate ("swing") from that straight path with respect to the rotating reference frame, i.e. Earth. In fact, the bullet never flies straight with respect to that frame, but undergoes apparent acceleration to the right as soon as it leaves the muzzle.

Your original wording left that unclear.
Aside - did you solve my puzzle without the spoilers?
Not sure what the puzzle is. If you understand the Coriolis effect to operate in 3 dimensions, then it is "maximal" everywhere on Earth, because the angular velocity is the same everywhere on Earth, and that would be equally true on a cylindrical or flat Earth if only it rotated 361⁰ per day.

You originally wrote, "you will indeed see the bullet swing left, then right". This describes e.g. the behaviour of some balls in the video I posted, due to friction.
The video you posted - as I already said - was an utter irrelevance. I could probably quote a verse from the bible which would have as much relevance.
The rest of your response just says "I didn't get FatPhil's point", and I really can't be bothered to word anything a different way. If you missed the point, so be it.

Jeremy Winters demonstrates how Coriolis effects bullet drop by shooting 1000 yards to the west and 1000 yards to the east and comparing the results.

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He's demonstrating the Eötvös effect, which is the Coriolis effect with only the vertical part considered. He does not consider horizontal deviation (which is typically less than wind effects, I expect).

West target was hit low:

East target was hit high:

the A4/V2 rocket, which with its five-minute travel time and mostly eastwards firing direction
Being a bit pedantic but weren't they mostly fired westwards?

V2's launched from the area of The Hague towards Antwerp and some other Belgian targets would have travelled eastward by a small amount, (The Hague is 52°04′48″N, 04°18′36″E, Antwerp, 51°13′04″N, 04°24′01″E) but the launch sites were moved progressively westward, so most V2s targeting Antwerp would have travelled pretty much due south or westwards.

...about 3,172 V-2 rockets were fired at the following targets:[63]

Belgium, 1,664: Antwerp (1,610), Liège (27), Hasselt (13), Tournai (9), Mons (3), Diest (2)
United Kingdom, 1,402: London (1,358), Norwich (43),[16]: 289  Ipswich (1)
France, 76: Lille (25), Paris (22), Tourcoing (19), Arras (6), Cambrai (4)
Netherlands, 19: Maastricht (19)
Germany, 11: Remagen (11)
Content from External Source
https://en.wikipedia.org/wiki/V-2_rocket, see Operational history and Targets

From http://www.v2rocket.com/start/deployment/mobile_front.html

...the launch sites were moved progressively westward
(Oops, "eastward", not "westward").

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