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Discussion in 'Long Range Pursuit TV, Gunwerks, GSeven' started by Len Backus, Sep 11, 2012.
[ame=http://www.youtube.com/watch?v=ouOYAlcvwOQ&feature=plcp]LRB Coriolis Effect - YouTube[/ame]
WOWZA…That is some piece of Physics!!! You got EVERY statement WRONG, including the graphic of the spinning earth. (it rotates in the other direction). The earth at the equator is 24,899 miles in circumference. With me so far? It does one rotation every 24 hours…thus, at the equator the ground is traveling West to East at 1037.45 mph. Well over MACH 1!!! You don’t notice it because you’ve NEVER IN YOUR LIFE left the boundary area and neither does the bullet. But just think of the public service you would be doing by sparing all those kids in Ecuador that are standing to the West playing catch as a 1037.45 mph fast ball hits them. Well that’s just crazy! So we’ll just forget about the horizontal component in our "understanding" of Coriolis and just keep the vertical component. Well my 300wm (not a Gunwerks) shooting 230grain Berger Hybrids takes 1.352 seconds to travel 1000 yards. The earth at the equator, will travel 632.8 yards to the East in the 1.352 seconds. So let’s just compute the vertical component that the earth’s curvature will rise over that 632.8 yards. That’s a whopping 1.4” and we’ve selectively tossed out the horizontal component. Not very sound Physics.
So what is Coriolis… Coriolis is a very simple physical phenomenon which can be observed when an object jumps from one location on the earth’s surface, which has a local rotational velocity due to the earth’s rotation, to another location on the earth’s surface which has a DIFFERENT local rotational velocity. During the jump, the object will maintain the rotational velocity it had at the source (Inertia), and can be observed, if the destination has a different rotational velocity. (ie. The difference in local rational velocity can only be observed in the North/South directions) OK, here some specifics that hopefully will clear things up. The earth rotates 24,899 miles / 24 hours at the equator. This equals 18,259.26 inches/sec of rotational velocity from west to east at the equator. As we move to the north in Colorado to( N40.50940deg) the earth is only 18,930.69 miles around at that latitude. So one rotation in 24 hours equates to 13,882.5 inches/sec of local rotational velocity. From there, if we shoot 1000yards to the north to(N40.51758deg) the rotational velocity slows to 13880.8 inches/sec which is 1.6838 inches/sec slower than our shooting position. My 300wm will take 1.352seconds to travel the 1000yards. Which will result in a 2.276 inch miss to the east. If we reversed directions, and shot from the North to the South we are jumping from a slower rotational velocity to a faster rotational velocity location. The bullet will land 2.276 inches to the west which would still require a L0.2MOA adjustment. NOTE: If you are shooting East/West, you are jumping to locations of equal rotational velocity and the Coriolis effect is virtually nil. NOTE: there is another effect: Eotvos, which deals with the East/West variations in centrifugal force, but the vertical displacement is even smaller than the Coriolis Effect.
Well shut my mouth!!
All I can say is that in Idaho the N/S error is less than Colorado which is better than I can shoot. Except for rocks the live stuff I shoot at is less than 1K yards and the N/S error is again way better than I can see or shoot.
I'm not going to sweat it.
You wouldn't believe how many things a video guy can screw up! The only time I've seen earth spin that way was on Superman!
We always refer to this effect as vertical Coriolis, because its easier to spell and speak than Eotvos effect. It is not technically correct, but it follows the same fashion as Bryan Litz. The effect is due to variations in centrifugal force, but when explaining the magnitude of the effect, it's usually easier to visualize target movement, and calculate with a simple rule of thumb.
We will get one together one of these days that is full blown scientific with correct nomenclature and exacting formulas. First thing, though, I'm going to figure out how to pronounce Eotvos...
Speaking of Bryan...Please correct the Shooter App (which I love) to correctly utilize the entered shooting Azimuth to NOT compute the same Left hold for Coriolis when shooting East/West as it computes (correctly) for shooting North/South.