Coriolis Effect Question

Slowdive

Slowdive

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Warning...geek alert....I had no idea what section to put this question.

Lately I've been thinking about the Coriolis effect and how it works. I read this article and it makes sense to me.

http://www.appliedballisticsllc.com/index_files/SpinandCoriolisDrift.htm

What I don't understand is why there would be a horizontal Coriolis component if you are shooting directly east or west. I get why there is a vertical component; if your shooting west your target is effectively rising, and conversely falling if shooting east. Spin drift I get, but not left to right shift b/c of earth spin. Can any of you long range gurus explain?

I understand this is of little practical use to me as I shoot mosty @ <200 yrds. I just like to know stuff.
 
This is something I've been curious about, and I'm with you: I don't get his explanation of the horizontal effect. I'm actually going to guess there's a problem in his explanation.

If you're standing at the north pole and shoot at something, by the time the bullet gets there the target will have moved to your left (right drift). Standing at the pole this is true no matter which direction you shoot. But I agree with you that at the equator direction matters.
 
visualize a lattitude line on a globe. You are standing on that line and the target is also on that line. If you were to draw a line from your head through your toes that line would to through the center of the globe.

Now look at the lattitud line with respect to the target. it curves to your left if you are looking west (in the northern hemisphere). If you were to levitate and let the earth spin under you, you will see a horizontal component in as your target moves.
 
NC, I'm getting closer, but have smoke coming out my ears and I'm not there yet.
Wouldn't the lattitude line curve to my right? For horizontal drift, wouldn't the direction you are shooting matter?
 
cockpitbob said:
NC, I'm getting closer, but have smoke coming out my ears and I'm not there yet.
Wouldn't the lattitude line curve to my right? For horizontal drift, wouldn't the direction you are shooting matter?
Click to expand...

I put the target on the latitude line so as you look at the target you would see the line bend out to the left and then back right to the target. Yes direction you are shooting would matter. In my example you are shooting west.
 
I think I am confusing myself (and you in the process). I may need to think about this a little more before I can explain it correctly. It's been a while since I understood it last. I don't think it matters which direction you are shooting I just have to remember why. [thinking]
 
Now I remember.

When looking at the target, and levitating, the target will always move to the right (northern hemisphere) weather you are looking west or east.
 
I think I'm seeing it. This is easy to visualize if you picture yourself say a few hundred yards from the north pole. Your latitude line would appear to curve sharply left if your facing east or sharply right if your facing west.

So if your facing west (Northern Hemi), the target moves to the left which means your shots end up right. If your facing east, the target also appears to move to the left, shots still go right. North/south is pretty intuitive. Target to the south is moving to the left faster than the shooter, shots go right. Shooting toward the north the shooter (and the bullets) are moving right (east) faster than the target..shots go right. So no matter which way you shoot, the shots go right in the Northern half.

Thanks NC!! Now I can sleep peacefully.... [grin].
 
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Slowdive said:
Warning...geek alert....I had no idea what section to put this question.

Lately I've been thinking about the Coriolis effect and how it works. I read this article and it makes sense to me.

http://www.appliedballisticsllc.com/index_files/SpinandCoriolisDrift.htm

What I don't understand is why there would be a horizontal Coriolis component if you are shooting directly east or west. I get why there is a vertical component; if your shooting west your target is effectively rising, and conversely falling if shooting east. Spin drift I get, but not left to right shift b/c of earth spin. Can any of you long range gurus explain?

I understand this is of little practical use to me as I shoot mosty @ <200 yrds. I just like to know stuff.
Click to expand...

It's very simple. The earth is round. Those latitude (and longitude) lines are curves and not straight lines. Wrap a string around a ball and you will get it.
 
terraformer said:
It's very simple. The earth is round. Those latitude (and longitude) lines are curves and not straight lines. Wrap a string around a ball and you will get it.
Click to expand...

Right, I see it now. If shooting N-S or S-N, its the disparity in surface speed that causes the shift. Whats interesting is that other than the equator, shooting E-W or W-E is an illusion. In reality your bullet is always partially traveling N & S.

For example: if you are 500 yards south of the north pole, and your target is 1000 yards away with the pole directly in line (also 500 yards south of the pole on the opposite side)....you and your target are on the same latitude. Even though your shooting a target that is directly E & W of you, the path of the bullet is going N for the 1st half of its journey, and S for the second. As you move further south some component of your bullet path is moving N & S even if you think you are shooting directly E or W. Unless you are on the equator, this is always true. Cool.
 
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Slowdive said:
Right, I see it now...whats interesting is that the same effect manifests itself for two different reasons. If shooting N-S or S-N, its the disparity in surface speed that causes the shift. When shooting E-W or W-E, its the fact that the latitude lines themselves are curved (surface speed is the same)
Click to expand...

Not really. It's changes in surface speed causing the E-W/W-E effect as well. Just one is a left/right shift and the other is high/low effect. As you deviate from the 90 degree marks, you have different combinations of each. I was serious about the string. Literally wrap a string around a basketball and look at it from different angles. It will become clear.
 
terraformer said:
Not really. It's changes in surface speed causing the E-W/W-E effect as well. Just one is a left/right shift and the other is high/low effect. As you deviate from the 90 degree marks, you have different combinations of each. I was serious about the string. Literally wrap a string around a basketball and look at it from different angles. It will become clear.
Click to expand...

I was editing my post as you wrote this...I see now that it's the same thing. The shooting directly E-W or W-E is an illusion (unless on equator)...in reality some component of the bullet path is traveling N & S, which means that the surface speed disparity is still in effect.

This only becomes clear if you wrap the string some other place than the equator of the ball and draw a line directly between two points on the string.
 
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This is a great Coriolis effect $cam:




I wonder how much I can make if I set up such a "Did you know?" tourist trap on the MA/VT border? I will also sell certificates to say that you have been there...

My father used to stand raw eggs upright on a table on the vernal equinox, too.

(And on Arbor Day, on New Year's Eve, on my birthday...)
 
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removed, to avoid hurting anyone's feelings.

virtually no shot you could POSSIBLY take will have any sort of significant movement due to a Coriolis effect. wind, barometic pressure, gravity, spin drift (IE following the twist of the bullet due to the direction of rifling), and even a squirrel farting on a tree branch 1/2 a mile away are going to have more of an effect.


either way at that kind of distance, even if you WERE shooting @ something/someone...you'd have enough time to run the bolt and fire (probably) 2 more shots before the first one ever got there. they'd be highly unlikely to hear it, as the bullet would have LONG since gone subsonic, and you'd be too far away for the shot to be heard by the intended target.

FYI the real life WORST CASE numbers are 2.5 inches or so @ 1000yds. and thats the worst case.

if you could hold a rifle (i dont mean machine rest), and hold 2.5" @ 1000 yards (1/4MOA)...well, i'd like to take lessons. we'll assume no wind and perfect conditions. on my BEST day, i have a 1-2MOA hold. my own personal hold error FAR outweighs 2.5" @ 1000yds
 
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Jasper said:
talk about mountains out of mole hills.


virtually no shot you could POSSIBLY take will have any sort of significant movement due to a Coriolis effect. wind, barometic pressure, gravity, spin drift (IE following the twist of the bullet due to the direction of rifling), and even a squirrel farting on a tree branch 1/2 a mile away are going to have more of an effect.


either way at that kind of distance, even if you WERE shooting @ something/someone...you'd have enough time to run the bolt and fire (probably) 2 more shots before the first one ever got there. they'd be highly unlikely to hear it, as the bullet would have LONG since gone subsonic, and you'd be too far away for the shot to be heard by the intended target.

this is keyboard warrior talk. nothing that's ever gonna to affect any of us in real life.

FYI the real life WORST CASE numbers are 2.5 inches or so @ 1000yds. and thats the worst case.

if you could hold a rifle (i dont mean machine rest), and hold 2.5" @ 1000 yards (1/4MOA)...well, i'd like to take lessons. we'll assume no wind and perfect conditions. on my BEST day, i have a 1-2MOA hold. my own personal hold error FAR outweighs 2.5" @ 1000yds
Click to expand...

Read the OP...I acknowledged up front that it was an academic exercise for the purposes of understanding the physics.

See....

Slowdive said:
I understand this is of little practical use to me as I shoot mosty @ <200 yrds. I just like to know stuff.
Click to expand...
 
terraformer said:
Clearly the OP understood this.
Click to expand...

I realize he understood it. I did read his post. I was also referencing a few other posts. Sorry if I didnt quote everyone I was thinking about while typing.

What I was getting at, is even shoot @ 1000 yards.....or 1500 yards....or even 2000 yards....the Coriolis effect is something that (1) you're never going to notice, and (2) barring knowing you exact physical location on the globe and the exact angle you're shooting at/from....you'd never be able to compensate for it


The Coriolis effect is something that effects objects in motion (I love physics), particularly over long distance. Now, if I could get ahold of a 16" naval cannon...we could do some Coriolis testing :D! other than that, it sounds good in books and dramatic hollywood flicks.
 
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The thing that got me thinking about it wasn't even shooting related. I was watching golf and this guy put his 200 yard approach shot in a lateral water hazard. My half drunk friend joked that he failed to account for the Coriolis effect. Got me to thinking.

Strangely, I calculated it and I think it affects golf balls more. A PGA touring pro can drive in excess of 300 yards w/ a 7+ second hang time (tof). By my math that's like 4"+ of drift. Now that's a useless application of physics. [wink]

Clearly this is the reason I slice. [smile]
 
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Slowdive said:
The thing that got me thinking about it wasn't even shooting related. I was watching golf and this guy put his 200 yard approach shot in a lateral water hazard. My half drunk friend joked that he failed to account for the Coriolis effect. Got me to thinking.

Strangely, I calculated it and I think it affects golf balls more. A PGA touring pro can drive in excess of 300 yards w/ a 7+ second hang time (tof). By my math that's like 4"+ of drift. Now that's a useless application of physics. [wink]

Clearly this is the reason I slice. [smile]
Click to expand...

I have GOT to use that the next time I shank one into the woods. "Damn Coriolis effect!"
 

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