If you want a proper, easily understandable explanation of the Coriolis Effect, read this.
I stumbled upon this thread while doing some research on the Coriolis Effect and felt that, from the replies that I have read, none of you are properly explaining it. I will attempt to do that now in a simple and easy to understand way.
What is the Coriolis Effect?The Coriolis Effect (Coriolis Force as is its true name) is an inertial (or non-accelerating) force which acts upon an object that is in motion relative to a rotating reference frame. The outcome of the Coriolis Force on said object is what is know as the Coriolis Effect.
How is the Coriolis Force/Effect represented, what does it do and why is it important to know?Well, popular (non-technical) usage of the term "Coriolis Effect" almost always implies that the Earth is the rotating frame of reference. If we assume the Earth is a sphere that spins on an axis, we must then account for the Coriolis Force to correctly determine the motion of an object and where that object will end up after its motion ends (You will understand why I said "If" in the beginning of this sentence if you read through my entire reply). For now, we will be assuming that the Earth is a sphere that rotates on an axis. The Earth completes one rotation per day, so the effect of the Coriolis Force on the motion of an object is usually going to be very small and unnoticeable; it will usually only become noticeable when an object travels a long distance and for a long period of time compared to that object's AVERAGE travel time.
Here is our first example:Pre-experiment explanation
You are in space looking down towards Earth. There is an object at the equator large enough for you to see. For this experiment, the only three forces that will be acting on this object are the Coriolis Force, a modified form of gravity, and a force that will cause the start of the object's movement (that way you can have a visual understanding of what the Coriolis Force looks like when it is acting upon an object). The only difference between true gravity and our modified form of gravity is, our modified form of gravity will keep the object at the same elevation above sea level from the Earth's surface throughout the entire experiment so that the object can move from the equator to the desired pole without coming into contact with the Earth's surface. Also, the force that causes the object's initial movement will not continue to act upon the object once that object begins moving; the force will only cause the object to begin movement. The speed at which the object moves will stay the same throughout the entire experiment, that way the motion of the object after motion starts is only caused by the effects of the Coriolis Force.
Experiment
Now we will begin the experiment. The object at the equator is acted on by an outside force that causes it to begin movement towards the Northern pole. The object leaves behind a red line that shows the path that it is taking. To the person that caused the object's movement, the object appears to be moving due North. As YOU view the object from SPACE, the object does not appear to be moving due North; the object appears to be moving in a NorthEASTERN direction (to the right and upwards). As you go Northward, the horizontal diameter of the Earth gets smaller at a consistent rate and as the horizontal diameter of the Earth gets smaller, the motion of the Earth's surface gets slower at an equally consistent rate. So, as our object moves North, (where the horizontal diameter of the Earth gets smaller at a consistent rate and the speed of the motion of the Earth's surface gets slower at a consistent rate) the object maintains its eastward speed instead of slowing down to match the reduced speed of the Earth's surface; this causes the rate of the object's movement eastward to appear to be growing. The growth of the object's movement East is NOT consistent however, because unlike the consistent rate at which the horizontal diameter of Earth gets smaller and the consistent rate at which the speed of the Earth's surface movement gets slower relative to the consistent rate of change of the diameter of the Earth as you move further North, the further North you go, the smaller the diameter of the Earth and the slower the speed that the Earth's surface is moving; that causes the rate at which the object moves East to appear to be getting greater at an increasingly faster rate (which means that the object appears to be moving further to the right at an increasingly faster pace).
Experiment Summary
So, to sum up that experiment, our object started moving from the equator to the North pole. As we viewed the object from space, we saw it draw a red line that started out going slightly Northeast. As the object continued to move North, the red line that was drawn by the object curved. The rate at which the object and the red line curved horizontally to the East kept growing increasingly faster, until it reached the North pole.
Now that you know what effect the Coriolis Force has on the motion of an object, I will give you a second example; one that explains how the Coriolis Force affects the movement of objects alongside all other forces. This example is going to fit in with the topic of this thread, which is sniping.
Pre-example Explanation
When a soldier goes to Sniper School, he is taught how hide, how to track an enemy, how to prevent enemies from tracking him, how to get to his target without being discovered, how to eliminate his target, how to survive and maintain himself indefinitely while on mission, and how to get out of the area without being discovered.
We will be talking about how they eliminate their target. A sniper is taught how to "Zero" his scope, how to properly hold his rifle so that he gets the best accuracy possible, how to accurately judge the distance between him and his target, how to make adjustments to his scope so that it is on target before he fires, how to adjust his scope if he misses so that he knows exactly what adjustments are needed to be made to make the second shot count, and how to judge what he needs to do and how to do it when he is lining up a shot. One of the things he is taught so that he can be more accuracy at longer ranges is the "Coriolis Effect".
Example
Now, here is our situation. We are a 2 man sniper team in the US Army. We are out on a patrol and we hear gunfire over the hill to our front. We rush up to the top and set up our rifle and your spotting scope. We see a small group of Taliban fighters with a sandbag fortification and a machine gun firing down on a squad of US Army infantrymen. Our guys are pinned down and won't last much longer. Our problem is that we are too far away to communicate with the squad, we don't know which radio frequency they are on and they won't last long enough for us to figure it out, our guys don't have enough time for us to try to get into a better position, and the Taliban gun emplacement is over 1,000 meters away from us. The distance between us and the Taliban means we will have to take into account the Coriolis Effect. Now, the Coriolis Effect in military terms refers to so much more variables than just what I explained in Example 1. With the military version, we will have to take into account the distance (which at that range will extend to the point where the curvature of the Earth is a factor in the bullets trajectory), the curvature of the Earth, the weather, wind speed, wind direction, a possible wind direction change during mid-flight of the bullet due to how long it will take the bullet to reach its target (and the wind speed of that possible wind direction change), gravity, how gravity will affect the bullet drop as the bullet travels along the curvature of the Earth, temperature, climate, humidity, our altitude, the altitude of our target, air resistance, the angle at which we are shooting, the possible visual distortion due to the heat waves that radiate in the distance if it is hot, AND we will have to take the gun into account. Why do we need to take the gun into account? Well, the M24 (the standard sniper rifle for US Army snipers) has a maximum effective range of 800 meters, though record shots have been made with the M24 at over 1,000 meters. Also, the standard scope that the US Army uses on their M24s has a maximum elevation adjustment of 1,000 meters. So, after we make a quick observation and estimation of all the factors, we take them into account and set up the shots accordingly. There is no way of knowing exactly where our shots will hit because each shot will have slightly different factors at play so we can only guess. We will more than likely hit our targets but we will probably also miss a few shots in the process due to the slight randomness caused by the factors that are constantly changing ever so slightly.
Explanation Summary
We are going to have to take the Coriolis Effect into account when shooting out passed 1,000 meters because if we don't, we will miss every time and our bullets will never hit our target. Now, an opposing argument could be made that, if the Earth is flat, taking into account the Coriolis Effect will cause you to miss every shot and be way off target because you are taking into account a factor which isn't even present. If that were true then the end result would cause your shots to miss, but that isn't the case. If you talk to any sniper, preferably military because civilian shooters don't have to worry about the Coriolis Effect nearly as much as military snipers (actually, the only time you'd ever have to worry about the Coriolis Effect as a civilian shooter is if you wanted to, because the civilian shooter has control over the range at which he shoots), they will tell you that the Coriolis Effect is a real thing and must be accounted for when firing long range shots if you actually want to hit what you intend to hit.
Also, saying that a sniper who has to make adjustments, in order to fire accurately, isn't very good at sniping and shouldn't be doing it shows how much you know about shooting in general. All shooters make adjustments when shooting. Aiming your firearm is an adjustment. Also, your reasoning behind that statement is obviously based on sniping in video games. Believe it or not, sniping in video games is a piece of cake compared to sniping in real life. Just because you can get a head-shot at 2,000 meters on a target that is sprinting straight across your line of sight from left to right or right to left on Battlefield 4 without changing your scope's zero distance does not mean you are a good sniper. A real sniper would make adjustments so that it is easier to hit his target and so he is more likely to hit his target. Snipers don't leave the success of their shots solely to the chance that a "Hail Mary" (a shot where the shooter makes an educated guess as to where he needs to aim in order to hit the target and fires without making any other adjustments) will be effective. Yeah, maybe they could but they want to increase the chance that their shots will actually connect with their intended target as much as possible, and I'm sorry but, a Hail Mary is the way to go if you want to have the smallest chance possible of hitting your intended target.
Also, here's a word of advice.Don't insult a man who can end your life from another zip code.That means don't insult snipers.