Re: What's the difference Mil vs. MOA
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: NineHotel</div><div class="ubbcode-body">mil-radian and the metric system line up so close that the two don't deviate until the 8th digit to the right of the decimal point..</div></div>
...it's not really that metric units especially "line up".
*DANGER. MATH NERDERY AHEAD*
Imagine you cut a piece out of a perfectly round pie -- and are very careful so that the cuts you make go exactly to the center of the pie and therefore the cut edges of the piece of pie are exactly the same length.
If the angle between your two cut edges are the pie is exactly 1 radian, then the curved part of your piece of pie, if you were to take a bendy measuring tape and measure it, would have the exact same length has each of the sides that you cut.
A milliradian (mil) is 1/1000th of a mil -- this would be a VERY skinny piece of pie where the length of your cut edges is exactly 1000 times the length of the "curved" part of your piece of pie (again, if measured with a bendy measuring tape).
When we are ranging a target or whatnot using MILs, we are basically "cutting off" the round outer "crust" portion of our pie, making a straight line between the original two cut edges of our piece of pie -- and then pretending that the distance of the line created by our new cut is the same distance as the curved edge of the original piece of pie. It's a very close approximation for the very small (milliradian scale) angles that we are dealing with (like NineHotel said, out to the 8th decimal point or something)...
But the point I want to make is that this isn't really that it "almost lining up" with metric distances -- it's that we are using a straight line distance to approximate a curved distance. We do this because it is a) A very very close approximation for the angles involved in shooting, so close that for our purposes, the error involved is completely insignificant; and b) it allows us to use simple ratios to estimate distance.
For shooting purposes it's best to think about the ratio aspect of it:
When your target appears exactly one mil high in your scope, then the distance TO the target is VERY close to 1000 times the height of the target. It doesn't matter what unit of distance you use: feet, meters, yards, inches... the ratio is the same.
If the target appears 1 mil tall, then:
A 1-inch tall target ~= 1000 inches away
A 1-foot tall target ~= 1000 feet away
A 1-yard tall target ~= 1000 yards away
A 1-meter tall target ~= 1000 meters away
etc.
Those are all 'extremely' close approximations. There's nothing innately special about metric measurements that make them "work" with MILs. Metric measurements are NICE sometimes because they are base-10 and you don't have to worry about dividing or multiplying by some arbitrary number to convert between units (feet, yards, inches..), and instead can just shift the decimal points.
Anyway, the moral of the story is that the association between MILs and metric measurements is purely in our heads (possibly encouraged by some scopes marking their .1 MIL clicks as "1cm @ 100 meters"... but really they could just as easily mark it ".01 yards @ 100 yards" -- it's just that it happens we aren't very good at thinking about ".01 yards"
)
-Matt
