How to estimate distance with only your arm and your eyes - and other science body tests

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How to estimate distance with only your arm and your eyes - and other science body tests

Have you ever wanted to measure long distances but can never work it out? This simple trick looks like a handy way to calculate distance, and a neat party trick as well.

Your arm is about ten times longer than the distance between your eyes. That fact, together with a bit of applied trigonometry, can be used to estimate the distance between you and any object of approximately known size.

Imagine, for example, that you're standing on the side of a hill, trying to decide how far it is to the top of a low hill on the other side of the valley. Just below the hilltop is a barn, which you feel reasonably sure is about 100 feet wide on the side facing you.

Hold one arm straight out in front of you, elbow straight, thumb pointing up. Close one eye, and align one edge of your thumb with one edge of the barn. Without moving your head or arm, switch eyes, now sighting with the eye that was closed and closing the other. Your thumb will appear to jump sideways as a result of the change in perspective.

How far did it move? (Be sure to sight the same edge of your thumb when you switch eyes.) Let's say it jumped about five times the width of the barn, or about 500 feet. Now multiply that figure by the handy constant 10 (the ratio of the length of your arm to the distance between your eyes), and you get the distance between you and the barn -- 5,000 feet, or about one mile. The accompanying diagram should make the whole process clear.

With a little practice, you'll find that you can perform a quick thumb-jump estimate in just a few seconds, and the result will usually be more accurate than an out-and-out guess. At a minimum, it will provide some assurance that the figure is in the ballpark -- which, in many cases, is as close as you need to get.

From http://www.almanac.com/outd...

distance-meaure.jpg - 10.01kb
By netchicken: posted on 27-8-2009

How long until sunset?

Make a fist, hold your arm out, put the horizon at the bottom of your pinky. Count how many knuckles up the sun is. # knuckles * 15 = # minutes to sunset. e.g. 3 knuckles = 45 mins.


How to measure temperature of a hot liquid from about 160 up to 200 degrees.

If you can barely dip your finger in once and it burns instantly, it's 200 degrees.

If you can dip your finger in once quickly, pull it out, and redip it before you go "ouch" it's ten degrees less, 190.

If you can dip your finger 3 times before the ouch, it's 180. 4 times, 170. Five, 160. On the other end, if it's already bubbling, it's over 200 degrees and don't stick your finger in it at all.

This is surprisingly accurate, to within about 5 degrees. Some people are more sensitive to heat and won't be able to do this, but most people can do it.


Sock size

To check if a sock fits your foot, wrap it around your fist. If the heel and toe just touch, it's the right size.

From: http://www.reddit.com/r/sci...
By netchicken: posted on 13-10-2009








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