The compass is an ancient, but still a topical invention of mankind. This subject is interesting in that its invention served purely scientific purposes. Compasses could not be used for hunting, like a bow and arrow, for movement, like a wheel, for cooking and scaring away animals, like fire. Only in the Bronze Age did it become necessary to draw regular circles on the ground. So, with attempts to draw, measure and isolate one or another circle, an understanding of what the compass is for and how to work with it has come.
The legend of the appearance of the compass
The tradition prescribes the invention of the compass to the legendary inventor, the nephew of the famous Daedalus - Talos. Talos lived in Athens. Already at the age of 12, he came up with a potter's wheel, with which it was possible to make various dishes. Walking along the seashore, Talos lifted the skeleton of a fish, and this prompted him to the idea of another invention - a saw. Connecting two identical sticks with a hinge, Talos invented a compass. Daedalus envied the genius of his nephew and once on a walk he pushed Talos from the city rampart.
Scientific hypothesis
There is another, more scientific hypothesis, which explains why the compass is needed , how this thing appeared among the objects of ancient people. In order to outline the circle, they took a peg and a rope. A coal or piece of chalk was attached to the rope, and thus a circle was drawn. Later, the rope was replaced with a thin branch or a plank. This made it possible to outline circles of only a given radius. Finally, this problem was solved - they attached another to one plank and fastened them together. Thus, the first compass was obtained.
The structure of the compass
The principle of operation of the compass and its structure has remained unchanged for several hundred years. Modern technology only made this device more convenient to use. Nowadays, the compass consists of the following parts:
- holder. The topmost part of the compass. The main purpose of the holder is to prevent slipping of the hand when drawing. Therefore, the holders and roughened or with special recesses for the fingers;
- rods. This is the main working part of the compass, its “legs”. Professional draftsmen prefer compasses in which the rods are made of high strength metals. This ensures line hardness and minimal error when using the device. And why do we need a compass with plastic or wooden rods? In children's and school tools, high precision is not required, therefore such compasses can be made of plastic;
- the needle. It must be very strong and sharp in order to fix the compasses as firmly as possible at the reference point and reduce the likelihood of the instrument slipping off the drawing;
- nozzles. Typically, nozzles are slate rods of different stiffness. The draftsman selects the rigidity of the stylus, depending on the type of work performed.
Using compasses in geometry
No one thinks for a long time about the answer to the question of what a compass is for. This subject is familiar even to elementary school students. The main thing for which a compass is needed is to draw circles of various sizes. Older students already know that they not only draw circles with a pair of compasses, but also solve many different geometric problems.
For example, dividing a segment into two equal parts without drawing tools is very difficult. Using a compass, you can divide the segment into two parts that are absolutely identical in length. As can be seen, for such an operation, the points denoting the ends of the segment must be made the centers of intersecting circles. We draw a line through the points of intersection of these circles along the chord. The intersection point of the line and the given segment will divide this segment exactly in half.
Here is another example of what compasses are for. Suppose you are given the sides of a triangle that you want to build on paper. “By eye” it is impossible to determine the correct angles such a triangle will have.
Using a compass to build a figure is very easy. We take a segment equal to one of the sides of the triangle. From the ends of the segment we draw
circles, the radius of each of which is equal to the given length of the side of the triangle. The intersection of the circles will become the angles of the triangle we need.
Now you have an idea of what compasses are for. The pictures above illustrate its use.
Using a compass gauge
Since ancient times, the compass has expanded its scope. For example, this tool is found without a stylus or pencil at all - on both legs it has sharp needles. One may ask, what is compass without a stylus for? Any engineer will say that this is a caliper. It is not intended for drawing circles and ellipses, but it is available in every workshop. What is a compass meter for? Using it, you can quickly and accurately measure the same distances on a drawing, or mark the drawing with almost invisible scratches on paper.
Use of compasses by surveyors
Use compasses and land surveyors. Only they have it, and the distance between its rods is strictly defined - usually one meter. Walking along with such a compass, the surveyor can accurately determine the size of the land, because with each step of the surveyor, such a compass measures one linear meter of area.
These examples only to a small extent give the concept of what the compass is for. The answers, deeper and more detailed, can offer mathematicians, geologists, engineers, builders and people of other professions.