The term diameter that concerns us now can establish that it has its etymological origin in Greek, since it is the result of the union of several components of said language:
-The prefix «dia-«, which means «through».
-The noun "metron", which can be translated as "measurement".
This is the name given to the line that, passing through the center, joins two points of a sphere, a closed curve or a circle. The greatest width of a circular body is also called diameter.
For example: "Alarm among astronomers: an asteroid 800 meters in diameter will pass very close to our planet" , "The drain will be made with a pipe two meters in diameter" , "A stone two meters in diameter rolled down the mountain and crushed a vehicle .
The Greek mathematician Euclid postulated, about three centuries before Christ , that the diameter of a circle is any segment that passes through the center of the figure and ends, in both directions, at its circumference . That same segment, on the other hand, establishes the division of the circle into identical parts .
The relationship established between the diameter and length of a circle is a constant known as the number pi . It is an irrational number that is usually cut off in the first figures, taken as 3.14 .
Knowing the diameter of objects is important on many occasions. The diameter of a ring , for example, will determine whether or not this item can be placed on a finger. If the diameter is very large, the ring will be large; On the other hand, if the diameter is very small, the ring will not fit. The diameter of a bottle , on the other hand, will depend on whether it can be stored in a certain space in the refrigerator or where it can be carried in a backpack.
Without a doubt, one of the diameters that is most interesting is that of the Earth. So much so that, throughout history, there have been numerous scientists who have worked to discover it. Thus, for example, we can establish that the first to try to discover this diameter was the Greek astronomer and geographer Eratosthenes of Cyrene (276 BC – 194 BC), who used a rudimentary method to make this measurement.
Specifically, this was based on shadows and the summer solstice, among other aspects, which led him to reach the conclusion that the circumference of our planet was about 40,000 kilometers and the diameter was about 12,800 kilometers.
Currently, we can establish that it has been established that the diameter of the Earth is about 12,756.247 kilometers, which makes it clear that the aforementioned Greek astronomer, despite not having the technology or knowledge that we have today , made a very approximate calculation.
When talking about diameter, we cannot fail to also mention another term: radius. We can establish that this is half the diameter and is the segment that joins the center of the circle with any point on it.