The easiest way to answer our question is for astronomers. Day is when the Sun is above the horizon, and night is when it is below the horizon. Thus, in terms of astronomy, time is a reflection of the visible motion of the Sun across the sky.
There is even a very simple formula in the astronomy course, which is so called: the time formula. In it, time is equal (with minor corrections) to the local hour angle of the Sun t plus 12:
t = t+ 12
By the way, time in astronomy can be counted both “forward” and “backward”, that is, there can be a “time machine” in astronomy. In fact, any planetarium (including a computer planetarium) or calendar is a kind of astronomical time machine.
Time in physics
Here everything is more complicated. Let us assume that in mechanics, as well as in astronomy, time is reversible, that is, it is counted both forward and backward.
For example, if we know the speed and position of a car on the road, we can easily calculate where it will arrive in 2 hours or where it was 2 hours ago.
But physics is not just about mechanics! In physics, there is such a section as thermodynamics, that is, the science of heat transfer. And here time is irreversible, in thermodynamics there cannot be a “time machine”.
For example, if we drive a car (mechanics), we can go forward as well as backward, and we can return to the point from which we started the journey. But if we fry a chicken (thermodynamics), it is very easy to turn a raw chicken into a fried chicken, but no one has ever been able to turn a fried chicken back into a raw chicken.
Time in math
In mathematics, time is very unusual. It is more correct to call it “the arrow of time” or “the direction of the solution,” whichever one prefers.
Suppose we are given an example:
5 + 4 = ?
It’s a first-grade problem, isn’t it? Of course, the answer is 9. Now let’s do a very simple thing: let’s turn our example the other way around:
9 = ?
How do we solve such an example? We can, of course, write that 9 = 5 + 4. But we might as well write that 9 = 3 x 3. Or the square root of 81. There could be millions of mathematical formulas resulting in 9!
This is why scientists talk about the “arrow of time” in mathematics: one way the example is easily solved, but the other way (without more information) cannot be solved at all.
Time in Logic
Do you like reading detective stories? About the adventures of great detectives like Sherlock Holmes or Hercule Poirot? Well, the logic so beloved by detectives is an integral part of mathematics!
And there is always that “arrow of time” in logic, too-if the boy Lyosha threw a stone at the window, it is clear that the glass will break. However, if the glass is already broken, can we (without more information, that is, without “evidence”) say who broke it and with what? That’s just it, we can’t! And here you have a real school detective…
Time in biology
You probably have heard about the so-called “biological clock”. For example, a flower clock: instead of hands they have flowers, and each flower opens and closes at the same time!
Time in Geology
In geology, time is absolute and relative.
Absolute time is the time determined by special methods, for example, radiocarbon analysis. If we found an ancient man’s camp or mammoth bones in the ground, radiocarbon analysis will allow us to get (with a good accuracy) the absolute age of the find – say, 12,000 years.
Relative time is determined using rock layers. Many of you probably remember that giant dragonflies lived in the Carboniferous period and that dinosaurs died out at the end of the Cretaceous period – but why are the periods called “Carboniferous” or “Cretaceous”? Because it was during that era that deposits of rocks of the same name were formed – in our case, hard coal or written chalk. If you’ve ever been in the mountains, pay attention to the horizontal layers of deposits – the older the rock layer, the earlier in time it formed.
Time in language.
Do you think there are three? Present, future, and past? Uh-uh-uh…
And in French there are 15 tenses! So let’s not talk about sad things…
Time in History
…It’s called “chronology” or “chronology.”
It is called “chronology” or “timekeeping”. Most of the time the starting point of the chronology is an important event. For example, the beginning of the reign of a new leader, the founding of a new city (the era from the founding of Rome – for the Romans) or the first Olympic Games – for the Greeks.
Each state had its own chronology. With the development of trade and science in Europe, the need for a unified calendar arose. In 525, the Roman abbot Dionysius the Less proposed a system of chronology from the Nativity of Christ.