**what's the time? The answer to this question can be different, if you were born on a different planet**

The basic astronomical cycle unit on Earth is the day and is defined as the time it takes for the Earth to rotate around its axis. The diameter of the earth is 40,000 km and the accepted unit of time to measure the duration of its rotation around its axis is the hour. The hour is divided into 60 minutes and each minute has 60 seconds according to this unit of time the earth rotates around itself once every 24 hours.

The division into lines of longitude and latitude is intended to indicate geographic points and for navigation purposes. The lines of longitude are also used to determine geographic time zones. The characteristic of this method is its simplicity. To locate any place on Earth, two data, longitude and latitude, are enough, and to determine a time zone, one data is enough - longitude. The simplicity of this method raises the likelihood of its universality on every planet where there is intelligent life. On the surface of the earth the distance between one longitude and another is 111.1 km, there are 1440 minutes in a day (1440 = 24×60), therefore the time difference between one degree of longitude and another is 4 minutes (4 = 1440:360). Hence the conclusion that 1 hour has 15 degrees of longitude (15 = 60:4).

When moving to other planets, whether it is our solar system or whether it is other solar systems, we encounter planets of different sizes not necessarily equal in size to those of the earth. There will be smaller planets and there will be larger planets. It is likely that their axial rotation speed will be different from that of the Earth and therefore the length of their day will be different from that of the Earth. The time difference between one degree of longitude and the number of degrees of longitude in 1 hour will not necessarily be similar to what we know on Earth.

These time measurements of other planets are done according to earthly standards. The length of the day of other planets is measured in terms accepted on Earth. However, if an intelligent population exists on these or other planets, it is not necessary that its terms of time be the same as those accepted in our world. Even in these planets the basic astronomical unit of time will be the day, since planets always rotate about their axis and naturally one side will be lit and the other side will be alternately dark. As an example, let's take a planet with a diameter of 8000 km, whose day has 9 hours (here we use the earthly term for convenience, when this unit of time is given a different name by the locals), each hour is 30 minutes and each minute is divided into 30 seconds (also Here the terms minutes and seconds are used for convenience). For the locals, the circle is divided into 100 degrees (also here the term degrees is used for convenience) and each degree lasts 10 seconds.

The day of that planet has 270 minutes (270 = 30X9). The time difference between 1 degree of longitude per second is 2.7 minutes (2.7 = 100: 270) and the number of degrees of longitude in 1 hour is 11.1 = 2.7: 30) 11.1). On Earth there are 24 time zones as the number of hours in a day, therefore the number of time zones on the same planet is 9.

Another example is that of a planet whose diameter is 15,000 km and whose day is 30 hours (in the terms of the local people). Each hour is divided into 10 minutes and each minute is divided into 5 seconds (in terms of the locals). The day of that planet has 300 minutes (300 = 10x30) and the circle is divided into 150 degrees (in terms of the people of the place). The time difference between 1 degree of longitude per second is 2 minutes (2 = 150:300) and the number of degrees of longitude in each 1 hour 5 = 10:2) 5). This planet will have 30 time zones.

The number of options is very large. In any case, a meeting between one group of extraterrestrials and another or with the inhabitants of the earth can be confusing and embarrassing, since in every place what is meant is something different when talking about an hour. There are three ways to overcome this. One way is to use mathematical transformations. A second way is that each culture will have to learn the time terms of the other culture and get used to thinking in these terms when a meeting between cultures takes place. A third way is the development of interplanetary standards that will be used by all.