This is a very interesting question. The ancient Silk Road spanned a small half of the world, and there was a long time difference between the easternmost section of eastern China and the westernmost section of western Europe. But could the ancients find jet lag? How do they see jet lag?
Lao Ba believes that due to the underdeveloped communication of the ancients, there is no very accurate timing tool and a very fast means of transportation, resulting in the inability to communicate in a timely manner between the two places that are far apart, so they cannot find the jet lag through direct observation.
Why? Here we first want to say what is called jet lag, and figure out the principle of jet lag.
Simply put, because the earth is constantly rotating, or taking the earth as a frame of reference, the sun is moving around the earth, constantly rotating from east to west. This makes the current time (referring to the time of morning, noon, and evening) in each of the two places on earth that are separated by a certain distance between east and west be different.
Near the east, the sun shines first, and the time is earlier than the people in the west. The east is brighter than the west, the sun is at its peak, and it gets dark early. If the distance between the two places is half a globe, then their time difference is half a day (12 hours), and the day and night are the opposite: noon in one place is exactly midnight in another.
Another example is the end of the Silk Road, Britain, which belongs to District 0, and Beijing is the East Eighth District, with a time difference of eight hours. That is to say, at 12 noon in the United Kingdom, it is eight o'clock in the evening in Beijing. In other words, about eight hours (one-third of the day) after the Beijing sun peaks, the United Kingdom will be the top of the sun.
So, how can humans discover this phenomenon of jet lag? There are two ways.
The first method is to directly compare the time conditions between the two places.
For example, the UK time zone is eight hours later than Beijing. Well, if we can compare the current time in the UK and Beijing at the same time, we can perceive the time difference. But one cannot compare oneself with Beijing at the same time in Britain, so how can one compare it? It can only be synchronized by the establishment of communication methods between the United Kingdom and Beijing.
An Englishman, John, and a Beijinger, Zhang San, made an appointment to call and chat. When they talked, Zhang San told John that it was eight o'clock in the evening in Beijing. John told Zhang San that it was 12 noon in England. This difference makes them understand the jet lag.
Or, in the absence of a clock, Zhang San told John that the sun in Beijing was empty at this time, around noon. John told Zhang San that at this time, the sky in England was not yet light, and the East had just faintly turned white. After eight hours (about one-third of the day), John told Zhang San that it was noon in England, and Zhang San told John that the sun had been setting in Beijing for a while. In this way, both parties can understand the time difference.
Simply put, you have to compare the difference between the two places at the current moment, or the time gap between the two places to reach a common moment, in order to perceive the time difference.
Another way, carrying a precise moment or time recording tool, personally travel between the two places, through the absolute length of time spent to travel between the two places, and the time difference between the time difference between the time before departure and the time after arrival in place B, the difference between the two is calculated.
For example, Zhang San has a watch that walks basically accurately (for example, the error does not exceed a few minutes per day). He adjusted the watch in Beijing and ran to England with it. At this time, he found that his indication pointed to eight o'clock in the evening, indicating that it was eight o'clock in beijing, but England was the noon of the sun. In this way, he can understand the time difference between Beijing and Britain.
Or to put it more simply, Zhang San got on a plane at 8 p.m. in Beijing and flew to London in about 6 hours (suppose), which is supposed to be around 2 a.m. in Beijing. But he found that England was still dusk at this moment. So he also found jet lag.
For the ancients, however, neither of these situations was possible.
At that time, traffic between East and West, cycling or boating was the upper limit of speed. The speed of sending messages is basically limited by the speed of people's travel. The distance between Beijing and Britain, without telephone or telegram, would take many days to deliver a message. At this time, Zhang San was in Beijing, and it was impossible to know what kind of state it was in England at this time. Since it is impossible to synchronize, it is naturally impossible to compare the time difference.
The second method can still be used in theory, but it is difficult in practice. The ancients had roughly two types of timing tools, one is the sundial, which was originally based on the sun, you run to different time zones, the sundial also lost its accuracy. The second type is the use of physical phenomena to time, such as more fragrant, hourglass, water droplet timer, etc. These things are mainly larger errors.
Let's assume that Zhang San has a very accurate hourglass that leaks exactly 24 hours at a time (or one hour or two hours). Then, Zhang San went all the way west from Beijing, constantly timing his hourglass along the way, and immediately re-timering every 24 hours. Zhang San will find out. Originally he started his first hourglass timer at noon, but as he continued to travel west, gradually when he began a new round of hourglass timer, it was no longer noon, but the morning before noon. The further west you go, the sooner the moment to start a new round of hourglass timing will begin. By the time he got to England, by the time each hourglass timer began, it was already early in the morning. Thus, Zhang San concluded that British time was about a third of a day later than Beijing's.
The above is an idealized situation. But in fact, the ancients could not make such an exquisite hourglass, which could be exactly 24 hours, and Zhang San's operation could not be absolutely accurate. According to the traffic of the ancients, it would take at least several months to run from England to Beijing. Eight hours of time difference, evenly spread over a journey of several months, equals a few minutes or so of time difference every day. According to the statistical tools of the time, this was completely undetectable. The impact of the error caused by the bumpy hourglass when Zhang San was running on the road may be greater than this. Even if Zhang San really found that the hourglass started in Britain was different from that in Beijing, he would only suspect that his so-called "hourglass of one day and night" was not really an accurate day and night, but only a deviation.
Therefore, the ancients could not observe jet lag.
However, do not think of the ancients as fools, thinking that the ancients did not know the existence of jet lag.
It is not observable, and it can be speculated.
After all, the sun rises in the east and sets in the west, then the west will usher in the dawn later than the east, and send away the dusk later, which does not need to calculate the time difference accurately, and can get the imagination directly from the mind.
Leaving aside the fact that Westerners have long proposed the concept of "earth", even the ancient Chinese people who said "heaven and round place" can fully understand the time difference between the east and the west.
The early mythological story "Father Kwa Day by Day" depicts the giant Kwa Father chasing the sun to the west. Although he wanted to use his strength to retain the sun, he was not trying to use his speed to catch up with the speed of the sun's travels, and to use the time difference to grab time to the west.
And the Song Dynasty lyricist Xin Abandoned Disease, but also with a song "Magnolia Slow", very vividly and vividly depicted the time difference between the East and the West:
Poor this sunset and moon, where to go, to leisurely? Is it someone else's world, only to be seen over there, the east end of the light and shadow? ......
The writer saw that the moon had fallen to the west, and wondered if there would be another human world, and had just seen the moon rise from the east. Isn't that jet lag? And it is a very simple model, as long as the west side of the traditional "heavenly round place" is supplemented with a piece of land inhabited by people, then the moon in the west will naturally go there.
It can be seen that although the ancients were subject to technology and it was difficult to directly observe jet lag, jet lag was not an unfathomable concept for them.