How did the ancient people of China know that "there is one day in the sky and one year underground"? What is the scientific basis?

"One day in the sky, one year underground"

The Journey to the West is one of China's four great masterpieces, written in the Ming Dynasty, and is a chapter-length novel of gods and demons. The author based it on the background of Xuanzang, a monk who traveled on foot to India during the reign of Emperor Taizong of the Tang Dynasty, and recreated it based on Chinese folklore, dramas, and operas. Thus, Journey to the West is essentially a fictional novel, not a documentary type.

In the novel Journey to the West, there is a passage that tells the idea that there is one day in heaven and one year on earth.

And this idea seems to have similarities with some of the conclusions of the theory of relativity, one of the pillars of modern physics. So, some people say that the ancient Chinese knew about relativity, and that "one day in the sky and one year on the earth" is a good proof of that.

Objectively speaking, this view is actually very far-fetched, so what is going on?

Let's talk about what's wrong with it.

Relativity

This thing we have to start with Newton, Newton is considered to be the granddaddy of classical physics, he proposed Newtonian mechanics and the law of gravity is the foundation of the classical physics, and Newton explored the theory of a set of methods are also inherited by later scholars.

Specifically, a rigorous definition of the object of study that can be quantified. Second, theories can be tested experimentally. In other words, Newton laid down the scientific paradigm based on math, experimentation, and logical reasoning at an early stage. This is presented in his work "Mathematical Principles of Natural Philosophy".

So science is an extremely process-oriented discipline, and there is no room for sloppiness in the process of proving a point right or wrong. That's why there's that famous saying: be bold in your assumptions, be careful in your evidence.

Later generations of scientists have followed this paradigm. Therefore, if we want to "one day in the sky, one year on the ground", in fact, can not be just such a sentence, but need to have a rigorous process of proof, and this process is written into a paper to be published. If we look carefully at the classical Chinese texts, we will not find any ancient person who has carefully tested this idea. Therefore, this does not fit the scientific paradigm, nor does it belong to the realm of science. In scientific terms, this can only be described as a guess at best. It is easy to realize that guessing is easy, the hard part is seeking proof. So, in essence, the ideas in the West have nothing to do with science.

Einstein, as the greatest scientist after Newton, followed Newton's set of rules. in 1905, he proposed the theory of special relativity, and by 1915, he had proposed the theory of general relativity. But he didn't seal the deal all at once, as most people think.

Einstein really wasn't recognized by the world until 1918, actually, and that's because in that year, Eddington led a team to prove Einstein's general theory of relativity.

From 1915 to 1918, Einstein was actually trying to figure out how to prove his theory. So we can see the importance of seeking proof for science. Secondly, in Einstein's theory, there are two main situations in which time will expand:

When the speed is close to the speed of light, time will expand, but this is relative;

When in a place where gravity is very strong, or accelerated motion, time will expand.

Based on the conclusion of the theory of relativity, it is easy to conclude that "one day in the sky, one year on the ground" is not reliable. Because if we want to realize "one day in the sky, one year underground", it means that either "the sky" is moving at a high speed relative to the Earth, and close to the speed of light; or "the sky" is moving at a high speed relative to the Earth. The gravitational pull of the sky itself is enormous, far greater than that of the earth itself.

But now that we've explored space, we know that the space around us doesn't move near the speed of light relative to the Earth. Secondly, only a few extraordinarily massive stars and dense objects (black holes, neutron stars) in the universe would have super-strong gravity.

And extra-massive stars and dense objects are actually a minority in the universe, with more small-mass stars and planets. In other words, what we often call "the sky", or space, is not expanding in time relative to the Earth, much less "one day in the sky and one year on the ground".

Unless the hypothetical "sky" is a black hole, a neutron star, or an object that is hundreds of millions of light-years away from us. But that doesn't seem very realistic, if it's in a black hole, light can't escape, not to mention the Monkey King can fly around.

If it is on a celestial body that is hundreds of millions of light years away from us, then that celestial body is moving away from us faster than the speed of light due to the expansion of the universe, which means that if the Monkey King wants to go to the Heavenly Court, he can't, no matter how fast he flies, unless the Monkey King is able to go superluminal. Similarly, if Sun Wukong were on that celestial body, then he would have no way to get back to Earth because he would be far away from speed space.

Summary

So the whole "one day in the sky, one year underground" thing is inherently incorrect. The gravitational pull of supermassive stars, black holes, and neutron stars is only strong enough to make time dilation drastic, and they are a minority in the universe. Beyond that, the only objects with huge time dilation are those that are exceptionally far away from Earth, but because they are so far away so fast, only FTL can get back and forth, but FTL has defies physics theory.