Rest. The wind and rain do not move, and it is as safe as a mountain".
The words and sentences are from Du Fu's "Song of the Thatched House Broken by the Autumn Wind" in the Tang Dynasty.
Because the mountains are there!
This sentence comes from the famous British mountaineer George Mallory.
The majestic peaks of the mountains always seem to be the landmark event when we identify the concept of stillness.
From the time ancient humans first opened their eyes to the world, to today's children, before modern education, our understanding of stillness is simple and pure, and we use it as a guide to our own actions, to help determine the direction of migration, or to believe that home will always be there, waiting for our return.
It's time to give a standard modern definition of the concept of stillness:
Philosophical: There is no way to prove that an object is in absolute rest, and that an object at absolute rest does not exist. Rest is simply an object that keeps its position unchanged with respect to another reference around it, so it can only be relative motion and relative rest, motion and rest are relative.
Mathematically: Choose a frame of reference, if the first derivative of the position vector of an object relative to the frame of reference is zero, that is, the velocity is zero, then it is stationary, otherwise it is motion.
It can be seen that when we talk about stillness, we have to mention motion, in whatever sense.
Motion. Since the mountains can't come, then I'll go over"!
This quote is from the Prophet Muhammad.
Then, the prophet led the ** people, and it took about half a day to come to the foot of the distant mountain and climb to the top of the mountain in one fell swoop.
This event is recorded in the Qur'an.
According to modern scientific methods, the above events may be described as the process of events in which the prophet changed from the beginning to the distant mountain peak in a time period artificially defined as half a day, using the earth's surface space as a frame of reference.
Now give a scientific definition of motion: motion is the process of changing its own position in the time and space of a specified frame of reference.
This process of change involves at least five elements: time, space, position, direction, and reference.
If you are well, it will be a sunny day, and if you are moving, the 5 elements will begin to entangle.
If you want to define motion, you must first define the frame of reference, under normal circumstances, most of the movement of people are willing to choose the surface of the earth as the frame of reference, if it is defined as something else, for example, the entire solar system as the frame of reference, considering the autobiography and revolution of the earth, the process of the prophet reaching the top is probably not as simple as going straight to the distant mountains.
To describe motion, at least give speed and direction. Velocity is related to the distance a position moves in time and space, while direction indicates that motion is a vector quantity, i.e., a quantity with direction. Under normal circumstances, the speed of human movement is 5 kilometers per hour, and half a day is about 4 hours, so the prophet and the ** are 20 kilometers away from the distant mountain, from which it can be seen that speed, time, and distance can be converted to each other.
Athletic absolutely.
In the second century A.D., Ptolemy put forward his own theory of the structure of the universe, known as the "geocentric theory".
This theory proposes that all stars move around a small circle that belongs only to itself, but the center point of the small circle of each star moves around the center of the universe, and the earth is at the center of the universe, maintaining absolute rest. This theory has been accepted and used for more than a thousand years, and it gives basically correct explanations for almost all the doubts we encounter in our daily life, which is in line with our organ perception and mental expectations, and it may not be bad to continue like this. However, ......
In the 16th century, Copernicus proposed the "heliocentric theory", in which the sun replaced the earth as the center of the universe, the earth rotated around its axis, the moon revolved around the earth, and the earth and all other planets revolved around the sun.
At this point, the absolute stillness we perceive is replaced by absolute motion, and the so-called absolute stillness on the earth can only be relegated to a relative position, not to mention what we later know about the solar system around the Milky Way and what galaxy the Milky Way continues to orbit.
Therefore, you can always find a frame of reference, and take the stillness you are sure of, sitting in motion, even if it is as stable as Mount Tai, you will "sit on the ground and travel 80,000 miles a day, survey the sky and see a thousand rivers from afar".
In short, the rest is relative, and the motion is absolute.
Principle of relativity.
When I was a child, I visited the planetarium and saw the dynamic model of the universe, and I was always stunned, watching the balls flying up and down, dazzling, thinking that we living on the earth are comparable to sitting in a roller coaster on a merry-go-round, and we should be dizzy under normal circumstances.
In order to explore the truth, in fact, it should be said that in order to justify itself, so that the series of theories complicated by it can be consistent with their own common sense** knowledge, in the 17th century AD, Galileo proposed the principle of relativity.
A monolithic system that is moving in a uniform linear motion is what Galileo called an inertial system, and the physical characteristics that exist within any inertial system are the same when viewed individually. This is an excerpt from the principle of relativity, and the meaning of the text can also be expressed as follows: relative to different inertial systems, the physical principles in each system are relatively consistent.
From the car driving at peak speed during peak hours in first-tier cities to the 1,300-kilometer carriage of the Beijing-Shanghai high-speed railway in 4 hours;From the plane at an altitude of 10,000 meters to the rotating earth, in this inertial system, the mountains on the earth and the water cup on the saddle are relatively the same stationary, and the walk of the plane to the bathroom and the trek on the ground to the distance are also relatively the same movement, and they obey the same physical laws.
As long as the inertial systems do not cross-reference, there will be no physical anomalies in the closed system.
But if you change an inertial system as a frame of reference, such as standing on the ground, you will see the water cup on the high-speed train is also flying, and the people on the plane are walking in the air, for the connection between this inertial system, Galileo gave a conversion method in the physical sense, that is, the relative change measure between the systems is introduced to correct it, and then it is expressed mathematically to make it simple and clear.
Everything seems to be in place again.
Finally, Newton made the most incisive conclusion for this stability: when there is no external force to interfere, the object remains in a uniform linear motion or a state of rest, which is the first of the famous Newton's three laws. This law illustrates from one side that uniform linear motion is equivalent to rest, and tells you straightforwardly that everything you operate in a stationary state is no different from what you operate in a uniform linear motion state;On the other hand, it shows that matter has the instinct to remain in its current state, and it shows a resistance to change, i.e., the inertial force, which also means that only the introduction of external forces can change all this.
This concept of inertia originated in physics, but now it has a deep and broad meaning, and this external force used to have only a physical meaning, but now it is by no means limited to that. For example, if you are bedridden, you have the inertia of lying comfortably, and only by adding the external force of your parents' slap can you change it.
Movement to the speed of light.
Fast to the extreme, moving in a straight line at a uniform speed to the speed of light, what will happen?
There are always some extreme people who are pursuing the ultimate in an unreasonable way.
With mm experiments, we suddenly found that the speed of light does not change, regardless of which reference system it is relative to. To put it more strictly this way, the determination of the speed of light has nothing to do with the movement of the light source. This phenomenon clearly contradicts the previous classical system of physical theory, which was founded in Galileo and capped to Newton.
The result of the extreme pursuit of perfection finally presents an incomprehensible phenomenon.
This incomprehensible phenomenon forces the same group of extreme people to pursue an extreme theory again and classify the phenomenon as rational and metaphorical.
In the middle, although the Austrian Mach questioned absolute space and absolute time, and the Dutchman Lorenz deduced the Lorentz transformation and obtained the relativistic factor, it was the German Einstein who finally completed the final word.
The movement of objects that we can understand is in a three-dimensional space, and it doesn't matter if it's up, down, left, right. Any trajectory can be projected onto changes in three dimensions, and conversely, numerical changes in three dimensions can synthesize any kind of spatial motion. This stereotypical description of the law will always make people lose some of the beautiful and flexible vision brought about by the movement of space, which is frustrating. For example, TV shows often do technical action replays, and the full moon scimitar of Beckham's set-piece into the net is broken down into data changes on the xyz axis for analysis, which will largely make people feel boring and vulgar, which can also understand why tennis games will limit the number of times players can apply for the use of "Hawkeye", because of the lack of beauty and fun.
Aesthetics belongs to aesthetics, and science belongs to science. Now, we add one dimension and time t to the three dimensions to form XYZT four-dimensional space-time, the previous concept of space becomes the current concept of space-time, and at the same time determine the four-dimensional equality, so that the movement in space-time needs to be projected to four dimensions at the same time, and the numerical changes of the four dimensions can synthesize all the behaviors of all matter in space-time.
In fact, this is also in line with our daily life, even if it is a simple dinner, in addition to saying the spatial location of the hotel, such as the street number in the plane sense and the floor room in the vertical sense, there will definitely be a table opening time at the end.
The next step for us to do is, first, to determine that the speed of light is the fastest, i.e., no object or information will travel faster than the speed of light in space-time;Secondly, to abandon the absoluteness of time and recognize its relativity, just as to admit that stillness is also relative, to realize that time only belongs to the individual existence of space and the space-time body of which it is composed, that is, each space-time system has its own independent space and time, an independent four-dimensional coordinate system. It is not difficult to imagine why the fourth dimension of time is not good when different three-dimensional spatial coordinates can speak their own words in their respective inertial systems
Motion to the speed of light is already the ultimate speed, all the changes in position motion have been completely projected to the three dimensions of space x, y, and z in space-time, and there is no longer any margin to project the time dimension t, at this time, the time dimension is 0, and if there is no time measurement, the speed will lose its meaning, or to put it another way, it can also be determined that the speed is the same in this case, regardless of any space system.
Therefore, the speed of light does not change, no matter to whom, no matter which spatial coordinate system it is relative to.
Only when motion descends from the speed of light, and moving objects produce projections in the dimension of time, does time begin to flow and the story unfolds.
This is one of the important theoretical expositions of special relativity, and classical physics has become a special case when its speed of motion is much lower than the speed of light, so that it is perfectly wrapped in unscathed. Since then, Einstein and later scientists have made a series of general corrections to classical physical formulas from the super field of view of the speed of light, the most famous of which is the upgrade of Newton's kinetic energy equation e=1 2mv 2 from the relativistic mass-energy equation e=mc 2, which has now become almost the iconic symbol of Einstein and his theory of relativity, and it also shows from another aspect that it is impossible for any object with mass to reach the speed of light, because it requires infinite energy.
It is conceivable that these corrections are so small in most cases that they are ignored when doing ordinary calculations, since motion close to the speed of light is too far away from our daily routine. As Stephen Hawking said, the life time that is shorter than a second through high-speed flight is far from compensating for the damage to your health caused by a bad airplane meal.
Because of this, except in individual fields such as GPS satellite positioning, aerospace, etc., the application of these corrections is not extensive, and we usually still use classical theory to solve most of the problems we encounter, because it is easy to understand and simple.