Time is a parameter used by human beings to describe the process of material movement or the occurrence of events. The determination of time depends on the law of material circulation that is not affected by the outside world. For example, the cycle of the moon around the earth, the cycle of the earth around the sun, the cycle of the earth's rotation, and the cycle of atomic oscillation. Einstein said that time and space are an illusion of people's cognition. The big bang theory holds that the universe starts from a starting point, and this starting point is also the starting point of time.
Chinese name: time
English name: time
Definition: Time is the time interval from the occurrence to the end of an event.
Applied discipline: physics (first-class discipline)
Time concept
Time significance
concept
Relationship between cognition and human lead (age)
How to increase your lead (time)
How to save time
How to manage time
mathematical logic
The abstract concept of time in physics analyzes the theory of time. The first section analyzes the establishment of time. The second section analyzes the basic properties of time and space. The philosophical concept unit China ancient time unit cherished time more. The famous sayings and aphorisms of people of different occupations expand the concept of time.
To explore the origin of the concept of time, we can start with the time units "day" and "year" recognized by the earth people. Since the birth of mankind, people have felt the phenomenon of day and night cycle, and defined a day and night cycle as time, and gradually realized that this is the performance of the earth's rotation (a thing). Furthermore, people understand that the earth revolves around the sun from behind the phenomena of spring, summer, autumn and winter, and the cycle of the sun, moon and stars, and define the process of the earth's revolution as one year. Not only that, people also divide a day into 24 hours or 12 hours, divide a year into four seasons,1February and so on. People also compare the length of a year with the length of a day, and 1 year (the process of the earth's revolution) corresponds to about 365 days. Through the analysis of time units "day" and "year", we can see that people's understanding of time actually revolves around the existence process of various things. On the basis of people's understanding of things, the concept of time is gradually formed and perfected by defining, dividing and comparing the existing process of things. The process and state of things are nothing more than movement, change or stillness. Things that change in motion can have both spatial displacement and property changes. Some things show periodic movements or changes, while others are not obvious or obvious. The existence process or stage of things with obvious periodic changes is often used as the basis for measuring the length of time. For example, the period of rotation and revolution of the earth, the period of motion of a simple pendulum, the period of oscillation of atoms and so on. Although people have established the concept of time by observing the movement and change of things, it does not mean that there is no time without movement and change or that stillness is meaningless to time. Static is also a form of things, such as the molecular structure of diamonds, which is generally stable, otherwise people will not say "diamonds last forever". Therefore, whether things are moving or static, as long as things exist, they can be described by time, that is, the concept of time should also reflect the static state of things. It is preliminary and one-sided to base the concept of time only on the movement and change of things. If we can further realize that stillness is also a state in the process of things' existence, it will be a progress in the concept of time. A basic purpose of establishing the concept of time is to compare time, that is, to compare the order of things or whether they are at the same time. In order to facilitate mutual communication and activities, people usually take the beginning and end of some landmark things as the sign of timing. For example, the year when Jesus was born was the beginning of a year, the year when Sun Yat-sen announced the founding of the Republic of China was the beginning of the Republic of China, and the sound of starting guns and smoke on the sports field was the beginning of a certain game. Another basic purpose of establishing the concept of time is to measure and compare the length of the existence process of various things. People generally don't regard the existence process of static things as the basis for keeping time, which may be a factor that people regard time as "the existence form of motion" for a long time. People usually choose something with stable periodic motion and take its motion period as the timing basis. Such as moon phase, standard watch, sundial, mechanical clock, quartz clock, atomic clock, etc. These things become people's natural or artificial timers. Timer is a device for people to measure the length of the existence process of other things through the existence process (especially periodicity) of a (class) changing thing under certain conditions. It should be noted that the time measured by any timer is a process of presenting itself and does not necessarily represent the process of other things. Even so, people can still describe the length or stage of the existence process of other things through the running state of a timer under certain conditions or through certain transformation. For example, about 365 earth rotation periods (days) correspond to 1 earth period of revolution (year) and about 29.5 days correspond to 1 moon, and stopwatches are used to measure athletes' performance. As can be seen from the above description, the concept of time should not be invented by people out of thin air, but comes from people's understanding of the existing process of various things and is produced through induction and summary. So the concept of time corresponds to the objective reality-the existence process of things. In addition to understanding "things"-objective things that exist in physical form, such as stars, planets, molecules, atoms, cells, etc., people can also produce corresponding concepts. After understanding the objective facts that are not "things", they can also produce corresponding concepts. For example, the physical quantities corresponding to the seven basic units of time, length, mass, current intensity, temperature, luminous intensity and material quantity in the international system of units, as well as people's concepts of space, information and consciousness, also reflect the objective facts of immaterial forms. Therefore, it is obviously absurd to deny the objectivity of the concept of time on the grounds that time is not a "thing". People not only use time to describe the existence process of material things, but also use time to describe the existence process of other immaterial things. For example, in terms of consciousness, when did Marxism come into being and how long did it last? If people realize that the existence process of things is the origin of time, it is not difficult to redefine time. Time is the existence process of things and the natural attribute of all things. As one of the seven basic dimensions in the international system of units, people use time to measure the length and order of the existence process of various things, including the speed of movement and change.
Time significance
Meaning-(physical definition) Time refers to the time interval from the occurrence to the end of an event. (The "moment" mentioned here is usually called "time". By definition, "time" is inappropriate and should be called "time".) What is time? The essence of time: time is a measure of the sequence or persistence of events. T = t (u，s，...)u-universe； S space, XYZ, S2, S3, T=(S 1 ..., Sn) The above is the essence, concept and formula of time: the order of world events. Where s is the event, S 1, S2, S3, ..., Sn is the event time model.
The sequence and time of 1, 2, 3, ... is a measure of the sequence and signs of these events. The basic concept of time: time is the process of material change. If matter remains the same, time does not exist. Even if it exists, it doesn't mean anything And the measurement of this continuous material change is called time. Others think that time is a concept that exists in people's minds. Some people think too much, so their time will slow down; Some people move more, and time will be faster. Speaking of which, some people may say that we live on the same earth, so time is not equal? Wrong. The time is equal, but the order is different. This is also the reason why some places develop rapidly and some places develop slowly. The value of time: time is the biggest cost of people, and it is also everyone's capital and wealth. Time is fair to everyone. Everyone's day is 24 hours 1440 minutes. From the day you came into this world, it has been with you every day. No matter whether you are poor or rich, expensive or cheap, time has never left you. Time is limited and infinite. What is limited is that there are only 365 days in a year, 24 hours a day, but he goes on and on, and life is only in a hurry for decades until the day of old age.
BIGBANG is the beginning of time, and time remains the same. Every minute seems to be infinitely long, but it gives each of us a limited life. The famous writer Lu Xun once said: Time is the material of life, and wasting other people's time is tantamount to killing people for money. Therefore, do everything seriously, don't waste your own time, let alone others' time. The origin of time: the origin of time is the existence process of things. Time is the natural attribute of everything. Time is a representation of existence, a record of process, and a parameter for people to describe the process of existence and its fragments. The existing state of things is nothing more than static and dynamic changes, and the dynamic changes of things not only have their spatial displacement, but also have their nature changes. Time is the key to judge whether general things are in a static stage or a moving stage. Everything has a beginning and an end. But there is at least one thing besides absolute space. Absolute space-the existence process of absolute time has no beginning or end. The existence process of other things can correspond to a certain part of absolute time. Of course, the time of other things can also correspond to each other under certain conditions. Time has its origin, just as the universe has its origin. The creation of the universe is accompanied by the creation of time. There is no time around an absolutely stationary object, but there is time around a moving object. The earth we live in is moving, and it will rotate, so there is time on the earth. If there is no rotation, then it will have time, because it is also revolving. If there were no revolution, there would be time on earth. The solar system is moving, so is the Milky Way and even the whole universe. If the whole universe is at absolute rest, then there will be no time.
concept
time scale
Timing system: it is a working system to determine and broadcast accurate time. Every hour, the radio that is listening to the radio will play the sound of "beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep beep It is controlled by the precise clock of the Observatory. So how does the Observatory know these precise times? As we know, the earth rotates once a day, so the stars in the sky rise and fall once a day. If the earth is regarded as a big clock, the stars in the sky are like the numbers indicating the hours on the clock face. Astronomers have well located the stars, which means that the hours on this natural clock face are very accurate. Astronomers' telescopes are like hands on a clock face. On the clock we use every day, the hands turn and the clock face does not move. Here, it seems that the hands are "motionless" and the clock face is turning. When the stars are aimed at the telescope, astronomers will know the correct time and use this time to correct the clock of the observatory. In this way, astronomers can always know the correct time from the clock face of the observatory. Then broadcast it on the radio at some time every day, such as the hour, so that we can go to school for our own clocks or other work needs. Astronomical time measurement depends on the earth's rotation, and the non-uniformity of the earth's rotation makes the time (universal time) accuracy obtained by astronomical methods only reach 10-9, which cannot meet the social and economic needs in the middle of the twentieth century. A more accurate and stable time standard came into being, which is the "atomic clock". At present, all countries in the world use atomic clocks to generate and maintain standard time, that is, "time reference". Then, the time signal is transmitted to users through various means and media, including short wave, long wave, telephone network, Internet and satellite. This whole process is called "timing system". Time zone: 24 regions of the earth's surface divided by longitude. When we saw the sun rise in Shanghai, it would take people living in Singapore half an hour to see the sun rise. Residents of London, England are still asleep, and it will take 8 hours to see the sun. People all over the world, if they use their local time in their life and work, will bring a lot of inconvenience and difficulties to their daily life and transportation. In order to take care of the convenience of use in various regions and facilitate people from other places to take their local conversion of time to other places. The relevant international conference decided to divide the earth's surface from east to west along the meridian, and stipulated that the time difference between adjacent areas was 1 hour. People at the eastern and western ends of the same area can see the sunrise within 1 hour at most. When people pass through an area, they will correct the clock to 1 hour (negative to the west 1 hour, positive to the east 1 hour), and when they pass through several areas, they will increase or decrease the hours. This is very convenient to use. Today, the world is divided into 24 time zones. Because in practice, 1 country or 1 province often spans two or more time zones at the same time, 1 country or 1 province is often grouped together for administrative convenience. Therefore, the time zone is not strictly divided by the north-south straight line, but by natural conditions. For example, when China has a vast territory, spanning almost five time zones, but actually only the Dongba time zone standard is used, it is based on Beijing time. Time zone: Time measured by the global unified time zone system. Whenever the sun shines, it is noon 12. But different places see sunshine at different times. For example, it is already noon in Shanghai 12, and it will take five hours for residents in Moscow to see the sunshine. It's already 2 pm in Sydney, Australia. Therefore, if local time standards are used everywhere, it will bring a lot of inconvenience to administration, transportation and daily life. In order to overcome this difficulty, astronomers came up with a solution: draw an area every 15 degrees in the world longitude, so there are 24 areas in this * * *. Every region adopts a unified time standard, which is called "time zone". However, the difference between adjacent areas is 1 hour. When people move eastward from one area to a neighboring area, they put the clock forward 1 hour. After passing through several areas, they set the time forward for several hours. On the contrary, when people go west from one area to the neighboring area, they will put the clock back to 1 hour. After passing through several areas, they delayed the time for several hours. In transportation centers such as airports, for the convenience of passengers, maps are often used to represent the corresponding areas of major cities in the world. Greenwich Mean Time: Also known as Universal Time. Greenwich mean time. Nowadays, not only astronomers use GMT, but also the term often appears in newspapers and periodicals. We know that every place has its own time. It will be complicated and inconvenient to record an important international event with local time. And it is easy to make mistakes in the future. Therefore, astronomers put forward an acceptable and convenient recording method, which is based on Greenwich local time. Greenwich is the location of the former Greenwich Observatory in the southern suburbs of London, England, and the starting point of the world geographical longitude. Major events in the world are recorded in Greenwich local time. Once Greenwich Mean Time is known, it is easy for people to calculate the local time. For example, when an event happened at 8 am GMT, China was in the east of England, and Beijing time was 8 hours earlier than GMT, we immediately knew that it happened at Beijing time 16, which is 4 pm Beijing time. China * * * is divided into five time zones: 1, and the Central Plains time zone: East longitude 120 degrees as the central meridian. 2. Longshu time zone: East longitude 105 degrees as the central meridian. 3. New Tibet time zone: 90 degrees east longitude is the central meridian. 4. Kunlun time zone: 75(82.5) degrees east longitude is the central meridian. 5. Changbai time zone: the central meridian is east longitude 135( 127.5) degrees.
Relationship between cognition and human lead (age)
Because guidance is relative to guidance, to judge a person's cognitive level, it is necessary to judge his objective and correct cognitive quantity of something, not physical quantity. In other words, it doesn't mean that the older a person is, the more things he knows and the more correct he is, but it depends on how much time he spends on the research and cognition of related things.
How to increase your lead (time)
Life is limited, so how to prolong life as much as possible, or let what you do continue to get help? (1) If you want to live a long life, you should always pay attention to diet, rest and fitness. It is good to know more about this information and exercise more. (2) In fact, a person's existence in this world is only guiding the existence of various things, so if some of the guidance he has guided can continue to be guided, then people basically have no regrets. In this regard, you can publish all kinds of guidance you have handled, explain its importance and significance to everyone, and then call on everyone to guide together; Or you can set up some specialized companies and institutions for long-term storage; Of course, you can also recommend it to your relatives, friends and children for storage; All the above methods can make your tour guide not interrupt his guidance.
How to save time
In order to save time, there are some methods, such as increasing "storage volume", reducing "storage difficulty" and selecting "storage focus" (1) Add Memory Wizard; The psychics here are not only human beings, but also various machines, animals and so on. In short, anything can provide a medium for a thing, so we must carefully consider which media can help us. (2) reducing the difficulty of memory storage; The main points here are: we can change some methods and paths of memory storage, and then we can reduce the difficulty of memory storage; For example: to calculate 899×887=? This problem can actually be worked out directly with a calculator. (3) selecting the stored key points; In fact, everything has its key points, as long as we find the key parts of storage, it will be easier, and what we need to know is: to tear down a dam, we only need to dig a few small holes in the middle of the dam; To crash a plane, just dig a few small holes in the plane; So a seemingly big thing actually found the key and breakthrough, and everything became simple. ◆ Applying logic: Everything in the world has something to guide its existence, which we call "guiding existence" for short, and "essence" and "law" are "guiding the first existence" (what guides our first existence); "Ideology" is "guiding existence for the second time" (what guides our existence for the second time); All "events" are "leading events" (leading events); And each "guide" has its corresponding "guide" (guide stored procedure); And each "lead" has its "length"; Finally, we find that the essence of time is the length of lead, which we call lead for short.
How to manage time
GTD is the most advanced time management method. GTD concept: The core concept of GTD is that only by writing down everything you think and arranging the next work can you do your current work wholeheartedly and improve efficiency.
mathematical logic
What is the time? Time is a measure of a series of events in the universe. T = t (u，s，x，y，z...)u-universe； S space, XYZ, S2, S3, T = (S 1 ... Deng's time formula: the order of world events. Where s is an event, S 1, S2, S3, ..., Sn is the order of events 1, 2, 3, ..., n and time are measures of the order and symbols of these events. The earth always rotates from west to east, and the east always sees the sun before the west, and the time in the east is always earlier than the west. The difference between eastern time and western time is not only calculated in hours, but also in minutes and seconds, which brings a lot of inconvenience to people's daily life and work. In order to overcome the time confusion, 1884 at an international J-Diameter conference held in Washington, D.C., it was stipulated that the world should be divided into 24 time zones. They are the central time zone (zero time zone), the eastern zone 1- 12 and the western zone 1- 12. Each time zone spans longitude 15 degrees and the time is exactly 1 hour. The last east-west zone 12 spans longitude 7.5 degrees respectively, and is bounded by east-west longitude 180 degrees. The time on the central meridian of each time zone is the time uniformly adopted in this time zone, which is called time zone. The time difference between two adjacent time zones is 1 hour. For example, the time of China East Zone 8 is always 1 hour earlier than Thailand East Zone 7 and 1 hour later than Japanese East Zone 9. Therefore, people who travel abroad must adjust their watches at any time to keep up with local time. Set your watch forward 1 hour every time you go west (for example, from 2 o'clock to 1). Every time you go east, you should set your watch back to 1 hour (for example, dial 1 until 2 o'clock).
The abstract concept of "time" in physics
The most widely accept physical theory about time is Einstein's theory of relativity. In the theory of relativity, time and space together constitute a four-dimensional space-time and constitute the basic structure of the universe. Time and space are not absolute, and the passage of time measured by observers with different relative speeds or different space-time structures is different. Special relativity predicts that the time of a clock with relative motion will pass slower than that of another clock at rest. In addition, the general theory of relativity predicts that the gravitational field generated by mass will distort the space-time structure, and the time delay of clocks near large masses (such as black holes) is slower than that far away from them. The existing instruments have confirmed the accurate prediction of time by these theories of relativity, and the results have been applied to the global positioning system.
As far as today's physical theory is concerned, time is continuous, uninterrupted and has no quantum characteristics. However, some unproven theories, such as quantum gravity theory, string theory and M theory, try to combine relativity with quantum mechanics and predict that time is discontinuous and has quantum characteristics. Some theories speculate that Planck time may be the smallest unit of time.
According to the Einstein equation in general relativity solved by Stephen W Hawking, it shows that the time of the universe has a starting point, starting from the Big Bang (or BIGBANG), and the time before that is meaningless. And matter and time and space must coexist. Without matter, time is meaningless.
Ever since the advent of mankind, people have known that time is irreversible. People are born and die, and there is no other way. The glass bottle fell to the ground and broke, but none of the broken bottles jumped up from the ground to make it complete. From the point of view of classical mechanics, the irreversibility of time cannot be explained. There is no substantial difference in the process of reverse elastic collision between two particles. The irreversibility of time can only be explained theoretically from the viewpoint of statistical mechanics and thermodynamics. The second law of thermodynamics says that in a closed system (we can regard the universe as the largest possible closed system), entropy can only increase, but not decrease. The entropy in the universe can't decrease after it increases, so time is irreversible.
Definition of time: the concept of time summed up by human beings in life is rooted in the sequence of events in daily life. Of course, what people get in life is not only the concept of the sequence of events, but also the concept of the length of time interval. This concept comes from the comparison of two processes-for example, two things start at the same time, but one thing ends and the other thing continues, so we say that the other thing takes longer. Here we can see that people use measurable processes to measure abstract time.
Similarly, in physics, time is defined by physical processes. First, in a reference system (inertial system or non-inertial system is needed, but the spatial scope of the process is infinitely small), a physical process is set as a time unit, and then this process is compared with other processes to determine the time.
However, the measurement time (that is, the above comparison process) must have the same concept. There is a simultaneity problem at the beginning of the process, and there is also a simultaneity problem at the end of the process-the simplest example: we require athletes to start at the same time as the starting gun is fired, and the timekeeper starts to time, and the timekeeper must stop timing when the athletes reach the finish line.
See various books on relativity for details. The problem of simultaneity makes classical Newtonian mechanics, special relativity and general relativity have different "times". The concept of intuition tells us that anyone can reach an agreement on whether events happen at the same time (maybe some people will cheat others, resulting in a situation similar to that in detective novels or political novels, but this is a manifestation of human's "high IQ", so we can completely replace it with measuring instruments:), so we will not talk about people later, but say observers.) In the theory of relativity, the observer's motion state causes simultaneous changes, or the observer 1 is V 66.
Mathematically, classical Newtonian mechanics has only one time parameter, which is common to all reference systems. This actually assumes that all reference systems and all spatial positions can share the same definition of simultaneity.
The special theory of relativity holds that different reference systems are different, that is, different reference systems have their own time parameters t, and the relationship between them is determined by Lorentz transformation. General relativity holds that different places will be different at different times. There are more complicated contents about time in general relativity. See the book on general relativity.
Of course, please note: strictly speaking, this is not a simple "thinking", but based on two assumptions: special relativity is the principle that the speed of light is constant. General relativity holds that the essence of gravity is the bending of time and space. These two hypotheses have been widely verified by experiments.
We have finished the time interval measurement problem above. But as mentioned above, the order of time is people's first impression of time in daily life. In classical Newtonian mechanics, it is easy to understand that we have a unique time parameter t, so any two events (one at t 1 and the other at t2) have a definite order. What about relativity? The determination of the sequence of two events in the same place in relativity can be directly seen from Lorentz transformation. But what is certain is that the sequence of two events in different places in the theory of relativity is also different with different reference systems (I would like to say that the motion state of instruments is different, so as to tell the essence of things). But there is a question here: Is it possible that in reference frame 1, event A occurred before event B, and the occurrence of event A affected the occurrence of event B (in the most extreme case, for example, a child killed a young grandfather), but in reference frame 2, the situation is just the opposite? If so, the law of causality, the most important basic principle in physics and even all principles, will collapse. So this question is very important. Let's describe this problem strictly: when event A happens, it sends a signal (the generalized signal covers all the ways that can affect B, but because A and B are different, it takes a while to spread) to affect B, but in another frame of reference, it is just the opposite. Fortunately, Lorentz transformation can prove that as long as the signal speed does not exceed the speed of light (the most used light, the speed of light), the signal cannot reach the position of B before B occurs.
In addition: another narrow hypothesis: the physical laws of any physics department have the same form, and the general theory of relativity also abides by it. In other words, when a physical process is measured in the reference frame 1, the result is l 1=v 1t 1. Measurement in reference frame 2 will also result in l2=v2t2, although it is possible that l 1, v 1 and t 1 are not equal to l2, V2 and t2. Of course, strictly speaking, this example is not suitable, because V defines the derivative of the position vector. But for some complex physical laws, such as Maxwell equations, this assumption is very important.
Time arrow
Let's talk about the arrow of time. In the above discussion, we discussed time from the perspective of time interval and sequence, but ignored a very important feature of time: time arrow. Confucius said: the deceased is like a husband, staying up all night. After a hundred years of life, there is no room for rebirth after death. But the water under the bridge is not just life! The theory of physics tells us that all physical processes related to thermal phenomena are irreversible. Irreversibility here is not irrecoverable in absolute sense, but refers to the fact that the results produced by these physical processes cannot be completely recovered without causing other effects. This is the famous second law of thermodynamics.
There are two ways to express the second law of thermodynamics:
1. It is impossible for a low-temperature heat source to spontaneously transfer heat to a high-temperature heat source (or to transfer heat from a low-temperature heat source to a high-temperature heat source without other changes).
2. It is impossible to completely convert the heat absorbed from a single heat source into mechanical work without causing any other changes. It can be proved that these two expressions are equivalent. The latter statement has obvious engineering traces-this comes from the study of construction machinery that converts heat into work, such as steam engines. Most of these studies are related to the industrial revolution era. There is not much theoretical value today, but there is one thing. Although the mainstream research has basically disappeared, non-professional scholars continue to study, which is the second perpetual motion machine. The second kind of perpetual motion machine is a kind of machine-give it some energy to start running, and then it can absorb all the energy dissipated by dissipation factors such as friction and put it back into the mechanical energy cycle. If such a perpetual motion machine is built, it means that we can use the energy mined today to maintain the mechanical perpetual motion machine (because all the dissipated energy can be reused), so that the world can run to the end of the world at the current energy consumption rate! But the second law of thermodynamics clearly tells us that this is impossible. Dissipated energy (internal energy) can never be completely transformed into the form before dissipation (mechanical work), which destroys the eternal orientation of the basic principles in classical Newtonian mechanics and relativity. So why is this?
entropy
In order to understand this, we must introduce the concept of entropy.