Time passes more slowly for people who live on the first floor than those who live on the top floor, although it is not enough to make people inside live longer. If you want to make a person younger, you just need to travel around the world by an ordinary plane. These are two incredible results, and the time effect is the same for everyone: time can be extended or shortened, depending on space, gravity and speed. This paper will lead readers to explore the seemingly close but mysterious time scale.
What time is it?
1000 years, people have been looking for the answer to this question. For example, in ancient Greece, the definition of time troubled philosophers more than mathematicians. After Galileo's great discovery, Newton finally defined time as a mathematical quantity. However, the great British scientist believed that time is an object covered with mystery, because time is independent of any object and absolutely above everything else. Time is so close to saints that God is compared to a clock.
Einstein believes that time is not like a "free dog" in nature at all, but a real measure. Even today, we still can't define time like doing anything practical. We can measure time, but we don't know what time is. We also hang "time" on the wall or wear it on our wrists. According to Einstein's theory of relativity, we know that time can be extended or shortened. This is why physicists simply use time as a series of events and mark them with time. Such as a person's birthday or the shelf life of food.
2. Does time flow like a river or is it intermittent?
Unfortunately, no theory or experiment can prove that time flows in a continuous way, or it gives people a continuous impression like every frame in a movie, that is, there is intermittent continuity. The study of the continuity or discontinuity of time also involves another question, that is, whether time has a beginning. So far, there is no clear answer. Because the famous big bang theory thinks that space-time has a beginning; Other scientists pointed out that the "time" scale does not have an instant beginning, which is unnecessary. This complicates things. Because according to the principle of quantum mechanics, the time interval less than so-called Planck time is unpredictable. Planck's unit of time is of the order of seconds. So it is impossible to calculate the new state of the universe in a very short time. In short, according to the current theory, the first cry about the universe is always unknown.
Now let's return to the "continuity" of time. Strangely, it can flow continuously or intermittently, but the smallest and computable time interval is the same as Planck time. In a word, time is a continuous belt, and physicists regard it as an interlocking and discontinuous necklace.
A few years ago, scientist David Finkelstein put forward a theory, but it didn't get much support in the scientific community. The physicist assumes that time atoms exist. These time atoms may show their discontinuity.
Does time pass in the same way for all people?
Einstein's theory shows that the answer isno. In fact, like space, time is relative. What does relative mean? That is to say, in order to describe an event completely rather than vaguely, it should be placed in a frame of reference. For example, I date one person at the end of the road, and that "end" may be just the beginning of the road for another person. If I add "in the square behind the end of the road", then this "dating event" is accurate. The same is true of things with time factors. If I say that 10 years have passed, then I must point out that 10 years have passed relative to which frame of reference. Obviously, there is no need to stick to details in daily life. But who knows if we will organize interstellar travel or communicate with aliens in the future? At that time, the time interval will no longer be so simple, and we will feel the relativity of time.
A famous example can explain all this. Alpha and Beta are 30-year-old twin brothers, both astronauts. In 2000, Beta began to take a spaceship with a speed of 240,000 kilometers per second to a planet 8 light years away from the Earth. At this rate, it will take 10 years for Beta to go back and forth. In fact, in order to achieve the desired average speed, β needs to accelerate and decelerate when it reaches its destination. Because their reference frames are no longer the same, we can separate the time of α and β by changing the direction of motion. In 2020, when Beta returns to Earth, he will see Alpha celebrate his 50th birthday (20 years older), and it has just passed 12 years for himself, and he is only 42 years old. This is not an intelligence test. The expansion of time has been measured by a real watch. 197 1 year, two physicists, J.C. Hafele of Washington University and Richard Keating of the U.S. Naval Observatory, traveled around the world and measured four atomic clocks on the plane. The speed of an airplane cannot be compared with the speed of light (by millions of times). However, scientists confirmed that they captured the elasticity of time: at the end of the trip, the clock on the plane indicated 59 nanoseconds later than the clock on the ground. In addition, height also affects the passage of time. Einstein's theory shows that the closer time is to the ground, the slower time passes. In fact, in the basement, time passes slower than on the top floor of the building. It has been calculated that if you live on the first floor, you can live one microsecond longer. Of course, this is too insignificant for longevity.
If time is a measure, why can't it go forward and backward as in space?
Crossing the future and the past is science fiction. As Kurt Godel, an Austrian mathematician, proved in 1949, travel in the past was not prohibited by the laws of physics, but the conditions were very special: the universe should be able to rotate (which is impossible in reality), and the pursuers of time must move at a speed greater than 7 1% of the speed of light. In short, the menu is available, but there are no ingredients. As physicist Stephen Hawking thinks, this may be a way for nature to protect itself. Preventing time travel will avoid possible paradoxes, such as meeting yourself or changing history.
5. Is a black hole really a time machine?
One possibility offered by black holes is to fall into a time tunnel and reappear in the past. What is a tunnel? There are all kinds of hypotheses, from anti-gravity to reflecting the world, to the replacement of the universe. Although there are many hypotheses, none of them are feasible. Just think about the super gravity of a black hole: time is like a rubber band, which is finally stretched. In this case, it is hopeless to get out alive. Time is a permanent topic, and people are still exploring and trying other methods.
References:
Science World Journal
Celebrities' views on time:
St Augustine: "When it comes to time, everyone knows what it means, but what is time? If nobody asks me, I know everything; If I have to explain ~ then I don't know!
Newton also explained "time": "Time is infinite, and it runs unimpeded whether the universe exists or not."
Leibniz overthrew Newton's statement: "Time is only the sequence of events; It doesn't exist. "
Einstein also agreed with Leibniz's argument. He said, "Once separated from the events evaluated by human beings, time cannot exist alone." .
In the dictionary, it is explained as follows: "Time is a continuum formed by a series of events in the past, present and future".
In this way, it seems that the slowdown of time in relativity is untenable, because time does not exist at all.
In general relativity, because of the expression of time and space in the formula, we can actually talk about the creation of time. The trouble is that in classical theory, when space and time "begin to form", the real point itself is a singularity in mathematics, and mathematics is a failure, so it can't give you a theory of creation. What you can say about traditional cosmology is that there are many different possible universes, all of which conform to Einstein's equations. We happen to live in this universe, which is purely accidental. You can't give any reason-not even in principle. All you can say is a conditional sentence: if the universe is in this state at the moment, it will be in that state at some later time. It is the evolution of conditional types.
However, when you talk about virtual time, there is a strange possibility that "now" doesn't have to have a series of past moments. If we go back to the past from the present moment, for a long time, everything will be completely normal, even in virtual time. As long as you use this phenomenological time, it looks like going back in time.
But as you go back and get closer to the origin of traditional real-time images, you will find that the nature of time is changing, and complex or imaginary things become more and more weighty. Finally, what should be a singularity in the classical theory is erased, and you get this beautiful picture, the bowl-shaped image created by these universes. There is no starting point, just some kind of smooth shape.
What hartle and Hawking discovered is that if you assume that the past historical images of the universe in virtual time are all possible shapes just consistent with our present universe, and you explain them more or less with traditional quantum mechanics, at least in principle, you will get the unique wave function of the whole universe.
In this way, you get this wonderful picture without the past, and the universe doesn't come from anything at all. Because it is a self-consistent mathematical structure, what you can really say is that the universe exists. Unlike the picture of the universe created from a certain point, this universe has no past because there is nothing in it.
In this way, the saying that the universe was born of "nothing" is actually a bit of a misnomer; This is a misuse of the word "nothing". This does not only mean that the universe appears in an empty space. You may call this space "nothingness": because there is no creation event, there is nothing at all!
In these theories, the use of verb past tense becomes inappropriate. Of course, tenses are established when people believe in real time. Unfortunately, we don't have a language form to express tenses in virtual time. So in this sense, saying "from scratch" is definitely misleading. It is suitable for this kind of cosmic image that suddenly appears in pre-existing time, but it is not an appropriate description of hartle-Hawking state.
[Name] Stephen Hawking (theoretical physicist, cosmologist and writer)
In order to predict how the universe began, people need laws that can be established at the beginning of time. There are only two possibilities for real time: either time returns to infinity or time has a beginning at a singularity. People can imagine real time as a straight line from the Big Bang to the Big Squeeze. However, people can also consider another time direction at right angles to the real time. This is called the imaginary direction of time. In the imaginary direction of time, there is no need for any singularity that forms the beginning or end of the universe.
In virtual time, there is no singularity in which scientific laws fail, and there is no edge of the universe that people need to beg from God. The universe was neither created nor destroyed. It is existence.
Maybe virtual time is really real time, and what we call real time is just our imagination. The universe begins and ends. But in virtual time, there is no singularity and no boundary. Therefore, perhaps what we call virtual time is really more basic, and what we call real time is just an idea we invented to help us describe what we think the universe looks like.
Kipa Thorne
There are two basic theories about how the universe ends. One is the concept of an open universe, which will continue to evolve and will not suddenly terminate; According to the second law of thermodynamics, things will slow down and reach thermal death. The other is the idea of closing the universe, and the universe will stop expanding and collapse back to itself. This is sometimes called a big squeeze, just like the Big Bang, but it is the opposite in time.
Zhan Mu hartle
The word "virtual" in virtual time does not refer to imagination: it refers to a very old concept in mathematics, that is, the imaginary number, such as the square root of-1, which is very important to understand. For a given observer, space and time can certainly be distinguished: we measure space with a ruler and time with a clock. Einstein and hermann minkowski pointed out at the beginning of this century that different observers' concepts of space and time are only different aspects of the same unified concept of time and space. Space-time is a four-dimensional space geometry with some space-like directions and some time-like directions. So in a sense, the concepts of space and time can still be distinguished there.
Although this concept has great power, we can still further unify these concepts. If the imaginary number is used to measure the direction of time, the complete symmetry between space and time will be obtained, which is a very beautiful and natural concept in mathematics. Using this mathematical simplification, the infinite hypothesis is the simplest theory among all possible initial conditions of the universe.
However, people should not think that we can directly experience virtual time in our daily experience. This is a beautiful mathematical concept used to express physical equations. In this case, it is a special idea to explain the initial state of the universe.
Don Page
Hawking's singularity theorem points out that Einstein's general relativity combined with some observations means that the universe must have a singularity at the beginning. If you go back in time, you can't go back to a certain point. We usually think that this is the beginning of time.
This makes many people who think that the universe is infinitely old feel uneasy. Hawking's thought points out that the universe has a beginning. Some people think that this is in line with the creation of the universe in time described in Genesis. Although other theologians say that God's creation does not necessarily happen in our time.
God may create an infinite universe, but Hawking's thought implies that time has a beginning. Now, of course, we know that Einstein's theory can't be established near that starting point. So we know that the theory itself fails here. This raises the possibility that maybe the universe is infinitely old, or maybe it is something else.
Nowadays, many people-including myself and I think even Hawking thinks that the concept of time itself is invalid near the beginning, so it is meaningless to talk about what is before the beginning: is there infinite time before that? Or is there only a limited time? Does the universe have an absolute beginning in time? Because the concept of time itself does not have much meaning in these very early moments, some of them are meaningless. What we can be sure of is that, as far as we know, time has a starting point, but the starting point has a point. Once we pass that point in time, our standard concept of time becomes invalid.
In hartle-Hawking's infinite vision, the way the universe began is: the behavior of time is very funny; Technically speaking, time is virtual. So time has no edge, and you seem to have a surface of the earth. For example, if you start from the North Pole and go out along the meridian. These meridians do spread out from the North Pole, which is completely regular.
This is Hawking's imagination of the universe: this virtual time has neither a beginning nor an end. It doesn't have to move forward forever. It is limited, just as the earth has only a limited area. It is impossible to go north forever on the earth. Because you can go to the northernmost point, in a sense, you will come to an end. But in another sense, there is no real end there.
So Hawking said that the universe had no boundaries at the beginning, so the universe was a self-sufficient whole. He also concluded that there is really no need for God to start the universe: the universe can exist there by itself and does not need God to create it.
[Name] Stephen Hawking (theoretical physicist, cosmologist and writer)
Many people think that God allowed the universe to evolve according to a set of laws, and God did not interfere with the process of evolution to make the universe violate these laws. However, it is up to God to wind up and choose how to start. As long as the universe has a beginning, we can imagine a creator. However, if the universe is really completely self-sufficient, will there be a place for the creator?
Don Page
Will the creator have a place? Whether God created the universe is not directly related to whether the universe has edges, although many people think so. They are not really related.
For example, I drew two lines on a piece of paper. This straight line has two endpoints: if I imagine that time advances in that way, you can call this endpoint the starting point and that endpoint the end point. If time goes in the opposite direction, the situation becomes the opposite. This endpoint is called the end point and that endpoint is called the starting point. You can think of this as a model of the universe, a universe with a beginning and an end.
This circle represents another universe. As time goes on, in a sense, there is an earliest moment; But if you walk along this round line, the line has no end, it just keeps turning.
But I drew these lines myself, so in a sense, I created them. But they have a beginning and an end. It doesn't matter whether I created them or not.
I think the situation in the universe is similar. In Hawking's old model, the universe has a beginning or an end. The new pattern is more like this cycle with no beginning and no end. In a sense, it has a leftmost endpoint; So you can say that there are things like the earliest moment and the latest moment. However, from a more professional point of view, there is neither a beginning nor an end. Both can be created by God. We must have faith before we can ask the question whether it was created by God. This is something that science can neither prove nor falsify.
I think Hawking is careful in his book to avoid publicly saying that there is no God. He only said: will there be a place for the creator? However, I think it is very obvious what conclusion he wants people to draw from here.