Some people believe that time is like a rubber band, while others believe that it is discontinuous. If time ever had a beginning, it dates back to 16 billion years ago. Let's take a look at what time is and how it works on such an irregular scale.

Time passes more slowly for people living on the first floor than for people living on the top floor, although it is not enough to make those inside live longer. All it takes to make a person younger is to travel around the world on an ordinary plane. These are two incredible consequences of the time effect that works the same for all people: time can be lengthened or shortened, depending on space, gravity, and speed. This article will lead readers to explore time, a scale that seems very familiar but is also very mysterious.

1. What exactly is time?

For more than 1,000 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, this great British scientist believed that time is an object covered by a mysterious atmosphere, because time is independent of any object, above everything, and is absolute. Time is so close to the saints that God is likened to a clock.

Einstein believed that time is not at all like a "free dog" in nature, but a real measure. Even today we cannot define time in the same way that we can define any actual thing. We can measure time, but we don’t know what time is, and we hang “time” on the wall or wear it on our wrist. According to Einstein's theory of relativity, we know that time can be lengthened or shortened. This is why physicists use time simply to establish a sequence of events and mark them with time. For example, a person's birthday or the shelf life of food.

2. Does time flow like a river or is there an intermittent succession?

Unfortunately, there is no theory or experiment that can confirm whether time flows in a continuous manner or whether it is like each frame in a movie, giving the impression of continuity, that is, there is Intermittent succession. The study of the continuity or discontinuity of time also involves another issue, that is, whether time has a beginning or not. There is still no definite answer to this. Because the famous Big Bang theory believes that time-space has a beginning; while other scientists point out that the "time" scale does not have an instant beginning, which is unnecessary. This makes things complicated. Because according to the principles of quantum mechanics, time intervals smaller than the so-called Planck Time are undetectable. Planck time units are on the order of seconds. Therefore, it is impossible to calculate the state of the newborn universe in a very short period of time. In short, as far as current theories are concerned, the first cry of the universe will always be unknown.

Now we return to the "continuity" of time. The strange thing is that it can flow in a continuous or discontinuous manner, but the smallest, calculable time interval is the same as "Planck time". In short, time is a continuous belt, while physicists treat it as an interlocking, discontinuous necklace.

A few years ago, scientist David Finkelstein proposed a theory, but it did not gain much support in the scientific community. The physicist postulates the existence of time atoms. These time atoms may exhibit their discontinuity.

3. Does time pass in the same way for everyone?

Einstein’s theory suggests the answer is no. In fact, like space, time is also relative. What does relative mean? That is, in order to describe an event completely rather than ambiguously, the event should be placed in a frame of reference. For example, if I date someone at the end of the road, then the "end" may be the beginning of the road for another person. If I add "in the square behind the end of the road", then this "date event" would be accurate. The same goes for things that have a time element. If I say that 10 years have passed, then I must point out which frame of reference it is compared to which 10 years have passed. Obviously, there is no need to get hung up on details in everyday life. But who knows whether we will organize interstellar travel or communicate with aliens in the future? By then, the time interval will no longer be so simple, and you 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 spacecraft with a speed of 240,000 kilometers per second towards a planet 8 light years away from the earth. At this speed, Beta would take 10 years each way, one way. The fact is that in order to achieve the desired average speed, the beta needs to speed up and then slow down when it reaches its destination. Because their two frames of reference are no longer the same, we can separate the time of alpha and beta by simply changing the direction of motion.

When Beta returns to Earth in 2020, he will see Alpha celebrate his 50th birthday (20 years older), which will be just 12 years later for him, who is only 42 years old. This is not an intelligence test. The expansion and contraction of time has been measured with real watches. In 1971, two physicists, J.C. Hafele of the University of Washington and Richard Keating of the U.S. Naval Observatory, traveled around the world and measured four atomic clocks on the aircraft. The speed of an airplane cannot be compared to the speed of light (the difference is millions of times). But the scientists were able to capture the elasticity of time: at the end of the trip, the clock on the plane was 59 nanoseconds behind the clock on the ground. In addition, altitude also affects the passage of time. Einstein's theory shows that due to gravity, time passes more slowly the closer you are to the ground. In fact, time passes more slowly in a basement than on the top floor of a building. Someone once calculated that in a person's life, if he lives on the first floor, he can live one microsecond longer. Of course, this is too insignificant for longevity.

4. If time is a scale, why can't we move forward and backward like in space?

Travel in both the future and the past is science fiction. As the Austrian mathematician Kurt Godel proved in 1949, travel in the past is not prohibited by the laws of physics, but the conditions are very special: the universe must be able to rotate (This cannot happen in reality), and the time seeker must move at a speed greater than 71% of the speed of light. In short, the recipe is there, but there are no ingredients. As physicist Stephen Hawking believes, this may be a way for nature to protect itself, and preventing time travel would avoid possible paradoxes, such as meeting oneself or changing history. .

5. Is a black hole really a time machine?

One of the possibilities offered by black holes is to fall into them after passing through a space-time tunnel and reappear in the past. What is a tunnel? There are all kinds of hypotheses, from anti-gravity to antipodal worlds to cosmic replacement. Although there are many assumptions, none of them are feasible. Just think of the super-strong gravitational pull of a black hole: time is like a rubber band that ends up being stretched, and there is no hope of making it out alive. Time is a permanent topic, and people are still exploring and trying other methods.

Reference: Science World Magazine