Time is something we touch all the time. For many people, time may not be mysterious because it surrounds us all the time. Every day we go to get off work, go to school, get out of school, go to bed and wake up, etc. are all determined by time.
The earth rotates once, day and night alternate, and there is time to participate in all seasons of the year. In our daily life, we don’t have an intuitive feeling about time. It is too common and common for most people, but is time really as common as we think?
In the cognition of many people, everyone has the same time in different places. When you and your girlfriend have an appointment to meet at a certain place at 8 o’clock in the evening, when 8 o’clock comes, under normal circumstances, you and your friends will meet at the agreed place.
One day, you arrived on time, and your girlfriend was one hour late or early. At this time, if your friend thought she arrived on time, how would you feel? If neither you nor your friend lied and arrived at the stipulated time, that can only show one problem, that is, your friend’s time is different from yours.
This seemingly unbelievable situation seems impossible to many people, because in our inherent knowledge, the time is the same. It is impossible that your time is 8 o’clock, but your friend’s time is. 7 o’clock.
One reason why people have this cognition is that the time we usually recognize is the same, and another reason is that Newton’s absolute space-time view is deeply rooted in people’s hearts and affects our persistence in thinking.
So is time absolute? the answer is negative. After Einstein put forward the theory of relativity, we have a more accurate definition and description of time and space, and time under the theory of relativity is not an absolute thing, time and space are distorted, and time is naturally distorted.
In the special theory of relativity: the elapsed speed of time is related to the moving speed of the object. The faster the object moves, the slower the time elapses. If the object moves infinitely close to the speed of light, then time is infinitely close to stillness.
In the general theory of relativity: the elapsed speed of time is related to the gravitational field. The greater the gravitational force (the greater the curvature of space-time), the slower the elapsed speed of time. If the space where you and your friend are in a major time-space distortion, then the time between the two of you will be very different, and it is normal to be late for an appointment.
In fact, time distortions are everywhere. The time and space of the earth we live in is also distorted, so there will be differences in time in different places, but this difference is very small, and we can usually ignore it. But when we step out of the earth, the time difference between the time outside the earth and the surface of the earth will become larger.
Many friends know about navigation systems, which use satellites to navigate things on the surface. The satellite navigation time we see is synchronized with ours. There seems to be no difference, but in fact, this time has been corrected.
There is a certain difference between the time on the navigation satellite and the time on the ground. If no correction is made, the navigation will deviate from the actual situation. Navigation is also an example of human initial application of time dilation.
The existence of distortion and expansion of time is already a scientific theory, and the theory of relativity tells us that as the speed of objects continues to increase, time also continues to slow down. When the time of an object is infinitely close to the speed of light, the time of the object itself will also be infinitely close to stillness.
After knowing that there is distortion in time, let’s look back at this issue. If a spacecraft flies out of the earth at the speed of light for one minute, for the people on the spacecraft, time is only a moment after one minute has passed, which is very short. But for people on earth, it may be an extremely long period of time, it may be a hundred years, a thousand years or even ten thousand years.
During the flight of the light-speed spacecraft, theoretically the time of the spacecraft itself will be at a standstill. No matter how long the flight is, the time hand will be still. If this is the case, there is no one minute for the spacecraft itself, because time has stopped moving.
However, according to Einstein’s theory of relativity, the speed of a mass object under this time and space can only be infinitely close to the speed of light, and cannot be reached, let alone exceed the speed of light. Therefore, the spacecraft can only fly at infinitely close to the speed of light for this minute, and this minute is relative to the spacecraft.
Due to the distortion of time and space, when the spacecraft is flying at the speed of sublight, the space it travels will undergo time expansion, resulting in a huge difference between the time of the spacecraft itself and the time of the outside world. In this way, people on the earth will see the spacecraft fly out of the earth and return after a very long time.
The people on the spacecraft only experienced one minute, and in such a short period of time, they basically did not change. But when they returned to the earth, the earth they saw had undergone earth-shaking changes. The relatives and friends who met a minute ago may be dead, and it is even possible that these relatives and friends are ancient people in distant history.
This situation is also relative to a kind of time travel, a spaceship that is infinitely close to the speed of light can travel to the future in a very short time. This kind of travel is not acceptable to everyone. Imagine that when you are preparing to fly at the speed of sublight in the universe, you may be destined to never see your relatives and friends on the earth again, even if you only leave for a minute, the earth Already vicissitudes of life
Of course, this kind of sub-light speed, which seems to us to be incredibly fast, is only a tortoise speed in front of the cosmic scale. At this speed, it is difficult for human beings to even get out of the Milky Way, let alone explore the entire universe.
And the speed that can enable us to realize the dream of exploring the universe is only faster than the speed of light, but under the theory of relativity, the speed of an object cannot exceed the speed of light. Does that mean that it is impossible to exceed the speed of light? Of course not. In fact, there is a phenomenon that exceeds the speed of light in the universe. For example, the expansion speed of the universe exceeds the speed of light.
The phenomenon of superluminal speed exists in the universe, and the existence is reasonable, which is in line with scientific theory. But the theory of relativity tells us that the speed of an object cannot exceed the speed of light. What is going on?
In fact, superluminal phenomena are not inconsistent with the theory of relativity, and they adapt to different ranges. The theory of relativity only says that the speed of an object cannot exceed the speed of light, but the theory of relativity tells us that space-time can be twisted, and the speed of twisted space-time has no upper limit and can exceed the speed of light.
Therefore, it is impossible for human beings to achieve super-light-speed flight in the future, relying on the power of objects to achieve it. They can only place their hopes on the research and exploration of time-space distortion. The spacecraft itself cannot achieve faster flight than the speed of light, but the space around the spacecraft may exceed the speed of light under a certain distortion.
Let the space that is distorted at the speed of light take the spacecraft forward, and then the object can fly at the speed of light. This mode is somewhat similar to a surfing sport on the earth. And this kind of interstellar voyage, we can often see in some scientific novels and movies, it is space jump or wormhole shuttle.