Voyage of the Stars.

Chapter 1269: The Clock Slows and the Ruler Shrinks
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If you want to truly understand the effects of relativity, you must start by understanding four-dimensional space-time.

According to the current cosmic theories of the civilizations of the Great Voyage Organization, the universe they are in is a three-dimensional space universe, and adding time makes it a four-dimensional space-time.

And in this four-dimensional space-time, the effects of relativity have indeed been proven to be correct.

Humans have conducted relevant experiments in the Earth era, proving that the space-time where the Earth is located is curved, and that the flow of time for artificial satellites orbiting the Earth is slower than the flow of time on the ground. There is nothing wrong with this.

So let’s get the question back to the voyage of the Great Voyage Organization.

Now all civilizations already know how to navigate. Simply put, it is to use conventional thrust to push the fleet to a speed very close to the speed of light, and then turn off the powerful magnetic thrust engine to let the fleet float to its destination.

It is just a matter of one sentence, but within this sentence, the fleet of the Great Voyage Organization has to go through many stages. In this process, they will experience two changes in the intrinsic time axis, their event light cone and the light cones of the departure and destination will also undergo a series of changes in this process, the four-dimensional space-time will also be flipped and reversed in this process, and the so-called past and future will also be staged in this process, and these changes are the inherent principles of the slow clock and the contraction of the ruler.

But to truly understand how the Great Voyage Organization managed to travel two million light years at the normal speed of light, we have to start with the twin paradox.

The twin paradox must be well known.

Simply put, it is about two brothers living on Earth. The elder brother gets on a rocket and flies into the universe at a speed that obviously has the effect of relativity. When the elder brother returns to Earth, he finds that his younger brother has grown old, while he is still young.

The reason why this is a "paradox" is that from the elder brother's point of view, it is the Earth where the younger brother is that is moving and moving away from him quickly, so the younger brother should be getting younger. But from the younger brother's point of view, it is the elder brother who is moving, so he is getting younger.

The two contradict each other, so it is a fallacy.

But the fact is, when my brother returned to Earth he did become younger.

This is the familiar idea of ​​traveling at the speed of light and stopping the flow of time.

But the fact is, those who cite the example of the twin paradox never tell us when the change in the speed of time for the two occurs, nor do they tell us that the so-called brother's return to Earth is just a return to Earth. They never tell us whether the so-called "return to Earth" means arriving at Earth and then being done, or whether after returning to Earth, he slows down his speed to the same level as that of Earth, and then makes his own intrinsic timeline coincide with his brother's intrinsic timeline again.

The two are different. The change in the speed of time flow between the twin brothers does not occur during sub-light speed travel as we have always thought, but occurs during the acceleration and deceleration process.

Let me first state the conclusion. In the twin paradox, if the elder brother travels to a star A 0.6 light years away from the Earth at 6 times the speed of light, and then returns to the Earth at the same speed, then when he returns to the Earth, 20 years will have passed for his younger brother, while 16 years will have passed for his older brother.

The process of the elder brother's time slowing down occurs when he accelerates to 0.6 times the speed of light from the earth, and then decelerates from 0.6 times the speed of light to 0 and then accelerates to 0.6 times the speed of light after arriving at Star A. The former 0.6 times the speed of light makes the elder brother move away from the younger brother, and the latter speed makes him move closer to the younger brother, so these two speeds are actually one positive and one negative.

The process of the elder brother turning after arriving at Planet A is actually the process of the acceleration direction changing. If the elder brother's U-turn is completed instantly, then the moment he completes the U-turn, the younger brother on Earth will immediately spend 7.2 years.

During this process, the elder brother's world line will sweep across the younger brother's timeline, with a length of 7.2 years.

So in the twin paradox, due to the clock slowing effect and ruler contraction effect, the elder brother travels at 0.6 times the speed of light. In his own eyes, the star A, which is 6 light years away from the earth, becomes 4.8 light years away. So it takes him 8 years to reach star A from the earth, and another 8 years to return to the earth, a total of 16 years. When the elder brother arrives at star A, 6.4 years have passed for the younger brother, and another 6.4 years have passed for the elder brother to return, a total of 12.8 years, plus the 7.2 years when the elder brother turned his world line across the younger brother's timeline, adding up to 20 years for the younger brother. But the process described in this story is actually the process in which the elder brother did not reduce his speed to the same as the earth after completing the acceleration and returning to the space where the earth is.

In other words, when the elder brother returns to Earth, his intrinsic timeline is different from that of his younger brother, and their timelines do not overlap. As the saying goes, everything within the light cone is destiny. The non-overlapping intrinsic timelines means that the two cannot communicate at this time, and any information exchange between them at this time violates the laws of physics.

In other words, their time difference is meaningless.

In fact, assuming that both of them were 20 years old when the elder brother set out, then from the perspective of God, the younger brother that the 36-year-old elder brother saw when he returned to Earth was actually the 40-year-old younger brother on another timeline. They could only "meet" from the perspective of a third person. In fact, neither the elder brother nor the younger brother could see each other at their own timeline.

Unless the elder brother returns to the earth and slows down again to bring his intrinsic time axis back to the same as his younger brother's, but these are two processes, that is, the change in the intrinsic time axis during the process of accelerating away from the earth must also be taken into account. By adding these two together, the elder brother will be able to meet his younger brother again in reality, and they will be able to achieve real information communication, because their intrinsic time axes overlap again, and at this moment, the ages of the two are magically the same.

Of course, there is a way for the two of them to communicate with each other in different timelines, and that is through Bulk in "Interstellar".

What is Bulk?

In string theory, the plane of three-dimensional space is called a membrane. Adding the time axis, it is a four-dimensional membrane universe. The strings exist on the membrane, and the membrane exists in the body, that is, the body universe, and Bulk exists in the body universe.

Back to the Great Voyage Organization’s routine 2 million light-year voyage.

If the fleet of the Great Voyage Organization travels at the normal speed of light, then from the perspective of the observer standing at the starting point, the time of the Great Voyage Fleet after completing the acceleration is stopped, and the fleet does not need to pass time to reach the galaxy two million light years away.

To this observer, it would take the Great Expedition Fleet two million years to reach its destination.

From the perspective of the Great Voyage Fleet, the time of the observer standing at the starting point is still. In the eyes of the Great Voyage Fleet after completing the acceleration, the flow of their own time is normal, but the destination two million light years away is no longer two million light years away from them, but zero light years.

To cross the distance of zero at the normal speed of time, the Great Long-distance Fleet naturally does not need to spend time, so the Great Long-distance Fleet arrives at its destination in an instant, but this is meaningless because at this time the relative speed between the Great Long-distance Fleet and the target galaxy that is stationary relative to the starting point is still the speed of light, that is to say, the intrinsic timelines of the two do not overlap.

Then the Great Voyage Fleet must pull its own intrinsic timeline back to coincide with the intrinsic timeline of the destination, which is stationary relative to the departure point. In this process, the destination world line will span the timeline of the Great Voyage Fleet, with a length of two million years.

For the Great Voyage Fleet, these two million years actually passed by minute by minute on its own intrinsic time axis, not in an instant. The reason is that the speed of light is constant. No matter what normal speed you travel at, the speed of light you measure is the same. As long as the Great Voyage Fleet is still within the principle of the constancy of the speed of light, its intrinsic time axis is normal for itself, and the Great Voyage still passes time at the normal time flow speed.

And if the long-distance fleet immediately turns around and returns to the departure point, and then communicates with the observers at the departure point again, the fleet will need to make its own intrinsic time axis coincide with the intrinsic time axis of the departure point again. The principle is similar to the process of arriving at the destination.

But this is somewhat different from the satellite orbiting the earth and then the satellite time slows down, or the time flow speed of objects near the strong gravitational space-time of a black hole. The acceleration of both points to the celestial body, the former is the earth and the latter is the black hole, and they always exist. But for the fleet conducting interstellar navigation, they do not always have acceleration, and the direction of acceleration is not always towards the destination.

This is also the reason why the Great Voyage Organization needs the hibernation technology of the Daya civilization. All civilizations in the organization know what is going on.

(End of this chapter)