# The spaceship travels at the speed of light for 100 light years, and how long does it really take?

As we all know, the universe is so big that it is unimaginable. In this infinite space, the distance that human beings can understand can no longer generalize it. Therefore, scientists choose the speed of light, the limit speed, to regulate the distance of the universe. Usually, scientists like to use the light year to describe the scale of the universe, so the light year is the distance that light has to walk for one year.

However, when we use light years to measure the universe, we will inevitably encounter some theoretical problems about time and space, and it is also a very unique existence. In modern physics system, traveling at the speed of light may involve some problems of time travel or time and space.

According to Einstein’s theory of relativity, no matter can exceed the speed of light. When it reaches the speed of light, it will cause another reaction in time and space, that is, the process of infinitely approaching the speed of light will make our time flow very slow. Some scientists even believe that when human beings approach the speed of light, they can avoid the influence of time and reach an eternal state, which is what scientists call time travel.

Therefore, when we really travel in the space at the speed of light, we will face many problems. One of them is if we travel in the spaceship at the speed of light, how long will the people in the spaceship stay after 100 light years?

Because of the basic characteristics of light, we can have many choices in answering this question. First of all, from the perspective of our bystanders, the speed of light spacecraft is used as long as it runs inside the spacecraft. For example, it has been running outside the spacecraft for more than 100 years. Of course, it also takes 100 years. But for people inside the spacecraft, this is a huge difference, because the material is reaching the target After the speed of light, with the increase of the speed, it will produce different changes from the external time.

So because of the different reference frame, people in the spaceship will feel that the flying distance of 100 light years is only a moment. Although the flow of time in their world is normal, compared with the outside world, time almost stagnates. For example, people in the spaceship lift their fingers. It may take billions of years for the outside world to see clearly, but for very ideal people, time is basically positive Often, there is no time barrier.

In fact, for thinking about this problem, we can refer to our feelings of taking the high-speed rail. Although we are standing still in the high-speed rail, from the outside, the high-speed rail has already run for several kilometers, so we will encounter such problems when driving the light speed spaceship. So the answers to the questions are divided into two categories, but for the people in the spaceship, time is still past.