It was another quiet night.

The bright stars shimmer like jewels scattered on the blue-purple sky.

After midnight, in the starry sky in the northwest, a star flashed, and the light was blazing, dozens of times brighter than before.

Ye Feihua looked at the star and let out a sigh.

The starry sky is still bright, and the gorgeous nebula is like a mist in a dream, no matter how the night wind stirs, it just can't blow away.

"What did you find?" After a long time, an ethereal voice sounded on the star-washing platform, without a trace of human fireworks.

It was the old man in the purple shirt, and he spoke.

"A star has perished. Just now, we saw the last splendor of the star's bloom. Strictly speaking, it is the last mark of that star left in the starry sky. Perhaps, eons ago, that star no longer existed. Ye Feihua said.

"Xiaoyou is young, and he knows so much, the old man admires it!" The purple-shirted old man's gaze fluctuated.

"The starry sky is bright, but unfortunately, the stars that fall in our eyes are only the marks of the stars. It's too far away! What we see is just what the stars looked like countless years ago. As for what the stars look like now, whether they are there or not, we don't know at all, and the mystery can only be left to the distant future to be revealed. The universe is too vast! Ye Feihua sighed.

The old man in the purple shirt was silent, and there was no trace of waves on his calm face.

After a long time, the old man in the purple shirt said lightly: "The starry sky is bright, which makes us dizzy. We were amazed by the magnificence of the starry sky. However, for us, the starry sky is a place of death, a real forbidden area for life. ”

"Yes! Although the starry sky is infinite, it is difficult to move an inch. One step forward, you may freeze for thousands of kilometers and disappear into darkness. If you take a step back, you may be scorched and turned into ashes. It's hard to find a suitable place to stay in the starry sky! Ye Feihua sighed.

"You're not just here to look up at the stars, aren't you?" The purple-shirted old man asked suddenly.

"We live far away in the Star Continent, and we heard that the prophet of the elf clan lives in seclusion in the Prophet Mountain, so we are not far away from 500,000 kilometers, and we specially came here to pay respects!" Ye Feihua said.

"The Prophet Mountain only has a star washing platform, and there is no prophet." The old man in the purple shirt said.

The purple-shirted old man looked at the starry sky, his hands behind his back, and his long figure remained motionless.

"I have been obsessed with the stars since I was a child, and I was attracted by the starry sky. As an adult, the more suspense in my heart becomes, and I have been thinking hard. It's just that the stars change and the universe is vast, how can we and other vulgar mortals understand! In the Huanyu Pavilion of the Nebula Library, I searched for classics and found nothing. Later, I heard a friend mention that the brave and wise elves came from outside the sky. Presumably, for the elves, the magnificent starry sky is no less than the courtyard of the home, and there is no mystery under the patrol. Therefore, the three of us went through hardships and dangers and came to the Prophet's Mountain, just to quench the thirst in our hearts, but we have been confused for many years! Ye Feihua said earnestly.

On the top of the peak of the Prophet's Mountain, the starry sky is extraordinarily clear, extraordinarily bright, and extraordinarily magnificent.

The old man in the purple shirt looked up at the starry sky, his expression was cold, and he did not make a sound.

"When the dawn goes out and the sun rises, we take in the shine of the sun and feel the warmth of the sun. And our galaxy has hundreds of billions of suns. And in this universe, there are hundreds of billions of galaxies. Every time I think about this, I am shocked and breathless! Ye Feihua continued.

"Within the galaxy, hundreds of billions of suns! There are hundreds of billions of galaxies in the universe! After a long time, the old man in the purple shirt muttered in a low voice.

"Tiny to tiny, indistinguishable to the naked eye; The vastness is so great that the line of sight is unreachable. The mystery is unfathomable; Contains truth, beyond imagination. Every time I think about it, I feel so small! Ye Feihua sighed.

"Actually, the universe is not complicated. Whether it is very small or very large, it is made up of the most basic energy. These energies come in many forms, some of which are real, both visible and sensible, such as light. There are also energies that can only be sensed or detected, not peered, such as microwaves and various forces. There are also energies that are formless and completely unpredictable. These foundational energies both influence and transform each other, and if they are materialized, they can incarnate all things in heaven and earth. As large as the stars of the universe, as small as a tiny dust, all come from this. The Dou Qi cultivated by you human beings is also a kind of energy, which originates from the Yuan Qi between heaven and earth. And Yuan Qi is precisely one of the manifestations of the basic energy of the universe. The old man in the purple shirt took Ye Feihua's words.

This can explain the formation of the universe, and it is also the consensus of a group of wise people. The universe is vast, and the truths contained in it are endless, and we can navigate the void with a scale and half a claw. However, I am puzzled as to why our knowledge is so limited. Why can we only be confined to this scale and half claw, can only be confined to this side of the heaven and earth, and cannot enter the real void? Every time I look up at the starry sky, I have a feeling that we came from the starry sky and should go to the starry sky. However, in the face of the vast starry sky, we are unable to move an inch, so weak! I wondered, if one day we could be like the light, free and fast, unfettered, if we could travel across the universe and the stars at will? Ye Feihua asked.

"Even if you become a light, you can't do whatever you want. True interstellar travel, it's not that easy! The purple-shirted old man sighed.

"Your Excellency does not touch the dust and mud, and your knowledge is outstanding, please give me advice!" Ye Feihua looked towards the purple-shirted old man and bowed slightly.

"As long as it exists, it will be affected by external objects, whether it is the slightest dust or the stars of the universe. Don't look at the starry sky so magnificent, its hidden ingenuity is like a mirror, unfathomable. The old man in the purple shirt said.

Once the conversation box was opened, it seemed to arouse the interest of the old man in the purple shirt.

The purple-shirted old man looked at the starry sky without blinking, and then said: "For light and microwaves, the travel of tens of billions of kilometers is just a short journey, and its propagation path is negligible due to the influence of foreign objects, so its propagation path is a straight line. However, in terms of interstellar travel, the journey across a galaxy cluster is too vast, and the propagation paths of light and microwaves are affected by the galaxy cluster. Under the strong gravitational pull of galaxy clusters, the propagation paths of light and microwaves will be bent to a certain extent. If you continue to cross the second cluster, the path of light and microwaves will bend again under the gravitational pull of the second cluster. As a result, light and microwaves cross two clusters of galaxies in succession, and their propagation paths are likely to be S-shaped. By analogy, if we continue across the third cluster, or even the fourth, the path of light and microwaves is likely to be wave-shaped. If there are enough clusters of galaxies spanned and complex enough, the propagation paths of light and microwaves may even be spiraling. This is one of them. In addition, the universe is full of all kinds of dust and unknown energy, and light passing through it will also be refracted and refracted. These two points are enough to show that the stars we see with the naked eye are most likely just an image. We see a star in a certain position, and its actual position is likely to be offset by countless kilometers. What's more, in the universe, there is no distinction between front and back, left and right, up and down. Therefore, without accurate coordinates of the stars, galaxies, and galaxy clusters, we only follow our eyes, and we will not only take detours, but also easily get lost in the universe. ”

Hearing more than a dozen words of "star coordinates, galaxy coordinates, and galaxy cluster coordinates", Ye Feihua couldn't help but jump in his heart.

Ye Feihua suppressed the fluctuating state of mind and said calmly: "In this way, one day when we travel the universe, we must not only have the speed of light, but also the coordinates of stars, galaxies, and galaxy clusters. ”

"Exactly!" The purple-shirted old man replied lightly.

"But what are star coordinates, galaxy coordinates, and galaxy cluster coordinates? Please do not hesitate to clarify your doubts! Ye Feihua bowed again.

"As you say, there are hundreds of billions of galaxies in the universe; Within the galaxy, there are hundreds of billions of suns. To find a certain galaxy and a certain sun in the vast universe is tantamount to looking for an invisible grain of sand in the vast desert. Naturally, the coordinates of stars, galaxies, and clusters are the coordinates of stars, galaxies, and clusters of galaxies in the universe. In fact, the coordinates of stars, galaxies, and galaxy clusters are only relative, because stars, galaxies, and galaxy clusters are all moving. The whole universe is in motion, like a vortex, spinning and expanding. Looking at the universe as a whole, the absolute positions of stars, galaxies, and galaxy clusters change from time to moment, but the relative positions of stars, galaxies, and galaxy clusters are relatively fixed. Although they are also in motion, relative to each other, the region of their motion is relatively fixed with reference to neighboring stars, galaxies, and galaxy clusters. When we talk about star coordinates, galaxy coordinates, and galaxy cluster coordinates, we also refer to the relative positions of stars, galaxies, and galaxy clusters. First, find the relative position of stars, galaxies, and galaxy clusters in the universe through coordinates, that is, a relatively fixed area in the universe. Then, according to the existing knowledge, a specific star, galaxy or galaxy cluster is selected in that relatively fixed area. The old man in the purple shirt said.

"Listening to Your Excellency's words, my mouth suddenly opened, and I was taught!" Ye Feihua bowed for the third time, then looked up at the starry sky, and her eyes gradually became blurred.

On the star-washing platform, there was silence for the time being.

After a while, Ye Feihua said to herself: "At this point in time, the starlight that reaches our eyes is actually emitted countless years ago. The position of the stars that we see in the light we see at this point in time is actually the position of the stars eons ago. The stars are in motion, and they don't stop in an instant. Therefore, the real position of the stars we see is long since it is countless kilometers away from the position we see at this point in time. It is even possible that some of the stars we see at this point in time are just the last images of the stars left in the universe, in fact, the stars themselves have long since died and disappeared. The universe is too vast and too far away. Even if we could incarnate as light, we would have limited travel. Perhaps, before he has traveled from one star to another, he has died of old age, leaving regrets! ”

"So, if you want interstellar travel, time and space jumping is essential!" The old man in the purple shirt seemed to be talking to himself, and it was like answering Ye Feihua.