To find out, let's go on a space trip together, starting from Earth and flying towards faraway space. When flying to a place about 300 kilometers away from the earth, that is, the height of the International Space Station, the earth you see appears very large at this time, and yo

To find the answer, let's go on a space trip together, starting from the earth and flying towards the distant space.

When flying to about 300 kilometers away from the earth, that is, the height of International Space Station , the earth you see at this time seems very large, and you cannot see the complete earth. You can see the main landforms on the earth clearly, and you can clearly see the city lights on the earth at night.

For example, the following two pictures are the appearance of the Great Lakes in the United States during the day and the lights of the earth's city at night.

Let us continue flying in the direction away from the earth. When we arrive at the earth, that is, looking back at the earth 380,000 kilometers away from the earth, we will see that the earth appears as a bright sphere, which is not much different from the moon we see on the earth, but the earth is larger.

The picture above shows the appearance of the Earth seen by the American Apollo astronauts on the moon.

set off from the moon and continue flying, and the appearance of the earth and the moon will be presented to us together. The picture below is a photo of the Earth's moon taken by the Voyager 1 spacecraft, which was about 12 million kilometers away from the Earth at that time.

continue to fly far away, cross Mars , and arrive at asteroid belt , and you can see such earth and moon.

set off from the asteroid belt and continue to fly to the outer solar system. The earth will slowly become a source of light, just like the stars in the sky, and will become dimmer and dimmer, and the moon will be no longer visible.

In 2013, the Voyager One spacecraft took a photo 6 billion kilometers away from the earth. It is a very classic photo called "Dark Blue Dot". As can be seen from the figure below, the earth is the blue and white spots in the red box. If it is not a special mark, it will be difficult for us to discover the existence of the earth.

So, if we continue to fly to far away, can we still see the earth? Or in theory, how far away can you see the earth?

Since the picture above is the farthest photo from the earth taken by a human probe, after Voyager 1 never took photos of the earth again, so we are not sure how far we can't see the earth.

However, theoretically speaking, before reaching Pluto , we should be able to see the earth directly with our naked eyes. Once you pass Pluto, it will be difficult to see the earth with your naked eyes.

Considering that as we get farther and farther away from the earth, the brightness of the earth has no advantage against the strong light of the sun, and the further away, the more obvious the impact of the sun's light. Even if we can see the earth, it will become very dim because we see more of the dazzling light of the sun.

Of course, if you use high-tech instruments, such as the powerful astronomical telescope , that is another matter. I believe that one day in the future, human beings will be able to watch the beautiful earth with their own eyes from a more distant place!