The spacecraft, which has flown 23.31 billion kilometers, finally sent back a photo that makes humans re-examine themselves

Once upon a time, human beings thought that the earth was the center of the entire universe, and the sun, moon, and stars all rotated around the earth. But with the development of astronomy, human beings gradually realized that the earth is just a planet in the universe, and the earth and seven other planets revolve around the sun.

The Sun appears to be nothing more than a small disk on Earth, but the Sun is actually much larger than Earth. The mass of the Sun can reach 333,000 times that of the Earth, and the sun can erupt a lot of flares that are much larger than the Earth, and a single sun can hold 1.3 million Earths.

The comparison of data may not be intuitive, but if we look at the Earth from a different perspective, we will re-examine how small the Earth is in the universe. 32 years ago, a starship that flew the farthest, from an unprecedented angle, took the last photo, brought us a huge visual impact, and deeply shocked our cosmology.

On the space station, which is about 400 kilometers above the surface, astronauts can see the beautiful Earth, the ocean, the land, and the white clouds. As NASA Apollo astronauts flew to the moon, they saw the Earth slowly shrinking. And around the earth, there is a darkness that cannot be seen at a glance.

After landing on the front of the moon, astronauts can also see the Earth when they look up. Because the Earth itself is larger than the Moon, the Earth seen in the lunar sky should also appear larger, and the size of the "full earth" is about 14 times the size of the full moon (apparent area). The azure earth is suspended in the dark space like this, which seems so incredible.

As you get farther and farther away from the Earth, the Earth will look smaller and smaller until it becomes completely out of detail, becoming a star in the sky. If future astronauts can set foot on Mars, they will see something like this:

There is one of the brightest stars in the sky, which looks slightly blue, and this is our earth. The image above was taken by NASA's Curiosity rover, when Earth was about 160 million kilometers away from Mars, slightly farther away than Earth's distance from the Sun.

The earth that turned out to be so different, hundreds of millions of kilometers away, looked like just a star, just like other stars in the starry sky, without any details. At this distance, the Earth is no longer so unique.

And if you look at it from a distance, the earth not only looks bland, but it is even difficult to detect the existence of the earth. In 1990, NASA's Voyager 1 flew 6 billion kilometers from Earth, and as it was about to end its solar system planetary exploration mission and start its interstellar exploration mission, it took a picture in the direction it set out in 1977:

Voyager 1 photographed the Earth, which had been 13 years away, only by this time the Earth had become a pale little bright spot, and its size in the photo was not even a pixel. When this photo was transmitted back to the earth, it deeply shook people's hearts.

Looking back so far away, the Earth looks like a tiny speck of dust suspended in an endless dark space, reflecting a faint glow under the sunlight. At this point, there is everything we strive for, everyone we love.

In the depths of space, our earth is actually so small, so isolated and helpless. As we lament the size of the universe, this "dim blue dot" photo is also a reminder of the importance of protecting the planet. Once the protection of the earth is lost, the current human civilization will not be able to continue in the universe, no planet can replace the earth, and we will not find a second planet suitable for human survival.

To save limited power, Voyager 1 turned off the camera after taking the final photos. But some of Voyager 1's scientific instruments are still working, and Voyager 1 is flying into uncharted interstellar medium space and constantly transmitting detected data back to Earth.

After 45 years, Voyager 1 has now flown 23.31 billion kilometers away, and it has long since become the farthest man-made object from Earth. At such a long distance, Voyager 1 could take up to 21.5 hours to transmit data on a single-way trip, even through radio waves at the speed of light.

Voyager 1's plutonium-core battery, which is expected to power the instrument for another 3 years, will continue to fly unpowered after the power outage, heading for interstellar space outside the solar system at a speed of about 16.9 km/s, becoming a silent messenger for humans wandering through the Galaxy.

For humans, the distance of more than 20 billion kilometers is very far, and if an aircraft with a speed of 800 km / h were to fly, it would take up to 3320 years to fly such a distance. But even billions or billions of kilometers away, the starry sky there looks no different than it does on Earth, which is not to say that the solar system is a huge screen, but that the universe is simply too big.

Here's a picture of the starry sky from another NASA starship, New Horizons:

New Horizons, which was about 6.5 billion kilometers from Earth at the time, shot in the direction of Proxima Centauri. It can be seen that the position of Proxima Centauri is slightly offset from the background starry sky compared to the viewing angle on Earth.

That's because Proxima Centauri is the closest star to the solar system, about 4.2 light-years away. As New Horizons moved further away from Earth, observing from different directions, the nearest Proxima Centauri exhibited the most pronounced parallax. The relative positions of the other stars have not changed, because they are so far away from Earth that even if they are observed billions of kilometers apart, there will be no noticeable change in relative positions.

At present, Voyager 1 and New Horizons have not yet left the gravitational dominance of the Sun (radius of 1 light-year), and at the current rate, Voyager 1 will take 17,700 years and New Horizons 21,700 years to actually fly out of the solar system.

Beyond the solar system, there is a vast interstellar space waiting for these starships. The Solar System is located in a corner of the Milky Way, and the entire Milky Way has a disk diameter of at least 100,000 light-years. In intergalactic space, the Milky Way is also a small existence, and the diameter of the observable universe is estimated to be as high as 93 billion light-years.

The observable universe is only a corner of the universe, and the whole universe does not know how large it is, perhaps infinitely large, perhaps there are infinite parallel universes outside the universe. We have to re-examine the place of humanity and earth in the vastness of the universe, and learn that humility may be the attitude necessary for us to survive in the universe.