When we think about the great distances of the universe we usually talk about light years, the distance that light travels in one year, that is, the result of multiplying 300,000 x the number of seconds in 365 days. The problem is that the expression has become so common that it has almost lost its ability to surprise. But there is another measure much closer to our daily experience: the light day, the distance that light travels in 24 hoursalmost 25.9 billion kilometers. Or, put another way, the distance that separates us from Pluto… 1500 times.
And soon humanity will reach a milestone that seemed reserved for science fiction. According to NASA calculations, on November 18, 2026, the Voyager 1 probe will become the first object built by our species located at a distance of one full light day from Earth. In other words: any message sent from our planet will take exactly one day to reach it. The history of Voyager 1 began in 1977. Its initial mission was to explore the gas giants of the outer solar system. It flew by Jupiter and Saturn, sent back images that transformed our understanding of both worlds, and once its work was completed, it continued moving into interstellar space.
No one then expected that it would still be working almost fifty years later. However, the spacecraft continues to send scientific data. Although its instruments and systems operate on increasingly limited energy, it remains one of the most extraordinary experiments ever conducted by humanity. At the moment It travels at about 17 kilometers per second, a speed sufficient to travel the distance between Madrid and Barcelona in less than a minute. But even at that breakneck pace, the dimensions of the cosmos make its progress seem almost insignificant.
Thus, from that date, When NASA engineers send an instruction to Voyager 1, the spacecraft will not receive it immediately, it will do so exactly 24 hours later. And the answer will take that same period of time to reach us.
It is true that Voyager 1 does not transport astronauts, nor state-of-the-art engines and even less artificial intelligence systems. It is a machine designed in the seventies, with a computing capacity lower than that of many current smart watches. And yet, she is still “alive.” And, on board, it carries the famous Voyager Golden Record, a golden record that contains greetings in dozens of languages, sounds from the Earth, music and photographs of our world. A bottle thrown into the cosmic ocean that hides our desire to be read.
The closest star to the Sun, Proxima Centauri, is more than four light years away. At Voyager 1’s current speed, reaching it would take tens of thousands of years. That is why this event has something poetic. It does not represent the end of a journey, but just the first step towards scales that defy the imagination. On November 18, 2026 we will not see fireworks or spectacular ceremonies. Nothing visible will happen in the sky. But that day a small ship built almost half a century ago will cross a symbolic border that no human creation has reached before.