Humans have been spied on by aliens?

Through decades of technological development, our human probes have reached the outer reaches of our solar system, and through radio telescopes and space telescopes, we have been able to get a glimpse of the general appearance of the distant universe. However, after all, the universe is so vast that the areas where we can get a full picture and details of its stars are still limited to the planets and moons closest to Earth, and we still know very little about even distant objects in our solar system, such as Uranus and Neptune.

Which planets in the universe, other than Earth, could have a life? Which planets have intelligent civilizations comparable to or more advanced than humans on Earth? These are two questions that have always troubled astronomers. According to the criterion that the Earth is a rocky planet located in the habitable zone of a star system, the number of planets in the universe that match the many characteristics of the Earth should theoretically be quite large, but why have we not found them? Where are they "hidden"?

On June 25 of this year, the Pentagon and the Office of the Director of National Intelligence released their much-publicized report on unexplained aerial phenomena, bringing the topic of extraterrestrial civilizations back to the forefront as both alien enthusiasts and skeptics await the final results of the investigation.

Through the continuous observations of scientists in recent years and the related deduction of conclusions, at least 1,700 stars have been in the "right" position to observe the Earth in the past 5,000 years, and the reason why the Earth can be observed is mainly based on the "sunset" method. The reason why the Earth can be observed is mainly based on the "sunset" method, which means that the Earth can be observed passing over the Sun from a star system that is relatively close to the Earth. In the next 5,000 years, more than 300 more stars will be in this optimal position. In these star systems, the existence of extraterrestrial planets similar to Earth, within the habitable zone of stars, has been confirmed, and life may exist on them.

To investigate this question further, two scientists at the American Museum of Natural History used the European Space Agency's Gaia satellite, launched in 2013, to count and track hundreds of millions of stars throughout the Milky Way galaxy, and then to use the "parallax" principle in these star systems, using the span of the Earth's orbit around the Sun as a baseline for observation. This allows them to effectively and accurately measure the distances and motions of celestial bodies, ultimately creating a "map of the universe" that shows which nearby stars can see Earth in the past and the future.

Considering that the Earth is already 4.6 billion years old, the two scientists conservatively chose a time window of 10,000 years, i.e., 5,000 years back and 5,000 years back. With such a time window, stars within about 300 light-years from the Sun were selected intensively. Using the superior observational capabilities of Gaia satellites, the orbits of these stars over time were simulated on the created "space maps" to determine when these neighboring stars would enter the orbits within which the Earth's sunset could be observed.

This method, which is based on the same principle as finding and studying planetary worlds around other stars on Earth, allows the observer to identify the regular pattern of "dimming and re-brightening" of shadow planets on the surface of the star as seen from the solar system by continuously monitoring a star, which not only allows us to know if the star is surrounded by a ring of planets but also allows the observer to roughly detect much of the chemical composition of the planet's air by the passage of starlight through its upper atmosphere, a "spectral fingerprint".

By this logic, the same results apply if the angles of the Earth and the exoplanet are swapped and the spatial position of the Earth about the Sun is viewed from the perspective of the exoplanet. If there are high-level intelligent civilizations on exoplanets, they may be lucky enough to see the Earth "crossing" the surface of the Sun.

You should be impressed by the last photograph of Earth taken by Voyager 1, man's most distant probe, in which a tiny point of light (Earth) hangs in diagonal sunlight against the darkness of space, its blurred cyan color suggesting watery oceans and clouds. This photograph is a visual representation of how we often describe the Earth as a "grain of sand" in the universe. Even a single pixel of planetary light falling on some distant detector can reveal a surprising amount of information about astrology. If we Earthlings can do it, so can close aliens.

Among these close exoplanets, the two scientists finally shortlisted seven planets that could have rocky surfaces and are in the habitable zone of stars, which are considered candidates to host liquid water and, of course, are potential candidates for planets with aliens. The planet Ross 128 b, for example, spent a long time in the Earth's "transit zone" between the 10th century B.C. and 2000 A.D., during the Earth's epoch.

For example, seven Earth-like planets orbiting a star called TRAPPIST-1, four of which have the potential for life, will also be in Earth's "transit zone" in about 1,600 years. Some astronomers say that these stars and related systems should be the priority in our current and future search for exoplanets capable of hosting life and possibly even extraterrestrial technological civilizations.

Imagine we live in a room with all the windows open, yet you don't know that everything you do will be public at all times. If you knew what you were doing and were completely visible to others, would you behave the same way as before? By the same token, back on Earth, if there were aliens on these close exoplanets, would Earth have been discovered by them? Is it already being watched by them?