Chapter 136: The Past

**The Subterranean Civilization Theory**

Some science fiction films suggest that while the Earth’s surface is a paradise for human evolution, a different civilization ruled by evolved insects exists within the planet. According to this narrative, these subterranean insects eventually launched a war against humanity to claim the right to live on the surface. It is reported that after the American satellite "Charlie 7" captured images of the Arctic Circle, a hole was discovered in the film footage. Could this be an entrance to the Earth's interior? Furthermore, geophysicists generally estimate the Earth’s mass to be millions of times greater than six sextillion metric tons. If the interior were solid, the mass would be even greater, which has fueled the "Hollow Earth Theory." Some oil prospectors have claimed to discover massive tunnels and giant underground beings. We might hypothesize that humans are divided into surface-dwellers and inner-dwellers; the latter, possessing technology far superior to our own, would naturally be able to traverse space in flying saucers—crafts that surface-dwellers have yet to master—as fellow inhabitants of the same celestial body.

The absurdity of this theory lies in the fact that the Earth is not hollow. All claims regarding a hollow Earth are rumors and fake news. Earth is the densest planet in the solar system; if a massive void existed inside, its mass could never reach current estimates. Moreover, Earth possesses a powerful magnetic field—a feature of planetary magnetic fields (which differ in generation from stellar magnetic fields)—implying a massive iron core, which definitively excludes the possibility of a hollow interior.

**The Coexistence Theory**

This perspective posits that extraterrestrials live and work among us. In photographs taken by researchers using a remarkable new type of radiation camera, some individuals appear surrounded by a pale green halo, possibly caused by rays emitted from their brains. However, when attempts were made to track down these halo-bearing individuals, they vanished completely, leaving no trace of their prior existence. This theory suggests aliens are hiding in plain sight while we remain unaware of their motives, though there is no evidence that they intend us harm. Much like a believer unable to prove the existence of God, this theory shifts all requirements for evidence onto unprovable premises.

**The Human Ancestor Theory**

There is a viewpoint that humans are descended from aliens. Tens of thousands of years ago, a group of highly intelligent extraterrestrials with advanced technological knowledge arrived on Earth. Finding the environment highly suitable, they initially intended to settle, but lacking the facilities to cope with Earth's gravity, they changed their plans and decided to create a new species by crossbreeding with terrestrial hominids. By impregnating female hominids, they produced the modern human race.

In reality, human genetic evolution follows a regular pattern, with no massive influx of new genes occurring in a short burst (relative to geological time). More importantly, hominids existed much earlier; humans were already fully formed tens of thousands of years ago. If extraterrestrials had intervened, it would have had to occur over four million years ago, spanning a geological period of over two million years—a timeframe far too vast for mere technological intervention.

**The Parallel World Theory**

The universe we perceive (the total stellar system) cannot be contained within a four-dimensional framework; our world is not solely formed by length, width, height, and time. The universe may consist of two adjacent worlds that are nearly transparent to one another, acting as "shadows" with minimal interaction. When these layered worlds were formed, the forces binding them were immense, causing matter to be highly intermingled. As the universe expanded, matter density decreased and gravity weakened, resulting in two distinct, independent worlds. In other words, it is entirely possible that an invisible parallel world exists in the same space-time, perhaps similar to or vastly different from our own. They may share physical and chemical laws while differing in reality. These two worlds have been independent for 15 to 20 billion years. Thus, UFOs might originate from this other world, entering ours either by chance or through mastery of interdimensional travel, demonstrating a level of technology far exceeding our own.

**The Four-Dimensional Space Theory**

Some believe UFOs originate from the fourth dimension. These phantom-like craft can vanish in an instant, evading even the most sophisticated satellite tracking networks. It is possible that UFO occupants are manipulating space-time. By creating local spatial curvature that expands into adjacent areas, they can enter our space. This explains eyewitness accounts of tangible beings appearing suddenly on the ground near a UFO rather than emerging from a doorway. The absurdity of these theories lies in the fact that it has been proven that all dimensions beyond the three spatial ones are severely curled.

**The Future Life Theory**

Some scientists argue that "aliens" are actually future humans. Data indicates that human evolution has accelerated significantly in the last century. We cannot rule out the possibility that after millions of years of evolution, humans will resemble what we currently call aliens, having mastered time-travel technology to visit our era.

Extraterrestrial races are not confirmed biological species, but rather common labels found within human society: Pleiadians, Sirians, Lyrans, Elohim, Reptilians, and Greys.

**The Search for Extraterrestrial Life**

As part of the quest to unlock the mysteries of the cosmos, scientists actively search for life beyond Earth and scan for signals from extraterrestrials. This scientific endeavor began in the 1950s.

In 1959, Giuseppe Cocconi and Philip Morrison published an article in the renowned British journal *Nature*. They posited that if intelligent life existed elsewhere in the universe with a level of technology comparable to our own, they should be able to receive radio signals transmitted by humans, and we, in turn, could receive theirs. Despite the immense distances—where a single exchange might take centuries—communication remains possible. They identified the 21-centimeter wavelength of hydrogen as the optimal frequency for interstellar radio communication, as hydrogen is the most abundant element in the universe and its signature is easily detected.

This article greatly inspired and bolstered public confidence in the search for extraterrestrial intelligence, confirming that communication is possible provided their technology is comparable to ours. This marked the beginning of the scientific search for extraterrestrial life.

Humans have lived on Earth for approximately two to three million years. Once, we believed ourselves to be the masters of all creation, the only intelligent life in the universe, and even the center of the cosmos. With scientific progress, our horizons broadened, and we realized the universe is vast beyond imagination, and Earth is but a tiny speck, certainly not its center. This led to the speculation that in such a vast universe, other intelligent beings—aliens—must exist. This idea has deeply captivated those dedicated to the search.

In the 16th century, observers using telescopes saw overlapping patterns on Mars and mistook them for "canals" built by Martians. In 1935, an American radio broadcast claiming Martians had arrived on Earth caused mass panic. British author H.G. Wells’s *The War of the Worlds* further fueled this fascination, sparking a wave of science fiction novels and films.

Do Martians exist? In the era of basic telescopes, this remained a mystery. By the 1960s, space probes finally reached Mars, solving the riddle: Mars is far colder than Earth, its surface a barren landscape of rock and dust battered by fierce winds. There is no life there, let alone Martians.

Following this discovery, astronomers concluded that within the solar system, no planet other than Earth possesses the conditions necessary for life. Therefore, humanity is the only intelligent species in the solar system, and to find others, we must look beyond.

In 1972, the U.S. launched the *Pioneer 10* probe, which left the solar system in 1987, carrying a metal plaque depicting human figures, our home planet, and the location of the solar system. In 1977, *Voyager 1* carried even more information to the outer world, including a sturdy record player and a gold-plated disc containing dozens of human languages and musical works (including Chinese classical music). People eagerly hoped that extraterrestrials would one day receive it.

Launched on September 5, 1977, the *Voyager 1* space probe represented humanity's first scientific attempt to reach out. While scientists acknowledge that the vast distances between stars make it unlikely that extraterrestrials could ever reach Earth, they have not ruled out the possibility of life existing in the outer reaches of space.