Chapter 149: Beyond the Horizon

In search of evidence supporting the existence of parallel universes, Hua Feng uncovered deeper insights.

British astronomers announced they had found evidence backing the multiverse theory. Through the study of cosmic microwave background radiation maps, they identified four circular patterns formed by "cosmic friction," suggesting that our universe may have collided with or entered other universes at least four times.

In August 2007, while analyzing cosmic microwave background (CMB) signals, scientists discovered a massive cold spot—a region entirely "empty," devoid of normal matter, dark matter, or radiation signals. Why would such a bizarre region of space-time exist within the universe?

To find the answer, scientists theorized this could be evidence of another universe. The cold spot phenomenon may lead cosmologists to conclude that parallel universes exist beyond the one we inhabit. Data observed by the Planck space telescope revealed that our universe might be one of a billion, marking the first time evidence has pointed toward the existence of parallel universes.

Maps rendered by the Planck telescope illustrate the distribution of cosmic microwave background radiation. Scientists believe that the residual radiation from the late stages of the Big Bang is evenly distributed across space, particularly in the southern sky. As early as 2005, Dr. Laura Mersini-Houghton, a theoretical physicist at the University of North Carolina at Chapel Hill, alongside Professor Richard Holman from Carnegie Mellon University, predicted the existence of this anomalous radiation, attributing the uneven distribution to the presence of parallel universes.

Dr. Mersini-Houghton asserted that the data from the Planck probe supports the hypothesis of parallel universes, implying that an infinite number of universes exist beyond our own, and that the uneven radiation in the southern sky is caused by the gravitational pull or drag effects of these neighboring realms.

Spanning nearly one billion light-years and located in the direction of the constellation Eridanus, the colossal cold spot within the cosmic microwave background radiation signal is viewed by Dr. Laura Mersini-Houghton as a signature from another universe. If confirmed, this discovery would represent the first universe ever found by humanity outside our local space-time.

Cosmic microwave background radiation originates from the lingering signals of the Big Bang and exists in the microwave spectrum. Images captured by NASA's Wilkinson Microwave Anisotropy Probe (WMAP) and the Sloan Digital Sky Survey also revealed massive voids in our universe, an evidence trail initially uncovered by scientists in 2004.

In fact, the mystery of the cold spot has become a focal point of astronomical research. Subsequent studies revealed that this enigmatic patch of space-time is not entirely devoid of matter; small-scale galaxies reside within its periphery. Compared to galaxies in other celestial regions, these galaxies are exceptionally small in scale and radiant output. Calculations indicate that the radiation emitted by celestial bodies near cosmic voids is roughly 20% to 45% lower than that of other visible space-time in the universe. Nevertheless, why would such bizarre space-time structures form in the universe?

For instance, a cosmic void roughly 90 light-years in diameter exists 8,000 light-years away from the Milky Way. Current Big Bang and cosmic formation theories struggle to explain how these voids could form; their formation mechanisms remain an enigma.

A research team led by Dr. Mersini-Houghton believes this is evidence of another universe. According to string theory, other universes exist beyond our own, each possessing unique physical properties. Another perspective suggests the cold spot is related to cosmic expansion; as a consequence of long-range gravitational forces, large voids have emerged within the cosmos. While currently observed major voids appear in the northern hemisphere, scientists predict that a massive cold spot also exists in the southern hemisphere, though the research team maintains that the appearance of cosmic voids involves an element of randomness.

Based on data from the Planck probe, Dr. Mersini-Houghton believes her hypothesis has been validated: additional parallel universes exist beyond the one we inhabit. The existence of these realms has caused anomalies in the background radiation, all of which manifest as the inexplicable cold spot in cosmological theory. Operated by the European Space Agency, the Planck space telescope possesses exceptional observational precision, and its meticulously mapped CMB images have opened a gateway to another realm of space-time for scientists.

According to The Sunday Times, Professor Malcolm Perry, a professor of theoretical physics at the University of Cambridge, stated that the discovery holds an exceptionally high probability of corroborating the existence of the "multiverse." His colleague, Professor George Efstathiou, an astrophysicist, echoed this support: "The notion of the multiverse still sounds bizarre to some people today, much like the proposal of the Big Bang theory once did. However, we now possess robust evidence, which will fundamentally alter humanity's perception of the cosmos."

Theoretical Progress:

On October 31, 2014, physicists announced that "parallel universes" do indeed exist, providing living space for different versions of "us." Furthermore, parallel universes influence one another, which accounts for various strange physical phenomena observed at the microscopic level. This theory was jointly proposed by scholars from Griffith University in the UK and the University of California in the US. They argued that parallel universes not only exist but interact with one another rather than evolving in absolute isolation, and this interaction neatly explains the bizarre reactions of particles discovered in microscopic physics research.

Professor Howard Wiseman, a physicist at Griffith University, stated: "Around 1957, the idea of parallel universes emerged within the quantum physics community. Following this line of reasoning, every time a quantum measurement is carried out, the universe branches into new, distinct universes. This generates infinite possibilities—in some universes, a meteorite did not strike the Earth, and the dinosaurs survived. In another universe, Australia became a Portuguese colony."

Previously, scholar Hugh Everett discovered that quantum particles can simultaneously possess two different states, leading him to propose the theory that particles exist in different states across different worlds simultaneously. According to this theory, a particle does not need to choose between two states in two worlds; instead, it can embody both. Wiseman and his colleagues believe that the universe we inhabit is merely a drop in the ocean among a vast multitude of realms. These universes coexist; some resemble our own, while others are vastly different. Wiseman also noted that "adjacent" or closely related universes repel one another, amplifying the differences between them.

Scientists will have multiple methods to test these parallel universe theories and potentially rule some out. Over the coming decades, driven by monumental advances in cosmological measurement technology—such as cosmic microwave background radiation detection and large-scale matter distribution surveys—scientists will further constrain the curvature and topological structure of space, thereby testing the first-tier multiverse theory. More precise measurements of cosmic inflation can be used to test theories of the second-tier multiverse.

Joint advancements in astrophysics and high-energy physics will also determine the degree of fine-tuning of physical constants, thereby weakening or strengthening the plausibility of the second tier. If current global efforts to manufacture quantum computers succeed, they will provide further evidence for the existence of the third tier, as quantum computing inherently leverages the parallelism of third-tier parallel universes. Conversely, experimental evidence of unitary non-conservation would rule out the third tier. Finally, the supreme challenge of modern physics—the success or failure of unifying general relativity and quantum field theory—will yield deeper insights into the study of the fourth-tier multiverse. Scientists may ultimately discover a mathematical structure matching our universe, or they may suddenly encounter the impenetrable limits of mathematical validity, forcing them to abandon the fourth tier.

Max Tegmark, a cosmologist at the Massachusetts Institute of Technology, is deeply passionate about researching parallel universes. He remarked: "To me, the most interesting question is not whether parallel universes exist, but rather how many types of parallel universes there are." In a 2003 article published in Scientific American, he categorized parallel universes into four distinct levels. According to Tegmark’s classification, universes higher up the hierarchy are more expansive and encompass those situated at lower levels.

Tier I: Beyond the Horizon

If space is infinite and matter is distributed with sufficient uniformity on a large scale, then even the most improbable events are bound to occur somewhere. Specifically, there should be an infinite number of inhabited planets, which includes not just one, but infinitely many individuals with the exact same appearance, name, and memories. Regions identical in size to the observable universe genuinely exist, and within them, every possible cosmic history is physically realized. This constitutes the first tier of parallel universes.

Chaotic Inflation Theory yields general predictions for an infinite, ergodic universe. This universe is infinite and should contain Hubble volumes capable of realizing every conceivable initial condition.

Consequently, an infinite universe contains an infinite number of Hubble volumes. While all of them share the same physical laws and fundamental constants, their configurations of matter distribution differ almost entirely from the Hubble volume we inhabit. Yet precisely because Hubble volumes exist, configurations similar or identical to ours can be found beyond the event horizon.

According to Tegmark’s calculations, a celestial body with a volume and configuration identical to the one we inhabit exists at a distance of roughly $10^{10^{115}}$ meters away from us (a number vastly larger than a googolplex). This deduction assumes a distribution patterned similarly to the Hubble state, but in reality, any conceivable distribution is possible. This implies that the specific Hubble volume we inhabit is practically unique in its existence.