Return to Earth?

Chen Tian's body was still drifting in the universe, but his consciousness seemed to have returned to the place he had longed for day and night.

His mind began to think about everything from the past, and many fragments of memories began to appear.

Finally, the scattered fragments of memory disappeared, and a picture began to emerge.

It was a picture he had seen before, at a lecture he attended, when he was obsessed with science fiction universes and bought all related books to read in detail.

The person in that picture was a very famous foreign science fiction universe lecturer he had attended at that time.

The two people were giving a passionate speech, and Chen Tian sat below listening with fascination. Vaguely, he seemed to hear the person talking about the Steady-State Universe Theory. In that instant, he remembered!

Chen Tian's soul consciousness awakened, and he remembered the two people and the theory they were talking about. They were called Hermann Bondi and Fred Hoyle. The Steady-State Universe Theory was proposed in 1948 by the young British astrophysicists Bondi, Gold, and Fred Hoyle.

Their view was: In relativity, space-time is unified. Since the cosmological principle holds that all spatial locations are equivalent, then all moments in time should also be equivalent.

That is to say, the large-scale distribution of celestial bodies (matter) should not only be homogeneous and isotropic in space, but also invariant in time.

In other words, the universe image observed by observers at any time and any location is the same on a large scale. This principle is called the "Perfect Cosmological Principle."

The Steady-State Universe Theory holds that the universe is infinite in time and space.

It argues that the universe never had a beginning, or more precisely, that the universe is in a continuous process of creation.

When the universe expands, the total density decreases, but more matter is created to increase the density.

Therefore, as the universe continues to expand, new matter is continuously created in celestial bodies to fill the gaps.

The biggest feature of the Steady-State Universe Theory is that it requires matter and energy to be non-conservative, and that the law of conservation of matter does not hold.

To this end, Hoyle proposed modifying the Einstein Field Equations, arguing that the newly generated matter is produced by the vacuum phase transition caused by the newly generated vacuum transitioning from a high energy level to a low energy level.

The Steady-State Universe Theory once caused a sensation when it was introduced, but such a fundamental change in principle cannot be easily adopted unless the new theory has achieved great success and is in good agreement with observational facts. In reality, however, the Steady-State Universe Theory does not agree well with observations.

There is also Brane Cosmology. Why did the Brane Universe explode from a point of infinite density, or Singularity?

But no one knows what triggered this explosion: the known laws of physics cannot tell us what exactly happened at that moment.

Niayesh Afshordi, an astrophysicist at the Perimeter Institute for Theoretical Physics, Waterloo, Canada, said, "All physicists know that dragons may have flown out of the Singularity."

At the same time, scientists find it difficult to explain how the universe left behind by such a violent Big Bang could have an almost perfectly uniform temperature, because there does not seem to have been enough time to reach temperature equilibrium since the birth of the universe.

For most cosmologists, the most reasonable explanation for consistency is that shortly after the universe formed, some unknown form of energy caused the young universe to expand faster than the speed of light.

This gives us the roughly uniform temperature universe we see.

But Niayesh Afshordi emphasized, "The Big Bang is too chaotic, so it's hard to figure out if this expansion really existed."

In one paper, Niayesh Afshordi and his colleagues turned their attention to a hypothesis proposed in 2000 by a research team including Gia Dvali, a physicist at Ludwig Maximilian University of Munich, Germany.

In this model, our three-dimensional universe is a brane floating on top of a "Bulk Universe" with four spatial dimensions.

Niayesh Afshordi's team realized that if the Bulk Universe contained its own four-dimensional stars, some of these stars would collapse and eventually form four-dimensional black holes—similar to how massive stars operate in our universe.

These four-dimensional stars would explode like supernovas and violently eject their outer layers of material, while their inner layers would collapse into a black hole.

In our universe, a black hole is connected by a sphere called the event horizon.

Since ordinary three-dimensional space requires a two-dimensional object to create the boundary inside a black hole, then in the Bulk Universe, the event horizon of a four-dimensional black hole should be a three-dimensional object—a shape called a Hypersphere.

When Niayesh Afshordi's research team simulated the death of a four-dimensional star, they discovered that the ejected matter could form a three-dimensional membrane around the three-dimensional horizon and slowly expand.

The researchers hypothesized that the three-dimensional universe we live in might be such a membrane, and the growth of the membrane we detect is considered the expansion of the universe.

Niayesh Afshordi said, "Astronomers observe this expansion and extrapolate that the universe must have started with a Big Bang—but this is just a mirage."

This model also naturally explains the uniformity of our universe.

Since the four-dimensional Bulk Universe may have existed for an infinitely long time in the past, it has had enough opportunities to bring different regions of the four-dimensional Bulk Universe into equilibrium, and our three-dimensional universe is likely to have inherited this.

Brane Cosmology is a branch of Superstring Theory and M-Theory in physics, specializing in the study of cosmic branes. The theory suggests that the universe is actually embedded on some higher-dimensional branes. This discipline also studies how those higher-dimensional branes affect our universe. The memory reached here and then there was another break. Chen Tian was puzzled. At that moment, he seemed to have really returned to Earth in a realistic illusion. Did it come from the depths of his memory, or was it just an illusion of the soul caused by some reason? He didn't know, and he didn't even know where he was. His memory kept repeating, and those scattered fragments seemed to contain some important information.

Chen Tian guessed why his memory would stop when he was on Earth listening to foreigners giving lectures, instead of other times.

What is the connection between them?

Could it be that there is something in the memory that is constantly reminding him?