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Why can we never know everything about the universe?

For a long time, uncovering the essence of the universe is what scientists dream of. Not only that, but scientists also want to control the laws of the universe, and know how each particle that exists from the birth of the universe to today.

But this ultimate scientific dream may not be realized in the future, even if scientists in the future have more powerful observation techniques. This is because the early universe is likely to have been inflated, and the part of the universe we can observe, both now and in the future, is still limited. In an observable universe with a radius of 46.5 billion light years, the amount of energy, the number of particles, and the information we can collect are limited.

Limited range of observation

At 1.38 billion years ago, the universe formed from a big explosion in a hot, dense singularity. Since then, the universe has expanded and cooled, eventually becoming the state of the present.

Even if the structure of the space itself is expanding, we can only see a finite distance even if the photon can pass through the space at the ultimate cosmic speed (speed of light). No matter how fast the spatial structure expands, how fast the speed of light, and how much time the universe has passed since its birth, these properties are not unlimited. Therefore, we can only see a limited distance, the observable universe contains only a limited amount of matter and energy, and the amount of information we can obtain is limited.

The universe known to man

As far as we know, our galaxy contains about 1,000 to 400 billion stars. The entire observable universe contains about 2 trillion galaxies, 10^80 atoms, 10^90 photons, and 10^54 kilograms of mass. We also know how the universe is integrated into clusters of galaxies, clusters of galaxies, and filamentous structures, and how they are separated by huge cosmic spaces. We also know the scale of the universe that defines these structures and how the universe evolves over time.

Under the framework of the Big Bang model and the general theory of relativity, we can best explain the evolution of the universe. Hubble’s major discoveries a hundred years ago changed our perception of the universe. A large number of galaxies that are far from the Milky Way show that the structure of space itself is expanding.

If the universe is expanding, then the universe is still cooling. Because over time, the wavelength of light is elongated and the energy is gradually attenuated. If so, we should see a afterglow with special properties – cosmic microwave background radiation, which can be traced back to the earliest stages of the universe.

In theory, we should also see an evolving network of cosmic structures; the earliest gas clouds should have a specific proportion of light elements, while heavy elements simply do not exist. All predictions about the universe have been confirmed by observations, and the Big Bang theory has been widely recognized.

If we can understand the beginning of the universe and the laws that control reality, we can know what is happening in the universe. Therefore, all we have to do is to use the laws of physics to infer. However, when cosmologists inferred the earliest stages of the universe and compared theoretical predictions with observations, they obtained unexpected results.

Inflated early universe

In the first moment, the universe is an infinitesimal singularity with infinite temperature and density. In theory, the entire universe will be annihilated, or re-collapsed almost immediately, and stars or galaxies will never form in the universe unless the initial expansion rate and initial energy density of the universe do not reach a perfect balance. The universe will have different temperatures in different directions unless something makes the temperature around the universe uniform. In addition, the universe will be filled with high-energy ruins that have never been detected.

But in reality, the universe is full of stars and galaxies. The temperature in all directions of the universe is the same. There are no high-energy ruins in the universe. The most successful way to solve this theoretical flaw is the inflation theory, which argues that the universe has experienced dramatic spatial expansion in a very short period of time, which replaces the concept of singularities and predicts the unpredictable initials of the Big Bang theory. condition.

In addition, the inflation theory has made six other important predictions, five of which have been proven, and one that exceeds the current human limit of observation.

The unsolved problems in the Big Bang theory and the unexplained mystery paved the way for cosmologists to propose the theory of cosmic inflation. The theory of cosmic inflation reproduces the success of the Big Bang theory, explains the unsolved mystery, and then it makes new predictions and produces observable results.

But new problems have emerged, why is inflation in the early universe?

According to the inflation model, the inflation of the universe occurs 10^-35 seconds after the birth of the universe, and the duration is only 10-33 seconds (10 billion billionths of a second). Because of the exponential expansion of space during inflation, this erases any information that has occurred before, separates it from the universe we can observe, and pushes it beyond the universe we can observe. The truth of the universe disappears.

Due to the inflation in the early universe, we can only understand the limited universe. Plus the universe itself may be infinite, and our understanding of the universe will never be infinite, so we may never know everything about the universe.

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