A lot of times I hear or read comments on the topic of the multiverse. Why did we come to this hypothesis and is it really proven? What does the existence of a multiverse mean?
In fact, the conclusion of the multiverse results from a proven scientific theory called “cosmic inflation.” In the beginning, how do we know that the universe started from a beginning event and that it was not in its present form from time immemorial?
Several physical evidence led scientists to conclude the Big Bang. The most important of these clues is the fact that our universe is expanding at an accelerating rate, as galaxies farther away from us are getting more and more distant. The beauty of science is that finding the answer raises more questions, so I will list a series of questions and answers that led us to conclude that there are multiple universes.
The scientist Hubble discovered that our universe is full of galaxies and that the previous assumption that our universe is a single galaxy is wrong. This new fact was the seed of curiosity to know how far these galaxies are from us, and when observing the galaxies, it was discovered that the frequency of the light coming from them reaches us with a redshift. This discovery means that the light coming towards us from those galaxies is moving away from us because of the Doppler principle, which describes the mechanism of waves in nature and how their frequency changes based on the direction they are traveling in. We all recognize the sound of an ambulance passing by and how loud and sharp it is and then lowers in the direction the car is heading. This phenomenon that makes the sound of the ambulance gradually decrease is the same that causes the brightness of galaxies to reach us with a redshift, due to their distance from us.
So we discovered that the universe consists of many galaxies and that these galaxies are in a state of movement in the opposite direction to us as a result of the expansion of the space between us and those galaxies.
From here the idea of the Big Bang began to appear, as if we go back in time, these galaxies must have been very close to each other until we reach a very small point.
cosmic background radiation:
Within the research on the subject of the Big Bang, the researchers launched an observatory to measure the radioactive effects of the beginning and expansion of the universe, and the result was what we call a map
of the universe’s microwave background radiation, or in other words, a map showing the radioactive impact of nuclear interactions in the universe. This map shows how the universe is homogeneous throughout and cannot be distinguished anywhere on the map.
This result raises a very important and difficult question. Since the universe is expanding, and since the age of the universe is about 14 billion years, this means that the edges of the universe are estimated at about 92 billion light years. This means that the information (physical properties) present at the two ends of the universe, which we discovered to be identical, is far enough away that light could not reach between its ends.
From this point, a theory arose called cosmic inflation, which explains how the universe expanded greatly in the beginning moments, which explains the homogeneity between the parties by virtue of the fact that they were one part and separated and then expanded.
Here I am not going into any technical details and only explaining the concepts briefly to reach the conclusion of the multiverse.
Now imagine that the universe is a bubble that has begun to expand exponentially. The conclusion that emerged due to the expansion theory is that not all parts of this bubble will expand at the same speed, which means that some slower than the other parts will form a bubble within the basic bubble or the original universe from which we started.
Imagine a large bubble expanding, but its parts expand at varying speeds. We will have many bubbles due to the difference in speeds, and each bubble will continue to expand, but under different conditions and speeds, which means that the conditions that arise within each bubble will be different.
Conclusion The emergence of different bubbles due to the difference in expansion velocities we reach due to the theory of cosmic inflation. The theory of cosmic inflation is a solid theory that has many tangible evidence that I did not go into in detail (expect that the universe is flat, the existence of cosmic homogeneity in all sides, the polarity of cosmic radiation, the theory of atomic evolution from hydrogen). It is a mathematical conclusion, and since the theory itself is proven, its conclusions are scientific conclusions, but they remain unproven.
These are conclusions that claim the existence of bubbles that we call a multiverse in which the physical laws are slightly different as a result of the expansion velocities that occurred within those bubbles at the beginning of inflation. We live inside one of these bubbles and there are other cosmic bubbles within the original bubble that we cannot observe because of their distance from our universe’s event horizon (the boundary of our universe).
Because our bubble expands faster than light, the light at the edge of our bubble will never reach the other end and we will always have a horizon that we think is the limit of the universe. It means that the light that emanates today from the borders of our visible universe will not be able to reach the other end because of the speed of expansion, which is accelerating faster than the speed of light.
We look at the sky and estimate the farthest light that reaches us at about 14 billion light-years, but this does not mean that this is the real age of the universe or that this is the size of the real universe, but that our visible universe (our bubble) is a bubble in which the physical laws we know and that our observation horizon cannot Exceeding its acceleration limits.
Our bubble expands faster than the speed of light, while all things inside it, even light, cannot move faster than the speed of causation (light), so it becomes what we call the visible universe.
If we want to imagine a universe parallel to ours, we have to move outside the event horizon of our universe at tens of times faster than the speed of light in order to be able to move faster than the speed of cosmic expansion. Assuming that we were able to do that and went faster than light by thousands of times to compensate for the years in which the universe expanded 14 billion years ago, and assuming that we crossed the 94 billion light-years that limit our current perspective universe and then stopped, we will observe that a “new perspective” other than our current universe is rapidly finite It expands from our point of arrival, so humans on planet Earth are so far away from us that the light from their planet does not shoot towards us, and even if it does, it will never reach us because we are outside the speed of expansion versus causation. Also, traveling at a speed a thousand times faster than the speed of light, in theory, means that we are going back in time, which means that we will notice that our universe is shrinking instead of expanding because we are traveling faster than it is expanding.
The idea here is that the multiverse is nothing but an expression describing causal bubbles that resulted from the inflation of the initial universe, and then the beings inside those bubbles became governed by the speed of causation and their inability to exit because the speed of expansion is greater than the causation within them.
The universe is everything and naming multiple universes is only our way of saying that there may be multiple visible universes, but they are all within one universe that may be infinitely expanding.
We are just one out of trillions of points in a cosmic bubble among the infinite number of universes visible to those who live within it.
The idea of a multiverse explains the fallacy of intelligent synthesis about the possibility of life appearing only if the physical laws are exactly the same as they are in our universe. These are the laws that we monitor.