Quantum universe
Speaking of parallel worlds, fans of the sci-fi series Sliders must be very excited! The general contents of this series are as follows: Quinn Malory, a college student majoring in physics, made a machine that can shuttle back and forth between different parallel worlds; In every parallel world, the development of history is different from what we know: dinosaurs still live in the world, and people over 30 enjoy political rights ... Of course, this is purely science fiction story, but theoretical physicists do not rule out the possibility of such a world.
This physics describes an infinitely small world: atoms and the basic particles that make up atoms. On such a small level, it is impossible to accurately describe things and their positions. It is the superposition of different states, and each state has different possibilities of existence. To understand this, let's give a real-world example. You have five blue beads and five red beads. You put them all in a paper box and seal the box. Then you can say, "There are some blue or red beads in my box." All right. Now, let's look at the quantum world. You should be mentally prepared! Because, here, every bead is red and blue. It has two colors at the same time (this is what we call superposition state). Only when you hold a bead in your hand can you "determine" its color: it is either red or blue, and the two possibilities are equal. Yes, don't be nervous Everyone, like you, thinks this phenomenon is very strange. Not only that, the next small experiment will show you a concrete result of this superposition.
Take four beads out of the box at random. For example, you take out three red beads and 1 blue beads. This result is valuable from the point of view of both traditional physics and quantum physics. But if you draw the lottery again with the four beads you got, the result will be confusing. Put it in another box and take it out one by one. From the perspective of traditional physics, you will definitely take out three red beads and 1 blue beads. In the world of quantum physics, you may take out four red beads, four blue beads, or even two red beads and two blue beads, and so on. Yes, your understanding is correct: some beads have changed color! This is possible because quantum beads have two colors at the same time. They may change their colors every time they draw lots. This sounds crazy, but through some very serious experiments, people have indeed observed similar results: some properties that distinguish different electrons (excluding color, because electrons have no color) will change like this.
Unlimited possibilities in the world
Take it easy. A particle can exist in two different states at the same time, which not only puzzles you, but also puzzles many physicists. In particular, they can't explain why the color of beads must be seen (in physics, this means measuring the state of beads) to determine. Physicists imagine the existence of quantum parallel worlds to solve this mystery. Take beads as an example. It was red and blue before it was extracted. When you take it out of the box, the universe is divided into two: in one universe, the bead is red, while in the other universe, it is blue. This solves the problem of determining the color.
Extending this idea into our daily life, the result is that a large number of parallel universes are constantly splitting. Are you hesitating to enter gate a or gate b? In one universe, you will walk into Gate A, while in another universe, you will walk into Gate B. Therefore, there are countless parallel worlds around us that we can't see. The world we live in is like a radio. If we can find the button to change the frequency, we can travel from one universe to another as described in Voyager. ...
Bubble universe
Why are some things fleeting? This is a realistic problem that physicists are trying to explore. The more carefully they analyze the laws of physics, the more lucky they feel that we exist. Not only we humans, but the existence of all stars and galaxies is a miracle created by physical constants. Thanks to them, physicists can explain the stability of atoms, why the moon revolves around the earth, and why the sun shines ... once a constant changes, the whole physics building will collapse. In this way, all these constants that have dominated the universe since its birth seem to be carefully designed! This idea is really warm ... but it's also ridiculous. Because these coincidences have no reason to happen. What makes these constants take these values instead of other values? Facing this question, we might as well seek the answer from the parallel universe. ...
In fact, as you can imagine, not only one universe is dominated by its own warm constant, but there are thousands, and each universe has its own different constant. Just like the lottery. Our universe hit the right combination of numbers, making atoms, molecules and even life appear. This is really a great reward! So, we can feel our luck here. Other universes have the wrong number, so there is no hope of life. Of course, since they will never have life, no one will lament.