Why are we still not crashed into another universe?

The universe in which we live, huge, full of matter and energy expanding faster and faster. Looking for billions of light years, we can see billions of years of our ancient past, to see the formation of planets, stars and galaxies. We've looked at so far, we've found gas clouds, which didn't make life any star, and galaxies that formed when our universe was 97% younger. Interestingly enough, we can observe the afterglow of the Big Bang, which has remained ever since, when the Universe was some 380,000 years old. But with all this cosmic grandeur we never found evidence that our universe collided with another universe in a huge multiverse. Why?

In fact, if the theory of multiple universes is correct, our expanding universe was to collide with another universe. Isn't it? In the end, our universe is now so big that some describe it as infinite in size.

And so says not only logic, but also a well-known authority, Roger Penrose. And Penrose, and the conventional wisdom here is wrong. Our universe is, and must be isolated and alone in the multiverse.

Although this topic is too popular and controversial, in favor of the existence of multiple universes say a strong physical hypothesis. If you combine two of our leading schools of thought about how the universe works, cosmic inflation, and quantum physics, we inevitably arrive at the conclusion that our universe is the multiverse. There is another conclusion: every single universe that is created, and each Big Bang, which precedes it, will be immediately and permanently separated causality from others. Why? Disassemble physicist Ethan Siegel.

Cosmic inflation came as a Supplement to the theory of the Big Bang, providing a mechanism to explain why the universe began with certain conditions. In particular, inflation responded to questions about...

the
• why the universe was everywhere the same temperature;

Why was she a spatially flat; the

• why isn't there high-energy relics like magnetic monopoles.

...while continuing to write new predictions need to be tested. These forecasts include a specific spectrum of density fluctuations, with which the universe was born; the maximum temperature reached of the Universe in the early stages of the Big Bang; the existence of fluctuations on scales exceeding the horizon of space, and a certain range of fluctuations gravitational waves. All of this, except the last, have since been confirmed by observations.

Cosmic inflation, if it is a period before the Big Bang, when the Universe was dominated by energy inherent to space. Now the amount of dark energy is too small, and in times of inflation, it was much higher: a lot more energy density when the universe was full of matter and radiation in the hot early stages of the Big Bang.

Since the expansion of the universe caused by the energy intrinsic to space, during inflation the expansion is exponential, to create a new space. If the universe doubled in size at the time n, after 10 periods of this time she was in the 2¹⁰ or even in the 2¹⁰⁰⁰ times larger. For a short period of time, any non-planar and contains matter a region of space became indistinguishable from the flat, and all the particles of matter were dilated so far from each other that the two particles will never meet.

However, inflation cannot go on forever. The energy inherent in space-cannot continue forever, otherwise the Big Bang would not have happened and the universe would not be born. Therefore, energy must be transmitted from the fabric of space matter and radiation. To consider inflation as a field, picture a ball on top of a hill. While the bowl remains at the top, inflation and the exponential expansion continues. But inflation ended, what would be the quantum field for it nor answered, he needs to roll from unstable high-energy state to low-energy equilibrium. This transition, the "rolling" of the ball from the hill, leads to the end of inflation and creates a Big Explosion.

However, there is one thing: what is described above works as a classical field, but inflation was, like all physical fields, to be quantum in nature. Like all quantum fields, is described by wave function and probability waves spreads with time. If the value of the field is rolling slowly down the hill, the quantum spread of the wave function will be faster rolling, which makes it possible — even probable — the onset of the Big Bang and the end of inflation.

Because the space is expanding at an exponential rate during inflation, which means that over time will appear exponentially large number of regions of space. The fact that inflation will not end everywhere at once; different regions will get different values of quantum fields and different directions. In some regions, inflation ends and the field will roll down to the valley. In other inflation will continue, giving life to a new space.

Hence comes the phenomenon of eternal inflation and the idea of multiple universes. Where the end of inflation, we get the Big Bang and the Universe — of which we can observe. But there are regions where inflation has ended, and there was a Big Bang, there are also regions in which inflation is not over, and the exponential expansion continues. In these regions there are more growing space, which pushes the region, which ended the inflation, faster than they can grow. Each of the new regions, which will be a Big Bang, will be causally separated from our region, absolutely and forever.

If you imagine multiple universe as a huge ocean, you can draw separate universes where a Big Bang, like little bubbles in the ocean. These bubbles, as these bubbles, which are created at the bottom of the ocean, will expand over time, as our universe expands. But, in contrast to liquid water in the ocean, "the ocean" inflationary space-time is expanding faster than the bubbles ever will be able to expand. And because the space between them is growing and will grow always, the two bubbles never touch.

It would be a huge surprise that would have happened despite the forecasts of inflation and the quantum theory, if the two Universes ever collided. Although the collision of bubbles would leave a bruise on our Universe that we are perfectly revealed in the afterglow of the Big Bang, no evidence of such bruises there. As predicted by our best theories.