We live in a multiverse

Why we definitely live in a multiverse

The cosmologist Andrei Lindewas one of the first to notice that we live in a multiverse: in other words, in a cosmos in which there is far more than a single universe.

But what does that mean exactly?

Here is the first and most important explanation for this:

Living in a multiverse does not mean that the individual universes that make up it have to be clearly demarcated from one another. Many of them flow into one another - just like landscapes of the most varied of characteristics on earth generally flow into one another: Northern Germany, for example, is absolutely flat, so completely different from e.g. Tyrol and the Alps. Nevertheless, one cannot say that there is a line somewhere that represents an exact boundary between high mountains on the one hand and absolutely flat land on the other.

But since the speed of light is finite, there is something we own Observation horizoncall. It forms a clear boundary between that part of the cosmos from which we can receive signals and the whole rest of the universe (which - according to everything we know today - could even be infinitely large). However, this horizon is constantly shifting (comparable to the edge of the light cone of a headlight, which will show more or less depending on whether the illuminated space in front of our car is moving away from us or coming towards us).

In addition, it must be taken into account that the cosmic space around us expands (its scale changes like yeast dough, which rises and thus increases its volume - and thus also the distances between the individual raisins that could be in it). Brian Greene has calculated that in 100 billion years from now, only about 30 galaxies will be visible from our solar system (assuming that it will still exist). All of the 100 billion or so others that can still be observed from Earth today will then be so far away that the inhabitants of our solar system can no longer reach the light emitted by them. So you will literally be seen from the sun in another universebe.

The limit of our "universe" is also still dependent on where we are at the moment. If we could move at half the speed of light, for example, it would move with us accordingly quickly, because each of us is always right in the center of the "universe" in which we live.

More generally: Every object, such as our sun, sits in the center of a spherical region of the universe, the surface of which is given by its event horizon (i.e. the places from which light emitted in the direction of the object can just reach the object). Since we humans all live very close to one another, our "universes" overlap extremely strongly and are even almost identical (= one and the same).

String theory suggests to us that universes in this sense, too, if they are far enough away from each other, can differ significantly in their physics and that the differences can be all the more clear the further away they are from each other. You can compare them with landscapes on earth, which flow into one another, but whose characteristics can change very clearly over great distances.

By the way:

The possibility,

that there could be universes with significantly different characteristics,

first suggested string theory to us. [1]

Linde is sure to think of her when he talks about the multiverse and presents his sketch to the audience. On ORF it was briefly explained in what sense he speaks of the multiverse. Even the fact that the terms space and time - in the sense of our universe - could not make any sense at all for those universes cannot be ruled out.

This also applies to universes which - as Lee Smolin imagines - could be born from black holes.

Black holes are - by the way - good examples that universes can also have horizons that can only be passed from one direction.

Worlds seem particularly plausible to me in the sense that Vilenkin's theory of eternal inflation describes.

But one thing is certain: if universes exist that differ fundamentally from ours, even mathematics will always only be that for us Possibilityshow their existence.

It shows once again that people in their attempt to research reality are in no way limited only in practice, but also in principle.

Worth knowing about "Multiverse, Cosmology, Physics"
compiled by Gebhard Greiter.
tags: stw5372UMP: Universenn against Multiversumn against Physiknegreit