Can there be life on a quantum scale?

Parallel universe

This term, often used in science fiction literature, means one universe or many universes that could coexist alongside ours. The resulting collection of universes is also called Multiverse. Of course, this hypothesis is very speculative, but there are some scenarios in modern cosmology that consider this possibility.

Stimulus from quantum theory

The idea of ​​parallel universes is older and goes on the Probability statements of quantum theory ('Schrödinger's cat') back: Quantum physical states are described with the wave function (Ψ, 'Psi'). The square of the magnitude of this wave function can be interpreted in such a way that it indicates a probability of a state's presence. If the wave function describes a particle, the absolute square of the wave function is a probability distribution for finding the particle at a certain location. The highest probability of encountering the associated particle is where the probability distribution assumes its maximum. in the Orbital atomic model the orbitals are just three-dimensional probability distributions of the electrons that envelop the nucleus in the atomic shell.

Role of the quantum mechanical measurement process

The relationship between Wave function and measurement process was explained with the Copenhagen interpretation (Max Born 1925/26): At the moment of the measurement, the wave function 'collapses' to a certain state, that of the Observable is observed. 'Schrödinger's cat' is found dead or alive.

Many worlds

The Many Worlds Theory (H. Everett 1957) extends this perspective: All possible states are also realized. Each realization exists in its own world, its own universe. In one universe, 'Schrödinger's cat' is dead, in the other it lives.
Inspired by these ideas of 'Everything is possible, probable and realized somewhere.', this culminated in a non-vanishing probability for a coexistent parallel universe.
The appearance of parallel universes in quantum cosmology received a more precise formulation. In this theory, the quantization apparatus previously applied to particles was carried over to the universe as a whole. This formalism leads to wave functions for a universe and the possibility of creating or destroying entire universes with creation and annihilation operators. The vacuum state - 'no universe' - becomes void called. Excited states are Baby universes. Many baby universes could coexist in the form of a quantum foam. On the quantum scale, individual macroscopic universes formed because they came out of the baby universes through inflation.

other brane worlds

A second idea that includes the term Parallel universe would justify is the ecpyrotic scenario of Steinhardt & Turok (2001). They use the brane formalism of string theories and came up with the idea that the Big Bang model suggested by observation is the consequence of a Collision of two universes was - namely our universe and a parallel universe. In this 'world collision' (Branches collision) would have completely reorganized and restructured both universes. With the existence of extra dimensions in addition to the classic four dimensions, string theories allow the two universes to be very close to each other even in one extra dimension: the 'cosmic neighbor' could be away on the Planck scale, i.e. only about 10-35 m!
The avant-garde cosmology of Steinhardt et al. goes further and speculates about a cyclical repetition of the eccyrotic scenario. This cyclic universe is created by a fluctuating scalar field, the radion. This field should manifest itself in the universe as dark energy. The existence of dark energy is supported by observation (WMAP). According to current measurements, it even accounts for 74% of all forms of energy in the universe. It thus dominates the cosmodynamics in the later development phases of the universe and drives the expansion of the universe. Currently, permanent measurements of dark energy in supernovae of type Ia corroborate the cosmological constant (Λ) rather than the radion field: the observation data prefer Λ as a time-constant form of dark energy over time-variable dark energies - and the radion is time-variable. Other types of variable dark energy known as quintessence are topological defects or phantom energy.

Are there one or more parallel universes?

In conclusion, on the subject Parallel universe say: The correctness of such speculations, the jump from the drawing board of theory into nature, must be proven by experiment or observation. So far it has not been possible to prove parallel universes. Until that happens, these scenarios have to be under the label hypothetical, avant-garde cosmology to run. At least cosmologists have a theoretical idea of ​​the Multiverse, a hypothesis that can be tested.