Lost in a multiverse

I recenti risultati pubblicati dal gruppo di Harvard sull’esperimento BICEP2 sono stati interpretati come la “prima evidenza diretta” dell’inflazione cosmica dovuta al passaggio delle onde gravitazionali primordiali le cui tracce sono state impresse nella radiazione cosmica di fondo (post). Non solo, ma c’è chi dice che questi dati potrebbero essere collegati a qualcosa ancora di più strano che gli astronomi chiamano multiverso. Secondo questa ipotesi affascinante, il nostro Universo non sarebbe l’unico ma sarebbe parte di una grande vastità di universi che formano una sorta di gigantesco “albero cosmico” il cui numero potrebbe essere dell’ordine di

quasi impronunciabile. Ma se questi universi esistono davvero, non li vediamo perchè dal momento in cui è nato il nostro Universo non c’è stato abbastanza tempo affinchè la luce si propagasse per raggiungere il nostro orizzonte cosmico. Dunque, essi si troverebbero al di là del nostro limite osservativo e perciò non potranno mai essere rivelati, almeno in linea di principio. Come fanno allora i cosmologi ad affermare che esistono invece delle evidenze a favore della loro esistenza?

Pubblicità

Max Tegmark ‘welcomes’ the multiverse idea

What is the Universe made of? The ancient Greeks conceived of the “atom”, the indivisible unit of matter. Today’s physicists talk of smaller particles, quarks and electrons, neutrinos, Higgs Bosons and photons. Understand them, and the forces that hold everything together, and we may finally get a handle on what makes it all tick. The trouble is, the more we drill down into the subatomic world, the more complexity we find. The bedrock of reality seems as elusive as ever. Perhaps, says a leading theoretical physicist Max Tegmark, we do not live in a world of particles and forces at all, but of pure mathematics.

The Telegraph: It’s goodbye to the universe – hello to the multiverse

The principle of naturalness

Alcuni tra i maggiori scienziati di fama mondiale stanno iniziando a considerare seriamente una proposta avanzata nel 1997 da tre fisici della University of Delaware. Se si dimostrerà corretta, essa potrebbe sfatare alcune delle scoperte che i fisici si aspettano dai prossimi esperimenti del Large Hadron Collider (LHC). Inoltre, questa idea andrebbe a supportare il concetto del multiverso, cioè l’idea che esistano infiniti universi paralleli caratterizzati da leggi fisiche proprie (post).

A Scientific American article, first published by Simons Science News, explains some of this. Linking to an influential paper by UD physics professors Stephen M. Barr, David Seckel, then-graduate student Vivek Agrawal, and John F. Donoghue, a professor and colleague at the University of Massachusetts, Amherst, the article examines the “principle of naturalness,” which for decades has been thought to govern the size of the numbers appearing in the laws of physics.

Generally, whenever some quantity was found to be much smaller than what physicists had thought to be its “natural” value, some new force, mechanism, or symmetry was discovered that explained the anomaly.

The UD professors’ 1997 publication remains one of the major documents on the subject. “It all has to do with one of the main theoretical puzzles in fundamental physics”, explains Barr. “Why is the mass of the Higgs particle 17 orders of magnitude smaller than its ‘natural’ value?” Two explanations have been proposed, and both of them predict new phenomena that should be seen by the LHC. But so far, there is no hint of them. “That is why our radical proposal nearly 15 years ago is attracting increasing attention”, he adds. Their idea is that the Higgs boson mass has to have an “unnaturally” small value for life to be possible. In other words, if it didn’t, we wouldn’t be here. Barr explains that “One way to account for this is to say that the Higgs boson mass varies place to place (which can happen in a multiverse) and only in those rare places where it has the right, unnaturally small value would life emerge and someone exist who could measure it”.

UD: Rethinking the universe - Groundbreaking theory proposed by UD faculty in 1997 suggests a 'multiverse'

Black holes as ‘products’ of the Universe evolution

The maths underpinning Darwin’s theory of natural selection could explain how the Universe may be ‘designed’ to make black holes. A new Oxford University research builds on the ‘cosmological natural selection hypothesis’, an idea first put forward in the 1990s to explain the apparent ‘fine-tuning’ of the Universe’s basic parameters to allow for the existence of atoms, galaxies, and life itself.

Cosmological natural selection proposes that, if new universes are born inside black holes, a ‘multiverse’ of many possible universes could be shaped by a process similar to natural selection so that successive generations of universes evolve to become better at making black holes. The Oxford team of evolutionary theorist Andy Gardner and theoretical physicist Joseph Conlon found that a basic equation from evolutionary genetics, called Price’s theorem, can capture the process of cosmological natural selection and explain how the Universe seems designed for the purpose of making black holes rather like a fish can seem ‘designed’ to swim underwater or a bird can appear ‘designed’ to fly. “This idea of cosmological natural selection is controversial, and physicists have pointed out all sorts of problems with it. But we were interested in seeing if its basic evolutionary logic actually works”, said Dr Andy Gardner of Oxford University’s Department of Zoology. “We found that a general equation from evolutionary genetics, Price’s theorem, can help us to model how selection can work not only at the scale of genes and organisms but also at that of something as unimaginably vast as multiple universes”, said Dr Gardner. “Our model uses maths similar to the mathematical theory underlying Darwinian adaptation in biology, which explains how the dynamics of natural selection leads to organisms appearing designed to maximize their fitness”. The researchers point out that the evolution of universes is in many ways very different from the evolution of animals. For a start, in a multiverse of many possible universes there is no real concept of change over time. However, their models of evolving universes are quite similar to models of bacterial evolution where generations evolve out of the asexual budding of cells.

Oxford University: Did the universe evolve to make black holes?

Complexity (abstract): Cosmological natural selection and the purpose of the universe

Research paper: Cosmological Natural Selection and the Purpose of the Universe