Tag: Erwin Schrödinger

The Case For Multiverses

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The Case for Multiverses

The  case for multiverses co-existing with our own is gathering more belief, indeed recently  The presenter, author and physicist Brian Cox says he supports the idea that many universes can exist at the same time.

The idea may sound far-fetched but the “many worlds” concept is the subject of serious debate among physicists.

It is a particular interpretation of quantum mechanics – which describes the often counter-intuitive behaviour of energy and matter at small scales.

In a famous thought experiment devised by the Austrian physicist Erwin Schrodinger, a cat sealed inside a box can be both alive and dead at the same time. Or any combination of different probabilities of being both dead and alive.

This is at odds with most common perceptions of the way the world is. And Schrodinger’s experiment was designed to illustrate the problems presented by one version of quantum mechanics known as the Copenhagen interpretation.

This proposes that when we observe a system, we force it to make a choice. So, for example, when you open the box with Schrodinger’s cat inside, it emerges dead or alive, not both.

But Prof Cox says the many worlds idea offers a sensible alternative.

“That there’s an infinite number of universes sounds more complicated than there being one,” Prof Cox told the programme.

“But actually, it’s a simpler version of quantum mechanics. It’s quantum mechanics without wave function collapse… the idea that by observing something you force a system to make a choice.”

Accepting the many worlds interpretation of quantum mechanics means also having to accept that things can exist in several states a the same time.

But this leads to a another question: Why do we perceive only one world, not many?

Schrodinger's cat - illustrationSchrodinger’s thought experiment was designed to illustrate problems with one interpretation of quantum physics

A single digital photograph can be made from many different images superimposed on one another. Perhaps the single reality that we perceive is also multi-layered.

The laws of quantum mechanics describe what happens inside the nucleus of every atom, right down at the level of elementary particles such as quarks, gluons. leptons, charm, muon et al with the now discovered Higgs Boson holding them all.

The weird and wonderful world of quantum mechanics reveals that nature is at heart probabilistic. Nothing can be predicted with any certainty.

“Everybody agrees about that” says Prof Cox. But where physicists don’t agree is about how these facts should be interpreted.

For decades, the Copenhagen interpretation of quantum mechanics, which allows for only one universe, dominated particle physics.

But Brian Cox supports the many worlds interpretation and, he believes, more and more physicists are now subscribing to this view.

The certainty of uncertainty

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The certainty of uncertainty

Quantum Physics is both a fascinating and frustrating branch of science. With ever-evolving sub-atomic  particle research technology like the Large Hadron Collider (LHC) probing deep into the mysterious and almost magical realm of fundamental matter that makes up the universe and us, below is an excellent hopefully easier to us laypeople a  guide  behind a famous thought experiment:

WHEN IT COMES TO its ability to formulate accurate explanations and make testable predictions, the science of quantum mechanics is one of the most successful theories of all time. Despite its astonishing successes, quantum mechanics has an unfortunate side effect – it can induce the cerebral equivalent of dropping a jellyfish into a blender and transform the human brain into a quivering mess of gelatinous denial.

Quantum mechanics is the theoretical construct that allows scientists to describe how matter behaves at the subatomic level. To say that it is weird is an understatement of galactic proportions and perhaps the weirdest of all its predictions is something called ‘Heisenberg’s uncertainty principle’.

Thought up by genius physicist Werner Heisenberg in 1927, the uncertainty principle states that, in the quantum world, it is impossible to simultaneously know where a particle is and where it is going – you can know its position, or you can know its momentum, but you can’t know both.

Ok, so perhaps that doesn’t sound so very strange, but the reason why you can’t know both quantities is very strange indeed.

If you were asked to describe a particle, chances are you would imagine it to be a discrete, spherical lump of matter (like a teeny tiny ball bearing), but you’d be wrong. In quantum mechanics a particle is more of a wavy smudge of spread out potential – a cloud of possibility where the particle exists in multiple states and in multiple positions.

The uncertainty principle allows you to only determine one of those possibilities by saying that as you zero in on a particle’s position, so your ability to measure its momentum slips away. It’s a bit like rolling a dice – as it scoots along the tabletop you can see where it’s going but the numbers are a blur (it could stop on anyone of them), only by stopping the dice can you ‘force’ it to choose a number.

This indeterminate nature of the stuff makes up the world around us didn’t well with scientists – after all, who wants to believe that the particles you are made of exist in a state of quantum flux? Even the physicists that created the science of quantum mechanics were uncomfortable with the predictions it made (which led Erwin Schrödinger to create his famous dead-and-alive cat in a box mind experiment).

For decades, some scientists have expected (and hoped) that uncertainly would one day be proved false and that predictability would be returned to the Universe. But it seems that their hopes might have been dashed by physicists at the University of York who believe they have proof that the limits imposed by uncertainty are just as Heisenberg described them.

By constructing a theoretical experiment in which measurements of particles with known values were compared with those of particles whose states were unknown, they found that the errors in their measurements matched with Heisenberg’s original predictions.

Ok, so it was a lot more complicated than that, but their conclusion could prove to be a boon for quantum cryptography – messages encoded in such a fashion would, in theory, be unbreakable because any attempt to ‘see’ the message would force the multiple-state quantum bits that make it up to ‘collapse’ to a single state (thus ruining the message).