Physics

# Insight to Quantum Physics 1: Parallel World Reality

## Introduction

Many Worlds Interpretation (MWI) states that the existence of many parallel similar worlds at the same time and space apart from the world that we all are aware of.  The fundamental idea of MWI was introduced by Everett in 1957 [1]. Think of a situation where each time a quantum experiment with different outcomes and non zero probability is performed. According to this interpretation, all outcomes are obtained in each different particular world though we are aware of and seen only one world outcome.

## Concept of ‘World’ and ‘Universe’

The concept of world and common attitude shared by human beings differ due to the variations of the perception based on religious beliefs. Even the concept of world in MWI is somewhat different with several features.As we all know that each object in this world is made up of elementary particles such as protons, neutrons, electrons etc. Consequently, the world and hence the universe can be explained as the totality of these particles. But in MWI, such microscopic elementary particles might be in a superposition.

For an example, the probability of an individual radioactive element’s atom that will decay is indicated by quantum theory but within the ranges of probabilities it is hard to tell the precise time of the particular decay that will take place. Think that you have some atoms of radioactive elements which have a decaying chance of 50% in two hours. Then in two hours, 50% of those particular atoms will decay. Until the measurement is made for a given atom, there is no possible way to tell whether it is decayed or not according to traditional quantum theory (Copenhagen interpretation). In fact you need to treat the atoms if it is in a superposition of states: both decayed and not decayed. If it is so, then MWI concludes that there should be two universes in existence: one in which the atom is decayed and one which is not decayed.

If we measure a quantum object, it causes an actual split of the universe according to Everett.  Here, literally the universe is duplicated by splitting each universe to accommodate for each possible outcome. For another example, think of an object’s wave function which is of both a particle and wave form. There are two possible outcomes if we measure this particular object as it can be either measured as a particle or a wave. So, a physicist in one universe finds out that the object can be measured in particle form. The same physicist in another universe measures the same object as a wave. This explains how one particle can be measured in several states.

Even if an action has several outcomes then the universe splits when that particular action is taken and it also happens when the chosen action is not put into action too. It means that if your pet is in a death situation as a possible outcome, then in a parallel universe to our one, your pet is dead.

In short in MWI, each time when a random event takes place, there is a split of universe between the various available options. A different outcome of that particular event is contained on each separate version of the universe. This results a creation of infinite number of quantum universes. In MWI, for each possible outcome of an action, the universe splits and it is an instantaneous process called as decohesion. This can be further explained using choose your own adventure story books. Here rather than choosing specific alternatives such as exploring the castle, reading old treasure map, find the treasure, fight with the enemy etc., the universe splits into copies so that each particular action is taken. When the universe splits, the particular person is unaware of his existence in other versions of universe. That means for example, the hero who found the treasure ends up living happily is completely unaware of his other version that entered the castle who now faces death and vise versa.
In fact, Everett postulated that all isolated systems evolve according to Schrödinger equation. In MWI, the universe is treated as an isolated system where there is continuous existence in a superposition of multiple states.

## Concept of ‘I’

‘I’ am an object like cat, table, car etc. ‘I’ can be defined at a particular time by a complete description of my body and its functions. For simplicity, let us use an example name called ‘Tom’. At this present moment, there are many different Toms in different worlds and not more than one in each world. It is not viewed as another ‘I’ because I have a well defined past; I correspond to a particular Tom in 2014 even though I do not have a well defined future. I can correspond to a multitude of Toms in 2014. According to MWI, it is disturbing and unsettling to ask, Which Tom in 2014 will I be? I will correspond to them all.Each time when I perform a quantum experiment with several outcomes, it only seems that I obtain a single definite result. Tom who obtains this particular result also thinks like this. However, this particular Tom cannot be identified as one and only Tom after the experiment as Tom before the experiment corresponds to all Toms obtaining all the possible outcomes. Parfit in 1986 [2] considered some artificial situations where a particular person splits into several copies. He argued that how can we answer to the question: Which copy is me?

This particular personal identity concept seems to be ambiguous to ordinary living beings. How can a person be aware of his other selves’ existence and death in parallel universes? How do we ever know MWI is either a fantasy or a correct theory?

## Myths of MWI

The parallel world/universe concept have provided as the foundation for number of science fiction series such as ‘Fringe’ recently. But none of these have provided a strong scientific background as science fiction authors have been very keen and creative in developing storylines among parallel universes. In MWI, when a particular universe is split, it is unique from each other and does not allow communication between the parallel universes that it proposes.

## Quantum Suicide

In late 1990s from a thought experiment which was an imagined experiment used to prove or disprove theoretically called quantum suicide gave an assurance that the MWI is theoretically possible. It was proposed by Max Tegmark in 1997.In quantum suicide, there is a man with a gun. When he pulls the trigger there are two possible outcomes: the gun either fires or not. Even the man either lives or dies as a result.

Each time the trigger is pulled, the universe splits to accommodate the possible outcomes. When the man dies, the universe is unable to split based on pulling off the trigger. The possible outcome for death is reduced to one continued death. Comparatively, with life there are two remaining chances: the man dies or continues living. When the man pulls the trigger and the universe splits in two versions. However the version where man lives will be unaware that in the other split universe he has died. He will continue to live and will again have the chance to pull the trigger. Each time he pulls the trigger, the universe will split again with the living version of the man continuing on an on while being unaware of all of his deaths that occur in parallel universes. In other words, he can exist indefinitely. This is what is known as quantum immortality.

If so, all of people who have attempted to kill themselves can be immortal? According to MWI, in some parallel universe they are. We are observers of another person’s suicide and this does not apply to us as the universal splitting is not dependent on our life and death situation. As observers we are subjected to probability. For example, when the gun went off in one particular universe in which version we witness the suicide, we are stuck with that particular outcome. Let us think that we continue to shoot the man but the universe will remain in a single state. Finally, once the man is dead, the number of possible outcomes for shooting the dead man is reduced to one.

Actually, this thought experiment renewed the interest of MWI which was highlighted for many years under arguments and debates in the scientific community. Yet, MWI is not only the theory that aids to explain neither our universe nor the suggestion of the existence of parallel worlds. MWI itself stands in contradictions with Copenhagen interpretation too. Hence it is not the most accepted quantum theory among physicists but it has become popular [3] over the years.

References

1. Everett, H., (1957) ‘Relative State Formulation of quantum mechanics’, Review of Modern Physics 29, pp. 454-462
2. Parfit, D., (1986) Reasons and Persons, New York: Oxford University Press
3. Tegmark, M., (1997) ‘The Interpretation of Quantum Mechanics: Many Worlds or Many Words?’, Fundamental Problems in Quantum Theory, eds Rubin, M.H and Shih, Y.H, Wiley

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1. shehan

November 2, 2015 at 9:41 pm

This is really helpful. Great article. I really like it. Got an idea about quantum physics. Thanks 🙂

• kimbra

November 2, 2015 at 10:55 pm

Wow great article

November 3, 2015 at 7:28 am

You have presented the MWI mostly wrong.That is not at all what it states. We have gone through this here in this forum a number of times. The following write up may help you.
First of all, MWI isn’t a theory. It’s a philosophy.
“Here’s what the many-worlds interpretation isn’t: Every time a quantum system is measured, instead of “collapsing” into one or another definite state, it actually exists in all states simultaneously, and which one we observe depends on which of the many worlds our minds are a part of at the time.
Complete hogwash.
What Everett’s doctoral thesis was actually getting at was the idea that measuring the state of a quantum system doesn’t “collapse” it at all, but rather causes the measuring equipment and the observer to become part of the system. In this way, the probability of finding the system to be in any of the other states all destructively cancel out, so you’re left with only one possible state in which to find the system. That’s the state the observer measures.
In other words, quantum systems only look “weird” — in the Schrodinger’s-cat sense of things being simultaneously this and not-this in a way that seems impossible — when you’re observing them from the outside. Once you interact with a quantum system, you — you the person doing the observing, as well as all the gadgets and gizmos you use to observe it — become part of the system, and classical, deterministic behavior is recovered.
This stands in opposition to the philosophy of the Copenhagen school, which holds that quantum systems exist in weird indefinite states only when nothing’s interacting with them, but then as soon as something does interact with them — be it another particle or a scientist in a lab — those systems “snap” into a definite state.
Basically, the difference between the philosophies is who’s “real” and who’s “indeterminate” at any given time. The Copenhagen school holds that isolated quantum systems are indeterminate, but become real when interacted with. The Everett school holds that isolated quantum systems are just as real as anything else, but only look real once the observer becomes a part of the system and starts canceling out possibilities that would otherwise contradict each other.
To the layperson — as well as, for that matter, the working physicist — none of that means a darned thing, of course. It’s pure philosophy. There’s no science involved whatsoever, really. It’s all just conversation about what the equations mean. Pretty much everybody who actually works with the equations agrees that they don’t mean anything, and that the universe is what it is, and our job as investigators of it is to describe it, not to try to superimpose some kind of woo-woo meaning on it all.”

• Nerdynaut Team ✓

November 3, 2015 at 10:13 am

There are different views from different academics about variations of this concept.
http://science.howstuffworks.com/science-vs-myth/everyday-myths/parallel-universe2.htm
http://stanford.library.usyd.edu.au/archives/fall2005/entries/qm-manyworlds/#Bib

• Nerdynaut USA Team ✓

November 3, 2015 at 10:47 am

The many-worlds interpretation is an interpretation of quantum mechanics that asserts the objective reality of the universal wave function and denies the actuality of wave function collapse. Many-worlds imply that all possible alternate histories and futures are real, each representing an actual “world” (or “universe”). In lay terms, the hypothesis states there is a very large—perhaps infinite—number of universes, and everything that could possibly have happened in our past, but did not, has occurred in the past of some other universe or universes. The theory is also referred to as MWI, the relative state formulation, the Everett interpretation, the theory of the universal wavefunction, many-universes interpretation, or just many-worlds.
MWI’s main conclusion is that the universe (or multiverse in this context) is composed of a quantum superposition of very many, possibly even non-denumerably infinitely many, increasingly divergent, non-communicating parallel universes or quantum worlds.
Many-worlds is often referred to as a theory, rather than just an interpretation, by those who propose that many-worlds can make testable predictions (such as David Deutsch) or is falsifiable (such as Everett) or by those who propose that all the other, non-MW interpretations, are inconsistent, illogical or unscientific in their handling of measurements; Hugh Everett argued that his formulation was a metatheory, since it made statements about other interpretations of quantum theory; that it was the “only completely coherent approach to explaining both the contents of quantum mechanics and the appearance of the world.” Deutsch is dismissive that many-worlds is an “interpretation”, saying that calling it an interpretation “is like talking about dinosaurs as an ‘interpretation’ of fossil records.”

November 3, 2015 at 7:36 am

Dark matter

4. Raul G Azcuna

November 3, 2015 at 7:37 am

true great man.

5. Sunny

November 3, 2015 at 12:39 pm

Informative and interesting…good job

6. Krishni Perera

November 12, 2015 at 1:38 pm

Helpful article.This is one of my favorite fields in Physics.Thank you very much.

7. niro

November 16, 2015 at 11:52 am

prefect article

8. Sachith

February 9, 2016 at 9:03 am

Nice article, very simply explained.
Keep it up….

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