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Four types of multiverses

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Most people believe that the universe began at the Big Bang, and that our universe is the only one that has ever existed. Others believe that the universe is cyclical, and that universes existed before ours: those universes, it is hypothesized, collapsed and were replaced by later universes.

When Georges Lemaître, a Belgian physicist and Roman Catholic priest, first began to develop the Big Bang Theory (in 1927), many scientists assumed the former – this is the only universe that has ever existed. In this view, it makes no sense to ask “what happened before the Big Bang?” as there was no before.

In more recent years, scientists have studied the possibility of a multi-verse. Our universe may not be the only one that has existed; perhaps others existed before our own, and others may exist after our own. Also, perhaps other universes  – in some way removed from our own – simultaneously exist.  In this view, one indeed may ask “what happened before the Big Bang?” as there was a time before our universe.

Is there evidence of a multiverse?

At the present time, most scientists say that we don’t have any direct evidence. However, astronomical and physics evidence, as interpreted through quantum mechanics and general relativity, may suggest that other universes may exist.

As such, physicists have developed models of how our universe may have been created, perhaps from the destruction of a previous universe, or perhaps ours branched off from some other.

On the other hand, some physicists hold that certain results of quantum mechanics experiments, indeed, are direct evidence of our universe physically interfering with other “nearby” quantum multiverse.

Two of the most well known adherents of this view are Max Tegmark (his work is the basis of this article) as well as David Deutsch.  See The Fabric of Reality by David Deutsch (Penguin, 1998)

A Physicist Explores the Multiverse Quantum Computers Predict Parallel Worlds by Susan Barber

David Deutsch’s multiverse carries us beyond the realms of imagination

New evidence for the multiverse—and its implications

Pilot wave theory really implies multiverse theory

Mag Tegmark Article – the four types of multiverse are

LEVEL I: REGIONS BEYOND OUR COSMIC HORIZON

Summary: The simplest type of parallel universe is simply a region of space that is too far away for us to have seen yet. The farthest that we can observe is currently about 4 ! 1026 meters, or 42 billion lightyears—the distance that light has been able to travel since the big bang.  (The distance is greater than 14 billion light-years because cosmic expansion has lengthened distances.) Each of the Level I parallel universes is basically the same as ours. All the differences stem from variations in the initial arrangement of matter.

How far away parallel Universe multiverse Tegmark

LEVEL II: OTHER POST-INFLATION BUBBLES

Summary: A somewhat more elaborate type of parallel universe emerges from the theory of cosmological inflation. The idea is that our Level I multiverse—namely, our universe and contiguous regions of space—is a bubble embedded in an even vaster but mostly empty volume. Other bubbles exist out there, disconnected from ours. They nucleate like raindrops in a cloud. During nucleation, variations in quantum fields endow each bubble with properties that distinguish it from other bubbles.

Level II Multiverse Tegmark

LEVEL III: THE MANY WORLDS OF QUANTUM PHYSICS

Summary: Quantum mechanics predicts a vast number of parallel universes by broadening the concept of “elsewhere.” These universes are located elsewhere, not in ordinary space but in an abstract realm of all possible states. Every conceivable way that the world could be (within the scope of quantum mechanics) corresponds to a different universe.

Yet these parallel universes might make their presence felt in laboratory experiments, such as wave interference and quantum computation.

Level III multiverse Tegmark quantum

LEVEL IV: Mathematical universe hypothesis

Existing outside of ur space and time, they are almost impossible to visualize; the best one can do is to think of them abstractly. We can at least create static sculptures that represent the mathematical structure of the physical laws that govern them.

For example, consider a simple universe: Earth, moon and sun, obeying Newton’s laws. To an objective observer, this universe looks like a circular ring (Earth’s orbit smeared out in time) wrapped in a braid (the moon’s orbit around Earth).

Other shapes embody other laws of physics (a, b, c, d).

According to Max Tegmark, this paradigm solves various problems concerning the foundations of physics.

Level IV multiverse Tegmark mathematical

A Level IV multiverse comes from the idea that our physical world is a mathematical structure. It means that mathematical equations describe not merely some limited aspects of the physical world, but all aspects of it.

 

External resources

Max Tegmark multiverse website. MIT.Edu

Scientific American article:Parallel Universes

Infographic: Inflation Meets Many Worlds

Are Parallel Universes Unscientific Nonsense? Insider Tips for Criticizing the Multiverse. Scientific American

The Physics of David Deutsch (older version)

David Deutsch homepage, Centre for Quantum Computation, Oxford Univ

Related articles

What Is (And Isn’t) Scientific About The Multiverse, by Ethan Siegel, Forbes

 

Learning Standards

2016 Massachusetts Science and Technology/Engineering Standards
Students will be able to:
* respectfully provide and/or receive critiques on scientific arguments by probing reasoning and evidence and challenging ideas and conclusions, and determining what additional information is required to solve contradictions

Next Generation Science Standards: Science & Engineering Practices
● Ask questions that arise from careful observation of phenomena, or unexpected results, to clarify and/or seek additional information.
● Ask questions that arise from examining models or a theory, to clarify and/or seek additional information and relationships.

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