Many-worlds interpretation of the infinite universe

Suppose I'm living in an infinite homogeneous universe. Then this universe must repeat itself at all scales, since the same laws apply and the conditions are all about the same everywhere.

Therefore there is another Henry Cobb who has copied my entire history (since the Big Bang) exactly, only with a huge (though finite) coordinate displacement. In fact I must have an infinite number of these history clones in all directions to infinity.

Each time I encounter some quantum event with a 50/50 chance then half my history clones turn left and stop copying me, while the other half turn right and continue to copy me. This happens a lot, but at only at a huge finite rate so I continue to have an infinite number of history clones.

Now, isn't this exactly the same as the Many-worlds interpretation of QM?

https://en.wikipedia.org/wiki/Many-worlds_interpretation

Consider a simplified model. The instant of the Big Bang has an infinite 3-D array of natural units density 1.0 smallest possible black holes packed end to end. There has been no time for signals to propagate so each history is a single unit of space, a single unit of time, and a single unit of mass-energy, so every history in the universe is identical.

https://en.wikipedia.org/wiki/Natural_units

The next tick of the cosmic clock starts cosmic inflation and the unit of space splits into eight pieces, left-back-down to right-forward-up. Ignoring decay the one unit of mass-energy will be in one of these eight locations. Therefore there is eight possible histories so far. Hence if we pick any one history there is a very good chance that it neighbors on an identical history and at worst the nearest identical history is only a few units away.

Over the next several ticks the size of each history expands greatly, giving more possibilities for what could have happened there, and the nearby histories each do their own random thing. With each 50/50 chance half the nearby identical histories continue to be identical and half diverge. Therefore the nearest remaining identical history gets further and further away on average.

That's an interesting thought, but what do you actually want to talk about it? Your OP did a good job of explaining the concept, so presumably now you have some questions you'd like to have as topics of conversation in this thread. I recommend that you post one or two of them, just to get the conversation going.

I think the problem is one of scale and human perception. You see, our corner of the universe is tiny. So while alternate histories do propagate as the OP described, the statistical odds of one where those significant changes took place in our corner of existence is actually very small.

It's a fun thought experiment, but realistically it's not very useful even if we had to technology to jump between these "worlds".

I find the "quantum immortality" thought experiment highly interesting. I hope it's for this topic. Is it?

Now, isn't this exactly the same as the Many-worlds interpretation of QM?

No, this grid of universes displays no coherent interference between universes and fundamentally as a statistical interpretation is inconsistent with any description of quantum mechanics.

Also, I think that the many world's interpretation requires a finite universe.

Hmm, how do I explain that. OK, imagine you are measuring the energy of a particle, in simple statistics say half are in the higher energy state and half in the lower so the average is in the middle and we know that the energy in will match the energy out when all the particles are used up but with quantum mechanics each particle could be either in every measurement with a finite possibility of all of them being in the highest state.

In the many world's interpretation (MWI) all of the universe starts off as one finite container of energy, measurements make it split apart into universes which will maintain energy conservation in themselves. This description requires finite containers.

edited 8th Nov '15 12:38:17 PM by SomeSortOfTroper

The basic problem that all quantum theories attempt to explain is how we can use a probability equation to predict the future location of a particle, such as treating a photon as if it were a wave, but when we actually observe the photon, it turns out to be a particle in a specific location. The Copenhagen Interpretation interprets the wave function as the particle existing in all possible states simultaneously, until it is observed, at which point the wave function collapses into one specific state.

The Many Worlds interpretation instead proposes that the particle only ever exists in one state at a time, but that at every point in time at which a quantum event occurs, the universe splits to allow all possible outcomes to occur. There is a different universe in which the photon ends up in every possible location. When we actually observe the particle, we find out which universe we are in. This implies that there are many, possibly an infinite number, of universes existing simultaneously.

One interesting wrinkle that many people ignore or are not aware of, is that Many-Worlds is a local theory, that is the effects of a split due to the collapse of a photon on Earth spreads through the universe at the speed of light. Nothing gets split until the effect of that split can reach them. So imagining a series of self-contained universes sitting side by side with each other can be considered a simplification of what the theory actually implies.

The difference in this wrinkle isn't for what's happening now, with our nearest history clone so far away, but in the first instants after the big bang when multiple identical histories would appear as the light cone expanded. Would this leave a record in the microwave background?

No. There is no communication between universes, and no evidence before the split occurs.

Difference is that we've got all same -> Differences randomly happen -> light speed communication merges the different histories.

Are we talking about eternal recurrence ? I thought that was different from the many worlds interpretation

A deep test of Quantum Physics to have finite information horizons merging over time as there's time for information to move around.

It's very difficult to visualize, but a random quantum even occurring light years away will split the universe at that location (in each universe the quantum event had a different outcome). However, we are not split into one of the different universes until the effect can spread to here at the speed of light.

The way I understand it is, if we take the wave function literally, than electrons and quarks just aren't particles.

They'll just sometimes act approximately like particles. Decoherence is the waves getting separated enough in configuration space, that they don't interact.

Something something entanglement etc.

Quick: Think of a measuring device that is not itself built out of quantum bits...

Perhaps you and I only seem non-quantum because our entangled masses move our wavelengths down to such tiny levels?

"Our entangled masses move us..." Sounds like a really geeky love poem...

That is ruthly right. Newtonian physics isn't true even on human scales and relative velocities, but it gives answers that are close enough.

Water finds its own level through quantum entanglement.