this post was submitted on 14 Nov 2023

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In the most scientific way possible? How real is the possibility that there might actually be alternative universes? (lemmy.ml)

submitted 1 year ago by [email protected] to c/[email protected]

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[–] [email protected] 54 points 1 year ago

As the others here are implying, the current consensus in the Physics community is that the many worlds hypothesis is not falsifiable, and so should be disregarded in favor of funding theories that can be proven or disproven. String theorists, the biggest proponents of the many worlds theory, are generally ostracized from greater physics academia since they have failed to produce any experimental designs to validate their claims for several decades after taking up a lot of tenured positions in the 90's, along with the "pop science" PR campaigning for their position that started then with some popular books and continues to this day in the works of Michio Kaku for example.

Relevant panels by leading physicists here: https://youtu.be/CNjckutR7BE?si=t88BigaInz01zamL
and here: https://youtu.be/eOvqJwgY8ow?si=5pbtgQqByJfi0Opi

[–] [email protected] 31 points 1 year ago (5 children)

Scientifically, we cannot yet talk about theories that are untestable and unfalsifiable. Sure, math or some other theory may imply other dimensions or parellel universes, but how will you measure one?

[–] [email protected] 15 points 1 year ago (1 children)

Would a ruler suffice?

[–] [email protected] 5 points 1 year ago (2 children)

Oof sorry. Gonna need a protractor.

[–] [email protected] 4 points 1 year ago

That doesn't measure up for me.

[–] [email protected] 3 points 1 year ago (1 children)

Is that a tractor that lost its amateur status?

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[–] [email protected] 6 points 1 year ago (8 children)

Scientifically, there are no theories that are untestable and unfalsifiable.

[–] [email protected] 5 points 1 year ago (2 children)

How can you test/falsify the existence of something you can't interact with in any way?

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[–] [email protected] 3 points 1 year ago (1 children)

If your mathematical model tells you something should exist, doesn't that necessarily mean that it's something you can interact with, and thus measure given sufficiently advanced technology?

[–] [email protected] 1 points 1 year ago

Perhaps but it's still not testable at that point.

[–] [email protected] 1 points 1 year ago* (last edited 1 year ago)

Interestingly, parts of this universe are right now becoming unmeasurable, un observable, unfalsifiable to us even now. With dark energy propelling the expansion of space at an increasing rate, far-away regions of space can be moving away from us faster than light. This means they’re no longer part of our observable universe - we’ll never be able to reach them, see light from there, interact with these places in any way. Not the same universe anymore.

Someday living beings in the Milky Way might believe it’s the only galaxy that exists because no others will be observed. If one of them postulates that maybe there are all these other galaxies that are just out of reach - pinched off from our universe - in parallel universes you might say…. if someone says all that, it could also be just as handily dismissed.

[–] [email protected] 23 points 1 year ago

In the most scientific way possible, there's no way these could affect our own. If they did, we'd consider that mechanism part of our universe. Real possibility - of course it's real. There's just absolutely no way to know, even if you made the question a lot more specific. (What does it mean, specifically? What would you expect to see if it were true vs false?)

[–] [email protected] 19 points 1 year ago

As real as math

[–] [email protected] 17 points 1 year ago (1 children)

Max Tegmark came up with different "levels" of multiverse, and the first level only depends on the universe (not just observable) being infinitely large in volume - which as I understand it seems likely to be the case. (Certainly hasn't been ruled out at least)

Given infinite space with accompanying infinite matter/energy, there will be infinite repeats and near repeats of the stuff in any given volume of space - the volume of the observable universe for example, meaning us and everything we can interact with (even just see) is repeated infinite times, and with all physically possible variations.

And that's without any particular interpretation of quantum mechanics.

[–] [email protected] 3 points 1 year ago* (last edited 1 year ago)

dang, cosmology is weird. I went to reply about the big bang, the age of the universe, and how it can't be infinite, but instead decided to look it up. I really don't understand this stuff.

[–] [email protected] 12 points 1 year ago (2 children)

Not everyone in this comment section uses correct nomenclature. It would be preferable for those bugged by it to use empathy to understand the true meaning of the comments (or, if impossible, to ask politely about the meaning) and to correct the mistakes in a nice way, avoiding the urge to take the wrong words litterally - that doesn't add to the discussion.

[–] [email protected] 5 points 1 year ago

Hopefully that can be the case in one of the multiverses. I doubt it will be this one.

[–] [email protected] 3 points 1 year ago* (last edited 1 year ago)

You mean I shouldn't react emotionally and impulsively because I disagree and feel personally offended by the first sentence in your comment?

[–] [email protected] 6 points 1 year ago* (last edited 1 year ago)

You might enjoy this recent lecture from Neil Turok: https://youtu.be/rsI_HYtP6iU

Over the past decade or so he's been putting out papers with a model that's only a slight change to the standard model - that at the point of the big bang there was an expansion in both directions of time leading to a CPT symmetric universe.

He and his coauthors have managed to address a number of the major outstanding unsolved challenges in cosmology with only this theory, and are perhaps only a few years away from having some of its testable predictions verified. And at least one of the recent CERN projects that would have falsified the idea came up short just the other year.

If he lives long enough, he may well end up with a Nobel for his efforts.

It's probably my favorite bit of theoretical cosmology these days.

[–] [email protected] 5 points 1 year ago

According to the many worlds interpretation of quantum physics there's not only alternative universes, but that there's an infinite amount of them including ones exactly like this one with just slight variations.

[–] [email protected] 4 points 1 year ago

This video from PBS Space Time is a good summary of the current state of science on this topic. https://youtu.be/z-syaCoqkZA?si=nRK78T_FAD5By-f0

[–] [email protected] 4 points 1 year ago* (last edited 1 year ago) (2 children)

As in the classic ~theory~ idea, that each time a decision is made a new reality is created for each choice? For it to be possible would break our fundamental laws regarding conservation of mass and energy. Where would this alternative universe get all that energy and mass from? It’s possible our current understanding of the law is inaccurate, but it’s extremely unlikely.

[–] [email protected] 11 points 1 year ago (1 children)

why would alternative universes share a single source of energy? couldn't each have their own?

[–] [email protected] 4 points 1 year ago* (last edited 1 year ago) (4 children)

I’m thinking about the ~theory~ idea that involves a new universe being created every time a decision is made. Like if I flip a coin and get heads, another universe suddenly pops up where I got tails. It would need to create its own energy and mass out of nothing, which would break the laws of conservation.

I’m not super well versed in multiverse ~theories~ hypotheses though. It is slightly more probable that when our universe began existing, so did all the other alternative universes, in which case they would all have their own energy and mass. But then there would be essentially no chance that we would have alternative selves like in classic multiverse theories, since each universe would have started from the very beginning of time and evolved on its own path.

Edit: some wording

[–] [email protected] 3 points 1 year ago* (last edited 1 year ago) (1 children)

Just to play around with the idea: If we assume that an infinite number of universes were created at the moment of the Big Bang, and these only differ in random outcomes of quantum fluctuations, the would imply that there exist an alternate universe for every conceivable choice made, simply because there are infinitely many universes. They didn't appear when the choice was made, but they just happen to diverge from our own in some specific moment.

Hell, just presuming that the universe is infinite actually implies that there are an infinite number of "observable universes" outside our own observable universe. That in turn leads to the same result: If there is an infinite number of "observable universes" then there must be one universe that diverges from ours exactly ant the moment of every coin flip and every decision made.

Someone please tell me why I'm wrong, this hurt my head a bit.

[–] [email protected] 3 points 1 year ago (1 children)

This is all definitely getting to a point where it hurts my head too haha. My husband (a mathematician) has talked to me about the idea that infinite = every possible permutation of circumstances exists. Think about all the numbers between 0 and 1, it’s infinite. Now think about how many numbers exist between 0 and 2: also infinite, but also double the amount of infinite from 0 to 1. And all of those infinite numbers still exclude every other number that exists outside of the range of 0 to 2. So even if we do have infinite universes, that doesn’t necessarily mean there is a universe for every single tiny variation.

[–] [email protected] 2 points 1 year ago (1 children)

Hmm, I'm not sure about the first part there: For every number between 0 and 2, I can divide that number by 2 to get a unique number between 0 and 1, so there must be exactly the same amount of numbers in [0, 2] as in [0, 1]. By the same argument, for every number in [0, 1], I can multiply it by 2 to get a unique number in [0, 2]. Infinities are funny like that, but I'm not a mathematician, so there may be a hole in that argument.

From that, I don't see the argument that there wouldn't be a universe for every possible option. If there is an infinite number of universes, than for every possible random event (at the quantum scale if you will), the probability is 1 that any outcome happened in some universe, in fact every outcome should occur in an infinite number of universes. The probability that any two universes remain "aligned", or in the same state, decreases extremely rapidly of course, but that doesn't matter, because there are infinitely many of them, so an infinite number will always remain "aligned".

For example, if there are (right now) an infinite number of universes that are perfectly identical to ours, and I flip a coin, there will be infinitely many where it lands heads and infinitely many where it lands tails. If we follow that argument backwards, that for every random event there are an infinite number of universes experiencing every possible outcome, we'll get back to a moment in time where there were an infinite number of identical universes right after the Big Bang.

[–] [email protected] 2 points 1 year ago (1 children)

Wait, you lost me in the first part. For simplicity sake, let’s have two sets of numbers. Set A has the numbers 4, 5, and 6, a total of 3 whole numbers. Set B has the numbers 1 and 2, a total of 2 whole numbers. The number 4 from set A can be divided by 2, giving us the unique number 2 from set B. Set A and set B still have different amounts of numbers in them.

My husband is also chiming in, to simplify my original statement. Set C is [0, 1], an infinite range. Set D includes both [0, 1] and the number 2. Subtract set C from set D, you are left with just the number 2. Therefore, the number of elements in set D is exactly one larger than set C, even with both sets being infinite.

[–] [email protected] 2 points 1 year ago* (last edited 1 year ago) (3 children)

Now we're speaking the same language, I'll try to reformulate what I was saying.

Let's say you have the set [0,2], and I have the set [0, 1]. To check which is bigger, we play a "game" where you pick a number from your set, and I respond with a number from mine. Whoever runs out first has the smaller set. What I do, is that every time you say a number, I just divide it by two, and respond with what I get. That way, I can find a number in [0, 1] for every number in [0, 2], so [0, 1] can't be smaller. If we flip the situation, you can take whatever number I say, and multiply it by two to get a number in your set, so [0, 2] can't be smaller. Since none is smaller, they must be the exact same size.

Now I'm on thin ice, but I would love to know if there's an error in the following argument: We play the same "game", but now you have the set [0, 1] + {2}. For every number you say, I can still divide it by two to get a number in my set, so my set still isn't smaller. For every number I say you can:

Multiply it by two if it is in {1, 0.5, 0.25, ...}, i.e. a power of ½
reply with the same number otherwise

That way, you can get every number in your set from a number in mine, and opposite, so the set [0, 1] + {2} is the same size as the set [0, 1]. In other words, an uncountable infinity + 1 is the same size as it was before (might have something to do with the uncountable part).

I believe what we have done is create a bijection, that is: find a way to map every unique number in one set to a unique number in the other.

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[–] [email protected] 2 points 1 year ago* (last edited 1 year ago)

Why would it need to create energy and mass out of nothing? Why are assuming the energy either comes from nothing or wasn't already there. Or better yet, that nothing as a source is a problem to begin with?

Conservation of energy applies to a universe. There are no such rules written out for imaginary multiversal mechanics. The "but mass and energy" thing gets thrown in the trash long before we reach this point, we stopped talking about matters of mass and energy two paragraphs ago. It's the same as asking "but why CAN you fly in your dreams? What about gravity, what happened to it?".

They don't exist. No one can prove otherwise yet. They're as bullshit as whatever we want them to be.

[–] [email protected] 2 points 1 year ago* (last edited 1 year ago)

I'm no expert either but I never got the idea of a new universe popping up everytime. Do other universes also cause popups of new universes or just ours? That'd escalate quickly :-)

I thought it goes that there's already infinite universes existing from the big bang on. Otherwise universes would be created without big bang. (The new universe would just pop up and you'd still believe it was created by the big bang but there never was one)

Also I'm not sure if laws of thermodynamics had to span accross universes. Take two theoretical perfect vacuum/radiation sealed boxes you put an energy source into. There's no way to communicate between boxes. Each box had it's own entropy and state of energy. Both would obey the laws of physics while being separate "systems".

That thought experiment wouldn't work, if new boxes had to pop up if one of the boxes wanted to.

[–] [email protected] 2 points 1 year ago (1 children)

Didn't our own universe create energy and mass out of nothing? Why couldn't others?

[–] [email protected] 5 points 1 year ago

IIRC, our universe didn’t create mass and energy from nothing, it was all packed into an exceptionally small point in space and the energy was likely in a form completely unknown to us before the Big Bang. I can’t discount that there may be more of those densely packed points somewhere in the universe that could be used to form new universes. We can’t detect anything like that now, but that doesn’t mean it doesn’t exist.

[–] [email protected] 2 points 1 year ago* (last edited 1 year ago) (1 children)

Where did all the energy in the universe come from? This is not physics, it's methaphysics. We are talking about things that are outside our knowledge and science is descriptive, not prescriptive. Extrapolations must be tested. This is not much different from saying that the most remote galaxies receding at speeds faster than light is impossible, because nothing can travel faster than light. Maybe it's just matter that can't break that rule, while space itself can expand at whatever speed, or maybe it's just an error somewhere in our assumptions. We still don't know. But we DO think they are receding faster than light.

[–] [email protected] 1 points 1 year ago

That's not a very good example I don't think. I'm no cosmologist, but my understanding is that we know pretty well that distant celestial objects are moving away from us faster than the speed of light. Special relativity doesn't really say anything about non local objects, and the expansion of space does not violate locality. No information is being transmitted faster than the speed of light. The medium through which light is traveling is changing. It's not some big unsolved mystery.

[–] [email protected] 2 points 1 year ago* (last edited 1 year ago)

I like Neil Degrasse Tyson's take on this one. At first we thought there was only one Sun, then we figured out the sun was a star, like so many others. Then we thought there was only one galaxy, then we figured there are much more than that.

Now we think there is only one universe, but it seems nature isn't very good at creating only one version of something. It's not unreasonable to think there are many universes. We just can't prove/observe it yet.

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