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.
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?
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?
As in the classic theory, 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.
why would alternative universes share a single source of energy? couldn’t each have their own?
I’m thinking about the theory 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 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
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.
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.
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.
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.
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.
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.
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.
Didn’t our own universe create energy and mass out of nothing? Why couldn’t others?
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.
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=5pbtgQqByJfi0OpiIn addition to what everyone else has already said, consider this: the “Universe” is by definition everything that exists. There cannot “be” things which do not exist. Therefore the question cannot be answered because it presupposes something could exist which is not part of the universe.
That’s a philosophical answer, not a scientific one.
No, it’s a logical answer. The definition of the word universe is “everything that exists”
So a multiverse can’t exist because it doesn’t match a Webster’s Dictionary definition or did you just not understand the question?
The question makes no sense because the terms aren’t well-defined. It’s like asking “are there other sets of integers besides the ones we know about?” There’s only one set of all integers. We know what the integers are by definition. If something looks like an integer, it is an integer. Similarly, you can’t ask about the existence of something which is not part of the universe, because if something exists, it is part of the universe.
The “Many Worlds” interpretation of quantum mechanics proposes that there are other universes separate from our own, perhaps even an incredible number of them if there’s one for every quantum interaction.
It’s consistent with our mathematical understanding of reality. But scientifically, it’s still an open question on whether the hypothesis is testable or whether those other potential universes will ever be observable. https://youtu.be/z-syaCoqkZA?si=5_KJB2rcscjhD9_e
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?)
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.
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
