Infinite number of universes
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warpus
Sommerswerd asked me to change this
Say that the Universe is infinite and the above is allegedly true. Wouldn't the uncertainty principle prevent you from comparing events to ensure that everything that is possible exists? Not only that, wouldn't it make every single event distinct, even if all measurement tests yielded equal results?
classical_hero
In whom I trust
The whole point of multiple universes is to deny the obvious fact that the one we live in is tailor made for us to live in. It is impossible to prove or deny this proposition, thus it is a philosophical matter and not a science matter.
warpus
Sommerswerd asked me to change this
If it's not a matter of science then you can't say that it is obvious. If it was obvious you could apply the scientific method and formulate a testable theory. You can't, so it's not obvious.
Mathilda
Queen
Moderator Action: Moved to S&T
BasketCase
Username sez it all
You've got it backwards. A drinking glass is not the perfect shape to match the shape of the water within it; it is the water that shapes itself to the glass. Similarly, it is not the universe that is perfectly tuned for life; it is life that is perfectly tuned for the universe.
....as we know it. Had those physical constants been different, some other kind of life would have evolved.
Nope. The same amount of space is still present inside an event horizon. If the Earth was a black hole, its event horizon would be nine millimeters across; the space inside is still a sphere nine millimeters across, and definitely finite. But if you bumped into it, whatever parts of you happened to cross the event horizon would disappear from your body (ow). You wouldn't be "sucked into" a black hole of Earth mass because it would only be pulling on you with the force you're feeling from the Earth right now, a force you can easily resist (try raising your arm).
Loppan Torkel
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So, is the Greek mythology likely true in some parallel universe?
Terxpahseyton
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Thank you.
holy king
Deity
i have no idea what the universe actually looks like, but i love how basket case knows it exactly and beyond any doubt.
There are two distinct interpretations of modern physics and mathematics that postulate an infinite amount of universes. Although the reasoning behind them is related, you nevertheless have to distinguish between those.
The first one is the Many-Worlds interpretation (MWI) of quantum mechanics. One of the unsolved problems of quantum mechanics is: If there is a state that supports multiple results with a certain probability and we always measure one exact result, when is it decided what the result will be. The MWI avoids this problem by postulating that every result happens, just in different universes.
If it was true, every universe would have the same starting point and every universe would follow the same laws of physics. So every outcome that is possible according to these laws would be realized in one universe. But scenario that violates our laws of physics would not be possible (and I think we can agree that Greek mythology is in this category).
The second is an interpretation of String Theory (although "theory" is a bit of a misnomer, I will use it here). The goal of String Theory was to show that the laws of our universe follow from the solution of the string equation. However, a few years ago it was shown, that there exist at least 10^500 and possibly infinite solutions of that equation. But some people, instead of acknowledging that String Theory has been a failure at deriving our laws of physics, postulate that every solution is realized in its own universe, leading to a (nearly) infinite amount of universes.
If this was true, each universe would have different laws of physics and no common starting point. Therefore it becomes very hard to predict what would be possible and what would not be possible as there is not much investigation what the actual effects of other physics would be.
These two frameworks for infinite universes are no mutually exclusive, so one could also postulate an infinite times infinite number of universes. But one has to keep in mind, that these are not scientific theories in any way, just interpretations, which we have no actual evidence for (and so far we do not even know whether it is in principle possible to collect evidence for them)
The first one is the Many-Worlds interpretation (MWI) of quantum mechanics. One of the unsolved problems of quantum mechanics is: If there is a state that supports multiple results with a certain probability and we always measure one exact result, when is it decided what the result will be. The MWI avoids this problem by postulating that every result happens, just in different universes.
If it was true, every universe would have the same starting point and every universe would follow the same laws of physics. So every outcome that is possible according to these laws would be realized in one universe. But scenario that violates our laws of physics would not be possible (and I think we can agree that Greek mythology is in this category).
The second is an interpretation of String Theory (although "theory" is a bit of a misnomer, I will use it here). The goal of String Theory was to show that the laws of our universe follow from the solution of the string equation. However, a few years ago it was shown, that there exist at least 10^500 and possibly infinite solutions of that equation. But some people, instead of acknowledging that String Theory has been a failure at deriving our laws of physics, postulate that every solution is realized in its own universe, leading to a (nearly) infinite amount of universes.
If this was true, each universe would have different laws of physics and no common starting point. Therefore it becomes very hard to predict what would be possible and what would not be possible as there is not much investigation what the actual effects of other physics would be.
These two frameworks for infinite universes are no mutually exclusive, so one could also postulate an infinite times infinite number of universes. But one has to keep in mind, that these are not scientific theories in any way, just interpretations, which we have no actual evidence for (and so far we do not even know whether it is in principle possible to collect evidence for them)
No. There is a wide range for these physical constants making all life impossible. If hydrogen was the only stable nucleus no complex systems could form.
Do you know what MWI does with the probability of the various outcomes? Say, we've got the following state: 3/5 |a> + 4/5 |b>, with a and b two distinct eigenstates of some operator C. If we measure C, we'd normally get |a> with chance 9/25 and |b> with chance 16/25. Now, in MWI, do we get |a> in 9/25th of all universes?
No, I don't think so. I am not exactly sure how MWI proponents count their universes, but I think every branch of the universal wavefunction that has decohered to the point where it does not interact with any other branch counts as one universe. The coefficient of each branch gives us the probability to end up in that universe.
So if we measure C, we end up in the state:
3/5 |we measure a>*|a> + 4/5 exp(i*phi) |we measure b>*|b>
where phi is a random phase. So there are two branches which correspond to two universes, each with their own probability. We'll find ourselves with 9/25th in universe A and with 16/25th in universe B (and here the philosophical troubles of the Copenhagen interpretation creep in again through the back door)
BasketCase
Username sez it all
No. The Greek Gods only exist as stories written by people.
A parallel universe wouldn't produce nonsensical new objects--it would contain different versions of the same objects. In a parallel universe, Greek mythology would still be stories written on paper; the stories would be different. The Trojans beating the siege and conquering the Achaeans, or Hector defeating Achilles, or some such.
Uhh....yeah. I know what it looks like because I can see it. I can look at how dimensions work. I look at the first dimension: width. A universe taking the form of a line. I can move left, and I can move right. The second dimension is perpendicular to the first, adding forwards and backwards. The third dimension is perpendicular to the first two; now I've got up and down.
Obviously all higher dimensions must follow the same rules: each successive dimension adds one new axis of motion which is perpendicular to all the others. The addition of these higher dimensions doesn't create any wierd new psychadelic space; they're all extensions of the space you're sitting in right now, and you already occupy a specific location in those higher dimensions (just as a two-dimensional object can occupy a location in three-dimensional space). And the Greek Gods can't be real in the higher dimensions, because they don't exist anywhere in the first three.
That we know of. Change the physical constants, and you don't only invalidate the current interactions--you also create new ones.
Second problem with your statement....how do we test it??
Sure they could. Complex systems made only of hydrogen. Our universe comes pretty close--everything in it is built from only three distinct building blocks (protons, neutrons, and electrons). Which in turn may be composed of only one (the quark).
Actually, strike that--our current universe already contains lots of pretty damn impressive objects made almost entirely from hydrogen. Stars.
Loppan Torkel
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Of course there could be different objects. If your parents didn't meet, you wouldn't be around. If that meteor/comet missed earth, dinosaurs could still be here, etc, and if laws of physics could exist that are different from ours, but still compatible, separate universes could exist where other entities, different from what we're used to, could exist.
PeteAtoms
FormulaRandom
That doesn't really sound right... maybe I'll go check it out myself.
Changing the physical constant neither invalidates nor creates new interactions, it just changes the strength of them. So your point is invalid.
And we could test it by building a quantum simulator in which we engineer the Hamiltonian to simulate a system with these different constants.
If the strong interaction was a bit different and hydrogen was the only stable isotope, the only molecule capable of existing would be the H2 molecule. And the only systems you could build with those would be a lot of hydrogen together. But even that would be quite dull, as no nuclear fusion would be possible and thus you would have no star but just a ball of hydrogen.
And your knowledge of the building blocks is quite limited as your statements are just wrong. The universe is not built from three building blocks, but there is a whole zoo of particles that we know of (and we do not even know what dark matter is made of).
And there is not just one quark, but there are twelve different types of quarks and antiquarks that we know of that form hadronic matter (and electrons are certainly not composed of quarks).
Gamemaster77
PC > Mac
He's right. There's six different quarks, neutrinos, and other particles such as *grabs my old quantum physics book* muons, baryons, mesons, etc.
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