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I am asking this question in this site as it involves some philosophy of physics...

I am trying to understand what would happen to the universe if it had no global symmetries (including those that imply conservation laws). One physicist that I found to be interested in this topic is Lee Smolin. He proposed a theory called "Cosmological Natural Selection" 1 in which the universe's laws would not be really fixed but instead they could vary with time. I have also read that he links this idea to the proposal that the universe may not have (global) symmetries (including those associated with conservation laws). In this review 2 that I found about one of his books it is said that the lack of these global symmetries would indeed imply that the laws of physics could potentially change:

Smolin is a strong proponent of Leibnitz and the principle of sufficient reason, which states that if there is more than one possibility for things to be as they are, then there must be a sufficient reason for the actual outcome being the case. He uses this to great effect in defining his principles for a new cosmology. In particular, “there should be nothing in the universe that acts on other things without itself being acted upon.” This expresses the philosophy of relationism, where every entity in the universe evolves dynamically, including the physical laws governing the universe. These laws then “become explicable only when they participate in the dance of change and mutual influence that makes the world a whole”. A consequence of relationism, Smolin argues, is that symmetries and conservation laws can only be approximations to reality.

(Bold text is mine and is added to give emphasis)

So, even if we put Smolin's own theories aside for a moment, it seems anyways that if the universe actually did not have any global symmetries after all, the laws of physics (even the most fundamental ones) could vary and evolve dynamically. Would this actually happen? I have been told both that this would actually indeed happen but also that we could live just fine without these symmetries and laws... If someone that is familiar with physics could confirm this it would be appreciated...

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  • Anthropic reasoning would seem to be more powerful
    – J Kusin
    May 29, 2023 at 18:24

4 Answers 4

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This is rather a longer comment than an exhaustive answer.

Quick answer: if the universe has no symmetries and conservation laws, then anything goes. There are no restrictions in what can happen.

Conservation laws and symmetries in a sense implement restrictions in what can happen and also some kind of causality. For example, energy cannot suddenly appear or disappear and this restricts what outcome is possible to be only from a set of outcomes compatible with fixed levels of energy.

But the above restriction also acts as causality, in the sense, that certain actions can lead only to some possible outcomes and not others. In other words, some kind of causality (for this, only that can happen, since that can only happen through this, this is the cause of that, you get the point..).

One can argue that any restriction can be expressed through some symmetry or conservation law. The term I prefer to collectively refer to all such restrictions is "compatibility conditions".

If these restrictions are not present, then really anything goes.

Note: the symmetries and conservation laws can (slowly) vary with time (eg some constants can slightly change value over time), the point here is that at any time there are restrictions in the form of symmetries and/or conservation laws even they have slightly changed from some time ago.

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Noether's Theorem tells us 'continuous symmetries under transformation', is another way of stating, what a conservation law is. Can we do physics without conservation laws? I'd say probably not, they are the basis for our predictions.

But can the symmetries change? Yes it seems like they can, like the violation of energy-conservation in an expanding universe. Eg see Sean Caroll, 'Energy Is Not Conserved'.

I would describe what Smolin is doing as looking for emergent symmetries explicable in our universe, by reference to a multiverse.

'What would happen?'

It depends on the details. The fundamental advantage of Smolin's approach would be explaining the Fine Tuning of the fundamental parameters of our physics, while maintaining a naturalistic account of how such an unlikely set occurred.

It's highly likely that without any possible access to these 'other universes', such theories will remain unfalsifiable, and so outside of science. It would be necessary for information to dissappear in some way transmitting influences away from our universes (tuning of parameters), for these new universes to 'seperate', and we just don't think there is evidence for that.

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  • "It would be necessary for information to dissappear in some way transmitting influences away from our universes (tuning of parameters), for these new universes to 'seperate', and we just don't think there is evidence for that." That is constantly happening already. Due to expansion and entropy, in the far future there will be no way to know cosmology to our standards today. That doesn't even require a multiverse.
    – J Kusin
    May 29, 2023 at 18:32
  • @JKusin: Got a reference for what you mean? The Conservation of Information is not a proven 'law', but it is a substantial expectation of mainstream physics, involved in the Blackhole Information Paradox, & the Holographic Principle. See en.wikipedia.org/wiki/No-hiding_theorem The only case I know of for information dissappearing, is blackhole three-body dynamics going below the Planck scale. See universetoday.com/145463/…
    – CriglCragl
    May 29, 2023 at 18:54
  • Oh information is never destroyed "ontologically" in any popular theory, that was clarified with the black hole wars resolving as they did, and future theories have yet to be definitive. But you said disappear, and information disappears into systems which are causally disconnected from us sans multiverse. And, this doesn't stop reasoning about these causally disconnected parts of the verse. Example, inflation is widely popular and means there is a much larger universe out there, but direct evidence there is not. We look at primordial gravitational waves, not those spacetimes out there.
    – J Kusin
    May 29, 2023 at 19:12
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Yes, this question belongs here, philosophy of science and the consequences to the rest of philosophy due to theoretical physics is a borderline issue that belongs in either forum. However the physics forum is focused on helping grad and higher physics students understand detailed issues that do not have the sort of general applicability that your question raises, so it may not be as welcome there.

That "physics theory is only an approximation to reality" is the current Popperian approach to all of science, so all our symmetries should be considered tentative, not "reality.

Relative to whether our universe HAS unbreakable symmetries, it does not. All our summitries break, so what "laws" we have in physics are regularities, not really laws. See this reference: https://www.pnas.org/doi/10.1073/pnas.93.25.14256#:~:text=Symmetry%20principles%20play%20an%20important%20role%20with%20respect,structure%20and%20coherence%20to%20the%20set%20of%20events.

Also, the Cosmological Constant of our universe has been changing. It was very high during inflation, then dropped dramatically, and has been slowly rising since the big drop at the end of inflation. Note that the CC is generated by properties of particle masses and strengths of forces in the SM so a CHANGING CC means our SM is -- changing slowly over time.

SO -- OUR UNIVERSE is one example of what it would be like to live in a universe that does not really have stable conservation laws. However, the NEAR stability and NEAR universality of our conservation "laws" are such that our universe closely approximates one in which the laws are not actually broken.

Fine Tuning theorizing has devoted some thought to the question of what criteria are needed for a universe to be able to support life, and one of the conditions needed is that at least a region of a universe have near stable constants for millions of years -- long enough for the molecular complexity creation to proceed long enough for chemical evolution to develop life. Near-stable symmetries need not actually be GLOBAL, they could be only regional.

A comment on Lee Smolin -- he is one of the best informed of physicists relative to how to do philosophy of science. He recognizes that the multiverse speculations appear NOT to actually be science, as they are basically untestable -- and in particular they can be tweaked to the point they can match ALL data, hence they are specifically unrefutable in principle.

Smolin ALSO relies upon the anthropic principle, and multiple events, to explain the apparent Fine Tuning of our universe. But rather than using a multiverse to create the large number of events that the Anthropic Principle relies upon, he uses Deep Time, and assumes we have repeated Big Bangs in our universe's history. In Smolin's approach, a prior Bang expands to near-zero density, before a new Bang occurs. There is in principle some potential for residual evidence in astronomy to discover some trace features of a prior Bang, so Smolin is trying to hold by an actually falsifiable science hypothesis.

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There are two questions here: 1) what are the consequence of symmetries that change slowly with time, and 2) what are the consequences of no symmetries at all? Here I will describe the no-symmetries-at-all case.

No symmetries means the concept of energy is meaningless. In orbital mechanics it means that there is no reason for one body (the earth, for example) to orbit another (the sun, say) at any particular radius, and at any particular speed. This means that planetary systems and galaxies and galaxy clusters and superclusters would not exist.

In chemistry it means that there would be no particular reason for one atom to covet the electron(s) of anther atom, meaning that molecules would not exist.

In atomic physics it means that there is no reason for one electron to occupy an orbital surrounding a nucleus at any particular average radius. In fact, orbitals as such would not exist, and so neither would atoms.

In nuclear physics, it means there would be no reason for one proton to bond to a neutron, and so nuclei would not exist.

Looking at quarks in this context, there would be no reason for them to occupy bound states and so neither protons nor neutrons would exist.

So: no neutrons, no protons, no nuclei, no atoms, no molecules, no planets, no stars, no galaxies.

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