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Here is a thought.

Let us assume the there is an infinite uni-directional line of balls. And it is being jumbled up again and again, randomly. (say by 'God'!)

I in my limited experience/capacity can 'observe' only 10 balls. And I see that the positions of balls alternate in pairs. Say if balls are numbered 1 to 10, ball at position 1 takes 2 position and 2 comes to 1's position and this keeps repeating. And similarly for balls (3,4) to (9,10) - I call this pattern a 'Law' - "Balls alternate with their immediate following neighbor if they are at odd position or with their immediate preceding if they are at even position". (That such a pattern will be there is guaranteed by the fact the line of balls is infinite and jumbling is random - an assumption about infinity and randomness)

Assume suddenly I'm able to observe 20 balls and the above rule breaks - so I come up with another cleverer rule that applies to all 20 balls and claim this is the 'new' universal law.

But in reality / in totality there is 'no' pattern - there is 'no' law - there are just local patterns that emerge in this game which is actually 'random'.

Is the above a valid way of looking at Physics? What are the arguments against it? How can we be sure that there are universal laws without having the capacity to observe the entire universe?

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    $\begingroup$ I'm voting to close this question as off-topic because it does not have the form of a question. The content seems to imply multiple questions, you could make actual questions out of it, it could be many, and interesting! $\endgroup$ – Volker Siegel Mar 14 '20 at 8:33
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    $\begingroup$ "How can we be sure that there are universal laws without having the capacity to observe the entire universe?" by itself is actually a pretty good question! $\endgroup$ – Volker Siegel Mar 14 '20 at 8:37
  • $\begingroup$ That it is possible to find laws that describe patterns valid over everything we can observe is already an amazing thing in itself. This much works, since that's precisely what physics is about. So the game is definitely not 'random'. Now if by universal laws based on the observation of all the universe you mean that every observed detail has to be mathematically modelled, then that IMO is confusing the map with the territory and set up a whole new ambition: that of ensuring that the whole universe is a mathematical model. $\endgroup$ – Stéphane Rollandin Mar 14 '20 at 9:06
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    $\begingroup$ @aman_cc You got a interesting answer and upvotes. It will get closed, but it will stay here as useful, which is pretty good. (It can not get new answers after closing, but it's not deleted). The last sentence alone asks a question much deeper than you might expect, it is a excellent way of looking at physics. I keep my close vote, but give it an up vote too. $\endgroup$ – Volker Siegel Mar 14 '20 at 12:47
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    $\begingroup$ this answer of mine is relevant physics.stackexchange.com/questions/349587/… $\endgroup$ – anna v Mar 14 '20 at 17:10
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One of the key aspects of a theory is to specify its domain of validity in which it is self consistent. In your example of when we observe just $10$ balls, we have a “law” that is valid in that domain. So you may ask what the is point of the “law” when it isn’t valid for $20$ balls? Well, in the domain of validity we can use that law and build a framework and all will be well and good. For example Newton’s laws are not valid in the atomic scale, so it isn’t universal. But are they of no use? Definitely not!

But if you begin with the assumption of existence of some property (pattern) of your infinite chain of balls that is independent of where you start looking at it, and show that this predicts all other local patterns with as little additional assumptions, then that “law” is more fundamental. These are called symmetries of the system.

This is something amazing about the way nature is! Some laws that we conjured up to explain local behaviour somehow can be extrapolated to understand phenomena that the laws weren’t derived from, or to make new predictions that are then observed to be true!

How can we be sure that there are universal laws without having the capacity to observe the entire universe?

At the end of the day science is empirical. Thus our laws are actually hypothesis that haven’t been disproven yet. And a sign of a good law is the measure of its (domain of) applicability. Any self-consistent theory that doesn’t make observable predictions is technically not science.

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  • $\begingroup$ Thanks I think I understand what you say. Q1 - Is there any law of physics which is then "truly" universal i.e. is a "symmetry of universe" as per your definition? Q2 - If ans to the above Q1 is no - then is there a understanding/research/theorem that such a universal law is NOT possible? (I know I'm hitting some kind of self contradiction if the ans to this Q is Yes). Guess I'm bit confused here - but thanks for your ans $\endgroup$ – aman_cc Mar 14 '20 at 11:39
  • $\begingroup$ Unable to edit the comment above but what I exactly meant in Q1 was - Q1 - Is there any existing law in physics which is then "truly" universal i.e. is a "symmetry of universe" as per your definition please? $\endgroup$ – aman_cc Mar 14 '20 at 12:01

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