Why do we assume that the laws of nature is the same everywhere in the universe...

Why do we assume that the laws of nature is the same everywhere in the universe? Is it simply because we want deterministic models or is there more to it than that?

Why would you assume otherwise when we have never observed otherwise...?

Because sci-fi?

"It hasn't happened before so it never will" is not logical. Surely, there's a better answer than that?

Blackholes don't have laws inside.

It isn't logical, but it's the foundation of all science. Everything has an uncertainty associated with it for this reason.

They dindu nuffin

There isn't more to it than that. We can't do better than that. To claim otherwise is to give up.

Conservation of linear momentum was shown to follow from the invariance of a Lagrangian under spatial translations. aka if shit don't change when you describe it somewhere else in space, then momentum is conserved.

Empirically, linear momentum is conserved. Thus when constructing a theory, an easy way to satisfy this fact is to make it translation invariant.

The same relationship applies with temporal translations and the conservation of energy. This is part of a wider principle called Noether's theorem. It is fundamental to theoretical and mathematical physics.

And of course, some theories have found ways to satisfy the empirical fact of conservation while also constructing a universe in which the "laws of physics" are not totally the same everywhere. These are often incredibly complicated and have of course not yet been tested to satisfaction.

So everything in science is basically hypothetical.

>doesn't understand science
>posts on Veeky Forums anyway

I do believe that some cosmologists have actually taken this question seriously and tried to take into account what it would imply if they observed data that showed that certain assumed constants varied.

That's great, but I could just claim that the Lagrangian is the wrong quantity to consider and you wouldn't be able to prove me wrong. Likewise, I could claim that for QM, the quantum Hamiltonian is the wrong quantity. The only reason we use these two functions is because they agree extraordinarily well with experiment. So you're back to square one.

>The only reason we use these two functions is because they agree extraordinarily well with experiment

So by what measure do you determine the accuracy of a scientific statement, how good it makes you feel inside? And we don't just use them because they accidentally work, as you seem to be implying. Lagrangian mechanics, especially when applied to field theory, is very well defined as a mathematical concept, not just some crap that a theoretical physicist came up with but can't explain.

I think you're missing my point. From completely mathematical arguments and a strict definition of a wave function, you can derive something that looks exactly like the time dependent Schrodinger wave equation for some operator. The reason we use the Hamiltonian is because it works. By analogy, we used to believe that velocities add such that the speed of a ball which is being thrown at 10 mph on a train which is travelling at 50 mph looks like its travelling at a speed of 60 mph to a person on the ground. According to SR (which is a more complete theory), the ball travels at a slightly different speed. In the same way, I could claim that we are using the wrong operator for the TDSWE, but under some implicit assumption, it reduces to the Hamiltonian. That would be ludicrous and I would never make that claim because there is currently no reason to believe this idea and the success of QM is extraordinary. However, to give all of the credit to the theoretical physicists is a huge mistake.

Lagrangian mechanics is not a well defined mathematical concept as you claim. In a way similar to the argument above, Noether's theorem only takes us so far. The Lagrangian as it is defined reduces to give the same results as Newtonian dynamics, but there is no pure mathematical reason to choose L = T - V. If you know of a way to show that L = T - V is the value that must be used in the functional without appealing to Newton's Laws or experiment, then write that up.

>there is no pure mathematical reason to choose L = T - V.

That's classical mechanics, and it's not what I'm talking about. In field theory, one constructs a Lagrangian such that the Euler-Lagrange equation (which is rigorously defined) yields the field equations.

If you can find a Lagrangian that yields the Dirac equation through the ELE, then that Lagrangian is THE Dirac Lagrangian. Then the spacetime translation invariance of this Lagrangian, meaning that the rules which govern the motion of matter - the Dirac equation - are the the same everywhere, implies that in this theoretical construct of matter (a field) satisfies the empirical truth of conservation of momentum and energy.

The process of building a theory like this can happen in reverse too. You can postulate a Lagrangian by throwing in combinations of fields and their derivatives and such that are Lorentz invariant by construct, and then apply a normalization procedure to scale these combinations to each other and find the Lagrangian that produces the correct wave equation via the ELE.

A theoretical physicist asks his theory to have certain properties since it is well known that they should be true, and then he is presented with the conditions of these properties and their consequences. This field is well defined. For example, the properties we've been discussing in this thread are the properties of invariance under a generalized coordinate transformation. This is something that was developed by mathematicians. A functional we call the Lagrangian (density) defined on a space being invariant under a change in coordinates necessitates by Noether's theorem that there is an object associated with the Lagrangian that is conserved in a specific way by these types of transformations. It so happens that matter and energy fall into the category of things we can describe in this way. Until we learn otherwise, consider it a coincidence that Energy (density), classically defined by T-V is that quantity.

Another example is general relativity. The Einstein field equations can be derived by simply requiring the Einstein-Hilbert action to be invariant under arbitrary variation of the metric and the curvature of the space. Just from that, you can construct theories for Gravity in an arbitrary number of dimensions. Interesting, it doesn't work for 2 dimensions or less.

Physical theories aren't as arbitrary as "L=T-V works because it works" in the way that you are making them out to be. The most amazing developments of the 20th century can be understood just by physicists seeing what the requirements of nature are if we decide to change things arbitrarily. It's as if we ask what must be true for a theory to be flexible, and the answer contains more than we ever expected or even put into the question.

Physical theories aren't arbitrary and I never claimed that. Pinpoint where the disagreement is. And let's bring it back from this one specific example of the Lagrangian, which has turned into a rabbit hole.

My underlying point is that there are many instances in which experimental results drive theory forward and that we cannot derive all of physics in a vacuum. You seem to have such an idealized vision of theoretical physicists, but the truth is that sometimes (rarely) it is "just some crap that a theoretical physicist came up with but can't explain" as in the case of the solution to the ultraviolet catastrophe and the birth of Quantum Mechanics. I would even boldly state that Rayleigh was doing better science than Planck even though his results were crap.

Maybe we are bringing too much science into a question which is philosophical in nature. What prompted all of this was the problem of induction and the uniformity of nature which are phrases that I haven't even seen in this thread.

Because if they aren't the laws of the Universe, they aren't the laws of the Universe.
If our laws don't cover everything in the Universe we have to formulate new laws to explain local phenomenon

Okay I see what you mean.
Historically, no development happens in the way that is most mathematically natural. Only with knowledge can we speak in retrospect and say that all we have learned can be explained by a small number of arguments. But nature can be explained that way, if you're good enough at manipulating the language with which we describe it.

If you want to talk about induction and philosophy, I'd suggest starting a thread on Veeky Forums. I like to talk about Hume, but it's not one of those questions that you can actually answer definitively one way or the other. And a question that cannot clearly be resolved by science, and most definitely not by today's science that is all done trapped in Earth's gravity, is not a question that many people on Veeky Forums can participate in. The way I see it, it's also not what OP wanted to know. he asked about models, not the unverifiable truth of a reality which may be inconsistent.

>
>I think you're missing my point. From completely mathematical arguments and a strict definition of a wave function, you can derive something that looks exactly like the time dependent Schrodinger wave equation for some operator. The reason we use the Hamiltonian is because it works. By analogy, we used to believe that velocities add such that the speed of a ball which is being thrown at 10 mph on a train which is travelling at 50 mph looks like its travelling at a speed of 60 mph to a person on the ground. According to SR (which is a more complete theory), the ball travels at a slightly different speed.

Can you tell me where I need to search for more info about it?

About what?

>deterministic models
>QM
Anyways meta-laws like symmetry and conservation necessitate the physical laws and rules that we see.
These "meta-laws" don't necessarily guarantee the same rules in other universes but they do here

>Why do we assume
What do you mean by "we", as/sci/tard?

Sure they do, right down to the singularity.

>Why do we assume that the laws of nature is the same everywhere in the universe?
Actually we don't.

There have been investigations if physical constants really are the same across the entire (visible) universe.

And I don't think anyone assumes the laws are the same inside a black hole singularity.

Universe is uniform, why shouldn't it be?

Cosmic Microwave Background.

It neither is uniform nor is it a good example.
In addition to the CMB pointed out by there is also the different matter concentrations on many levels: starts, galaxies, superclusters and more.

Yes, allowed for by the primordial lumps created by quantum energy density fluctuations at the beginning of time.

The gravitational waves produces by such fluctuations would have been frozen in place during inflation, however those which began to oscillate when the universe was approximately 380,000 years old (the age of the CMB) would be detectable.

These waves would have distorted space in such a way that radiation would appear polarised and if we can detect such a signal, then we can calculate the nature of the quantum fluctuations that are responsible for the slight deviation from uniformity observed throughout the universe, and subsequently the formation of galaxies, stars, planets, people and quantum skeletons.

cost a few hundred millions to prove it
>Wilkinson Microwave Anisotropy Probe
and get this picture

It COULD sell the whole notion of god particles... but neh

this guy There are no laws of nature. That is just a shorthand way of saying we have a story about the world that is consistent and reflects the world for the intent of the story.

All we ever have is a story, and a story should reflect the world. The question about why we assume the laws of nature are the same everywhere shows that you have confused the world, which is indistinguishable from a story of randomness without a story to give meaning to actions, with the story in your head which has turned on itself.

You can't corroborate the world without a story, and that story making process introduces biases simply by the way we make stories. You can't tell a story about the world without using a story, and so you put an actor in the story - your laws.

But besides that, why would you then doubt that the story would apply everywhere? What about the story you have or the story making process makes you wonder if the story is valid somewhere else without any flaw in your story to make you think so?

>Why do we assume
What do you mean by "we", Peasant?