"As Roberto Mangabeira Unger and I argue in our new book The Singular Universe, the most important discovery cosmologists have made is that the universe has a history. We argue this has to be extended to the laws themselves. Biology became science when the question switched from listing the species to the dynamical question of how species evolve. Fundamental physics and cosmology have to transform themselves from a search for timeless laws and symmetries to the investigation of hypotheses about how laws evolve."
and
"Neurosciences are a fabulous area to work in, ripe for great discoveries. I’ve always felt this and indeed the only alternative to a career in physics that ever attracted me was a brief flirtation in college with neuroscience. But that is a field which is as bedeviled by outdated metaphysical baggage as physics is. In particular, the antiquated idea that any physical system that responds to and processes information is isomorphic to a digital programmable computer is holding back progress."
When you listen to some contemporary physicists like Nima Arkani-Hamed they seem to disagree, i.e. they believe that neither time nor space are fundamental properties of our universe but instead emerge from something more fundamental. [1] This leads of course to some really hard problems and especially it is no longer clear what physics is even about. It used to be the science of things moving through space over time, but what if you lose space and time?
> they believe that neither time nor space are fundamental properties of our universe but instead emerge from something more fundamental.
Yes, this has gained increasing acceptance ever since its first (?) suggestion from the late illustrious John Archibald Wheeler in the 1960s, and it is a very compelling idea, although yes, it makes it hard to conceive what we may be talking about.
> like Nima Arkani-Hamed they seem to disagree,
I missed it, who's disagreeing with whom about what? The parent comment doesn't seem to have content disagreeing, unless I'm missing something.
I agree. Indeed, Einstein used a this principle to formulate relativity: the principle states that the laws of physics don't vary across time or space. Indeed, properties of spacetime change from one location to another, so one could be inclined in formulating only "local laws of physics", and stating those laws change from location to location according to mass distribution among other things. But it's much more elegant to simply formulate "global laws of physics" and have constants/parameters vary in space or time.
> Indeed, properties of spacetime change from one location to another, so one could be inclined in formulating only "local laws of physics", and stating those laws change from location to location according to mass distribution among other things.
Ummm...you got it right on the first try, whereas this restatement has gone into the weeds. Local conditions (values of variables, you could say) change; the laws do not.
The final part seems to go back on track again, but by then I'm confused what you're saying.
Perhaps you're just using some kind of counterfactual as a rhetorical method or something.
>>the principle states that the laws of physics don't vary across time or space.
> This is a special case of a Noetherian invariant: all global conservation laws follow from a symmetry.
No, it isn't. I'm afraid you don't know what you're talking about.
Spatial translation symmetry lead to conservation momentum, time invariance lead to conservation of energy. No symmetry leads to "physical laws are same everywhere". That's just something you have to assume and can't derive.
"Spatial translation symmetry" is what I usually think people mean when they say "physical laws are same everywhere" -- nor is that foolish of me, that's exactly what it sounds like.
> I'm afraid you don't know what you're talking about.
Quoting from the link I posted,
> Noether's (first)[1] theorem states that every differentiable symmetry of the action of a physical system has a corresponding conservation law.
What I said was a simplified rephrasing of that, for someone who apparently did not understand physics.
Jeez. If I even so much as know the term "Noetherian invariant", then I am not totally clueless, even if you disagree about my phrasings.
Get over yourself.
Wait, you are pissed that I criticized this phrase of yours:
> Indeed, properties of spacetime change from one location to another, so one could be inclined in formulating only "local laws of physics", and stating those laws change from location to location according to mass distribution among other things.
That phrasing is either someone who doesn't know physics, or, since you claim to be a theoretical physicist, alternatively it means you are a terrible writer.
> "Spatial translation symmetry" is what I usually think people mean when they say "physical laws are same everywhere" -- nor is that foolish of me, that's exactly what it sounds like.
The thing is, it's not meant to be an insult --you literally don't know what you're talking about (or you're trolling). When we talk about symmetry, we mean a symmetry of the Lagrangian (density) that describes the system.
The Lagrangians everybody write down a priori assume that laws of physics are same everywhere.
The spatial symmetry for example just means L(x, v, t) = L(x', v, t) where x and x' are different by a small amount. An example of this in the classical context is a flat space-time with no potential (U = 0) everywhere. This just means the space "feels" the same everywhere (that is, there are no forces), which in turn means momentum will be conserved (due to the form of the action). This doesn't mean we have proved the laws of physics are same everywhere. That's an assumption we had from the beginning when we wrote down the Lagrangian.
Lack of spatial invariance in realistic systems doesn't also mean "laws of physics depend on where you are". Again, we always assume that it is true; the broken spatial symmetry just means there is a non-uniform field.
And the term that you proudly "know" ("Noetherian invariant") doesn't exist, so I wouldn't hurry and say "you're not clueless" about what you're talking about. You might wanna read that Wikipedia link you gave.
Since you're a theoretical physicist (which you didn't originally sound like), and I'm not, that would presumably mean you know a lot more about the subject than I do.
Further, my past experience is that physicists tend to frequently misunderstand physics that is outside of their own narrow speciality, so since you're more interested in being insulting than in educating, I can assume nothing about your supposed superior understanding. Seems like just ego.
Well, educating random people on the internet in physics is not my job.
I was just pointing out to a piece of misinformation before someone takes it to be true. And again, it wasn't meant to be an insult, I literally meant it and it is true --you literally didn't know what you were talking about. I only meant to state a fact. There's no need to make this something personal. For what it's worth, I'm sorry if it offended you.
In my view, not knowing things is not something bad. You can always learn things. But spreading misinformation about something you don't know (and insisting on it) is not.
> Further, my past experience is that physicists tend to frequently misunderstand physics that is outside of their own narrow speciality
???
Are you talking about physicists (faculty), or students?
Physics is a lot more connected than you think, and I haven't yet met a single physicists who doesn't know undergrad-level classical mechanics.
Edit: After reading your reply, I take that "sorry" back. For me, you're not someone worth spending even single second for. You can take this as an insult if you think otherwise.
On the one hand you say educating is not your job, on the other hand you are very concerned about misinformation -- which is a matter of education.
You thus contradict yourself for purely rhetorical reasons.
Worse yet, saying "you are wrong" is not correcting misinformation for the sake of onlookers. You need to tell them why -- which you failed to do.
I don't think you interpret English very well, and certainly you don't explain well, so it's impossible to see whether this is an area of physics you actually know or not.
So far, I am doubting that you understand this area well enough to correct others. All I see so far are two beside-the-point nitpicks.
Explain physics or stop kvetching. If it's not your job to explain, then it's unhelpful to say "you're wrong but it's not my job to explain!" Fish or cut bait.
"As Roberto Mangabeira Unger and I argue in our new book The Singular Universe, the most important discovery cosmologists have made is that the universe has a history. We argue this has to be extended to the laws themselves. Biology became science when the question switched from listing the species to the dynamical question of how species evolve. Fundamental physics and cosmology have to transform themselves from a search for timeless laws and symmetries to the investigation of hypotheses about how laws evolve."
and
"Neurosciences are a fabulous area to work in, ripe for great discoveries. I’ve always felt this and indeed the only alternative to a career in physics that ever attracted me was a brief flirtation in college with neuroscience. But that is a field which is as bedeviled by outdated metaphysical baggage as physics is. In particular, the antiquated idea that any physical system that responds to and processes information is isomorphic to a digital programmable computer is holding back progress."