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Simple Rules ‘Bootstrap’ the Laws of Physics

quantamagazine.org

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Re: Simple Rules ‘Bootstrap’ the Laws of Physics

#41

Post by hammock »

throw0101a wrote: post #40
jetrink wrote: post #8

The content of the article is very interesting and worth reading, but the framing feels circular. Some laws of nature are fundamental and other laws are inevitable consequences of those laws. If the inevitable laws were not inevitable, then they would be fundamental. As our knowledge and explanatory power grows, some laws that first appeared fundamental have been explained in terms of deeper laws, but we must still a…

> ... but we must still ask why the deeper laws exist. Don't things have to stop somewhere, otherwise there's an infinite regress ("turtles all the way down")?

That's the question.

Re: Simple Rules ‘Bootstrap’ the Laws of Physics

#42

Post by jordanpg »

discreteevent wrote: post #37
jordanpg wrote: post #29

Earlier quoted context omitted.

I agree with this. I've always found theories of everything to be unsatisfying in this way, because they never explain how the laws of physics got the way they are. Assuming the existence of some abstraction called spin to derive the fundamental forces is a great exercise in internal consistency, but hardly meets any definition of "bootstrapping" as I understand the term. The only theory I've ever encountered that pa…

As to how the laws got where they are Lee Smolin and Roberto Ungar say that it's possible they were not always the way they are and that they evolved spontaneously over time. And that the spontaneity just is the way things are i.e. there's no explanation for it. At least that's my recollection from reading their book. https://en.m.wikipedia.org/wiki/The_Singular_Universe_and_th... The other explanation seems to be th…

> not always the way they are and that they evolved spontaneously over time

But how did they get any way at all? How and why do they evolve?

> multiverse. i.e. we just got a random set of self consistent laws.

This raises even more questions. Why are there any multiverses with any laws at all? From where did the stuff in the multiverses come from? What initiated this chain of multiverse creation, or why is it inevitable?

A bootstrapping theory would explain why anything is inevitable, or why there is something rather than nothing. Otherwise it is just a low-level physics theory.

Re: Simple Rules ‘Bootstrap’ the Laws of Physics

#43

Post by fanf2 »

ISL wrote: post #11
hn_throwaway_99 wrote: post #3

Wondering if anyone could recommend a layman's introduction to "spin". I've read the Wikipedia article, I broadly understand it, but just curious as to how it was discovered, why it is considered an "intrinsic" form of angular momentum, and why it is so fundamental a concept in our universe.

Objects with spin can be point-like but carry angular momentum. The electron is one such particle. It is "intrinsic" because it has no known moving parts. If it had moving parts, and that motion had net angular momentum, we would refer to it in many contexts as "orbital angular momentum". Spin should seem counterintuitive. There are no macroscopic objects that I am aware whose spin you can feel with your hands. Our r…

I thought that magnetism is the result of lots of aligned spin?

Re: Simple Rules ‘Bootstrap’ the Laws of Physics

#45

Post by tus88 »

Iwan-Zotow wrote: post #36
tus88 wrote: post #2

> When bootstrapping, physicists determine how elementary particles with different amounts of “spin,” or intrinsic angular momentum, can consistently behave. In doing this, they rediscover the four fundamental forces that shape the universe. They have derived gravity through quantum mechanics? What rock have I been living under?

Feynman lectures on Gravitation, 1962

Thanks.

Re: Simple Rules ‘Bootstrap’ the Laws of Physics

#46

Post by huu »

Vysero wrote: post #20

"That solution is the graviton: a spin-2 particle that couples to itself and all other particles with equal strength." So, has this been discovered recently? I was under the impression that the graviton was theoretical?

The existence of a solution to abstract equations that involve gravitons does not imply the existence of gravitons. Designing an experiment to measure and confirm the existence of the particle is a different endeavor.

Re: Simple Rules ‘Bootstrap’ the Laws of Physics

#47

Post by smallnamespace »

jordanpg wrote: post #42
discreteevent wrote: post #37

Earlier quoted context omitted.

As to how the laws got where they are Lee Smolin and Roberto Ungar say that it's possible they were not always the way they are and that they evolved spontaneously over time. And that the spontaneity just is the way things are i.e. there's no explanation for it. At least that's my recollection from reading their book. https://en.m.wikipedia.org/wiki/The_Singular_Universe_and_th... The other explanation seems to be th…

> not always the way they are and that they evolved spontaneously over time But how did they get any way at all? How and why do they evolve? > multiverse. i.e. we just got a random set of self consistent laws. This raises even more questions. Why are there any multiverses with any laws at all? From where did the stuff in the multiverses come from? What initiated this chain of multiverse creation, or why is it inevita…

I don’t think what you’re asking for is possible, and the answer lies more in the realm of philosophy than in physics.

You can always keep asking the question ‘why?’ At some point, either you have just accept something as fundamental, or the answer justifies itself, or you have an infinite regress of whys.

Re: Simple Rules ‘Bootstrap’ the Laws of Physics

#48

Post by yters »

jejones3141 wrote: post #24

"...bootstrappers find that many different spin-0 particles are possible." Is that a typo, or is it really possible to have spin -0?

I think with some equations there is a discontinuity at zero, like tan, but it still makes sense to talk about what happens asymptotically approaching zero and then it matters from which side you approach zero, hence positive and negative zero.

Re: Simple Rules ‘Bootstrap’ the Laws of Physics

#49

Post by Iwan-Zotow »

tus88 wrote: post #45
Iwan-Zotow wrote: post #36

Earlier quoted context omitted.

Feynman lectures on Gravitation, 1962

Thanks.

Basically, Feynman starts with microscopic approach. We want to describe interaction where each piece of mass/energy is attracted to each other. So lets introduce a boson (whole number spin - 0, 1, 2, ...) to carry interaction. Then he talks about spin properties, rejects spin-1 boson (aka photon), somehow rejects spin-0 boson (I don't remember arguments) and start building microscopic theory of interacting via spin-2 massless bosons. Because they carry energy there is a self-interaction. He builds interaction rules, Feynman diagrams, and then goes to classical limit, where he derives macroscopic classic GR from microscopic quantum interactions. That's what I remember from reading this book. Apparently he did it on the fly, lots of errors in derivations which were noted and corrected in footnotes. Nevertheless, very entertaining approach...

Re: Simple Rules ‘Bootstrap’ the Laws of Physics

#50

Post by qubex »

jetrink wrote: post #8

The content of the article is very interesting and worth reading, but the framing feels circular. Some laws of nature are fundamental and other laws are inevitable consequences of those laws. If the inevitable laws were not inevitable, then they would be fundamental. As our knowledge and explanatory power grows, some laws that first appeared fundamental have been explained in terms of deeper laws, but we must still a…

The fact that the “line of reasoning is circular” is kind of the point: they are invariant fixed points in the space of possible sets of laws, such that they remain unaffected by iteration upon themselves. Kind of like Y Combinator or Turing’s Theta Combinator.
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