Discovering the Fundamental Ideas of Physics: From Atoms to Conservation Laws

[americanforest]

Here is an interesting question that my urge for simplification and basic/fundamental understanding has lead me to ask:

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What would you say are the most fundamental ideas of Physics, the most fundamental science? By fundamental what I mean is, what laws/ideas do you think are the minimal theoretical basis from which all our current knowledge (and possibly more) can be derived?

Or more succinctly:

What are the ideas that comprise the foundation of Physics as we know it today?

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On a similar subject, Richard Feynman states (from The Feynman Lectures on Physics):

"If, in some cataclysm, all scientific knowledge were to be destroyed, and only one sentence passed on to the next generation of creatures, what statement would contain the most information in the fewest words? I believe it is the atomic hypothesis (or atomic fact, or whatever you wish to call it) that all things are made of atoms — little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another. In that one sentence you will see an enormous amount of information about the world, if just a little imagination and thinking are applied."​

I hesitate to give my opinion because I am only an second year Physics student and I still have an immense amount to learn but I will try just to start off:

1. The discreteness of matter at the smallest scales

-Feynman's "Atomic Fact"​

2. Conservations of Energy and Momentum

-The most basic conservation laws​

3. The Idea of a phase space cell

-This is my attempt to condense the Exclusion and Uncertainty and other key Quantum Mechanics principles into one idea​

4. The constancy of the speed of light

-Special Relativity can mostly be derived from this idea​

5. All fundamental forces are manifestations of four "forces" and are described by certain properties (charge, etc.) and respective conservation laws

-I'm sure this can be put more succinctly​

6. The Idea that we live in the middle of a spectrum of sizes in our universe that ranges from incomprehensibly large to incomprehensible small and that both of those extreme domains cannot be understood using our "middle of the road" intuition.

 

[Q_Goest]

That's a good question and I think you have a good start on the answer.

On number two, add conservation of mass to momentum and energy.

The other one that always comes to mind is locality. No information can be transmitted faster than light.

Conservation laws and locality lead to local, causal interactions.

In physics, the principle of locality is that distant objects cannot have direct influence on one another: an object is influenced directly only by its immediate surroundings. This was stated as follows by Albert Einstein in his article "Quantum Mechanics and Reality" ("Quanten-Mechanik und Wirklichkeit", Dialectica 2:320-324, 1948):

The following idea characterises the relative independence of objects far apart in space (A and B): external influence on A has no direct influence on B; this is known as the Principle of Local Action, which is used consistently only in field theory. If this axiom were to be completely abolished, the idea of the existence of quasienclosed systems, and thereby the postulation of laws which can be checked empirically in the accepted sense, would become impossible.

Ref: http://en.wikipedia.org/wiki/Principle_of_locality"

 

[Marco_84]

Thats all good, but i also think that the main principle that it has been used more frequently in modern knwoledge is OCKHAM RAZOR!

i, sometimes, ask my self if that is a "good" way to make science!

regards
marco

 

[americanforest]

On number two, add conservation of mass to momentum and energy.

There are a couple of reasons I didn't include conservation of mass:

1. Unlike the two other conservation laws, Conservation of mass is only a non-relativistic approximation to Physical reality. Thus, although certainly useful in Chemistry and some domains of non-relativistic Physics, it is not completely true.

-As an example, consider an atomic nucleus. The total mass of the full system (the entire nucleus) is smaller than the mass of its constituent particles.​

2. Conservation of mass is simply a manifestation of conservation of energy and thus, cannot be considered truly "Fundamental"

To quote Einstein on the subject (from What is the Theory of Relativity?, 1919):

"The most important upshot of the Special Theory of Relativity concerned the inert mass of corporeal systems. It turned out that the inertia of a system necessarily depends on its energy-content, and this led straight to the notion that inert mass is simply latent energy. The principle of the conservation of mass lost its independence and became fused with that of the conservation of energy: "

$$E_{0}=m_{0}c^{2}$$​

The other one that always comes to mind is locality. No information can be transmitted faster than light.

The fact that no information can be transmitted faster than light can be derived from the Special Theory of Relativity. I included in my original list (at number 4) the constancy of the speed of light with the idea that this theory could be derived from this one fundamental axiom. Thus, the impossibility of speeds above c no longer seems fundamental, being nothing more than a indirect result of the constancy of the speed of light.
Locality does seem to be independent of any of the axioms on my original list so you're right, it should be included as it is certainly fundamental.

Conservation laws and locality lead to local, causal interactions.

It is interesting to consider the four fundamental forces as being simply "enforcers" of these conservation laws and of the locality axiom instead of being something independent. In this case, number 5 of my original list appears clumsy and non-fundamental and can be restated as:

5. There exist four fundamental forces, which act to maintain all of the above axioms.

Thats all good, but i also think that the main principle that it has been used more frequently in modern knwoledge is OCKHAM RAZOR!

Ockham's razor is certainly an important principle which states, in the words of William of Ockham:

"Entia non sunt multiplicanda praeter necessitatem" or "Entities should not be multiplied unnecessarily."​

​

Although a good theoretical guideline for the development of all science, this isn't a fundamental Physical axiom, which is what we're after.

 

[Q_Goest]

The conservation of energy plus mass is more fundamental than the conservation of energy or conservation of mass alone of course.

There have to be many papers on this topic in philosophy of science, though I don't know what the important ones may be. All this seems to be fairly basic stuff, so I wonder what a good reference for this would be. Maybe someone can suggest one (or many).

 

[Marco_84]

Ockham's razor is certainly an important principle which states, in the words of William of Ockham:

"Entia non sunt multiplicanda praeter necessitatem" or "Entities should not be multiplied unnecessarily."​

​

Although a good theoretical guideline for the development of all science, this isn't a fundamental Physical axiom, which is what we're after.

so tell me what is a PHYSICAL reasoning, postulating isotropy of space you get conservations... and so on... but to follow theese insights you need a guide principle that tells you which is the best frame to work in!
am i wrong?

regards
marco

 

[Q_Goest]

so tell me what is a PHYSICAL reasoning, postulating isotropy of space you get conservations... and so on... but to follow theese insights you need a guide principle that tells you which is the best frame to work in!
am i wrong?

regards
marco

Hi marco,
I tend to agree with americanforest on this one. Ockham's razor isn't a physical principal (axiom) on par with conservation principals. It's more of a guide.

This question is one that always intrigues me, so I'm interested in hearing what others may have to say also.

 

[rbj]

4. The constancy of the speed of light

-Special Relativity can mostly be derived from this idea​

i would say it as

4. The constancy of the laws of physics, independent of who the inertial observer is.

-Special Relativity can mostly be derived from this idea​

and leave the constancy of the speed of propagation of E&M as well as the other fundamental forces as a consequence of the constancy of the laws of physics for every inertial observer.

 

[LURCH]

I think the most fundemantal principle in the physical sciences is causality. For any other scientific idea to make sense, we must start with the understanding that every "thing" (event, physical reality, whatever we wish to call it), is caused by some other thing. This can be broken down into two principles; that no physical event happens "for no reason" (or without being caused), and that nothing is its own cause. All other scientific principles derive from this one. Without it, one can claim with validity that things are as they are, "just cause they are," and no science can take place.

 

[americanforest]

so tell me what is a PHYSICAL reasoning, postulating isotropy of space you get conservations... and so on... but to follow theese insights you need a guide principle that tells you which is the best frame to work in!
am i wrong?

No, you're not wrong; We do need ideas like Ockham's Razor to "follow these insights" but my intent in this discussion wasn't to "follow" them (i.e. use them to derive more specific, non fundamental, laws). We just want to find out what these original Physical "insights", or laws, are.
Now that I think about it, I think that for the same reason we can cut my original statement of #6 off of our list

6. The Idea that we live in the middle of a spectrum of sizes in our universe that ranges from incomprehensibly large to incomprehensible small and that both of those extreme domains cannot be understood using our "middle of the road" intuition.

for the same reason that we reject Ockham's Razor.
I've never heard your point about the isotropy of space providing conservation principles before but I don't want to divert this thread so I won't ask you to explain here. However, I'd really appreciate it if you could send me a private message with an explanation or some reference.

i would say it as

4. The constancy of the laws of physics, independent of who the inertial observer is.

-Special Relativity can mostly be derived from this idea

and leave the constancy of the speed of propagation of E&M as well as the other fundamental forces as a consequence of the constancy of the laws of physics for every inertial observer.

Yes, this is much better than my original version. Let me be a little bit nit picky and state it as:

4. The constancy of the laws of physics, independent of any physical characteristics of the inertial observer.

I think the most fundemantal principle in the physical sciences is causality. For any other scientific idea to make sense, we must start with the understanding that every "thing" (event, physical reality, whatever we wish to call it), is caused by some other thing. This can be broken down into two principles; that no physical event happens "for no reason" (or without being caused), and that nothing is its own cause. All other scientific principles derive from this one. Without it, one can claim with validity that things are as they are, "just cause they are," and no science can take place.

I know that causality is obviously fundamental in macroscopic Physics but, as I have little experience with Quantum Mechanics, I can't really speak for causality in that context. Causality there certainly seems much less obvious to me.

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So, the current list is:

1. No Physical event happens without a cause, and no event is its own cause.

-Once again, I'm not sure about this in a Quantum context​

2. Conservations of Energy and Momentum

-perhaps should be replaced with a statement concerning the "isotropy of space" according to Marco​

3. The Idea of a phase space cell

-This certainly presents the fact that particles are localized in a certain spatial volume which is why I felt justified in getting rid of the original statement of number 1, which was Feynman's "Atomic Fact"​

-I am no expert on the subject but, as I understand it, for a event to take place the phase space cells of the interacting particles and of any intermediate vector bosons must all overlap, thus implying locality and making this statement more fundamental than one of locality. If I misunderstand the concept please correct me.​

4. The constancy of the laws of physics, independent of any physical characteristics of the inertial observer.5. There exist four fundamental forces, which act to maintain all of the above axioms.

-I'm not sure about this one, it seems too simple. What do you all think?​

 

[rbj]

No, you're not wrong; We do need ideas like Ockham's Razor to "follow these insights" but my intent in this discussion wasn't to "follow" them (i.e. use them to derive more specific, non fundamental, laws). ... Let me be a little bit nit picky and state it as:

4. The constancy of the laws of physics, independent of any physical characteristics of the inertial observer.

actually, your "nit picking" made it worse. you must have had some nits on your fingers that got into your subject's hair.

besides Occam's Razor, there is a Einstein's related warning:

Things should be described as simple as possible, but no simpler.

 

[americanforest]

actually, your "nit picking" made it worse. you must have had some nits on your fingers that got into your subject's hair.

Well then let me try to get those nits back out with more picking.

I don't see how I made your original version worse. I only tried to make it sound more physical by replacing the statement involving a specific "who" with a statement concerning a set of "physical characteristics".

I propose we compromise on Wikipedia's statement of this:

The laws of physics are invariant for the transition from one inertial system to any other arbitrarily chosen inertial system

By invoking Einstein's quote, were you implying that my statement was not "as simple as possible" or that it was "simpler"?

I don't want this discussion to degenerate into a exercise in semantics but after all, with a subject as important as the fundamental axioms of Physics, it is important to be careful with wording and meaning.

 

[Dr. Courtney]

Thats all good, but i also think that the main principle that it has been used more frequently in modern knwoledge is OCKHAM RAZOR!

Occam's Razor is a philosophical preference, not an epistemological principle, and certainly not a scientific result.

Strictly followed, Occam's Razor demands that we accept the simplest possible theoretical explanation for existing data. However, science has shown repeatedly that future data often supports more complex theories than existing data. So why should we be so sure that the simplest theories are the right ones?

We shouldn't. Science has a preference for the simplest explanations that are consistent with the data, but history shows that these simplest explanations often yield to complexities as new data becomes available.

Occam's Razor rejected DNA as the carrier of genetic information in favor of proteins, since proteins provided the simpler explanation. Occam's Razor rejected the sun-centered model in favor of the geocentric model, and it would have certainly viewed Kepler's or Newton's laws as unreasonably complicated had they been offered in Galileo's time. Theories that reach far beyond the available data are rare, but General Relativity provides one example.

Michael Courtney

 

[Marco_84]

Occam's Razor is a philosophical preference, not an epistemological principle, and certainly not a scientific result.

Strictly followed, Occam's Razor demands that we accept the simplest possible theoretical explanation for existing data. However, science has shown repeatedly that future data often supports more complex theories than existing data. So why should we be so sure that the simplest theories are the right ones?

We shouldn't. Science has a preference for the simplest explanations that are consistent with the data, but history shows that these simplest explanations often yield to complexities as new data becomes available.

Occam's Razor rejected DNA as the carrier of genetic information in favor of proteins, since proteins provided the simpler explanation. Occam's Razor rejected the sun-centered model in favor of the geocentric model, and it would have certainly viewed Kepler's or Newton's laws as unreasonably complicated had they been offered in Galileo's time. Theories that reach far beyond the available data are rare, but General Relativity provides one example.

Michael Courtney

I agree wth your main line reasoning, but not all of them!
I posted that because, especially in physics, we use paradigms, principles etc. that just fit our current data... citing your're words...

marco

 

[Dr. Courtney]

I agree wth your main line reasoning, but not all of them!
I posted that because, especially in physics, we use paradigms, principles etc. that just fit our current data... citing your're words...

marco

Should not all sciences play by the same set of epistemological rules?

Is not the foundation of all that repeatable experiment is the ultimate arbiter of theoretical validity?

If Occam's Razor was one of the epistemological rules, then we should demand that it is completely general and applicable to all of the sciences. But it is not completely general in any single discipline, much less all of them.

Consider the theory that the Earth is round that was espoused by the greeks and supported with measurements that provided a reasonable estimate of the Earth's diameter. This theory was largely rejected by the europeans for many centuries since it seemed simpler to them that the Earth is flat.

The atomic theory was also originally espoused by the greeks, but reasoning akin to Occam's Razor delayed its acceptance until Einstein's description of Brownian motion. Even though chemistry had provided considerable support for the atomic theory, the notion that matter is continuous seemed simpler.

Likewise, Newton's idea of light particles seemed simpler than Young's idea of waves, so many clinged to it. And once the wave idea was accepted, the idea of aether as a transmission medium seemed simpler than transmission through a vacuum.

The point is that it's not possible for Occam's Razor to be a scientific principle rather than an aesthetic preference because a suitable definition for "simpler" is absent. Which is simpler, particle or wave, aether or vacuum, flat Earth or round?

Occam's Razor is also much less than general in biological matters. For example, DNA testing would conclude with a very high level of certainty that I am the natural father of seven children. My birth certificate says that I was the result of a single birth. All of the children were born after I was married, although only four were born to my wife. It would seem that my wife has a solid case for divorce, and the mothers of the other three children have a solid case for paternity suits. Occam's Razor would have me in dire straights indeed!

But the fact is that I only fathered the four children that were born to my wife. The other three children were fathered by my identical twin brother. But Occam's Razor would conclude that I must be the father of all seven until paternity analysis progresses to the point of distinguishing between children of identical twin fathers. This might not ever happen. My birth certificate that says "single birth" is in error because it is a re-issued certificate that is simply wrong. We suspect that since we were born in New Orleans, hurricane Katrina destroyed our original birth records.

Which is simpler, to believe that a man whose DNA matches paternity for seven children really fathered all seven or to believe that three of those children were fathered by an identical twin brother whose existence cannot be proven because the birth records were destroyed in hurricane Katrina?

Michael Courtney

 

[Marco_84]

Should not all sciences play by the same set of epistemological rules?

Is not the foundation of all that repeatable experiment is the ultimate arbiter of theoretical validity?

If Occam's Razor was one of the epistemological rules, then we should demand that it is completely general and applicable to all of the sciences. But it is not completely general in any single discipline, much less all of them.

Consider the theory that the Earth is round that was espoused by the greeks and supported with measurements that provided a reasonable estimate of the Earth's diameter. This theory was largely rejected by the europeans for many centuries since it seemed simpler to them that the Earth is flat.

The atomic theory was also originally espoused by the greeks, but reasoning akin to Occam's Razor delayed its acceptance until Einstein's description of Brownian motion. Even though chemistry had provided considerable support for the atomic theory, the notion that matter is continuous seemed simpler.

Likewise, Newton's idea of light particles seemed simpler than Young's idea of waves, so many clinged to it. And once the wave idea was accepted, the idea of aether as a transmission medium seemed simpler than transmission through a vacuum.

The point is that it's not possible for Occam's Razor to be a scientific principle rather than an aesthetic preference because a suitable definition for "simpler" is absent. Which is simpler, particle or wave, aether or vacuum, flat Earth or round?

Occam's Razor is also much less than general in biological matters. For example, DNA testing would conclude with a very high level of certainty that I am the natural father of seven children. My birth certificate says that I was the result of a single birth. All of the children were born after I was married, although only four were born to my wife. It would seem that my wife has a solid case for divorce, and the mothers of the other three children have a solid case for paternity suits. Occam's Razor would have me in dire straights indeed!

But the fact is that I only fathered the four children that were born to my wife. The other three children were fathered by my identical twin brother. But Occam's Razor would conclude that I must be the father of all seven until paternity analysis progresses to the point of distinguishing between children of identical twin fathers. This might not ever happen. My birth certificate that says "single birth" is in error because it is a re-issued certificate that is simply wrong. We suspect that since we were born in New Orleans, hurricane Katrina destroyed our original birth records.

Which is simpler, to believe that a man whose DNA matches paternity for seven children really fathered all seven or to believe that three of those children were fathered by an identical twin brother whose existence cannot be proven because the birth records were destroyed in hurricane Katrina?

Michael Courtney

OK,
I think i'll have to make some examples to let me understan, because i cannot explain my self as good as u can, obvi. this is not my mothertongue.

What I am trying to say is that, theories like Spec.Rel. had been chosen because they introduced less postulates wrt others.

QM has less postulates therefore is easier to explain chemistry reactions, bindings etc..
against the complicated explanations of the XVIII century chemistry, obvious they put the first stones..

The geocent system is easier then tolomeo's with cycles and epicycles...

About u're DNA argument i think it is true if we use okkam razor we have to choice for the 7 children option; but in this moment i think we are using a knife not a razor :)
I mean that if the twins are present and we can recognize that they are twins for real we could admit the first possibility ; this because now we have more datas (we can prove the existence of the twins) and now we can move to another theory right?

What I am trying to say is: occam razor is not a science principle (you were right) but as a science tool that is/had been used many times.
I personally think that we have to use it with caution, in fact science roughly is: BUILDING MODELS; and until Brahe, Copernico,Galielo... The Tolome's model was good enough to predicts many things. hope you understan what i mean.
So at the end what say: It's not always good to make postulates (fundamental also) because growning technologies and knowledges it is possible to disprove some of them, but they are necessary to the development of conossaince. In all our progress i think that the razor has been used many times and that's why i said it was a very fund postulate. maybe yes it is more an instrument to make knowledge instead of a postulate; But if we make the discipline of knowledge i believe that we agree that occam razor could be a good principle.
regards
marco

 

[Dr. Courtney]

What I am trying to say is that, theories like Spec.Rel. had been chosen because they introduced less postulates wrt others.

The postulate thing works pretty well in physics, but not so well in biology.

In other words, physicists are adept at separating the postulates from the consequences, so it's not to hard for us to eventually understand that the one postulate of special relativity is simpler than competing models even though it introduces a multiplicity of consequences that on the surface appear complex and hard to swallow:
1) No more aether.
2) Space and time not absolute.
3) No absolute reference frame.
4) Galilean relativity is wrong.

Biolgists, on the other hand play by a different set of rules. The cell theory originally said that "all living things are made of cells." Instead of making an exception for viruses, they re-definied living things to only include stuff made of cells. Thus the "cell theory" is no longer a simple principle testable by experiment, it is a tautology: true by definition.

Biologists have similar confounding difficulties with definitions of species.

But is this really so different than re-defining planethood to exclude Pluto?

How would we apply Occam's razor to classification of objects in the system?

How would we apply Occam's razor to defining and classifying living things?

What would Occam do with stuff like prions and viruses that seem more than mere molecules but that currently are not classified as living things?

Michael Courtney

 

[Marco_84]

u're right, in biology we amke data base full of data and try to classify, the time for modeling is less wrt othere sciences... and in those times it is not clear the distinction beetwen one theory and another, at least not as much as inphysics or math.

I think that basically that's the distinction between exact sciences and human ones...
regards
marco