What Does "Physical" Really Mean?

[Polymath257]

Of course, by defining "physical" by way of "a completed physics," there is nothing that is "unquestionably physical". The alleged "completed physics" might eliminate mass as something related to physics.

Unlikely. The range of phenomena described as physical has always increased, not decreased.

 

[siti]

The alleged "completed physics" might eliminate mass as something related to physics.

I don't think the idea that "physical" is what is related to "a completed physics" will ever become coherent.

But might not a "completed redness" eliminate some things that are currently considered "red" and a "completed humanness" might eliminate some characteristics that are currently considered "human". In fact those two are far more likely than mass becoming non-physical don't you think?

I ask again - is "red" "utterly meaningless" as an adjective because we don't know exactly what all the red things are yet? Then why should you claim that "physical" is "utterly meaningless" as an adjective because we don't know what all the physical things are yet? There is no difference - you can't define "red" precisely any more than you can define "physical" precisely and no matter where you currently draw the line between red and non-red, there is always the possibility that this could be changed. If I am wrong please kindly provide a precise definition of 'red' that is inviolable, unchangeable and irrefutable.

 

[Polymath257]

Are you saying that empty space (or the void) is physical, and time is physical?

Certainly, both are. Both interact with mass, for example, as described by general relativity. Both have dynamics and are described by physical laws.

 

[siti]

Photons and information are not identical.

No - but can you separate them? Can you separate a photon from its momentum and still have a photon?

 

[Polymath257]

As others have already noted or alluded to, it was photons whose speed was measured. Was it not? Photons and information are not identical.

Is a photon the same as the physical state of that photon?

Semantics, bleh.

 

[Nous]

BTW, I wish I had thought of noting this in the OP: John Wheeler said something to the effect that “all physical things are information-theoretic in origin”. Do you agree or disagree?

 

[Nous]

Is a photon the same as the physical state of that photon?

Define "physical state".

 

[siti]

If someone defined "God" in terms of what we supposedly will know in the future, would you be happy that definition?

Not really sure what the devil God has to do with it but...

Absolutely - that is almost my definition of God anyway - my definition of God - if there is one at all and if it is even appropriate to use the term for what I am describing would be something like "the continually evolving overarching whole of all that has objective existence" - you might think that "utterly meaningless", but if God is anything less than that then "he" ain't God in any sense of the word and if "he" is anything more than that then we have no hope of ever knowing what God is. The definition might be wrong - but it defines where it is sensible to look - and that's the same with 'physical' - IMO.

 

[siti]

BTW, I wish I had thought of noting this in the OP: John Wheeler said something to the effect that “all physical things are information-theoretic in origin”. Do you agree or disagree?

Define "physical", "information-theoretic" and "origin". Or another way - hit your thumb with a hammer and then convince yourself that both your thumb and the hammer are "information-theoretic" in "origin".

 

[Nous]

Unlikely. The range of phenomena described as physical has always increased, not decreased.

It would be unbelieveable to people in the 18th century to learn that the concept of and issues about "matter" have become really unimportant to physics these days. It's easy to imagine the concept of "matter" being dispensed with in the future.

 

[blü 2]

I'm imagining a pink elephant at the moment. For some reason she's wearing a shower cap. So, you're saying that image is not physical?

The brain process involved is physical. However, the pink elephant (in this allusive sense) is a concept with no counterpart in reality, hence is imagination. The simile may be a drawing (physical) of a unicorn (imaginary) on a piece of paper (physical).

So, in the universe prior to the existence of any brains or computers, there was no information?

No. Nor even data. Those are concepts, and concepts only exist in brains.

The late John Wheeler said that “all physical things are information-theoretic in origin” (I may not have the quote exactly right). You're saying that he was wrong. Right?

What definition of 'information' was he using?

 

[Nous]

But might not a "completed redness" eliminate some things that are currently considered "red"

Not except by changing the definition of "red". What's currently incomplete about the color red?

I ask again - is "red" "utterly meaningless" as an adjective because we don't know exactly what all the red things are yet? Then why should you claim that "physical" is "utterly meaningless" as an adjective because we don't know what all the physical things are yet?

We can define red today, and distinguish red from other colors:

Red - Wikipedia

Red is the color at the end of visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometers. [2] It is a primary color in the RGB color model and the CMYK color model, and is the complementary color of cyan.​

The definition of red, and the ability to distinguish red (and red things) from other colors (and things of other colors) does not depend on future events. That is entirely unlike defining "physical" according to the inscrutable idea of what will be related to "a completed physics".

The same goes for defining "human". We don't have difficulty distinguishing humans from our closest living relatives nor any other animals.

 

[Nous]

Are you saying that empty space (or the void) is physical, and time is physical?

Certainly, both are. Both interact with mass, for example, as described by general relativity. Both have dynamics and are described by physical laws.

General Relativity describes the geometrical relationships between a 4-dimensional manifold called "spacetime" and an energy-momentum tensor. Does the fact that the geometry of spacetime is relative to such factors make spacetime "physical"? What is your definition of "physical" again?

 

[siti]

Not except by changing the definition of "red". What's currently incomplete about the color red?

We can define red today, and distinguish red from other colors:

Red - Wikipedia

Red is the color at the end of visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometers. [2] It is a primary color in the RGB color model and the CMYK color model, and is the complementary color of cyan.​

The definition of red, and the ability to distinguish red (and red things) from other colors (and things of other colors) does not depend on future events. That is entirely unlike defining "physical" according to the inscrutable idea of what will be related to "a completed physics".

The same goes for defining "human". We don't have difficulty distinguishing humans from our closest living relatives nor any other animals.

Please define what is meant by "next to orange" and "opposite violet", "approximately 625-740 nanometers"...how do these phrases constitute a precise definition? Suppose some radiation had dominant wavelength of 624.9nm would that be red - or another colour? All that is just a matter of convention. As is the definition of what it is (what characteristics) make us human. Would the definition of "human" have been the same 200,000 years ago? Will it still be the same in 200,000 years time? And we certainly do have trouble distinguishing between human and non-human creatures that lived a very long time ago and between very closely related species of other animals today. The defining characteristics of species of animals is also largely a matter of evolving convention but that doesn't make their associated adjectives meaningless does it?

 

[Nous]

Not really sure what the devil God has to do with it but...

Absolutely - that is almost my definition of God anyway - my definition of God - if there is one at all and if it is even appropriate to use the term for what I am describing would be something like "the continually evolving overarching whole of all that has objective existence"

That isn't even close to what is meant by the term "physical" being defined according to what is "related to" the dubious concept of "a completed physics".

 

[Nous]

Define "physical", "information-theoretic" and "origin".

"Information-theoretic" refers to information theory, and "origin" has the ordinary definition found in dictionaries--to have as a particular source. I don't know what Wheeler had in mind as "physical things"--probably something like I do as "empirical things," i.e., things from which we can (at least in principle) acquire a sense datum.

Or another way - hit your thumb with a hammer and then convince yourself that both your thumb and the hammer are "information-theoretic" in "origin".

How would that make thumbs and hammers any less information-theoretic? The act would provide more information about thumbs and hammers.

 

[siti]

That isn't even close to what is meant by the term "physical" being defined according to what is "related to" the dubious concept of "a completed physics".

And that isn't even close to a sensible response to anything that I wrote. You brought "God" into it and as I said - I don't know what the devil God has to do with your topic. But God is always defined - at least partially - by what "he" will become in the future (e.g. try looking up the real meaning of the Hebrew words ehyeh asher ehyeh). That's all I'm going to say about "God" - its irrelevant to the topic except in the same sense that other evolving definitions are relevant.

 

[siti]

"Information-theoretic" refers to information theory, and "origin" has the ordinary definition found in dictionaries--to have as a particular source. I don't know what Wheeler had in mind as "physical things"--probably something like I do as "empirical things," i.e., things from which we can (at least in principle) acquire a sense datum.

OK - so that boils down to "things from which we can (at least in principle) acquire a sense datum have their origin in 'non-things' from which we cannot (even in principle) acquire a sense datum"?

 

[Nous]

The brain process involved is physical. However, the pink elephant (in this allusive sense) is a concept with no counterpart in reality, hence is imagination.

So this doesn't mean that the images and other features of things that are imagined do not exist, but they are merely non-physical.

[/quote]No. Nor even data. Those are concepts, and concepts only exist in brains.[/quote]Thinking about the case law that premises a court decision, and how that case law justifies that decision but not another seemingly closely related proposition is quite different than and distinguishable from thinking about the topic of this thread (what does 'physical' mean?). Is there any evidence that one can distinguish those topics by examining what's happening in another person's brain?

What definition of 'information' was he using?

The one from information theory.

 

[Nous]

And that isn't even close to a sensible response to anything that I wrote. You brought "God" into it and as I said - I don't know what the devil God has to do with your topic. But God is always defined - at least partially - by what "he" will become in the future (e.g. try looking up the real meaning of the Hebrew words ehyeh asher ehyeh).

I've never heard anyone speaking of God as without characterization until she is completed. I've lived a very sheltered life.