What Does "Physical" Really Mean?

[suncowiam]

Well, the information here was still a state of a physical device. It is still true that information is 'tied to a physical representation'. The crucial fact here is that information isn't simply negative entropy. And that is a very significant fact. It may well open things up to 'zero-energy' computation.



On the contrary, that is precisely what is at the heart of his scenario: the question is the difference between logical irreversibility and physical irreversibility. The latter does always produce an entropic effect. The former is now know not to in some cases.

In any case, the topic of this thread concerns what “physical” means. Does Landauer's assertion that “information is physical” contradict Norbert Wierner's statement in Cybernetics, “Information is information, not matter or energy”?

Weiner was considering a mathematical analysis and divorced himself from the physical aspects in order to do his analysis. There will still be the question of how information is produced or exists in the real world.



I see the term 'physical' as being defined inductively: start with any particular material thing (like the chair in my room). Declare that to be physical. Then, anything that interacts with something physical is also defined to be physical. So, light, neutrinos, bosons, etc are all physical.

I see information as being our description of a physical situation. When the system changes, so does our description, and hence the information does also. Furthermore, we assign certain physical states to have meanings *we* give to them: in the experiment mentioned above, the information was the amount of twist in a piece of material. In modern computers, the information is the voltage in certain electrical lines.

Finally, the phrase 'useful purpose in the context of metaphysics' is self-contradictory: metaphysics is never useful.

This best describes my understanding also. Very nice description.

 

[suncowiam]

Ruin the joke, eh.

I thought the question was about whether it made a noise.
It did.

I know... I'm actually pretty good at ruining jokes.

Well, here's the kicker. You believed my premise to be true, but I LIED! HAHAHAHAHA. The tree never fell.

Ok, ok... But that's the point of this question, is that the person in the forest would never have known. In his world, no tree has fallen until physical evidence would suggest so.

Again, I'm of the mindset that information has to be conveyed for it to be information.

 

[suncowiam]

Spooky Action at a Distance - Wikipedia

IMHO, it is not correct to consider physical apart from non-physical. Who knows if energy changes into substance and who knows how energy arises?

When you say who knows, to me, it just means someone hasn't discovered the process yet.

Spooky action has been observed and can be considered faster than the speed of light, possibly instantaneous.

So yes, I have to retract my assertion that information is limited to the speed of light.

But this doesn't negate our discussions of information to be physical or not.

Thanks

 

[Polymath257]

I don't disagree with any of that....except that I use the word, "information", to refer to
something we've encoded. Light & other emanations from celestial objects coming to
us are physical phenomena from which we interpret, thereby creating information.
Examples....
Words from your post are information.
Light from the star, Betelgeuse, is not information.

I go back and forth on this. It certainly seems that the light carries information about Betelgeuse from that star to us. In that case, the information is a particular physical state. And I am ok with that.

But, as you say, we need to interpret this light in order to know what it is like over at Betelgeuse. So, in this case, the information is our interpretation of that physical state. And I am ok with that also.

So, it seems to be a matter of definition: is it the physical state that is (or carries) the information? Or is it our interpretation that creates the information? Both ways seem reasonable, but we are only using one word for the two distinct concepts.

In the first definition, information would be created whenever a physical state is created that is causally linked to a previous physical state but one that could not result from other previous physical states (or, potentially could only result from a limited number of previous states). Then, the latter state carries information about the previous state.

As an example, the light from Betelgeuse has wavelength, directionality, polarization, etc all of which limit how Betelgeuse could have been to produce that state. because of this, we can use the light to determine, say, the temperature of the star. On the other hand, if too many prior states in the star could lead to the same physical state for the light (say, many different sizes of the star), then the light would not carry information about those aspects of the star.

And I am ok with that.

 

[Polymath257]

That is information. We can discern from the light if that is a star, what type of star, how big of star and so on...

Here's the chicken/egg question then. Is it information if it can't reach the destination? Is it information if the words I'm typing now never reach you? What use is there if none of my thoughts or typing fails to reach you?

Again, this seems to depend on the specific definition used. Certainly, the typed message is a particular physical state, and so is information in one sense, but if it does not reach you, you do not interpret it, so it is not information *to you* (although it would be to the writer).

Communication happens when information at one location is transfered to another location 'reliably'. So, I would say that the typed message was information, but it was not communicated if it doens't reach you.

 

[Revoltingest]

I go back and forth on this. It certainly seems that the light carries information about Betelgeuse from that star to us. In that case, the information is a particular physical state. And I am ok with that.

But, as you say, we need to interpret this light in order to know what it is like over at Betelgeuse. So, in this case, the information is our interpretation of that physical state. And I am ok with that also.

So, it seems to be a matter of definition: is it the physical state that is (or carries) the information? Or is it our interpretation that creates the information? Both ways seem reasonable, but we are only using one word for the two distinct concepts.

In the first definition, information would be created whenever a physical state is created that is causally linked to a previous physical state but one that could not result from other previous physical states (or, potentially could only result from a limited number of previous states). Then, the latter state carries information about the previous state.

As an example, the light from Betelgeuse has wavelength, directionality, polarization, etc all of which limit how Betelgeuse could have been to produce that state. because of this, we can use the light to determine, say, the temperature of the star. On the other hand, if too many prior states in the star could lead to the same physical state for the light (say, many different sizes of the star), then the light would not carry information about those aspects of the star.

And I am ok with that.

You're certainly an agreeable fellow.
Stop that! We're boring the masses.

 

[Revoltingest]

I know... I'm actually pretty good at ruining jokes.

Well, here's the kicker. You believed my premise to be true, but I LIED! HAHAHAHAHA. The tree never fell.

Ok, ok... But that's the point of this question, is that the person in the forest would never have known. In his world, no tree has fallen until physical evidence would suggest so.

Again, I'm of the mindset that information has to be conveyed for it to be information.

Would you say a book contains no information until it's read?

 

[suncowiam]

Again, this seems to depend on the specific definition used. Certainly, the typed message is a particular physical state, and so is information in one sense, but if it does not reach you, you do not interpret it, so it is not information *to you* (although it would be to the writer).

Communication happens when information at one location is transfered to another location 'reliably'. So, I would say that the typed message was information, but it was not communicated if it doens't reach you.

Well, science articles in the past assuming data has a finite speed called it information. I usually debate from a scientific perspective where I can. This is my unification of the language.

I understand Revolt's definition. It's probably more of a classical definition. There's information all around us not being interpreted, not being seen, not being heard, not being felt. Information is everywhere. But to make it actually pragmatic, it has to be conveyed and interpreted.

 

[suncowiam]

Would you say a book contains no information until it's read?

Before I even see or feel the book, I wouldn't know if it existed.

Then after seeing the book, I know for certain there are pages in the book. Then after opening it, I know for certain there are words and which language it was written in. Then after reading it, I know for certain what topic it was about...

 

[Polymath257]

There really is no disagreement about what happens when a tree falls in the forest and there is no ear to apprehend that fact. It generates waves of a certain frequency and amplitude in the atmosphere around it that travel out in all directions at a characteristic speed, attenuating with distance.

That is what I understand has happened, and I would suggest that most people reading these words would agree. Where we might differ is regarding what to call that. Shall we call it a noise?

It doesn't really matter what we call it. Call it Keith.

As I indicated, a lot of these semantic knots unravel if we simply make a distinction between unapprehended phenomena and their conscious perception, saving one set of terms for the former and another for the latter. So for me, it's not sound or a noise until and unless it is heard by a conscious agent. We might call it sound waves to indicate that if perceived, it will be perceived as sound, but we don't consider it sound until heard.

My main hesitancy on this is that it flies in the face of standard convention in physics. So, for example, a sound wave might have a frequency that no person could hear. Physicists regularly call any form of electromagnetic wave 'light', even if it is a radio wave.

At that point, form - ripples in the ambient atmosphere that when unheard are without meaning - comes into a theater of consciousness and informs it of the presence of something happening in the vicinity, at which point it is information of a specific type: sound.

But what if it is ultra high frequency sound that we cannot perceive, but can detect through instrumentation? Is it then a sound or not?

Notice that none of this is about what is real or true, just what to call it.

Agreed. The problems come when there are conventions that use the same words for different concepts. Sound and light for physicists mean *very* different things than they do for most people.

By this reckoning, DNA does not carry information until it is apprehended, at which time its form - its double helix shape, its sequence of codons and their atomic arrangements within the molecule - becomes information. This didn't happen until relatively recently.

But while going about its work unapprehended, it can be thought of as a form - a template - which generates other forms like mRNA, which then it turn with the help of matter formed into what is now called a ribosome, another form is generated: a polypeptide, perhaps an enzyme.

The enzyme assumes a characteristic conformation (there's the syllable form again), which along with its pattern of charges, also form, interacts with matter of a characteristic form (the enzyme's substrate) converting it to another form, and so on.

All of this goes on outside of consciousness - form transforming (there's that syllable again) into other forms, not being information until a mind apprehends it.

And what I would say is that the forms are carrying *something*. Whether we want to call it information or Keith is irrelevant, but the causal connection to a state in the past is something that propagates and can legitimately be called information.

I realize that as with all matters of nomenclature, that this is an artificial construct, but one with increased value relative to alternate formulations because with it, many semantic riddles evaporate away. There is no more need to think about whether a tree falling in a forest unheard makes a sound. If a sound is defined as energy apprehended by a particular sense organ, the ear, then there is no issue any longer.

And part of the difficulty is that we want a simpler phrase than 'pressure waves propagating through a medium' for the phenomenon that is not apprehended. The same is true for the causal connections that are linked to previous physical states via limited causality. For technical work, calling the first 'sound' and the second 'information' seems quite reasonable.

 

[Polymath257]

You're certainly an agreeable fellow.
Stop that! We're boring the masses.

I'm a math professor. Of course I bore the masses! That's my JOB!

 

[Nous]

And it can also refer to objective reality in contrast to the imaginary.

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?

Information is that which informs brains, or brain-like things (eg computers capable of making choices; perhaps too the Jacquard loom).

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

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?

 

[Nous]

I think her definition is OK and I'm happy with that.

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

Your position here seems to be that because we do not have a full account of what might ultimately be included in the "catalogue" of phenomena that are "physical" (i.e. amenable to explanation by a more complete physics) that consciousness will never be amenable to explanation by a more complete physics.

No, my point was (in part) the same as Hempel's: to say that "physical" is what will be "related to" physics when "physics" is "complete" makes the adjective "physical" utterly meaningless. No one can today or will ever be able to say what are the items that are "physical". We will never know when physics is "completed," i.e., we will never know when there will not be a new discovery or new idea in the future. For all we know, physics is a "completed" subject matter now. Therefore we can say with confidence that muskrats and maple syrup are not physical since they are part of the subject matter of physics, but algebraic structures are physical.

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

Its a bit disingenuous to suggest that because we cannot know all that the adjective 'physical' refers to at any given point it is not a useful adjective because there are very many phenomena that we can know that the adjective refers to. Think about other adjectives like 'red' or 'human' for example - is it possible to know precisely the limits of what those adjectives refer to at any given time?

What? Of course we can say today what is red and what is human. Today we can distinguish those things that are red and those things that are human from things that are not red and not human.

Anyway, all that apart, even if information were to turn out to be a "disembodied abstract entity" - we still have the problem of how we could possibly interact with it without the unquestionably 'physical apparatus' required to receive and interpret the information.

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.

 

[Nous]

Information is not physical. Information is descriptive of the physical.

The definitions provided are ok, but limited.

The question is what does "physical" mean.

 

[Nous]

Actually information is physical. It travels at the speed of light.

Can information travel faster than light?

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

 

[Nous]

There's no way you can win this.
In the material world....natural world...physical world....whatever it's called,
every phenomenon has physical aspects, eg, thoughts being held by neurons.
So it's possible to argue that everything detectable is "physical". Only the
supernatural would lie outside of it. This view isn't of much use to materialists.

I prefer using "physical" to make a distinction between information & other things.
Information is about communication representable by patterns in matter of many
forms, & transferable to other forms, where the forms themselves have no
significance, but the the information does.
Contrast this with forms of matter where it's all about a physical process, &
not about communication.
Example....
Information in a book isn't physical. It can be transferred to our brains.
The information remains unchanged throughout the processes involved.
But the paper, ink, thread, glue & leather cover are physical. Electromagnetic,
electrical & chemical means means of transfer to our neurons are also physical.
The material & the processes are physical. But the info transferred is not physical.

This is hard to convey.
(It's late...my eyes are tired.)
How'm I do'n?

You cited examples of "physical" phenomena, but you didn't define the adjective. What definition of "physical" would include all that you noted here?

 

[suncowiam]

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

Information is an abstraction of various mediums that stores and transfers data.

Information cannot exist without storage. It cannot be transferred without a medium. Photons is just a subset of the bigger equation. You will find various fundamental physical elements with information.

 

[Nous]

Well, the information here was still a state of a physical device.

This and the rest of that paragraph sounds so reasonable to me. But it leaves me with questions:

Did the information cause the device to be in that state?

Did information exist prior to the existence of any conscious creatures in the universe (assuming there was a time when there were no conscious creatures in the universe)?

Weiner was considering a mathematical analysis and divorced himself from the physical aspects in order to do his analysis.

(1) Define "physical" in that sentence.

(2) So are you saying that Wierner was wrong? Information is matter and/or energy? (If so, which? Matter or energy?)

There will still be the question of how information is produced or exists in the real world.

I see the term 'physical' as being defined inductively: start with any particular material thing (like the chair in my room). Declare that to be physical. Then, anything that interacts with something physical is also defined to be physical.

This definition of "physical" is a denial of the thesis of physicalism in which nothing exists but that which is physical. Your definition does not and cannot rule out the existence of non-physical phenomena.

 

[Polymath257]

This and the rest of that paragraph sounds so reasonable to me. But it leaves me with questions:

Did the information cause the device to be in that state?

No. In this definition, the physical state *is* the information.

Did information exist prior to the existence of any conscious creatures in the universe (assuming there was a time when there were no conscious creatures in the universe)?

Once again, this depends on specific definitions. Using the information=physical state definition, the information would have existed prior to creatures able to interpret it. Using the definition in terms of apprehension, it would not have.

(1) Define "physical" in that sentence.

The contrast I was attempting to make was between the situation in the 'real world' and the abstract mathematics.

(2) So are you saying that Wierner was wrong? Information is matter and/or energy? (If so, which? Matter or energy?)

Neither. Information, under this definition, is the physical state.

There will still be the question of how information is produced or exists in the real world.

Well, physical states give rise to new physical states under the action of physical laws. At times, the possible start-states leading to a given end-state have significant restrictions (possibly only one state-state is possible), in which case the end-state is information about the start-state.

This definition of "physical" is a denial of the thesis of physicalism in which nothing exists but that which is physical. Your definition does not and cannot rule out the existence of non-physical phenomena.

What does it mean to exist? That also requires a definition and the definition turns out to be identical to that of what it means to be physical.

Here is the basic question: does it make sense to say something exists that does not interact with anything physical? I would say no. In that case, everything that exists is physical.

 

[Nous]

For me, physical refers to space-time . . .

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

I need more time to read and assimilate the rest of your post. Will get back to you (don't let me forget).