Entities and attributes in science

[Guestfornow]

Hmmm.... spacetime. Are you sure that's not a concept? And what about that curvature thingy you mentioned? That sounds like maths.

Are you here saying gravity is a concept? I don't understand.

Yes. All that means is that if you calculate a number at the start of some process, you'll get the same number when you recalculate at the end of the process.

Ok. That doesn't mean you can conclude anything about a photon's energy because numbers won't tell you.
Energy is a conserved numerical quantity; it's also a physical quantity in that you can 'measure a quantity of energy'. In fact that's what a photon is, a discrete amount or quantity.

A measure.

 

[James R]

Guestfornow:

Where does the equation say energy is a number?

What is an equation? An equation is a mathematical statement containing an equals sign. It equates a mathematical expression or quantity on the left of the equals sign with a mathematical expression or quantity on the right of that sign.

Suppose we write an equation like:

Total energy = kinetic energy + potential energy

The way this is used, in practice, is that we plug in three numbers that we label as "the total energy", "the kinetic energy" and "the potential energy". We perform numerical addition on two of them to find the third.

If energy is not a number, then what is this equation about? What is it operating on?

Can this equation do anything in the physical world? Or is it just some writing on a screen and some operations and concepts in your head?

The thing about qualitative statements, about saying you know what something is, is that it has to line up with what other people in the scientific community say.

The "scientific community" strikes me as a conveniently ill-defined collection of people. If we're talking about energy, who qualifies for this "scientific community" that we're all expected to line up behind?

Is it only experts in physics - say PhDs who teach graduate-level courses? Or does it include undergraduate science students? Does it include journalists who write for popular science magazines?

I'm aware of how energy is defined by scientific experts. Typically, the first definition of energy that you see as a physics student is W=Fs (work is force times displacement). This is a precise definition of what is meant by "work". From there, we can go on to build up definitions and derivations of lots of other "forms of energy". But here's the thing: in every case, without exception, "forms of energy" are only rigorously defined using mathematical equations.

Not a single rigorous textbook on physics would try something like "energy is a photon".

Sure, a google search turned up lots of wrong statements about photons and energy, from the internet. Well, what do you know? Sometimes, people on the internet get things wrong! Especially non-experts. Fancy that.

Suppose instead of energy and light, the subject is time. Is time a number, why does it move in the same direction, at an apparently (up to quantum measurements) linear pace? How do numbers flow?

This is taking us away from the topic of the thread, I think.

You might ask "Is time an entity?" Answer: no. "Is time an attribute (of objects)?" Answer: probably not. "Is time a concept?" Answer: yes. "Is time 'physically real'?" Answer: it seems so.

Time is complicated. Energy is a lot simpler. Having said that, we can (and often do) associate numbers with passage of time; that does not mean that time is a number, however.

Can you tell us, since you know energy is a number? I maintain this is not what physics says about energy.

Why? Because you googled "are photons energy" and got some hits that said "yes"?

It could be that it's an entirely human invention, but maybe time is too. Can you say?

There's a thought. Maybe energy is entirely a human invention.

Hold that thought for a moment.

Questions come to mind. If energy is just an arbitrary human invention, then it seems strange that nature appears to obey lots of "rules" that we associate with energy. What are the chances of that happening, just by chance?

Maybe, then, energy is not completely arbitrary. Maybe energy is an idea we introduce to build a conceptual model of the natural world. If so, then energy can't be arbitrary if it is to be useful. It must, at some level, correlate with real-world observations and truths. But even so, at the end of the day it's still part of a mental model. It isn't like the actual stuff that's out there in nature.

 

[James R]

Are you here saying gravity is a concept? I don't understand.

Drop a coin onto the table. You say "the coin fell onto the table because of gravity", or something like that. What role is the word "gravity" playing in that sentence? It is labelling a concept. You have in your mind some concept that something causes the coin to be attracted to the table; you call it "gravity".

What's hard to understand about gravity being a concept?

Can you detect the gravity directly? Or can you only infer its existence by observing things like coins falling onto tables?

Ok. That doesn't mean you can conclude anything about a photon's energy because numbers won't tell you.

What are your trying to conclude about the energy that the numbers won't tell you?

Energy is a conserved numerical quantity; it's also a physical quantity in that you can 'measure a quantity of energy'.

Can you, though? Can you put a "quantity of energy" in a bottle by itself, so we can look at it? What does it look like?

Invisible, you say? Then how do you know it's a "thing" that's actually there, in reality?

In fact that's what a photon is, a discrete amount or quantity.

Repeating the same claim over and over doesn't advance the discussion. You need to try to make an actual logical argument, if you want to assert that photons are energy or that energy are photons. You should also address the specific objection that origin raised regarding that hypothesis, because that's a real, obvious problem for the "photons are energy" claim.

 

[Guestfornow]

Claiming that energy can take the "form of" electromagnetic waves is just hopelessly muddled. Energy just isn't stuff. It has no form. You can't turn energy into light, or light into energy.

I was reading back over this thread to gauge the thinking, and I couldn't see what this is trying to say at first.

Forms of energy are standard physics. About turning energy into light: the only problem is the energy has to have a form.
That follows since energy is conserved, at least it is locally. Energy doesn't exist by itself, it takes a form.

In natural units, energy and mass are equivalent. Matter is a form of energy. This is essentially true for all nucleons--the matter bulk in the universe--whose mass is due to internal quark/gluon kinetics.

And maybe you can't turn energy into light, but if you pass a current through a lightbulb the filament will do it for you.
We say the energy in the electric current is converted to energy in the filament. Maybe it's all smoke and mirrors, but it works at the level of analysis, which in physics is rather important.

 

[Guestfornow]

Repeating the same claim over and over doesn't advance the discussion.

And you aren't doing that, are you?

You need to try to make an actual logical argument, if you want to assert that photons are energy or that energy are photons.

I haven't asserted that. I've asserted that photons are a discrete form of energy. This form is, well, physical.
Photons really do exist and they are a form of energy, namely electromagnetic energy. Perhaps it is the case that energy in whatever form it has, is a concept. I can't say, because physics doesn't say either. It doesn't tell you anything about it beyond a combination of physical units, it doesn't tell you it's a number in that case.

You should also address the specific objection that origin raised regarding that hypothesis, because that's a real, obvious problem for the "photons are energy" claim.

What objection? Which hypothesis?

 

[Guestfornow]

I'm aware of how energy is defined by scientific experts. Typically, the first definition of energy that you see as a physics student is W=Fs (work is force times displacement). This is a precise definition of what is meant by "work". From there, we can go on to build up definitions and derivations of lots of other "forms of energy". But here's the thing: in every case, without exception, "forms of energy" are only rigorously defined using mathematical equations.

And so, how does that lead to the, logical, conclusion that energy is mathematical?
What was your reasoning?

If I count some grains of sand, does that mean sand is mathematical. Or just the counting part?

 

[James R]

I think it might be useful to remind (some) readers of the fundamental distinction between a description of a thing and the thing itself.

A common example is of a map and the territory shown on the map.

Suppose I point at a map on the wall and tell you "That's Australia, right there."

Of course, you know I'm not pointing at Australia. I'm pointing at a representation of the territory of Australia. The "real" Australia is a continental landmass thousands of kilometres across.

But you understand what I mean when I say "That's Australia", while I point at the map. You understand that the map presents a (grossly simplified) model of the real continent we call Australia.

There are correspondences between the map and the territory. If it's an accurate map, you could use it to find the real-world location of the city of Sydney, for example. This works because features of the map correspond to or represent things that can be observed in the real world.

You might imagine a young child making a particular mistake. You point at the map and say "That's Australia." Later, when the child is asked "What is Australia?", he says "Australia is a funny shape in a picture on a wall." This is the point at which you'd gently correct the child and say "Oh, no. The picture is a map of Australia. Australia is really a big country that lots of people live in. The picture just shows where to find various places in that country."

To summarise, you understand that the map is not the territory.

Now consider what you understand me to mean if I tell you "The energy of each photon in this laser beam is 3 electron-volts."

You might hear the words "energy ... in the beam" and conclude that there must physically be some kind of substance in the laser beam called "energy". But there's more of a hint in what I said: "The energy of each photon ...". So, you might thing that whatever this physical substance called "energy" is, it must be in the photons (and the photons, whatever they are, are in the beam).

Although I didn't say it, you might even infer that photons in the beam are the energy.

All of this would be a mistake. The map is not the territory. The energy of a photon is not a photon. The "energy of a photon" represents something about the photon. It describes the photon, in some sense. It corresponds to certain features of the real-world photons in the beam. It provides part of a map for better understanding the photons. But the energy is not the photon. The photon is not the energy. A photon is something that exists in the real world. The energy of a photon is part of a conceptual mind-map in your head.

The map is not the territory.

Another thing that is sometimes forgotten is that things don't spring into physical existence when we name them. We have the word "unicorn", and a mental map of ideas and concepts that go along with the label "unicorn". We can reason about unicorns. We can draw conclusions about unicorns. But none of this implies that unicorns are something that we can find out in the physical world. A map does not have to represent any territory that actually exists. Maps are often useful insofar as they correspond to real-world territories, but they don't have to do that.

If energy is a glowing substance in your imagination, it is important to realise exactly that: it's just in your imagination. That glowing substance is not something that can be found out there in the world. And don't confuse energy with light. Light is something that exists in the world. We can see light. We can't see energy. Energy is only in our minds.

 

[Guestfornow]

Questions come to mind. If energy is just an arbitrary human invention, then it seems strange that nature appears to obey lots of "rules" that we associate with energy. What are the chances of that happening, just by chance?

Maybe, then, energy is not completely arbitrary. Maybe energy is an idea we introduce to build a conceptual model of the natural world. If so, then energy can't be arbitrary if it is to be useful. It must, at some level, correlate with real-world observations and truths. But even so, at the end of the day it's still part of a mental model. It isn't like the actual stuff that's out there in nature.

I think the conceptual model falls out of the analytical model.

Energy is a thing, in that it makes it much easier to analyse how physical systems evolve in time. Again, analysis doesn't offer any real clues here about the nature of energy. I'm sure you've seen how to derive the kinetic energy of a moving object from equations of motion.
What that tells you is, energy is algebraic.

 

[Guestfornow]

What's hard to understand about gravity being a concept?

Can you detect the gravity directly? Or can you only infer its existence by observing things like coins falling onto tables?

It isn't hard to have a concept of gravity. I can infer its existence as an external force, like Newton did, acting on all objects made of matter.
These all accelerate at a constant rate near the surface of the earth. This motion is due to an external agent, not because of a concept.
My concept of gravity has no effect on falling bodies. Gravity isn't inside my head, my concept of it is.

 

[James R]

Guestfornow:

I was reading back over this thread to gauge the thinking, and I couldn't see what this is trying to say at first.

I'm glad you're giving it some thought. That's more than some people here have been willing to do.

Forms of energy are standard physics. About turning energy into light: the only problem is the energy has to have a form.
That follows since energy is conserved, at least it is locally. Energy doesn't exist by itself, it takes a form.

Doesn't this idea that energy has many forms strike you as very nebulous - especially when energy magically changes from one "form" to another?

People in this thread have claimed, for instance, that "light energy" can "change into "electrical energy". If so, then what's the actual process that goes on when the energy changes from one "form" to another? What's happening to the energy? Can we see the energy changing form? Can we catch it in the act of changing form? What does it look like as its form is changing?

Another specific problem I have raised is that sometimes the energy doesn't seem to be located in any specific place. If I hold a rock with mass m at height h above the ground and say "The gravitational potential energy here is E=mgh, where g is the acceleration due to gravity", where is the energy, exactly? What is its "form"? What process went on to make it have the "form" of gravitational potential energy. And doesn't that word "potential" worry you, even a little? What does it mean for the energy? Is the energy still there, if it's only "potential energy"? How can you tell?

In natural units, energy and mass are equivalent.

You're talking about a mathematical equation, there, without making it explicit.

Matter is a form of energy.

NO! That's the same mistake as "photons are a form of energy". The map is not the territory.

And maybe you can't turn energy into light, but if you pass a current through a lightbulb the filament will do it for you.

A hot filament doesn't "turn energy into light". How could it?

We say the energy in the electric current is converted to energy in the filament.

Okay. There's no problem with that. You're talking about a conceptual thing, there, not making silly claims that the energy can be turned into matter, or similar.

Maybe it's all smoke and mirrors, but it works at the level of analysis, which in physics is rather important.

Maps are important for understanding territories.

And you aren't doing that, are you?

Yes, but I have not merely repeated my assertion. I have explained why it is correct, in a number of different ways. I have justified my assertion. I have made logical arguments in support of it, which so far stand unrefuted by any logical counterargument.

Most of the responses I have had from those who disagree with me have been simple denials. I couldn't possibly be right, because those people all just know that energy isn't just conceptual. That's not an argument against my position, nor an argument for the opposite position.

Recently, we've seen a few attempts at argument-from-authority. That argument goes: some internet sources say photons are a form of energy, so they must be right (for some yet-to-be-specified reason). People looking for safety in numbers, rather than trying to muster a rebuttal of my argument (not just mine, of course: full credit to exchemist and origin, who both clearly understood the argument the first time they encountered it, and who made valuable contributions in finding new ways of explaining it to those who are still struggling).

I haven't asserted that. I've asserted that photons are a discrete form of energy.

Photons are not a "form of energy".

Photons have momentum, spin, polarisation, frequency, etc. Energy has none of those things.

It makes no sense at all to claim that photons are energy, if energy lacks the most of the properties that photons have.

Photons really do exist and they are a form of energy, namely electromagnetic energy.

The question of whether photons "really do exist" is a question that might need it's own discussion, later. I think we can agree that light really does exist. But it cannot be a "form of energy", if for no other reason that all "forms of energy" lack certain propertie that light has. (What's the colour of energy, for instance?)

Perhaps it is the case that energy in whatever form it has, is a concept. I can't say, because physics doesn't say either.

Physics does say. Unfortunately, this point is not explicit in most introductory textbooks. Rather, it is assumed that students will intuitively understand that the map is not the territory. Experience shows that this is a bad assumption. We're seeing that play out right here.

And so, how does [the mathematical definition of energy] lead to the, logical, conclusion that energy is mathematical?

How could it logically lead to any other conclusion? If something is defined to be a mathematical thing, then it's a mathematical thing.

If I count some grains of sand, does that mean sand is mathematical. Or just the counting part?

If you count grains of sand, you'll end up with a number. You will call it "the number of grains of sand". You will, in all likelihood, understand that the number of grains of sand is not the sand itself. You probably won't confuse the number of grains for some sand, or the sand for a number of grains.

After your counting, you'll have a more comprehensive mental map of the sand. Before counting, you knew there was "some sand". After the counting, you know there's "2720 grains of sand" (assuming you've counted correctly).

You'll be very unlikely to say things like "the sand turned into 2720" or "2720 turned into some sand" or "2720 is a form of sand". Because, most likely, you know how to tell the difference, in this case, between a number and some stuff.

Next, you need to work out how to tell the difference between a number called "energy" and some stuff.

 

[James R]

Guestfornow:

I think the conceptual model falls out of the analytical model.

I'm not sure what you mean, but I don't think it matters much. Whether you have one model or ten, they are still conceptual.

Energy is a thing, in that it makes it much easier to analyse how physical systems evolve in time.

Yes. Energy is a very useful concept.

Again, analysis doesn't offer any real clues here about the nature of energy.

What analysis?

I'm sure you've seen how to derive the kinetic energy of a moving object from equations of motion.

Yes. In fact, the concept of kinetic energy is invented because it turns out that a very useful mathematical theorem then holds; it's called the "work-kinetic energy theorem".

What that tells you is, energy is algebraic.

Are we now in agreement that energy is a mathematical concept, then? If so, my work here is done.

It isn't hard to have a concept of gravity. I can infer its existence as an external force, like Newton did, acting on all objects made of matter.

When you start describing gravity as a "force", you're already using a conceptual model.

It's quite hard to pin down exactly what gravity is. The context in which you use the word is very important.

These all accelerate at a constant rate near the surface of the earth. This motion is due to an external agent, not because of a concept.
My concept of gravity has no effect on falling bodies. Gravity isn't inside my head, my concept of it is.

That sounds reasonable enough.

Do you now agree with me that photons can't possibly be a "form of energy"? Or not?

Do you agree with me that energy is mathematical: a number? Or not?

 

[Guestfornow]

Do you now agree with me that photons can't possibly be a "form of energy"? Or not?

Do you agree with me that energy is mathematical: a number? Or not?

I'd like to wait for the rest of the physics community to catch up with you first.

I already explained why I don't take the concept of energy as being an explanation of what it is. I don't know what it is beyond what the equations say. The equations don't say it's a number. They don't tell me it's an invention. They don't have a lot to say about what energy is.

And once more I'd like to remind you that time isn't understood in terms of what it is, but in terms of how we can measure it, how to build accurate clocks. But accuracy is a concept, right? No, it's not. Understanding a thing in physics doesn't mean you find out what it is.
And you seem to be insisting that you do know what a physical thing "is", but you don't.

 

[James R]

Guestfornow:

I'd like to wait for the rest of the physics community to catch up with you first.

In my own experience, I have found that the professional physicists I have talked to about this tend to either agree with me already, or else to agree with me after I explain the point to them. Not everybody's on board, certainly. Maybe I should write an article or a book that covers some of this stuff.

Probably, some physicists could learn a few things from talking with philosophers every now and then.

I already explained why I don't take the concept of energy as being an explanation of what it is. I don't know what it is beyond what the equations say. The equations don't say it's a number. They don't tell me it's an invention. They don't have a lot to say about what energy is.

None of the equations say it is a substance. That's a good start, surely?

And once more I'd like to remind you that time isn't understood in terms of what it is, but in terms of how we can measure it, how to build accurate clocks. But accuracy is a concept, right? No, it's not. Understanding a thing in physics doesn't mean you find out what it is.

My own view is that physics is about building mental models of the physical world. "Understanding", in that context, means that the predictions and results from the models match results gathered from real-world experiments and observations.

The question of the extent to which the mental constructs of the models reflect "real things" about the physical world is a philosophical one. Science mostly doesn't concern itself too much with such things. It's more concerned with using the models to help guide the making of new technological stuff and to "understand" things, in the sense given previously.

And you seem to be insisting that you do know what a physical thing "is", but you don't.

I don't know what gave you that impression.

Where do you think I have insisted that I know what a physical thing is?

For the purposes of this current discussion, I have defined the words "entity" and "attribute" in a particular way, because it's no use if we're all using different definitions and talking at cross purposes about different things. But I'm not welded onto the definitions I have used here. I have, in fact, already said that I think there are difficult philosophical problems lurking just a little way below the surface of this discussion - ones that most likely threaten the tidy distinctions I have tried to make so far. We've gone near some of those problems a couple of times in this thread, but nobody has gone all-in on them, so far. In any case, there seems little point, until we can reach some agreement about the "easy" cases.

 

[davewhite04]

What is an equation? An equation is a mathematical statement containing an equals sign. It equates a mathematical expression or quantity on the left of the equals sign with a mathematical expression or quantity on the right of that sign.

Suppose we write an equation like:

Total energy = kinetic energy + potential energy

The way this is used, in practice, is that we plug in three numbers that we label as "the total energy", "the kinetic energy" and "the potential energy". We perform numerical addition on two of them to find the third.

If energy is not a number, then what is this equation about? What is it operating on?

Can this equation do anything in the physical world? Or is it just some writing on a screen and some operations and concepts in your head?

Since this didn't get much thought time, I think it's interesting so my 2p...

Objectively speaking, No, Yes. Where else is it? It's in your head.

Subjectively, thoughts could actually be sub-atomic particles, so we're picking up on other peoples thoughts in our head everyday, and sharing ours. Think Telepathy. Which I know exists.

 

[James R]

Think Telepathy. Which I know exists.

You should start a separate thread on that in the Parapsychology subforum. I'm interested to find out how you know - but not in this thread.

 

[Guestfornow]

My opinion of why this thread isn't going where everyone wants it to.

Philosophers ask what is the universe. Physicists ask what is the universe doing.

Zeno, an early philosopher, discussed the nature of motion and introduced his paradox.
That has been resolved, but only fairly recently, and not by philosophers.

So that paradox, basically asking how is motion possible in an infinitely divisible distance, isn't a paradox any more, but why?

 

[Guestfornow]

Light is not a form of information. Information, like energy, is a concept. Light is made of physical particles.

I'd like to discuss this with you.

You claim, above, that information is a concept. I'd like to know how you came to this conclusion.

Suppose two people agree to communicate using ordinary battery powered torches. They agree on a signalling protocol, composed of long and short on/off light signals from their torches. How do they communicate information with each other? Or send each other a message?

How is the turning on and off of an ordinary torch a concept? How do the short or long flashes turn into concepts?
Moreover, if light is not a form of information, why do TVs emit light?

 

[DaveC426913]

You claim, above, that information is a concept. I'd like to know how you came to this conclusion.

Suppose two people agree to communicate using ordinary battery powered torches...

Your example employs thinking (AKA conceptualizing) beings.

Moreover, if light is not a form of information, why do TVs emit light?

Light - like any medium - can be used to transmit information, but light itself is not information.

 

[billvon]

Moreover, if light is not a form of information, why do TVs emit light?

?? Stars are not a form of information. They emit light.

 

[Guestfornow]

Light - like any medium - can be used to transmit information, but light itself is not information.

But that protocol, agreed upon by two people so they can send messages to each other, is based on whether a lightbulb is emitting light or not.
On or off, the presence or absence of the information (i.e. light), is the messaging protocol.

What about back when people lit signal fires to send messages, like, the enemy has landed? Are you saying the light from a signal fire is not information? Because if that's what everyone agreed to, then it is.

Otherwise the information might be only "there's a fire over there".