# Is mass a number?

Discussion in 'General Philosophy' started by arfa brane, Apr 14, 2022.

1. ### James RJust this guy, you know?Staff Member

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Good!
Yes, of course. I assumed that ambiguity would come up sooner or later, so it's good you've brought it up.

People often talk about "a mass" when what they really mean is "an object with mass". Objects are made out of matter, so "a mass" is a euphemism for an object made from matter.

But that's not the problem that arfa brane is having here. arfa seems to think that "mass" is something inherent in an object, rather than just being a number with units that we associate with an object.
Yes, you could say that, but x would still be a number with units, which would be "the mass of the object". The point is: the mass of an object is a number. You and I agree on this. arfa begs to differ.
No!

See above.
Mass is a quantifier of matter.
Strange. You started with what sounded like the right concept, but by the end of your post you'd gone completely off the rails, making the same error arfa brane has been making - confusing a property of a thing for the thing itself.

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3. ### James RJust this guy, you know?Staff Member

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It occurs to me that this might be a useful analogy:

Consider a red ball.

We can all agree, I hope, that a ball is an object. Nobody would say "red is an object", I hope. I think we can agree that "red" is "the colour of the ball". Ultimately that colour is not inherent in the ball. The "red" is in our heads. It is due to a series of sense perceptions we get when we view the ball under appropriate lighting conditions.

The ball doesn't contain any "red" essence. We can't separate out the "red" and bottle it separately from the ball. We understand that "red" is a descriptive property that we use to describe the ball.

Now consider a 1 kg ball.

Are you going to say that "1 kg is an object"? Are you going to say that "1 kg" is inherent in the ball? Are you going to say there's some sort of "essence of mass" in the ball? If so, can you separate out the "1 kg" from the ball and bottle it, so we can just see the "1 kg" in its own bottle?

This is essentially what arfa brane is asking us to do.

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5. ### Motor DaddyValued Senior Member

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Like I said, a rock is a massive object. There is no quantification going on in that statement. A massive object is not quantified with a number. A Galaxy is a massive object, whether you measure it or not. If you measured it, then you would need a number and a unit. If you don't measure it, and there is no number and no unit, it is still a massive object. It is a matter object, which we call massive object.

It's not about numbers, it's about terminology, and mass is matter. After all, what is matter??? It is a massive object, comprised of components.

Again, you are making statements like there is some fundamental object that everything is made of, and that just isn't the case. Everything is motion, there is no basic solid object that everything is made of.

"Matter" and "mass" are two words for objects that can be measured with numbers and units. They are physical objects, not just a number.

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7. ### Motor DaddyValued Senior Member

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No, I wouldn't say that, I would say the ball is a MASSIVE OBJECT. How massive, you ask? Then what you want to do is measure it, and then claim that the ball doesn't have mass, because mass is just a number.

Mass is NOT just a number, it is a WORD that's used to represent an object of matter. It is not a number to attach to the ball, but a word that represents the concept of matter.

I'm guessing you would say a ball's matter is not just a number, so why would you say the ball's mass is just a number?

Mass and matter are two peas in a pod. They represent the concept of substance, not just the measure of the substance.

8. ### James RJust this guy, you know?Staff Member

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That's right. In that statement, saying that the rock is "massive" just means that it "has mass". Or perhaps you're using the word more loosely to just mean that that rock is rather large in some sense.
It will be, as soon as I ask you "how massive is it?"
You're assuming that galaxies also have non-zero mass. A fair assumption, but an assumption none the less.
I explained how mass is different from matter in my previous post to you.

No. Nothing I have said has realised on some fundamental object.
Okay, but I don't see any relevance of that to this discussion.
I covered that ambiguity in my previous post. If you have questions, please ask.

9. ### Motor DaddyValued Senior Member

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Would you say that a ball has matter, or that matter is just a number?

10. ### James RJust this guy, you know?Staff Member

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When we say "the ball has mass", what we really mean is that there's a number (called the mass) that we associate with an object (called the ball). Balls are not made of numbers. They are not made of mass.
Flip flop you go, back again the other way.

We're now in agreement again, more or less. But maybe you'll flip back in a sentence or two.
Yes. That's the ambiguity I explained in some detail above. No problem there, unless you don't have it straight in your head yet what mass is.
Because mass is a quantitative measure of how much matter is in the ball. As such, the mass is in your head, not in the ball. I have explained this many times, now.
They are closely related, but not the same thing, for reasons I have explained.
Are concepts in objects, or are they in your head?

11. ### James RJust this guy, you know?Staff Member

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I'd say a ball is made of matter. I would also say that matter is not a number. It is "stuff" that things can be made of.

12. ### Motor DaddyValued Senior Member

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No, when you say "the ball has mass" you really do mean the ball has mass. Sure you can measure the ball's mass, but the measure of the ball's mass means just that, that the ball has mass and you are going to measure it and give it a number of units.

Now the mass of the ball is measured with numbers and units.

If the ball doesn't have mass, as you claim, then there is nothing to measure.

What are you measuring when you measure the mass of the ball?

13. ### Motor DaddyValued Senior Member

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So you say the ball has matter, but you can't quantify your statement?

14. ### James RJust this guy, you know?Staff Member

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38,035
I explained what I mean. If you have questions, please ask.
Explain to me what you think you're measuring when you measure the mass of a ball. Are you extracting some mass stuff from the ball? Or what?

Do you agree that balls aren't made of kilograms?

15. ### arfa branecall me arfValued Senior Member

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No, that's kind of ridiculous.
If the bottle is made of transparent glass, is the transparency in my head? Is the shape and size of the bottle in my head?
If I hang an an object with mass on the end of a vertical spring, is the distance the spring extends a measurement? Why does it matter what it's called? Why are some things in a measurement "in my head", others are in the lab?

16. ### arfa branecall me arfValued Senior Member

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But in a symmetrical object like a thin disk or a solid cylinder, the radius of gyration is fixed by the geometry of the object and its mass. Not just by the geometry.
The object's geometry can change without changing the amount of matter, and this might also change the radius of gyration.

This radius isn't in my head, it's in the object.

17. ### Motor DaddyValued Senior Member

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I asked you questions and in return I get the same question back at me? That's not an answer, it's a sign of weakness! Feeling the heat now that you have to answer what you mean when you say the ball doesn't have mass, but you are going to measure the ball's mass??

I claim the ball has mass and I can measure it using numbers and units.
You claim the ball doesn't have mass, but you can measure its mass.

No brainer here to see who looks like a football bat and who thinks straight!

18. ### arfa branecall me arfValued Senior Member

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What he actually said was, "In physics today, it's important to understand that nobody knows what energy is".

What rhetorical flourish can you see in what looks like a pretty definitive claim?

19. ### Motor DaddyValued Senior Member

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Energy is power times time.

Work=force x distance
Power=work/time
Energy=power x time

So energy=((force x distance)/time) x time

Energy is watts x time

Energy has units of kilowatt - hours, which is power times time.

Your electric meter will click off 1 kw-hr if you run ten 100 watt lightbulbs for 1 hour. That is 1 kw-hr of energy

Energy is a CALCULATION of POWER times TIME!

20. ### arfa branecall me arfValued Senior Member

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Don't tell me about how you know something Feynman said nobody does!

Which doesn't seem to have stopped him trying to find out. Or tell people what he understands about it, if not "what" it is.

He also does a pretty good explanation of the moment of inertia in the lectures which James R may have spotted. So what does it say about mass, or numbers? One thing it does say is something about inertial mass. But what? Or is inertia just in our heads?

Stay tuned.

21. ### Motor DaddyValued Senior Member

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It's similar to man - hours of work.

If 3 people work for 4 hours, that is 12 man - hours of work.

If 12 people work for 1 hour, that is 12 man - hours of work.

Same for watts and time, which is energy.

22. ### James RJust this guy, you know?Staff Member

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Ghost:

I was attempting education using a Socratic method. Never mind.

Okay. I can measure the ball's mass by sticking it on a set of scales, for instance. Or I could hang it from a spring balance. Or I could put it on a balance against some object or objects whose mass I already know. There are lots of ways. The only slight hiccough with using scales is that I need to know the acceleration due to gravity in order to determine the ball's mass, since the scales only tell me the ball's weight. But that's okay - the readouts of scales usually have information about the acceleration due to gravity on the Earth's surface already built in. That is, they are calibrated.

In principle, there's another way I could measure the mass of a ball. If I knew the mass of its individual atoms, and if I could count up all of the atoms, I could just add up all the mass and that would give me the total mass of the ball. This can't be done directly, though, so using the scales is more practical.

When I put the ball on the scales, I'll see a number like "0.345 kg" on the display. That number is the mass of the ball. It's right there on the display! Then - miracle of miracles - it goes into my eyes and before you can say Bob's your Father's Brother it is in my head! The number "0.345", right alongside the units "kilogram".

Strangely, when I put the ball on the scales, nothing was sucked out of the ball into the scales. At no time did I see any mass transfer from the ball to any part of the scales. So how did the scales "know" how much mass was "in" the ball, if there was actually mass in it? Did the scales magically have access to some "mass stuff" in the ball, perhaps? Or was something else going on?
Fine. I claim the ball "has mass", too, by which I mean that a number called "the ball's mass" can be associated with the ball.
No. You misunderstood again. Hopefully, things are clear now.

23. ### James RJust this guy, you know?Staff Member

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38,035
arfa brane:

You tell me. Can you put "transparency" in a bottle on its own? Can you put "shape" and "size" into their own separate bottles?

Why is this so hard for you? I've asked you many times, yet you can't even seem to bring yourself to attempt an answer.
Yes. If you measure it.
Who said any of them are in the lab?

Where in the lab can I find "1 metre" or "250 Watts" or "25 degrees Celcius"? Do they have bottles of distance and temperature handy?
Yes. So?
Then you should be able to extract it, put it in a bottle and photograph it. Right?

Where can I get a bottle full of radius?
That statement is in a lecture of his. Have you ever given a lecture? If you had, perhaps you'd understand where the rhetorical flourish comes into it. I guess there's always the alternative: a dry, boring, fall-asleep lecture where the presenter just drones on in an uninteresting way. Maybe that's how you'd do it. Feynman, on the other hand, was good at it.
Feynman understood that energy is a number. I told you that before. In fact, I give some credit to him for helping to bring me to that same realisation. You're just slower to catch on, that's all. But you can get there, maybe.