What has a shape but no volume?

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Discussion Overview

The discussion revolves around the concept of objects that possess a shape but lack volume, exploring various interpretations and examples. Participants reference states of matter, mathematical constructs, and philosophical considerations, with a focus on theoretical and conceptual implications.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants suggest that a Klein bottle exemplifies an object with a shape but no volume, noting its non-orientable properties.
  • Others argue that while a Klein bottle can hold water on its surface, it does not possess volume in a traditional sense due to its lack of an interior.
  • A few participants introduce the idea of 2D surfaces in 3D space, asserting that such surfaces can have shape without volume, citing examples like the Möbius strip and infinitely thin spherical shells.
  • There is a discussion about the ambiguity of the term "volume" when applied to open surfaces, with participants questioning how flat a surface must be to be considered as having no volume.
  • Some participants propose that mathematical constructs, such as fractals with dimensions between 2 and 3, could also fit the criteria of having shape but no volume.
  • One participant mentions that in a higher-dimensional context, such as 4D, the properties of 2D objects change, affecting their ability to contain liquids.
  • There is a critique of the definitions of states of matter presented in a chemistry book, with some participants suggesting that the descriptions may be misleading or overly simplistic.
  • A participant humorously states that there are no solids, liquids, or gases, only fields, introducing a more abstract perspective.

Areas of Agreement / Disagreement

Participants express a range of views, with no clear consensus on what constitutes an object with shape but no volume. Multiple competing interpretations and examples are presented, leading to ongoing debate and exploration of the topic.

Contextual Notes

Participants highlight the limitations of definitions and the context-dependent nature of volume, suggesting that assumptions about dimensionality and physical properties are crucial to the discussion.

MevsEinstein
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TL;DR
what the title says.
I was reading a Chemistry book when I read about the three states of matter. Everyone knows what they are, but I didn't know the simplest way to describe each of the three until I read this book. It said that a solid has a shape and a volume, a liquid has no shape but has a volume, and a gas has no shape or volume. How about something that has a shape but has no volume? It couldn't be plasma, since it doesn't have a shape.
 
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I guess it means "not fixed" instead of "no", etc. (But even that's not really true - have you ever made pizza?).
 
A non-rigorous definition
in a container
A solid has a constant shape and volume
A liquid has the shape of the bottom of the container and a constant volume
A gas has the shape of the container and the volume of the container
If you look at the ordering, you need to have a constant volume before having a constant shape.
 
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MevsEinstein said:
What has a shape but no volume?
A Klein bottle :smile:
 
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phinds said:
A Klein bottle :smile:
mine does :-p
76617F7C-A29D-4622-A2C9-87E9C00B70F2.jpeg
 
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caz said:
mine does :-p
Does what? It can't have a volume because it has no inside.
 
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phinds said:
Does what? It can't have a volume because it has no inside.
Really? I can fill it water.
 
In case you want to get your own. It’s the best physics thing my parents ever got me.
https://www.kleinbottle.com/
It is also a very amusing website.

”At last, Acme Klein Bottle has conquered topological and engineering frontiers to manufacture genuine glass Klein bottles. These are the finest closed, non-orientable, boundary-free manifolds sold anywhere in our three spatial dimensions.”
 
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caz said:
Really? I can fill it water.
Yes, you can put some water on part of the outside. That doesn't mean it has a volume.
 
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  • #10
phinds said:
Yes, you can put some water on part of the outside. That doesn't mean it has a volume.
If I place it in a bowl of water, the level rises; however, Acme does advertise it as volume and magnetic monopole free.
 
  • #11
caz said:
Really? I can fill it water.
Volume is a sloppy idea in everyday speech for open surfaces. We would all agree that a measuring cup has some volume, but what about a watch glass? What about an upside down watch glass?

57867WATCHGLASS.JPG-250.jpg


How flat does a surface have to be to have no volume? Wouldn't you also have to specify other things like how it's filled, how it's oriented, what the boundaries are?
 
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  • #12
DaveE said:
Volume is a sloppy idea in everyday speech for open surfaces. We would all agree that a measuring cup has some volume, but what about a watch glass? What about an upside down watch glass?

View attachment 298040

How flat does a surface have to be to have no volume? Wouldn't you also have to specify other things like how it's filled, how it's oriented, what the boundaries are?
I was being flippant. You did raise some interesting questions about open surfaces. Here’s a picture from their website with volume calibration marks. They clearly anticipated your and @phinds concerns.

1646593361595.jpeg

Check out the numerical values.
 
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  • #13
DaveE said:
Volume is a sloppy idea in everyday speech for open surfaces.
Indeed.

In everyday English I suppose you can say it has a volume but mathematically (i.e. topologically) it is identical to a Mobius strip --- it's a one-sided construct. You can get from any point on the surface to any other point on the surface without ever crossing an edge. Even a flat sheet of paper can't do that.
 
  • #14

What has a shape but no volume?​


A shadow!
 
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  • #15
Menger sponge.
 
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  • #16
Tom.G said:
A shadow!
Anything 2D really.
 
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  • #17
I agree. Specifically I would say any 2D surface in 3D or higher space has shape but no volume. It may enclose a volume of space, such as an infinitely thin spherical shell, or not such as the Möbius strip or Klein bottle but it has no volume itself.
 
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  • #18
bob012345 said:
I agree. Specifically I would say any 2D surface in 3D or higher space has shape but no volume. It may enclose a volume of space, such as an infinitely thin spherical shell, or not such as the Möbius strip or Klein bottle but it has no volume itself.
In 3D a 1D object can't hold water. It will leak out into the second horizontal dimension.

A 2D object embedded in 4D can't hold water. It would leak out into the third horizontal dimension.

So in 4D a Klein "bottle" couldn't hold water. Models of the surface in 3D can hold water because the third horizontal dimension doesn't exist in 3D.

"It's only a model." -- Monty Python and the Holy Grail.
 
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  • #19
Anything of 2 dimensions?
 
  • #20
valenumr said:
Anything of 2 dimensions?
Right. It will fail to hold water everywhere no matter what you do. You could gin up some highly convoluted object to simulate 3D but that's cheating.
 
  • #21
Hornbein said:
Right. It will fail to hold water everywhere no matter what you do. You could gin up some highly convoluted object to simulate 3D but that's cheating.
It's still an interesting question in a sense. The closest thing I can think is something like a sheet of graphene, but it still necissarily has volume (think mass density as a concept). But physically, I guess one would have to talk about point particles like an electron to ponder the question.
 
  • #22
valenumr said:
It's still an interesting question in a sense. The closest thing I can think is something like a sheet of graphene, but it still necissarily has volume (think mass density as a concept). But physically, I guess one would have to talk about point particles like an electron to ponder the question.

In our world, in order for an object to exist it has to have 3 dimensions greater than zero. When I say 2D this means that one of the dimensions is insignificant.

In the 4D world then a 2D object has two dimensions are insignificant. There can be only one vertical dimension so that means a 2D object has a horizontal dimension that is insignificant. A liquid would then flow out in this dimension/direction. Either that or the object can hold only an insignificant amount of liquid.

But it is neater to imagine an ideal 2D object that magically is impermeable to fluids than to continually have to hedge with these messy qualifying statements.

---

In 4D tortillas have to be 3D. Who wants a tortilla that can support only insignificant toppings? The natural shape would be a 3D ball (solid sphere). It's flat in the 4th dimension.
 
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  • #23
MevsEinstein said:
I was reading a Chemistry book when I read about the three states of matter. Everyone knows what they are, but I didn't know the simplest way to describe each of the three until I read this book. It said that a solid has a shape and a volume, a liquid has no shape but has a volume, and a gas has no shape or volume. How about something that has a shape but has no volume? It couldn't be plasma, since it doesn't have a shape.
I think that that is a terrible way to describe the three states, in the UK we like to stick to the facts: https://www.bbc.co.uk/bitesize/guides/z93jfcw/revision/1

But I think you are misquoting: I expect that the book talks about fixed or specific shapes and volumes and in particular says a gas has no specific shape or fixed volume.
 
  • #24
There are no solids, liquids or gasses, only fields. :)
 
  • #25

What has a shape but no volume?​

Taken as an isolated general question, then if shape is considered to be surface area one could argue that an object with a fractal dimension between 2 and 3 would have shape but no volume.
 
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  • #26
What has shape and no volume? This is an interesting question in pure mathematics (not the place for it), but in chemistry we can say that a gas has no fixed volume, but has the volume of the enclosure fully surrounding it, while a liquid of the enclosure supporting it against gravity.
 
  • #27
dextercioby said:
What has shape and no volume? This is an interesting question in pure mathematics (not the place for it), but in chemistry we can say that a gas has no fixed volume, but has the volume of the enclosure fully surrounding it, while a liquid of the enclosure supporting it against gravity.
This appears to be true on some scales but not all. The atmosphere around the Earth acts more like the liquid example you give. It is not fully contained yet has a finite volume while a liquid drop may be contained by surface tension and not fill a small enough container. These behaviours are scale dependent.
 
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  • #28
bob012345 said:
This appears to be true on some scales but not all. The atmosphere around the Earth acts more like the liquid example you give. It is not fully contained yet has a finite volume while a liquid drop may be contained by surface tension and not fill a small enough container. These behaviours are scale dependent.
I was thinking about the same (atmosphere). It is I'll defined. My favorite part is how it drives flat-earthers nuts though.
 
  • #29
Why would you say the atmosphere has a finite volume? What is it?
 
  • #30
pbuk said:
I think that that is a terrible way to describe the three states, in the UK we like to stick to the facts: https://www.bbc.co.uk/bitesize/guides/z93jfcw/revision/1

But I think you are misquoting: I expect that the book talks about fixed or specific shapes and volumes and in particular says a gas has no specific shape or fixed volume.
Apparently glasses and plastics aren't solid in the UK...
 

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