One long hole.
One hole, two openings.
This thread has me wondering - topologically, what’s the difference between a solid ball and a hollow sphere with no openings? Most of topology I’ve heard has put a lot of stock into stretching and flattening things into flat planes with some number of holes in them, but I don’t recall anybody talking about the terms for ‘bubbles’.
One
Zero. It’s not a hole unless it’s an opening cut into something that started out solid.
Topologically, they are.
A straw has the same number of holes as a donut - 1.
A straw is a hole. With sides.
My brother used to muse on how one would go about carving a hole (the premise being that one carves by cutting away the parts you do not want, so, what would be left).
“The Zen philosopher Basho once wrote, ‘A flute with no holes is not a flute. And a doughnut with no hole is a danish.’”
- Ty Webb
This is correct. I supposed there could be a few rare examples where a hole is drilled into a solid rod to make a straw, but 99.999% of all straws never start off as a solid.
Pixie Stick? 
Try drinking milk through a cylinder with only one hole, let me know what happens.
Two.
No, a cup (at least, a properly functional one) has zero holes. Anyone who says “my cup has a hole in it” is upset by that fact.
There is no hole.
To make a hole, one must remove/displace material. Straws are made with no material in the middle to be removed.:eek:
Drinking milk from a cylinder with no holes would be no problem because that is the definition of a straw. Drinking milk from a cylinder with only one hole could be difficult depending on if the hole is above or below the level of the liquid (the only way to put a hole into a cylinder is to put it through one of the solid sides.)
A water pipe is a cylinder… the only time people have a problem with their plumbing is if there is a hole in the pipe.
These ‘bubbles’ are described by homology and homotopy groups. For example, your hollow 2-dimensional sphere has Betti number 1 in dimensions 0 and 2 (reflecting the fact there is a 2-d ‘bubble’), while the solid ball has zero homology in every dimension except 0, reflecting the fact there are no higher-dimensional holes. (The homology in dimension 0 corresponds to connected components, so it is not zero.)
It is worth adding that the solid torus under discussion has homology groups of ranks 1, 1, 0 in dimensions 0, 1, 2, so from this algebraic point of view you could say there is a single 1-dimensional hole, to be contrasted with the 2-dimensional torus which has 1, 2, 1, corresponding to a single connected component, two independent 1-dimensional holes, and the hollow interior which is a 2-dimensional hole/bubble.
My cup has exactly one hole in it - I put my fingers through that hole to pick it up. Actually, it might be a donut.
I agree on all of this and I am trying to resolve how we count the holes in a different object (I have only a superficial understanding of topology). Imagine a solid ball into which we drill three times, at points equidistant along the equator, toward the centre and meeting at the core. There are three openings, all of which are linked to one another internally - how many holes are there? (I don’t know)
I would argue that yes, in fact they do - plastic drinking straws are continuously extruded via a die - that is, a ‘solid’ stream of plastic is parted by a central plug in the die to create the hole. There isn’t a lot of difference between:
Pushing a drill through a solid material
vs
Pushing a stream of material over a central plug