B Is There Truly an Inside and Outside?

[ddjj77]

Are there any such locations in reality as "Inside" and "outside" anything, except as concepts?
We say "Inside a circle," while circles exists only as concepts.
Specifically, is there an inside of me?
Or, is there an inside to a 1" OD x 3/4" ID x .000001" L pipe?
Is there an inside to a similar pipe that's a mile long? Where exactly is the border between the inside and outside of the pipe?

 

[jbriggs444]

An important coming-of-age realization is that not everything is black and white. Another is that this does not rob "black" and "white" of all meaning.

 

[andrewkirk]

Where exactly is the border between the inside and outside of the pipe?

To do science, we need to get rid of the word 'exactly'. Science is not exact. It does not need to be, and attempts to be exact only hinder progress.

Consider Newtonian mechanics. It is not exactly correct, but it is enormously useful. We have replaced it with Einstein's theory of gravity. We do not expect that to be exact either, since we know it is incompatible with quantum mechanics, yet it is more accurate than Newtonian mechanics, and useful in even more situations. One day we expect Einstein's theory will be replaced by something even better, which will later on be replaced by something better again, and so on.

Turning to the pipe. When you zoom right in, ambiguity arises about exactly what the border of the pipe is. Indeed, from a quantum mechanical perspective, there is no such thing as the exact border of the pipe. Fortunately, we don't need to identify an exact border, so the fact that the question has no answer doesn't matter.

For most purposes, if the pipe wall's thickness is approx h and the pipe has radius approx R to the approx outer wall of the pipe, we can work by simply assuming that all points of distance less than R - 1.001 h from the pipe's approx centre are inside the pipe and all points of distance more than R + 0.001h are outside it.

 

[ddjj77]

Turning to the pipe. When you zoom right in, ambiguity arises about exactly what the border of the pipe is. Indeed, from a quantum mechanical perspective, there is no such thing as the exact border of the pipe. Fortunately, we don't need to identify an exact border, so the fact that the question has no answer doesn't matter.

Good points. Thanks.

 

[berkeman]

The inside of this thread is closed for Moderation. Hopefully we can figure out what to do with it inside of a day...

 

[berkeman]

After a Mentor discussion, the thread is re-opened. Thanks for your patience.

 

[olgerm]

I think there is a clear distinction between inside and outside for closed surfaces in 3D euclidean space.

 

[gmax137]

Specifically, is there an inside of me?

Ask your heart

 

[DrClaude]

When you zoom right in, ambiguity arises about exactly what the border of the pipe is. Indeed, from a quantum mechanical perspective, there is no such thing as the exact border of the pipe. Fortunately, we don't need to identify an exact border, so the fact that the question has no answer doesn't matter.

This reminded me of

 

[ZapperZ]

I actually do not understand the problem with this whole thing.

"Inside" is defined as a region encompassed by a closed boundary. When you have a spherical shell, there is no ambiguity on where "inside" the sphere is, since one volume is bounded by a closed surface, the other isn't.

Note that this is more math than physics, and I'm sure there are clear and unambiguous set of definitions for this. And we use such math in many instances. In Gauss's law, you'd BETTER know the difference between inside a closed surface versus outside of it.

Zz.