The building blocks of strings

[Sophrosyne]

TL;DR

How can we know for sure that strings or anything else are "fundamental" building blocks, and not always in turn made of smaller things? Is there some theoretical/conceptual way to know we have finally touched bottom?

I know string theory is already controversial enough and may even be falling out of favor among many physicists. But assuming it is right, I have heard string theorists say that strings are the "fundamental building block" of the universe. How do they make this assertion so confidently (seemingly)?

My question is a broader question of "how do we know we have hit a fundamental level" of the components of matter? That question holds even if string theory eventually falls completely out of favor and something else begins to take its place.

It seems strings have very peculiar properties, like that they can close in on themselves to form loops or open up, they can attach to branes, etc... How do they do that? Doesn't this sort of behavior imply that there is some sort of fine structure to them? Maybe there are hook-like structures at each end or things like Lego pieces at each end that allow them to stick. What are those things made of? What forces/energies are at play that allow them to do that?

At one point, everyone thought atoms were the fundamental building blocks. Then we found out atoms were made of other things, and now we are suggesting all those other things are in turn made of strings. How do we know that NOW we have hit the most fundamental level? It gives one a sense of vertigo to start thinking in that way. But if it's right, how far down does this go, and is there any fundamental level which we can confidently say is "fundamental" and not just another level of organization? How would we know we have truly and finally gotten to the truly fundamental level? How do we know it's not just "turtles all the way down"?

Is it wrong to think that, even if string theory turns out to be right (or any other theory that might replace it), it is unlikely that we can ever be sure it is the final "fundamental" level? Or is there some theoretical criterion by which we will know (eg, a single small neat formula explains it all)?

 

[Vanadium 50]

How can we know for sure that strings or anything else are "fundamental" building blocks

We don't know that.

 

[B.C.]

My pitiful human brain cannot accept either of these statements:

There is a lowest level of description that not only explains how the higher level stuff works, but also explains why it itself exists, with no need for further explanation.

or

There is no lowest level, structure just goes on forever (turtles all the way down.)Like to hear an alternative proposal.

(Yeah, I know, that's philosophy, not science...)

 

[BvU]

Keep digging !

 

[Sophrosyne]

My pitiful human brain cannot accept either of these statements:

There is a lowest level of description that not only explains how the higher level stuff works, but also explains why it itself exists, with no need for further explanation.

or

There is no lowest level, structure just goes on forever (turtles all the way down.)Like to hear an alternative proposal.

(Yeah, I know, that's philosophy, not science...)

I remember reading about how we are fairly sure that there are likely only 3 generations of leptons ( electrons, muons, tau in the Lepton family) and very likely there aren't any more- based on the fact that no one has found the neutrinos for anything heavier. They were saying if there was anything heavier, it would likely have had a neutrino that would have been detected already. Maybe there's some empirical observation like that, or some mathematical construct, that would convince us we have reached that "fundamental" rock bottom layer with string theory or some other fundamental theory.

For example, there could be some way to mathematically prove that string theory and only string theory is right, and there cannot be anything further underlying it (although that might get into the whole business of Godel's incompleteness theorem).

Anyway, like you said, this is all philosophy, not science (yet).

 

[BvU]

The world is full of broken symmetries ...