"Mental experimentation" strikes me as an insane expression in such a scenario.

By definition we experience a device in reality not through thought.

One can for example quite imagine a staircase of

**penrose**:

Le

**Zeno paradox** exposes very well the difficulty between apparent logic and physical reality:

* ***The dichotomy** : movement is impossible, because before the moving object can reach its destination, it must first reach half of its course, but before reaching half, it must first reach a quarter , but it must first reach the eighth, etc. So the movement can never even begin.

http://www.philo5.com/Textes-references/ZenonD'Elee_LyceeInternational.htmSo if we can halve the distance between an archer and his target, we can logically deduce that any arrow must necessarily reach half of this distance, then half of this half etc ... mentally one can imagine an enlargement of the smallest segments and divide them again and again to infinity ...

We can therefore logically deduce that the arrow never reaches its target, and that it is impossible to scratch your nose!

Physically, such a phenomenon does not make sense, because if we subdivide matter: molecule, atoms, particles, quarks, we arrive at an ultimate stage:

**Planck's length**, indivisible by nature and where the concepts of time and space disappear ... practical because it allows you to scratch your nose or go from point A to point B!

"Engineering is sometimes about knowing when to stop" Charles De Gaulle.