I like the imagery of the last post because it was tapping into the idea of waves and how sub-atomic particles behave like waves.

However, erm actually 🤓 …

you pet your dog and the electron-orbitals of your skin overlap with the electron-orbitals of his fur

No, they don’t overlap. Electrons are negatively charged, and like repels like. The orbitals will repel each other. This repulsion is the reason why you can feel the fur.

Edit: I’m getting nay-sayers that reckon they do. Please provide a reference that explains inter-molecular orbitals that cause bonding for a hand touching fur. The only thing I can think of this happening is for transition states. This would require a chemical reaction. I don’t think we categorise “touch” under “requiring a chemical reaction”.

Because the structure of the transition state is a first-order saddle point along a potential energy surface, the population of species in a reaction that are at the transition state is negligible. Since being at a saddle point along the potential energy surface means that a force is acting along the bonds to the molecule, there will always be a lower energy structure that the transition state can decompose into. This is sometimes expressed by stating that the transition state has a fleeting existence, with species only maintaining the transition state structure for the time-scale of vibrations of chemical bonds (femtoseconds).

Source: https://en.wikipedia.org/wiki/Transition_state

Can someone explain the joke?

Yes, but you don’t need lights if there are only bikes. Lights are there to prevent heavy vehicles from colliding. If there are no heavy vehicles, then the lights aren’t needed.