[layoutIfNeeded]

What you wrote has no basis in reality whatsoever. In fact, nerve conduction is slower in children than adults due to underdeveloped myelination.

[whatshisface]

Furthermore, "constrained by physics" would imply the speed of light, which is so much faster than nerve conduction...

[hypertele-Xii]

There are other constraints in physics than the speed of light.

[strbean]

My flippant guess would be that time perception changing with age would be related to the NMDA receptor. NMDA receptor function decreases with age[0]. My personal anecdotal experience with NMDAR antagonists is that it feels like the `Turbo` mode on old IBM compatibles[1] -- i.e. downclocking. And the slower you process, the faster the world seems to move around you.

[0]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3181613/

[1]: https://en.wikipedia.org/wiki/Turbo_button

[User23]

My even more flippant guess would be that adults drink more alcohol than children.

[shadowofneptune]

From what I remember from development 101, there are also more possible synaptic connections in early childhood, and these get pruned down over time. This would also reduce the amount signals travel.