The stretches you cannot say

The metric walks each address and finds the longest unbroken stretch containing none of the five vowel letters. The bars show the answer per address, and the answers are long.

Vowels have no meaning to the format. The encoding treats every letter identically and has no idea which ones are vowels. The measure exists purely because vowels matter enormously to a reader: a stretch without them cannot be pronounced, and anything that cannot be pronounced cannot be held in working memory as sound.

People hold short sequences by saying them internally. That is why a phone number is manageable and why you repeat a name under your breath after being introduced. The trick needs the sequence to be sayable.

A run of consonants of this length is not sayable in any language, so the usual mechanism has nothing to work with. What is left is remembering the shape of the characters, which is far weaker, decays in seconds, and is exactly the mechanism the traded symbol set attacks.

The practical result is a hard limit. You will not carry a nexus market address across the room in your head. Not because you are careless, but because the equipment for doing it is not engaged by a string of this shape.

The third tile counts vowels in each seventh of one address. The line moves around, and the low points are the parts that read as noise even to a careful reader.

As with every block metric on this board, the specific shape belongs to this address alone. Run it on another and the peaks move. What holds across all three is that there is always at least one long dry stretch, and that is enough to make the general point.

• Reading an address aloud to somebody is unreliable in both directions and gets worse the longer the vowel free run is. The panel on reading aloud goes into how it fails.
• Spelling it out with a phonetic alphabet is slow and works better, at the cost of taking several minutes for one address.
• Neither is a good idea when a copyable version exists. Both are what you do when there is no alternative.

It is not a difficulty score. There is no scale here, no comparison against other strings, and no threshold at which an address becomes hard. It is one number about one property.

It is also not a criticism of the addresses. Nobody chose these letters. They fell out of an encoding, and any other address would produce a similar figure. The reason to measure it is to explain a real experience people have, which is that these strings slide out of memory instantly and it is not their fault.

Since the string cannot be held in the head, everybody develops a substitute, and the substitutes vary a lot in quality. The common ones are a bookmark, a note in a file, a message sent to yourself, a photograph of a screen, and a piece of paper.

Each of those has a different failure mode, and none of them is memory. That is the practical consequence of a long unpronounceable run: the address has to live somewhere outside you, permanently, and choosing where is a real decision rather than an afterthought.

It also explains a common frustration. People feel they should be able to recognise their own address after using it for a while, and they cannot, because recognition also leans on the sayable form. What you end up recognising is the shared opening, which every address in the set has, so the feeling of recognition is real and carries no information at all.