About
Proofs are an art. This is the gallery.
Ask how many proofs there are of the Pythagorean theorem and the honest answer is: hundreds, and people are still finding more. Nearly everyone learns exactly one. The board is for the rest: several proofs of the same statement, side by side, and readers saying which one made them see it.
What the board is for
Mathematicians do a peculiar thing: they prove what they already know. Nobody doubts the Pythagorean theorem, and yet people keep finding new reasons for it, because a proof is more than a certificate. A proof can be correct and explain nothing. Another can be rough at the edges and still be the one that makes you see why the thing is true. The board keeps both kinds side by side, and lets the room say which is which, as two separate questions, because they are.
Problems are reviewed before they go up, so the board stays a short list rather than a feed. Proofs are not reviewed at all: anyone signed in can post one to any problem at any time, even one that already has a recognized proof. Taste is subjective, and the board does not pretend otherwise. Arguing about it is the point.
The founding set
The board opened with seven problems, signed The Thinking Board. Everything signed with a person’s name was written by that person.
The founding problems have not been refereed: if one is badly stated, or turns out to be wrong, say so in its room.
Every founding problem starts with no proof, which makes it the easiest place to be first. Whatever you post is the argument the board starts from, and the recognition is not fixed: it moves whenever someone posts something better.
The three marks
Marking is not rating. Each mark asks a different question, and they get scarcer as the question gets harder to answer honestly.
As many as you like
The argument that actually persuaded you. Give it to every proof that earns it — a problem can have several. The proof holding the most carries the board’s recognition. If one did not persuade you, the downward triangle cancels a convincing mark and counts against it instead.
One per problem
Not the clearest proof, the one you would show someone. You get a single beautiful mark per problem, so giving it to a second proof takes it off the first.
One a year
For the proof you are still thinking about a week later. One per reader per calendar year, anywhere on the board. You can take it back — but you only ever have the one.
No mark can be spent twice and every one can be taken back. Nothing on the board is closed: the brass rule moves whenever the convincing marks move.
The room can also turn something away. A problem that collects five downvotes drops off the board. A proof whose net convincing score falls to −5 is greyed out, and leaves the board if it is still there three months later. Nothing is deleted: an editor can restore either, and a restored one stays.
Badges read the same record back — what a person has posted and what the room did with it. They are not awarded and nothing is stored: each one is a sentence about the board, checked every time the page is opened, and a mark you place on your own proof never counts toward one.
Who runs it
The board is run by its founder and by editors. Editors decide what goes on the board and nothing else — they cannot mark proofs on your behalf, edit what you wrote, or remove a proof because they disagree with it. The role is granted, not applied for by password: you ask from the review page once signed in, and the founder grants or declines it.
Accounts, and what the board keeps
Reading takes no account. Posting a proof, writing in a room, or placing a mark takes one, because marks have to belong to somebody for the counts to mean anything.
Signing in with Google tells the board your name and email address. Your email is how the board recognizes you between visits and it is never shown on the board — what other readers see is the alias you choose on your page, or your Google name until you set one. You can change the alias whenever you like; it changes everywhere your name appears.
Corrections
If something here is wrong — a proof, a statement, or this page — the room under the problem is the place to say so, and it stays on the record when it is. The board would rather be visibly corrected than quietly right.
You can edit anything you wrote — a proof, a reply, a message in a room — at any time, and only you can: an editor approves problems and cannot touch your words. Marks already given stay where they are, and the board shows that the argument has been edited, because a proof can change under the marks it was given.