03 From zero · Crypto markets

Bitcoin

The first application of that ledger, and the only one with a cap nobody can change alone. Where the twenty-one million limit comes from, what the halving does, and what mining actually is.

Renato UlianovOpening · 21 s · in Portuguese

The sentence

The halving cut the reward in half, the difficulty adjusted two weeks later, and issuance kept walking towards the cap of twenty-one million.

Blurred on purpose. Five words, and all of them are calendar.

The rule nobody changes

Twenty-one million, and not one more

Every currency has somebody deciding how much of it will exist. For the dollar it's the Fed — that was lesson 05 of the other track. For bitcoin the answer is odd: nobody decides, because it is already decided.

The program the network runs has an issuance rule written into it. Every new block creates an amount of bitcoin out of nothing and hands it to whoever closed the block. That amount is the reward, and it is the only door bitcoin comes into the world through — there is no other.

The reward started at fifty per block. And every two hundred and ten thousand blocks — about four years — it halves. That's all. Everything that follows comes out of that one-line rule.

The schedule

Each cut delivers half of what's left

Halving forever has a less obvious effect than it seems: the first era, on its own, creates half of all the bitcoin that will ever exist. The second creates half of the remainder. And so on.

Tap each era to see the numbers. They are not estimates or forecasts: they are the rule divided by two, and they were settled on day one.

The sum never passes twenty-one million because each era delivers exactly half of what was left. After the last cut the reward reaches zero and issuance ends — the ledger carries on, and whoever closes a block lives on fees alone.

What mining does

Not finding — trying

The word mining gets in the way. Nobody is looking for hidden bitcoin anywhere. What the machine does is assemble a candidate block, compute its summary, and check whether the result landed below a target. If it didn't, it changes an arbitrary number inside the block and computes again.

There is no shortcut: the summary is unpredictable, so the only path is trying. Whoever finds one first announces the block, and the network checks it in a single computation — hard to find, easy to check. That is what lesson 02 called expensive.

Try it. Raising the difficulty shrinks the target, and the number of attempts explodes.

Difficulty: the summary must start with

Summary found —

Attempts: 0
Expected average

The summary here is the same toy one from lesson 02, and the target is just the number of leading zeros. On the real network the target is a 78-digit number and machines do this trillions of times per second. The relation between difficulty and work, though, is exactly this: each extra zero multiplies the work by sixteen.

The adjustment

The pace is fixed, the competition isn't

If more machines join, blocks start coming out too fast. If many quit, too slowly. Either way the issuance schedule would fall apart — and the halving would stop being a four-year thing.

So the network recomputes the difficulty every two thousand and sixteen blocks, about two weeks, aiming at an average of ten minutes between blocks. Difficulty chases the competition so that the clock does not move. It is the mechanism that makes the cap a promise that can be kept.

The proof

Now read the sentence

It's the same one from the top, unblurred. Tap each highlighted part.

The cut the in half, the adjusted two weeks later, and kept walking towards the of twenty-one million.

Start here

Five words

None of them is an opinion: all five are written rule. Tap one.

Five taps and the sentence is done.

You can already answer these

If this landed, the lesson did what it promised

The block reward is the only door new bitcoin comes in through.
Every 210 thousand blocks it halves — and each era delivers half of what's left.
Mining is trying until the summary lands below a target, not finding coins.
Difficulty adjusts so the interval between blocks always looks the same.

Renato UlianovClosing · 38 s · in Portuguese

Educational material. This page describes the issuance rule and the mining mechanism, which are fixed, and therefore quotes no price, no amount already issued, and no current era — those change. It is not a recommendation to buy or sell.