It's linear.
Technology, on the other hand, is exponential.
Take it from Ray Kurzweil, the bestselling author, futurist, and Google chief engineer.
"The reality of information technology is it progresses exponentially," he told the Financial Times. "30 steps linearly gets you to 30. One, two, three, four, step 30 you're at 30. With exponential growth, it's one, two, four, eight. Step 30, you're at a billion."
Citing that exponential growth, Kurzweil has confidently claimed that computer intelligence will outpace human intelligence by 2029 and that medicine will soon get to the point that he'll be able to basically live forever.
But the "exponential growth" can be hard to wrap your mind around.
So Kurzweil likes to use an old folktale, variously attributed to Ancient India and Ancient China.
Here's his telling from the 2001 essay, "The Singularity is Near":
I am fond of telling the tale of the inventor of chess and his patron, the Emperor of China.
In response to the emperor's offer of a reward for his new beloved game, the inventor asked for a single grain of rice on the first square, two on the second square, four on the third, and so on. The Emperor quickly granted this seemingly benign and humble request.
One version of the story has the emperor going bankrupt as the 63 doublings ultimately totaled 18 million trillion grains of rice. At ten grains of rice per square inch, this requires rice fields covering twice the surface area of the Earth, oceans included. Another version of the story has the inventor losing his head.
Kurzweil contends that we're in the middle of that chessboard.
So things are about to get way, way more exponential.
"As exponential growth continues to accelerate into the first half of the twenty-first century," he writes. "It will appear to explode into infinity, at least from the limited and linear perspective of contemporary humans."
Kurzweil and his peers have a name for that explosion: the Singularity, the moment when computer intelligence supplants human intelligence as the smartest thing around. It's either very good - or very terrible - news.