Questions with no right answer

// question one

Is my blue your blue?

We both look at the sky and say "blue". We'd both pick the same swatch, and a computer would call it #0000FF. But is the experience in your head the same as the one in mine? Maybe what you see as blue is what I'd call orange, and we've just both learned to name it "blue".

Philosophers call the raw feeling of an experience a quale (plural: qualia), and this is the "inverted spectrum" problem. Brain scans can show which neurons fire, but not what it's like to be the brain they're firing in.

My take: it's probably close, since we share the same kind of eyes and brains. But "probably" is all anyone can ever say. You'll never see through my eyes, and that's slightly terrifying.

// question two

Why 42?

In The Hitchhiker's Guide to the Galaxy, a supercomputer called Deep Thought spends 7.5 million years calculating the Answer to the Ultimate Question of Life, the Universe, and Everything. The answer: 42. The problem: nobody actually knew what the question was.

Douglas Adams said he picked it because it was an ordinary, slightly funny number. The internet, naturally, refused to accept that:

• 42 is 101010 in binary: a perfectly alternating pattern.
• Drill a straight tunnel through the Earth and jump in. Ignoring air and friction, gravity would carry you to the other side in about 42 minutes. Wherever you dig the tunnel.
• It's 6 × 7, which is a strangely satisfying pair of neighbours.
• And 4 + 2 = 6. Hold that thought.

// question three

Tesla's 3, 6, 9

Nikola Tesla supposedly said that if you knew the magnificence of 3, 6 and 9, you'd have a key to the universe. (There's no reliable source he ever said it, which somehow makes it more fun.)

Here's the trick that makes it feel mystical. Keep doubling a number and adding up its digits until you get one digit:

The doubling cycle never touches 3, 6 or 9. They live in their own little loop, and 9 never changes at all. Spooky!

The boring truth: digit sums are just remainders when you divide by 9 (plain old modular arithmetic). It works because we count in base 10, and 10 is one more than 9. Count in a different base and the "magic numbers" change. Still beautiful, though. And 42's digits add up to 6, so Deep Thought and Tesla were secretly on the same team.