String theory from an outsider theorist’s perspective

ME: The Standard Model is weird. Twelve non-spatial internal dimensions — three different gauge-fiber spaces (U(1), SU(2), and the especially complicated SU(3) one) — all rigged just so to give us the particle zoo and the forces.

STRING THEORIST: I’ve got an idea that might make it all make sense.

ME: I’m listening.

ST: Keep ordinary spacetime, but add tiny vibrating strings whose modes are the particles and forces.

ME: Love that. Clean, elegant.

ST: But there’s more. Spacetime isn’t actually 4D — it’s 10D.

ME: Uh.

ST: Not to worry — the 6 extra ones are spatial. Just… very small.

ME: Small like “invisible”? Or small like “mathematically decorative”?

ST: Curled up. Planck-scale. Only strings notice them.

ME: So: six more spatial dimensions… but effectively nonexistent.

ST: Exactly! Elegant, right?

ME: Let’s say “ambitious.” Continue.

ST: And these six tiny dimensions aren’t all the same. They have intricate, highly constrained topologies.

ME: Let me guess: the topologies are tuned just so to give the strings exactly the right vibrational patterns to reproduce the Standard Model we were trying to explain.

ST: Yes! That’s exactly the magic.

ME: Magic. Sure.

ST: Plus, gravity comes “for free.”

ME: For free, huh?