Collapse

Before you looked, this site was every version of itself at once. The moment something conscious attended to it, the superposition resolved and one world became real. That is the conceit of the intro, and it is borrowed, almost without exaggeration, from how quantum mechanics actually works.

The concept

A quantum system is not in one state with unknown value; it is in a genuine superposition of states at once, evolving smoothly and deterministically. Measurement is the strange step: the smooth evolution gives way to a jump, and the system is found in one outcome with a probability set by how much that outcome was "present" in the superposition. What counts as a measurement, and why it looks like a jump, is the unfinished business at the heart of physics.

The math

A state is a vector $|\psi\rangle = \sum_i c_i |i\rangle$, a weighted sum over possibilities. The probability of finding outcome $i$ is the Born rule:

$P(i) = |c_i|^2, \qquad \sum_i |c_i|^2 = 1$

Between measurements the amplitudes evolve unitarily (Schrödinger's equation), preserving the total $\sum_i |c_i|^2 = 1$. On measurement the state "collapses" to the observed $|i\rangle$ and the other amplitudes vanish. The intro maps your attention to a collapse parameter: until you move like something alive, the layers hold in superposition; once you do, they resolve.

Why it stays strange

The equations never tell you when collapse happens, only its statistics. Decoherence explains why large things look classical, the superposition leaks into the environment and stops interfering, but the question of why you see one outcome rather than the branching whole is still open. The site does not solve it. It just lets you feel the seam: attention deciding what is real.

Further reading

• Feynman, The Feynman Lectures on Physics, Vol. III, ch. 3.
• Zurek (2003), "Decoherence and the Transition from Quantum to Classical."

@article{zurek2003,
  author  = {Zurek, Wojciech H.},
  title   = {Decoherence, Einselection, and the Quantum Origins of the Classical},
  journal = {Reviews of Modern Physics},
  volume  = {75},
  number  = {3},
  pages   = {715--775},
  year    = {2003}
}