The math says a particle is a spread of possibilities until measured, then one fact. The math never says what a measurement is, or why looking should matter.
Documented
The formalism works, the meaning is missing
The Schrodinger equation evolves systems smoothly into superpositions; experiments yield single outcomes with Born-rule probabilities; the formalism contains no rule for when one replaces the other. The documented responses: Copenhagen's shrug, collapse is fundamental, von Neumann and Wigner's consciousness-caused collapse, Everett's many worlds (1957), Bohm's hidden variables (1952), GRW's spontaneous collapse (1986), decoherence, which explains the appearance of collapse without producing the outcome.
Assessment: All documented positions with live defenders. The problem is not ignorance of data; every experiment ever run matches the math. The problem is that the math refuses to say what it means, and that is a documented, unsolved, foundational gap.
Stories
The cat that ate philosophy
Schrodinger invented his cat (1935) to mock the idea, not to endorse it: a creature simultaneously dead and alive until the box opens. Pop culture took the joke literally, and the cat became the mascot of a thousand takes about minds creating reality, Your thoughts collapse the wavefunction sold as self-help.
Assessment: The cat is documented as satire. The consciousness-creates-reality reading was proposed seriously by Wigner and later abandoned by him, and no experiment has ever shown a mind doing anything a Geiger counter cannot.
Interesting claims
Observation as the engine of reality
The interesting claim persists anyway: that consciousness is not a bystander but the mechanism, that unobserved reality stays liquid, and that the universe's habit of producing observers is not an accident but a requirement, wheeler's participatory universe raised to a worldview.
Assessment: Wheeler did propose the participatory phrase, and it remains interpretation, not measurement. Decoherence research has steadily shrunk the role anything mind-like could play. The claim survives because the problem it exploits is real, and because nobody can run the decisive experiment.
Sources and further reading
Schrodinger, The Present Situation in Quantum Mechanics (1935), the cat as satire
Everett, Relative State Formulation of Quantum Mechanics, Reviews of Modern Physics (1957)
Bohm, A Suggested Interpretation of the Quantum Theory (1952)
Ghirardi, Rimini, Weber, Unified Dynamics for Microscopic and Macroscopic Systems (1986)
Wheeler, the participatory universe essays, and Wigner's retreat from consciousness-collapse
Zurek, Decoherence and the Transition from Quantum to Classical, Physics Today (1991)
Worth asking
If reality needs an observer to settle, what settled it for thirteen billion years before anyone looked?