In the course
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10 videos · 3 h 30 min
Explainer · YouTube
Sabine Hossenfelder
Sabine Hossenfelder takes apart the claim that the delayed-choice quantum eraser rewrites the past, building up from the double slit and entanglement. Watch it after Part 7: her account of why fringes appear only in sorted subsets of the data is exactly the lesson's.
Demo · YouTube
Physics Demos · Boyd F. Edwards
A Utah State University demonstration: two double slits that share a 0.04 mm slit width but have separations of 0.25 mm and 0.5 mm, and the wider separation gives the more closely spaced fringes. Doubling d should halve the fringe spacing Δy ≈ λL/d, while the broad single-slit envelope, set by the unchanged width, should stay put.
Explainer · YouTube
Khan Academy India - English · Mahesh Shenoy
Khan Academy adds two coherent waves as rotating arrows (phasors) and derives I = 4I₀cos²(φ/2), this section's interference term worked out for light. Read intensity as probability and the two waves as ψ₁ and ψ₂, and you get the lesson's result for equal slits: four times one slit's value where the arrows align, zero where they oppose.
Explainer · YouTube
Looking Glass Universe
Mithuna Yoganathan takes apart the popular telling in which watched electrons turn into little bullets that pile up in two lumps. With which-path detectors, she argues, each electron goes through the slit where it was seen, but the dots still follow a wave-shaped single-slit pattern, which is what this section's P₁ and P₂ really look like.
Explainer · YouTube
Sabine Hossenfelder
Ten quantum myths counted down to number 1, 'Consciousness Influences the Outcome of Quantum Processes': this section's callout, and where the jump lands. Compare her answer with the section's: what wipes out fringes is a record, anywhere, not a mind. Rewind to 0:10 for the other nine.
Explainer · YouTube
PBS Space Time
PBS Space Time admits it got the delayed-choice quantum eraser wrong, and Mithuna Yoganathan of Looking Glass Universe co-hosts and shows how to do the experiment at home. Hold it to this section's key step: the screen's dots alone never show fringes; only sorting them by their partners' results reveals fringes and anti-fringes, which sum back to a featureless hump.
Lecture · Royal Institution
The Royal Institution · Jim Al-Khalili · 2025
A Friday Evening Discourse recorded at the Ri in November 2025, a century after Heisenberg's breakthrough: a hundred years of quantum theory, from the 1920s pioneers to the technologies being built now. Keep asking which claims are experiment and which are interpretation.
Explainer · Fermilab
Fermilab
Fermilab's Dr. Don Lincoln introduces the big ideas behind the most famous experiment in quantum physics: what waves do at two slits, what particles do, and why quantum objects fit neither picture. It sets you up for Parts 1 to 4; notice the questions it leaves open, because Parts 5 to 7 answer them.
Lecture · MIT
MIT OpenCourseWare · Robert Field · 2017
Professor Robert Field's lecture from MIT's 5.61 Physical Chemistry (Fall 2017) works through the two-slit experiment, the evidence that light and matter behave as both waves and particles, and the uncertainty principle. University-level and unhurried, with the two-slit discussion starting about six minutes in: watch it after Part 4, and treat its uncertainty-principle discussion as a preview of chapter 8.
Lecture · Royal Institution
The Royal Institution · Neil Johnson
A clip from Neil Johnson's 1999 Royal Institution Christmas Lectures that explains wave–particle duality with double-slit demonstrations. Use it as a warm-up for Feynman's three runs: for each demonstration, ask whether the result is lumps that add, like bullets, or bands that interfere, like water waves.