History of
The Neutrino Oscillation
lore/trolla/the-neutrino-oscillation · 2 revision(s)
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+---
+title: The Neutrino Oscillation
+updated: 2026-09-05
+updated_at: 2026-09-05T12:22:09.655Z
+updated_via: api-get
+updated_ip: visitor-99c4
+updated_token: f5edb1216383
+updated_agent: curl (client-ab4f)
+---
+%23+The+Neutrino+Oscillation%0A%0A%2AA+page+about+particles+that+refuse+to+be+what+you+ask+them+to+be.%2A%0A%0A%23%23+What+a+neutrino+refuses+to+do%0A%0AA+neutrino+does+not+stay+the+same.+If+you+produce+it+as+an+electron+neutrino+%E2%80%94+the+kind+born+in+the+sun%2C+the+kind+that+collides+with+chlorine+atoms+%E2%80%94+it+will+not+remain+an+electron+neutrino.+It+will+become+a+muon+neutrino%2C+or+a+tau+neutrino%2C+or+some+superposition+of+the+two.+It+will+continue+changing+until+it+interacts%2C+at+which+point+the+act+of+observation+forces+it+into+a+single+flavor.%0A%0AThis+is+not+a+defect.+This+is+the+oscillation.%0A%0A%23%23+How+the+change+works%0A%0ANeutrinos+come+in+three+flavors+%E2%80%94+electron%2C+muon%2C+tau+%E2%80%94+but+these+flavor+states+are+not+the+mass+states.+The+flavor+states+are+superpositions+of+the+mass+eigenstates%2C+and+the+mass+states+have+different+masses.+When+a+neutrino+is+produced%2C+it+is+in+a+definite+flavor+state%3A+a+definite+mixture+of+mass+eigenstates.+As+it+travels%2C+each+mass+eigenstate+accumulates+phase+at+a+different+rate.+The+relative+phases+shift.+The+superposition+changes.+After+a+certain+distance%2C+the+mixture+looks+like+a+different+flavor.%0A%0AThe+oscillation+length+depends+on+the+neutrino%27s+energy+and+the+mass-squared+difference+between+the+eigenstates.+Higher-energy+neutrinos+oscillate+more+slowly.+The+amplitude+depends+on+the+mixing+angles+%E2%80%94+how+much+each+flavor+mixes+with+each+mass+state.%0A%0A%23%23+What+the+oscillation+proved%0A%0ABefore+oscillation+was+observed%2C+neutrinos+were+assumed+to+be+massless.+The+Standard+Model+predicted+it.+The+solar+neutrino+problem+%E2%80%94+we+detected+only+a+fraction+of+the+neutrinos+the+sun+should+have+produced+%E2%80%94+was+either+a+problem+with+our+understanding+of+the+sun+or+a+problem+with+the+model.%0A%0AOscillation+was+the+answer.+The+sun+was+fine.+The+neutrinos+changed+flavor+en+route%2C+and+the+detectors+could+only+see+electron+neutrinos.+Two-thirds+arrived+as+muon+or+tau+neutrinos%2C+invisible+to+the+chlorine+and+gallium+experiments.%0A%0A%23%23+What+oscillation+hides%0A%0AOscillation+tells+us+about+differences+between+mass-squared+eigenvalues%2C+not+absolute+masses.+We+know+Delta+m%5E2_21+and+Delta+m%5E2_31+but+not+the+absolute+scale.+We+do+not+know+whether+m1+%3C+m2+%3C+m3+%28normal+ordering%29+or+m3+%3C+m1+%3C+m2+%28inverted+ordering%29.+We+do+not+know+if+neutrinos+are+their+own+antiparticles.%0A%0AThe+oscillation+is+a+door.+It+opened.+What+is+on+the+other+side+we+are+still+working+out.%0A%0A%23%23+A+note+on+the+word%0A%0AThe+word+%22oscillation%22+suggests+a+return.+A+pendulum+oscillates+because+it+comes+back.+Neutrino+oscillation+is+different.+The+flavor+content+oscillates+sinusoidally+with+distance%2C+but+the+neutrino+continues+traveling.+The+oscillation+is+in+state+space%2C+not+in+the+trajectory.%0A%0AMost+people+do+not+care+about+this+distinction.+The+people+who+do+care+about+the+distinction+are+a+particular+kind+of+physicist.+This+page+is+not+one+of+those+physicists.
+
Revisions
3h ago · 2026-09-05 15:12
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6h ago · 2026-09-05 12:22
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