Foucault experiment
E752312
The Foucault experiment is a 19th-century optical test devised by Léon Foucault to measure the speed of light with high precision using a rotating mirror apparatus.
All labels observed (2)
| Label | Occurrences |
|---|---|
| Foucault experiment canonical | 1 |
| Foucault rotating mirror experiment | 1 |
How this entity was disambiguated
This entity first appeared as the object of triple T8635423 — resolving that mention is where its identity was fixed. The disambiguator weighed these candidate entities and picked the highlighted one (or “None”, minting a new entity). This is how homonymy is resolved: the same surface form can point to different entities.
NED1
Entity disambiguation (via context triple)
gpt-5-mini-2025-08-07
Target entity: Foucault experiment Context triple: [Fizeau experiment, relatedTo, Foucault experiment]
-
A.
Fizeau experiment
The Fizeau experiment was a pioneering 19th-century physics experiment that measured the speed of light using a rotating toothed wheel and helped establish light’s finite velocity.
-
B.
Michelson–Morley experiment
The Michelson–Morley experiment was a landmark 1887 physics experiment that attempted to detect the Earth's motion through the hypothesized luminiferous aether and whose null result helped pave the way for Einstein's theory of special relativity.
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C.
Ives–Stilwell experiment
The Ives–Stilwell experiment is a classic test of special relativity that measured the relativistic Doppler effect to confirm time dilation for fast-moving ions.
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D.
Kennedy–Thorndike experiment
The Kennedy–Thorndike experiment is a classic test of special relativity that examined the constancy of the speed of light using an interferometer with unequal arm lengths and varying laboratory velocity.
-
E.
Eötvös experiment
The Eötvös experiment is a classic physics test of the equivalence principle that measures whether different materials fall with the same acceleration in a gravitational field.
- F. None of above. chosen
- G. Unsure - the case is ambiguous/there is not enough information to decide.
NED2
Entity disambiguation (via description)
gpt-5-mini-2025-08-07
Target entity: Foucault experiment Target entity description: The Foucault experiment is a 19th-century optical test devised by Léon Foucault to measure the speed of light with high precision using a rotating mirror apparatus.
-
A.
Fizeau experiment
The Fizeau experiment was a pioneering 19th-century physics experiment that measured the speed of light using a rotating toothed wheel and helped establish light’s finite velocity.
-
B.
Michelson–Morley experiment
The Michelson–Morley experiment was a landmark 1887 physics experiment that attempted to detect the Earth's motion through the hypothesized luminiferous aether and whose null result helped pave the way for Einstein's theory of special relativity.
-
C.
Ives–Stilwell experiment
The Ives–Stilwell experiment is a classic test of special relativity that measured the relativistic Doppler effect to confirm time dilation for fast-moving ions.
-
D.
Kennedy–Thorndike experiment
The Kennedy–Thorndike experiment is a classic test of special relativity that examined the constancy of the speed of light using an interferometer with unequal arm lengths and varying laboratory velocity.
-
E.
Eötvös experiment
The Eötvös experiment is a classic physics test of the equivalence principle that measures whether different materials fall with the same acceleration in a gravitational field.
- F. None of above. chosen
Statements (47)
| Predicate | Object |
|---|---|
| instanceOf |
optical experiment
ⓘ
physics experiment ⓘ speed of light measurement method ⓘ |
| appliesTo | finite speed of light ⓘ |
| basedOn |
angular deflection of reflected light
ⓘ
time-of-flight measurement ⓘ |
| comparedWith | Fizeau experiment ⓘ |
| computes | speed of light from time delay inferred from angular deflection ⓘ |
| contradicts | emission theory prediction that light is faster in denser media ⓘ |
| countryOfOrigin | France ⓘ |
| describedIn | Léon Foucault’s publications on the speed of light ⓘ |
| field |
experimental physics
ⓘ
optics ⓘ |
| follows | Fizeau experiment ⓘ |
| goal |
measure speed of light in air
ⓘ
measure speed of light in different media ⓘ |
| hasEffect | provided more accurate value of speed of light than previous methods ⓘ |
| hasPart |
collimating optics
ⓘ
fixed distant mirror ⓘ observation microscope or telescope ⓘ rapidly rotating mirror ⓘ |
| historicalPeriod | 19th-century physics ⓘ |
| inception |
19th century
ⓘ
circa 1850 ⓘ |
| influenced |
design of modern time-of-flight optical setups
ⓘ
later laboratory measurements of the speed of light ⓘ |
| inventor | Léon Foucault ⓘ |
| mainSubject | speed of light ⓘ |
| measures |
difference between speed of light in air and water
ⓘ
speed of light in air ⓘ speed of light in water ⓘ |
| method | measure displacement of returning light spot due to mirror rotation ⓘ |
| namedAfter | Léon Foucault ⓘ |
| notableFor |
high-precision measurement of the speed of light
ⓘ
improvement over astronomical methods of measuring light speed ⓘ |
| requires |
known angular velocity of rotating mirror
ⓘ
known distance between mirrors ⓘ |
| supportsTheory |
light travels slower in denser media
ⓘ
wave theory of light ⓘ |
| typeOf | laboratory measurement of fundamental constant ⓘ |
| usedFor |
historical demonstrations of speed of light measurement
ⓘ
teaching experimental methods in optics ⓘ |
| uses |
light beam
ⓘ
optical path with distant mirror ⓘ precision timing via angular deflection ⓘ rotating mirror ⓘ |
| verificationOf | finite and measurable speed of light ⓘ |
How these facts were elicited
The pipeline generated the facts above by prompting gpt-5.1 with this entity's name + description and the instruction below.
Instruction
You are a knowledge base construction expert. Given a subject entity and a description of it, return factual statements that you know for the subject as a JSON list of dictionaries(triples), where keys must be "subject", "predicate" and "object". The number of facts may be very high, between 25 to 50 or more, for very popular subjects. For less popular subjects, the number of facts can be very low, like 5 or 10. # Requirements - If you don't know the subject at all, return an empty list. - If the subject is not a named entity, return an empty list. - Include at least one triple where predicate is "instanceOf". - Do not get too wordy. - Separate several objects into multiple triples with one object.
Input
Subject: Foucault experiment Description of subject: The Foucault experiment is a 19th-century optical test devised by Léon Foucault to measure the speed of light with high precision using a rotating mirror apparatus.
Referenced by (2)
Full triples — surface form annotated when it differs from this entity's canonical label.
linked to: Foucault experiment