Speed of LightSpeed of Light

Jonathan Richards

HistoryHistory• Galileo: 1667• Roemer: 1675• Bradley: 1728• Fizeau: 1849• Foucault: 1862

Galileo 1667Galileo 1667• Used laterns to measure speed of light• Not very accurate• Speed of light > 10x speed of sound

Roemer and JupiterRoemer and Jupiter• Studied the moons• Moon not on schedule• 2x10^8 m/s

Current ValueCurrent Value

c = 2.9979 x 10^8 m/s

Foucault's MethodFoucault's Method

Lab MethodLab Method

Fixed MirrorFixed Mirror

Uncertainty:3.35 x 10^6 m/s

Moving MirrorMoving Mirror

c = 2.9068x10^8 m/s

Error: 3.406 x 10^6 m/s

Linear CorrelationLinear Correlation

r = .9477, .9164, -.5617, -.8984

Chi SquaredChi Squared

6.04, 3.08, 6.64, 8.71

Residual GraphResidual Graph

ConclusionConclusion• A good model for testing speed of light• The longer the distance D, the more accurate• Accepted value for speed of light: 2.9979x10^8

m/s• Would like to try a longer distance D to see if it’s

more accurate• Would like to get the image in microscope focused

better.

ReferencesReferences• Error Analysis, Taylor, John R., 2nd edition• http://www.speed-

light.info/measure/speed_of_light_history.htm