This paper describes an experiment regularly presented to advanced undergraduate Physics students at the Universidad de los Andes in Bogotá, Colombia. The purpose of the experiment is to use high-resolution solar spectra to measure the horizontal speed of the laboratory caused by terrestrial rotation. Using this result, the radius of the Earth can be deduced. It is also possible to observe the Earth’s motion towards or away from the Sun, and hence compute our planet’s orbital eccentricity.

1.
See, for example, HyperPhysics on Relativistic Doppler Effect at http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/reldop2.html.
2.
B.
Oostra
and
D.
Ramírez
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ESPARTACO, a high-resolution, low-cost spectrograph for students
,”
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2
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2011
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3.
P.
Hlubina
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Measuring dispersion between two modes of an optical fibre using low-coherence spectral interferometry with a Michelson interferometer
,”
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1595
1604
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1999
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4.
iris software is superbly documented and can be downloaded from http://astrosurf.com/buil/us/iris/iris.htm.
5.
C. E.
Moore
,
M. G. J.
Minnaert
, and
J.
Houtgast
, “
The solar spectrum 2935 to 8770 Angstrom
,” National Bureau of Standards Monograph (
1966
).
6.
Spectroweb: The Interactive Database of Spectral Standard Star Atlases is available online at http://spectra.freeshell.org/spectroweb.html.
7.
T. D.
Nichols
,
D. C.
Harrison
, and
S. S.
Alpert
, “
Simple laboratory demonstration of the Doppler shift of laser light
,”
Am. J. Phys.
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(
7
),
657
660
(
1985
).
8.
R. H.
Belansky
and
K. H.
Wanser
, “
Laser Doppler velocimetry using a bulk optic Michelson interferometer: A student laboratory experiment
,”
Am. J. Phys.
61
(
11
),
1014
1019
(
1993
).
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