A clear view of the ocean may be used to measure the radius of the Earth. To an observer looking out at the ocean, the horizon will always form some angle θ with the local horizontal plane. As the observer's elevation h increases, so does the angle θ (see Fig. 1). From measurements of the elevation h and the angle θ, the radius R of the Earth may be found. This paper describes an experiment in which measurements were taken at an elevation of approximately 485 m in the Santa Monica hills of Los Angeles, CA. The average refraction-corrected value for the radius of the (assumed spherical) Earth was found to be 6100 ± 420 km. The accepted value at the equator is 6380 km.
REFERENCES
1.
Dennis
Rawlins
, “Doubling your sunsets or how anyone can measure the Earth's size with wristwatch and meter-stick
,” Am. J. Phys.
47
, 126
–128
(Feb. 1979).2.
Zachary
Levine
, “How to measure the radius of the Earth on your beach vacation
,” Phys. Teach.
31
, 440
–441
(Oct. 1993).3.
Frank O.
Goodman
, “Measure the Earth's radius while boating on one of its lakes
,” Am. J. Phys.
61
, 378
–379
(April 1993).4.
R.
O'Keefe
and B.
Ghavimi-Alagha
, “The World Trade Center and the distance to the world's center
,“ Am. J. Phys.
60
, 183
–185
(Feb. 1992).5.
Readers can download the online appendix at http://ftp. aip.org/cgi-bin/epaps?ID=E-PHTEAH-47-016908. For more information on EPAPS, visit http://www.aip.org/pubservs/epaps.html.
This content is only available via PDF.
© 2009 American Association of Physics Teachers.
2009
American Association of Physics Teachers
AAPT members receive access to The Physics Teacher and the American Journal of Physics as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.