More than Meets the Eye: Geometry and Our Perception of Reality Richard G. Ligo The University of Iowa
Overview Introduction The shape of the Earth Determining Earth’s size Making maps of the Earth Curvature applied to reality The shape of the Universe
Hints of the Earth’s shape Lunar eclipses:
Hints of the Earth’s shape Horizon of the ocean:
Hints of the Earth’s shape Constellation visibility:
Hints of the Earth’s shape Eratosthenes and the gnomon
Eratosthenes and the gnomon
Mapping the Earth Theorema Egregium (Gauss) The Gaussian curvature of a surface is invariant under isometries. Intuitively, the theorem says that a surface may be “bent” without stretching or squishing it and have the same Gaussian curvature.
Mapping the Earth Definition: A surface is called developable if it has zero Gaussian curvature.
Maps: central stereographic projection
Maps: azimuthal equidistant projection
Maps: central cylindrical projection
Maps: equirectangular projection
Maps: Lambert cylindrical projection
Maps: Mercator projection
Derivation of the Mercator projection ?
Derivation of the Mercator projection Globe Projection
Derivation of the Mercator projection
Derivation of the Mercator projection
Maps: Natural Earth projection
The curvature of a surface K = 0 K < 0 K > 0 K ? 0
The curvature of a surface K = 0 C = 2πr
The curvature of a surface K > 0 C < 2πr
The curvature of a surface K < 0 C > 2πr
The curvature of space
The shape of the universe
The shape of the universe
The shape of the universe
The shape of the universe
The shape of the universe
The shape of the universe ?
References Stewart, Ian (2001). Flatterland. Cambridge, MA: Perseus Publishing. Oprea, John (2007). Differential Geometry and Its Applications. Washington, DC: Mathematical Association of America. Osserman, Robert (1995). Poetry of the Universe. New York, NY: Anchor Books.