Earth’s Core and Mantle
Year of Discovery: 1914
What Is It? The earth is made up of layers, each of a different density, temperature, and composition.
Who Discovered It? Beno Gutenberg
Why Is This One of the 100 Greatest?
It is impossible to see, to venture, or even to send probes more than a few miles under
the surface of Earth. Almost all of the 4,000+ miles from the surface to the center is unreachable to humans. Yet scientists could not begin to understand our planet and its formation without having an accurate knowledge of that interior.
Beno Gutenberg provided the first reasonable accounting of Earth’s interior. His discovery proved that Earth wasn’t a solid homogeneous planet, but was divided into layers.
Gutenberg was the first to correctly estimate the temperature and physical properties of
Earth’s core. His discoveries have been so important that he is often considered the father of
geophysics.
How Was It Discovered?
Born in 1889 in Darmstadt, Germany, Beno Gutenberg loved science as a boy and always knew he’d be a meteorologist. As he began his second year of university meteorological study in 1907, he saw a notice announcing the formation of a department of the new
science of geophysics (Earth physics) at the University of Göttingen.
The idea of a whole new science fascinated Gutenberg. He transferred to Göttingen
and, while holding onto a major in meteorology, studied under Emil Wiechert, a pioneer in
the emerging science of seismology—the study of seismic waves caused by earthquakes
and earth tremors.
By the time of his graduation in 1913, Gutenberg had shifted from meteorology (study
of the atmosphere) to geophysics (study of Earth’s interior). It was a case of being in the
right place at the right time. Gutenberg had access to all of Wiechert’s data and studies, the
most extensive and comprehensive collection of seismic data in the world. Wiechert had focused on collecting the data. Gutenberg focused on studying the patterns of those data.
Gutenberg found that, typically, seismic waves did not reach all parts of the earth’s
surface, even when the tremor was strong enough to have been detected everywhere. There
always existed a shadow zone more or less straight across the globe from an event where no
seismic waves were ever detectable.
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