Final answer:
Seismic data is pivotal for scientists to investigate Earth's internal structure, as it provides evidence of the varying densities and compositions of the core, mantle, and crust. This is achieved through the study of P and S waves generated by earthquakes, which is analogous to ultrasound used in medicine.
Step-by-step explanation:
Scientists utilize seismic data to understand the physical properties of Earth's internal structure because they cannot observe it directly. Seismic waves, including primary and secondary waves (P and S waves), provide critical evidence. These waves change velocity as they pass through different densities and compositions within the Earth, providing a snapshot of its internal structure. The seismic wave patterns suggest that Earth consists of various layers, including the core, mantle, and crust. Additionally, reflections and refractions of these waves create 'shadows' detected by seismographs, allowing scientists to map out the internal layers as either solid or liquid.
Another aspect of studying Earth's interior are the distinctions based on mechanical properties, primarily the lithosphere and the asthenosphere. Information derived from earthquakes and computer modeling furthers our knowledge of these regions. Together, these methods reveal the complex composition and behavior of Earth's interior, contributing to our understanding of geological phenomena and the Earth's early atmosphere.