How We Know What's Deep Inside the Earth, Despite Never Traveling

The extreme conditions of inner Earth make it impossible to explore. But seismic waves during earthquakes, volcanic eruptions and light waves from the Sun all have helped reveal fascinating insights about our planet’s mantle, crust, and core.
The extreme conditions of inner Earth make it impossible to explore. But seismic waves during earthquakes, volcanic eruptions and light waves from the Sun all have helped reveal fascinating insights about our planet’s mantle, crust, and core.

What's Actually Inside the Earth's Core?

Do we know as much about what lies beneath the Earth's crust as we do about outer space? - Quora

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Earth's inner core - Wikipedia

Scientists Detect Signs of Hidden Structure Inside Earth's Core : ScienceAlert

Solved The answer in this case, is seismic waves. Although

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Earth's Core: What Lies At The Centre And How Do We Know? BBC Science Focus Magazine