Since no one can go there, how do we learn about the inside of the earth?

Answer 1

seismographs detect the vibrations from the earth, and sound waves aka sonar can aid in detecting the objects under the crust

Answer 2

Like many other situations, models (guesses) are made, then tested, forming theories. Some models fall apart, others 'hold water' - no pun.

Hypothesis: This is an educated guess based upon observation. It is a rational explanation of a single event or phenomenon based upon what is observed, but which has not been proved. Most hypotheses can be supported or refuted by experimentation or continued observation.

Theory: A theory is more like a scientific law than a hypothesis. A theory is an explanation of a set of related observations or events based upon proven hypotheses and verified multiple times by detached groups of researchers. One scientist cannot create a theory; he can only create a hypothesis.

In general, both a scientific theory and a scientific law are accepted to be true by the scientific community as a whole. Both are used to make predictions of events. Both are used to advance technology.

The biggest difference between a law and a theory is that a theory is much more complex and dynamic. A law governs a single action, whereas a theory explains a whole series of related phenomena.


Big Models and Small Models.
Even the most rudimentary science course contains some of the grand, all-encompassing, models that scientists have discovered. The periodic table of the elements is a model chemists use for predicting properties of the elements. Physicists use Newton's law to predict how objects will interact, such as planets and spaceships. In geology, the continental drift model predicts the past positions of continents. But these three models are atypical because they are immensely successful. Most models used are nowhere near so powerful or widely useful. But scientists use these less-successful ones anyway. Models are used at every turn in a scientific study. Samples are models. Ideas are models. Methods are models. Every attempt at a scientific study involves countless models, many of them small and of interest only to a small group of other scientists. The primary activity of the hundreds of thousands of U.S. scientists is to produce new models, resulting in tens of thousands of scientific papers published per year.

Answer 3

A good question. The deepest anybody has been in the Earth's crust is about 5km at the bottom of a South African gold mine. The deepest hole ever drilled was about 12 km. Almost everything we know about the deep mantle and outer and inner core is from earthquake shock waves that have travelled through the Earth.