can scientists gain direct knowledge about materials deep within the earth? yes or no and why or why not.?

Answer 1

It depents on how deep, and how direct...

Seismic waves are used to determine the deep structure of he earth. They can give infromation on some of the physical properties of materials/phase state (i.e. solid or liquid) throughout the earth.

Rocks from the upper mantle (i.e. the layer below the crust) are sometimes exhumed, or fragments are caried to the surface by volcanic activity, and can be studied directly.

Answer 2

They can't look directly at very deep materials, because of the intense heat and pressure. If drilling was attempted to the deep earth, the drill would melt.
However, scientists have used indirect, or proxy measures, to determine the basic structure of the interior of the earth and even some of its possible mineral constituents.
These include analysis of how different kinds of waves travel after an earthquake and also analysis of kimberlite veins, which are basically the cooled veins resulting from extremely high pressure streams of material racing up from the mantle to the earth's surface. These also contain diamonds.

Answer 3

Deep how Deep?
Skin deep - yes, say a few hundred meters by drilling
More than few hundred meters is rare - ~3km in deep Gold mines.
beyond this depth answer is NO.
The pressure and temperature is very high so direct access to earth’s interior is not feasible.
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