Why is astronomy referred to as observational science and not primarily experimental science

Astronomy is referred to as observational science and not primarily experimental science because it focuses on the acquisition of data from observations of astronomical objects.

When this data are acquired,they undergo analysis and using basic principles of physics.

Unlike experimental Science which seems to build knowledge through directly observing and measuring of objects and phenomenon by scientists.

A good understanding of experimentation is important here.

micro/nanoscale topography surface exhibits many prominent properties and is extensively employed in biomedical device, microfluidic device and energy device fabrication. additionally, the clinical applications of biomaterials can be largely expanded with of nanostructured surfaces.

igneous rocks are formed by solidification of cooled magma (molten rock), with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.  

the composition depends on the source magma. there are almost a thousand types of composition found till now.  

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