Which two pieces of evidence did Isaac Newton use to support his claims about light?

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Isaac Newton's investigations into the nature of light led to several foundational principles in optics. The correct answer focuses on two significant characteristics: that light travels in a straight line and is capable of casting shadows.

When light travels in a straight line, it demonstrates one of its key properties, which is essential to understanding how we perceive objects in our environment. This characteristic supports the notion that light must be structured in a particular way to interact with other objects. The ability to cast a shadow occurs because when an opaque object obstructs the direct path of light, it prevents the light's rays from reaching the surface behind it, creating an area devoid of light. This phenomenon underscores the idea that light does not simply spread out in all directions uniformly, but rather travels along defined paths.

Together, these observations helped Newton establish fundamental principles regarding the directionality and behavior of light, paving the way for further scientific exploration into its properties.