Einstein’s view of gravitation emphasizes the equivalence of gravitation and acceleration, known as the principle of equivalence. He used this principle as a foundational idea in his general theory of relativity, which explains gravitational effects as the curvature of space-time.

To demonstrate the equivalence of inertial and gravitational masses, Einstein proposed a simple thought experiment. Imagine a person inside a small box, known as the “Einstein box,” which is at rest on Earth’s surface and subject only to gravity. In another scenario, the box accelerates through interstellar space at 9.8 m/s², with an external force causing this acceleration.

In both situations, the person inside the box cannot distinguish between the two by conducting experiments within the box. For example, the platform scale on which the person stands reads the same weight in both cases. Additionally, if the person observes an object falling past them, it accelerates at the same rate in both situations. This demonstrates the equivalence of inertial and gravitational masses.