Einstein and The Special Theory of Relativity

Around 1900, what fundamental aspect of physics presented a significant challenge to physicists, including Einstein?

• The inability to explain the existence of gravity.

• The difficulty in understanding how objects could move.

• The lack of a unified theory for electromagnetism.

• The problem of measuring extremely small particles.

In the "old-fashioned principle of relativity," which of the following quantities was considered absolute, meaning it remained unchanged regardless of the observer's motion?

• Position

• Velocity

• Separation distance between objects

• The speed of light

The conflict in physics prior to Einstein arose because the established "old-fashioned principle of relativity" could not reconcile the relative nature of motion with which experimentally observed absolute quantity?

• The mass of an object.

• The force of gravity.

• The speed of light.

• The rate of chemical reactions.

What revolutionary concept did Einstein introduce to resolve the conflict between the relativity of motion and the absolute speed of light?

• The idea that energy and mass are equivalent.

• The proposal that time itself is relative and not absolute.

• The discovery of new subatomic particles.

• The theory of quantum mechanics.