Albert Einstein's theory of special relativity, published in 1905, revolutionized physics. It deals with the relationship between space and time and is based on two fundamental postulates.

The Two Postulates of Special Relativity

1. The Principle of Relativity: The laws of physics are the same for all observers in uniform motion (i.e., not accelerating). This means that the outcome of any physical experiment will be the same, regardless of the constant velocity of the laboratory in which it is performed.

2. The Principle of the Constancy of the Speed of Light: The speed of light in a vacuum (c) is the same for all observers, regardless of their motion or the motion of the light source. This is a very counter-intuitive idea. No matter how fast you move towards or away from a light source, you will always measure its speed to be the same value, approximately 299,792,458 meters per second.

Key Consequences

These two postulates lead to some strange and fascinating consequences:

- Time Dilation: Time passes more slowly for an observer who is moving relative to another observer. This is often summarized as "moving clocks run slow." - Length Contraction: Objects are measured to be shorter in their direction of motion as their speed increases. - Mass-Energy Equivalence: Mass and energy are interchangeable. This is expressed by Einstein's most famous equation: E = mc² Where: - E is energy - m is mass - c is the speed of light