What are the Postulates of special relativity

The Theory of Special Relativity, proposed by Albert Einstein in 1905, is based on two fundamental postulates:

1. Principle of Relativity (First Postulate)

The laws of physics are the same in all inertial frames of reference.

This means that no matter how fast you are moving (as long as it's at a constant speed and not accelerating), the basic laws of physics—like gravity, electromagnetism, etc.—work exactly the same.
There is no absolute rest frame—motion is always relative.

2. Constancy of the Speed of Light (Second Postulate)

The speed of light in a vacuum is constant (approximately 299,792,458 m/s) and is the same for all observers, regardless of the motion of the light source or the observer.

Unlike sound or other waves that depend on the observer’s motion or the medium, light always travels at the same speed, whether you're moving toward it or away from it.

Together, these postulates lead to surprising consequences:

• Time Dilation – Time slows down for moving objects.

• Length Contraction – Objects shorten in the direction of motion.

• Relativity of Simultaneity – Events that appear simultaneous in one frame may not be in another.

• Mass-Energy Equivalence – Expressed by the famous equation E=mc2E = mc^2E=mc2.