Special relativity.

Definition

Special relativity is a theory proposed by Albert Einstein that describes the physics of moving bodies at speeds close to the speed of light. It introduces the concepts of time dilation and length contraction.

5 Must Know Facts For Your Next Test

1. Einstein's first postulate states that the laws of physics are the same in all inertial frames of reference.
2. Einstein's second postulate states that the speed of light in vacuum is constant and independent of the motion of the source or observer.
3. Time dilation implies that a moving clock ticks slower compared to one at rest, mathematically expressed as $t' = t / \sqrt{1 - v^2/c^2}$.
4. Length contraction means an object in motion appears shorter along the direction of motion, given by $L' = L \sqrt{1 - v^2/c^2}$.
5. The theory leads to the famous equation $E=mc^2$, indicating mass-energy equivalence.

Review Questions

• What are Einstein's two postulates in special relativity?
• How does time dilation affect a clock on a spaceship traveling close to the speed of light?
• Write down and explain the formula for length contraction.

Related terms

Time Dilation:

A phenomenon where time appears to move slower for an object in motion relative to a stationary observer.

Inertial Frame:

A frame of reference in which an object is either at rest or moving at constant velocity, implying no acceleration.

Lorentz Transformation: Mathematical equations that describe how measurements of space and time by two observers are related in special relativity.