Special Relativity

What is a reference frame?

A reference frame is a perspective (technically, a set of coordinates), used to determine positions and velocities in that frame.

What does it mean when different frames move relative to one another?

Different frames move relative to one another which means observers in different reference frames will measure different velocities for the same object - ‘all motion is relative’.

What is an inertial reference frame?

An inertial reference frame is a frame that is moving at a constant velocity. This occurs when the frame has no net force acting on it and therefore Newton’s 1st Law of Motion applies.

What are the two postulates that Einstein’s theory of special relativity is based on?

Einstein’s theory of special relativity is based on two postulates:

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

2. The speed of light is an absolute constant; it is the same in all inertial reference frames.

What is time dilation?

For both postulate’s of Einstein’s theory of special relativity to be simultaneously true, time must not be absolute and independent, but run at different rates in different reference frames. This phenomenon is known as time dilation, with time passing more slowly in a reference frame which is moving relative to an observer.

What is proper time?

Proper time is the time measured by an observer at rest relative to the event.

What is dilated time?

The dilated time is measured by an observer for when the events occur at different points in space.

When are the effects of time dilation negligible in most contexts?

For v < 0.3c, Lorentz Factor = approximately 1, and the effects of time dilation are negligible in most contexts.

When are the effects of time dilation increasing exponentially?

As v approaches c, and Lorentz Factor approaches infinity, the effects of time dilation increase exponentially.