Question

In SPECIAL RELATIVITY, what or why is - choose one of the three alternatives each for a) - d)

a) AN EVENT (1. A line in spacetime - 2. A point in spacetime - 3. A space in spacetime)

b) GENERALLY REFFERED TO AS "THE INTERVAL" (1. Time interval between events - 2. Space interval between events - 3. Spacetime interval between events)

c) TIME MULTIPLIED WITH SPEED OF LIGHT (1. To give time the same unit as space - 2. To make sure time is always moving forward - 3. to avoid particles to move faster then the speed of light)

d) FOR ALL OBSERVERS (1. Space is euqal - 2. Time is equal - 3. Spacetime is equal

Answer 1

1) An EVENT: 2. A point in spacetime

In particular relativity, an event is the instantaneous physical situation or occurrence associated with a point in spacetime (that is, a specific place and time). For example, a glass breaking on the floor is an event; it occurs at a unique place and a unique time.

2)Generally referred to as "THE INTERVAL": 1. The time interval between events

Interval is generally referred as the difference in the time of occurrence of to events. However, it can also be spacetime interval other than the usual time interval.

3)TIME MULTIPLIED WITH SPEED OF LIGHT: 1. To give time the same unit as space

The spacetime interval is given by ?s²=r²?c²?t² . ?s² compares the distance light travels between the occurrence of the events with their spatial separation.

4) FOR ALL OBSERVERS: 3. Spacetime is equal

There is a tradeoff between space and time. The velocity of light is same in each frame of reference making the overall space-time constant. However, otherwise, space and time can be different in two different frames as can be seen by length contraction and time dilation.