❖The Special Relativity Theory•Special Relativity Theory is a theory which predicts how events are measured with various observers who are inmotion with respect to an event. An “event” is just a physical happening, e.g., exploding firecrackers, a passingrocket, or a flash of light.•What’s so “special” about the Special Relativity Theory? It is because each observers’ reference frame, orperspective, is a special type of reference frame called inertial reference frame. This means that the observer is atrest and not accelerating from the observers’ perspective.The Consequences of the Postulatesof Special Relativity Theory

85For example:•Observer A is sitting on a train station. Observer A’s position is an inertial reference frame because he/she is atrest or does not move from his/her perspective.•Observer B is sitting on atrain approaching the train station with constant velocity. Observer B’s position is stillan inertial reference frame because although the train is moving, it is not accelerating, or not gaining or losingspeed.❖The Special Relativity Theory has two postulates or assumptions:1. The Relativity Postulate, where it is assumed that the laws of physics are the same in all inertial reference.2. The Speed of Light Postulate, where it is assumed that the speed of light in a vacuum is always the same.❖Consequences of The Postulates of Special Relativity Theory1. Relativity of Simultaneity-The relativity of simultaneity is a concept in Special Relativity Theory which says that if two events are separated in spaceor position, it is absolutely impossible for the two events to occur simultaneously for two observers.2. Time Dilation- Time dilation is the apparent difference in the time interval between two events as measured by two clocks. AlbertEinstein concluded that the faster you move through space, the slower one moves through time. This concept is bestdemonstrated through another thought experiment.Δt =𝜟𝒕?√?−𝒗?𝒄?where Δt = dilated time interval/ time interval from Observer B’s perspectiveΔt0 = proper time interval/ time interval from Observer A’s perspectivev = the velocity of the moving object, in this case, the spaceshipc = speed of light at 300,000 km/sFor example, the Observer A’s ship is moving constantly at 80% speed of light, or 0.8c. We can compute how long is 1 yearon that spaceship compared to one year on Earth. Plugging in the values and computing for Δt,Δt =?𝒚𝒆𝒂𝒓√?−(?.𝟖𝒄)?𝒄?Δt = 1.67 years3. Length Contraction-Length contraction is the phenomenon in which an observer at rest would observe a moving object’s length to be shorterthan its proper length. In everyday lives, length contraction, just like time dilation, is negligible- For this concept, we will use another example. A ship is travelling from Earth to another planet. We will look at this eventagain, at the perspective of Observer A on the ship, and the perspective of Observer B on Earth. The distance betweenEarth and the other planet is L0, which we will refer to as the proper length as observed by Observer B. The Observer B onEarth observes the ship moving at a constant velocity, v. On the perspective of Observer A on the ship, distance betweenEarth and the other planet will be different, and will be denoted as L, which is the contracted length of the journey, asobserved by Observer A. The relationship between L and L0, is given by the equation

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