The Consequences of Postulates of Special Relativity Theory

• The Special Relativity Theory was developed by Albert Einstein in 1905
• Special Relativity Theory


  Explains how time and space are connected for objects travelling at uniform velocity
• Speed of light (c)


  Approximately 300,000 km/s
• As an object approaches the speed of light, strange things start to happen
• Twin Paradox


  A thought experiment in special relativity involving identical twins, one of whom undertakes a journey into space in a high-speed rocket, returning home to find that the twin who remained on Earth has aged more
• Speed of light


  Commonly denoted as c, and is approximately 300,000 km/s
• The speed of light is one of the aspects that concerns Special Relativity Theory
• In the previous modules, we have discussed Newton's Laws and worked with different speeds that we experience in our everyday life. In this module, we will be dealing with far greater speeds. And as we go along the module, we will learn that as an object approaches the speed of light, strange things start to happen
• If the circumference of Earth is 40,000 km, then light would travel the Earth more than 7 times per second
• The Twin Paradox

  A story about two identical twin brothers, one an astronaut and one a scientist, and how they age differently due to the effects of relativity
• Special Relativity Theory


  A theory which predicts how events are measured with various observers who are in motion with respect to an event
• Special Relativity Theory


  • It has two postulates: The Relativity Postulate (the laws of physics are the same in all inertial reference frames) and the Speed of Light Postulate (the speed of light in a vacuum is always the same)
• Relativity of simultaneity


  The concept that if two events are separated in space or position, it is absolutely impossible for the two events to occur simultaneously for two observers
• Relativity of simultaneity

  Observer A inside a train sees two lightning strikes as simultaneous, but Observer B outside the train sees them as not simultaneous
• Time dilation


  The apparent difference in the time interval between two events as measured by two clocks, where the faster you move through space, the slower you move through time
• Time dilation

  Observer A on a spaceship has a "light clock" that measures time differently than Observer B on Earth due to the spaceship's constant velocity
• Length contraction


  The phenomenon in which an observer at rest would observe a moving object's length to be shorter than its proper length
• Length contraction

  Observer A on a ship travelling at 80% speed of light observes the distance between Earth and another planet as 6 light-years, while Observer B on Earth observes it as 10 light-years
• Mass-energy equivalence

  The principle that anything that has a mass also has an equal amount of energy, as described by the equation E = mc^2
• Cosmic speed limit


  The speed of light is the absolute and ultimate speed that can never be attained or surpassed by any massive object
• The twin's parents were shocked to find that their identical twin is not identical anymore, with John looking younger than Paul after John's 10-year space mission
• John's spaceship is travelling at 90% speed of light

  1 year on Earth is equivalent to 1.67 years on John's ship
• The distance from Earth to the outer reaches of the Solar System is 4.3 light-years

  From John's perspective on the spaceship, this distance is shorter
• Albert Einstein's Special Relativity Theory predicts how events happen when moving at speeds that approach the speed of light
• No two events appear simultaneous from the perspective of different observers
• Time moves slowly for objects that are in motion
• Distance appears much shorter for moving objects
• Every mass has an equivalent energy, no matter how small it is
• As objects move faster, they acquire more mass
• The speed of light is the absolute speed
• Albert Einstein's Special Relativity Theory predicts how events happen when it is moving at speeds that approach the speed of light
• No two events appear simultaneously from the perspective of different observers
• Inertial reference frame


  A special type of reference where an observer does not accelerate
• Length contraction


  An observer perceives length differently while moving at constant speed
• Time dilation


  The difference in time experience by an observer moving at a constant speed
• Einstein


  The scientist who proposed the Special Relativity Theory
• As the mass of an object becomes massive


  The energy needed to move it becomes infinite
• E=mc^2


  Energy is equal to the mass multiplied by the square of the speed of light
• The fastest speed known to man is equal to the speed of light
• If an object moves at exactly the speed of light, time will stop