According to Isaac Newton Space Is Uniform, Linear and Continuous. Time Passes Independently
Relativity
According to Isaac Newton space is uniform, linear and continuous. Time passes independently of where you are and always at the same rate. Consequently, your position and speed are well defined and predictable. As an example lets determine the speed of the ball in figure 1 as seen from the outfielder’s point of view. The ball is traveling to the right at 30 m/s as shown. The fielder is running toward the ball at 10 m/s. As a result the fielder and the ball are approaching each other at a speed of 40 m/s. This “addition of velocities” is a consequence of relative motion and holds true for all reference frames governed by the laws of classical physics.
As discussed previously, the Michelson and Morely experiment showed that the speed of light was independent of the motion of the source or the observer. This results in some strange behavior (see fig. 2). The stationary observer will measure the sped of light coming from his flashlight to be approximately 3 x 108 m/s. According to Newton the pilot should observe the beam of light to be traveling toward her at 4 x 108 m/s. In actuality, the pilot observes the light to be traveling at 3 x 108 m/s. If the two astronauts are traveling at different speeds how can they both observe the light to be traveling at the same speed?
In Einstein’s theory of relativity, time and space are not two separate quantities. They are intertwined so tightly that they are a single four dimensional entity called spacetime (one word). Our everyday experiences are at speeds much, much less then the speed of light. Someone traveling at 70 mph on our fast highways is considered speeding, and subject to fines. The speed of light is 186,000 mps over 650 million times faster then the speeding car. Since we travel at such small speeds compared to light we are unable to notice the effects of speed on the universe.
How can the speed of light be the same for both astronauts. Einstein figured it this way. Since speed equals the distance traveled divided by the elapsed time, then distance and time must be dependent on the relative speed of the observers (or inertial reference frames). Many scientists had a hard time accepting this notion at first. Scientific investigations have validated the theory innumerable times.
Time Dilation
Imagine you have two identical clocks. You are holding one stationary and the second one is moving passed you at a speed v. According to Einstein’s theory, the clock moving with respect to you will tick more slowly then the clock at rest with respect to you. So if the clock you’re holding ticks off 60 s the moving clock will tick off less time. How much less?
The formula for time dilation is
t = t0/(1-v2/c2)1/2
where t is the elapsed time on the stationary clock, t0 is the elapsed time on the moving clock, v is the relative speed of the two clocks, and c is the speed of light. For a numerical example let’s say the stationary clock (the clock you’re holding) tics off 60 s. The speed of the second clock relative to you is 0.75c (i.e. 75% the speed of light). How much time has elapsed on the second clock? Plugging the given values in to our time dilation formula…
t = t0/(1-v2/c2)1/2
60s = t0/(1-(.5c)2/c2)1/2
60s(1-(.5c)2/c2)1/2 = t0
t0 = 52s
Length Contraction
Another consequence of Einstein’s postulates is that the length of an object depends on the relative motion of the observer and the object. Just as a moving clock will run slow compared to a stationary clock, the length of a moving object will depend on the relative motion of the observer and object. The formula for length contraction is similar to the formula for time dilation.
L = L0/(1-v2/c2)1/2
where L0 is the length of the stationary object, L is the length of the moving object, v is the relative speed of the two objects, and c is the speed of light. For a numerical example let’s say the stationary train is 100 m long The speed of the second train relative to you is 0.25c (i.e. 25% the speed of light). How long will train moving with respect to you be? Plugging the given values in to our length contraction formula…
L = L0/(1-v2/c2)1/2
L = 100/(1-(.25c)2/c2)1/2
L = 100(1-0.0625)1/2
L = 88 m
A similar effect occurs with mass. Notice that as an objects approaches the speed of light the mass of the object increases to infinity. This alone is a good reason why objects can’t travel at the speed of light. As they approach the speed of light they become infinitely massive which means they need an infinite force to accelerate them to higher speeds.