be the same, regardless of the motion of the observer or the light source.

We will use the letter “c” to represent the speed of light.

The speed of light is 3 108 m/s, or 186,000 miles/second.

The speed of light is so fast that it can make about 40 round trips across the USA in one second!

In order to explain how the speed of light can stay the same Einstein developed an idea called time dilation.

Distance distance

C = ----------- = ---------------- in other words, if you go a big distance, then in order to keep the speed

Time time of light the same you have to make time get bigger!

If you are moving quickly, your seconds are bigger than someone who is at rest.

The faster you move through space, the slower you move through time!

If a person traveled at speeds approaching light speed, then at the end of the trip she would have aged very little compared to her friends who stayed at home.

No object can ever accelerate to or beyond the speed of light. This is true for several reasons.

As you reach the speed of light your time becomes infinitely large, one of your seconds is an infinite amount of seconds for the rest of the universe – you reach the end of time (if there is one)

As you reach the speed of light your mass becomes infinitely large, so it would take an infinite amount of force to accelerate you, and you would have an infinite amount of kinetic energy.

You would not get fat when your mass increased, but rather each atom would possess much more mass than it would at rest.

In order to understand why your mass would increase you need to know that kinetic energy )the energy of motion) is defined by the equation K.E. = ½ mv2 a fast car has more energy than a slow car, the increase in energy is due to the increase in velocity.

Imagine that your are traveling close to the speed of light and then you double the energy of your spaceship. Normally this energy would manifest itself as an increase in velocity, but at “relativistic speeds” your velocity “gets stuck” due to time dilation v=d/t and time is getting bigger, so v doesn’t get bigger.

Einstein asked himself where did the extra energy go if it couldn’t go into velocity, and since K.E. = ½ mv2t he only place it could go was into mass. From this fact he developed his famous equation e=mc2 where e is energy, m is mass and c is the speed of lightAcceleration is any change in velocity: speeding up, slowing down, or turning

Speeding up = positive acceleration

Slowing down = negative acceleration

Turning = angular acceleration

Acceleration is the rate at which velocity changes.

Example: if a car accelerates at 15 miles/hour/second,