3.1   The Way Ahead


Now we know that the constancy of the speed of light in any frame of reference means that we have to change our understanding of how the universe works. We are used to thinking that the distance between two points or the time taken by a specific events are what they are: everyone will measure the same values for them, regardless of how they themselves may be moving. Now we know that this is not true. 

In this chapter, we're going to pick up these ideas and run with them. We're going to find more weirdness:  implications for the conservation of momentum that we'll have to deal with. Then a redefinition of kinetic energy which will lead us, inadvertently, to Uncle Albert's most famous result. It will also lead us to to an understanding of how photons can have momentum, even though they have no mass. And this, will set us up for our first steps in quantum theory, which we'll get to in Chapter 5.  We'll begin by looking to see what relativity has to say about momentum.