@ IVY
Let's play some experts and non experts game here.
Imagine John (an expert) shoots and arrow and hits James (a non-expert) with the arrow.
The arrow is indeed in the body of James. So James decides to accuse John. James says John shot me with an arrow, here is the evidence, the arrow is in my body.
John answers using his expert abilities and says that the accusations are completely false and that he can prove it despite the fact that the arrow is stuck in James's body!
So John develops his expert theory and says that the distance between John and James was 10 meters.
So in order to hit James the arrow must fly a distance of 10 meters.
Before flying 10 meters, first it has to fly the half of the distance, which is 5 meters.
But before reaching 5 meter distance it has to fly half of the distance, which means 2,5 meters.
Before reaching 2,5 it first must reach its half: 1,25!
Before 1,25 -> 0,625
0,625 -> 0,3125
0,3125 -> 0,15625
etc, etc,....
untill the infinite, which means that the arrow before reaching the half of half of half can never reach 10 meters!
Resolve this!
The 3 tracks are the arrow, which hit the cd and we can't prove the path they flew to get to the cd. All we have is our James's ears against John's explanation!