Re: What is Ki?
Some people are more naturally aware of the energy currents (ki) than others. While on a very basic level, you are correct Dirk, he is just leading the others movement, on a much deeper level he is making use of the energy currents that influence that movement.
If you watch someone in an aikido movement carefully you will begin to see where the spirals are inclined to take them. You just need to learn to see it with your inner eye. Sort of use your imagination.
The best thing I have found so far, and I am so much a beginner here, is learning to meditate and quiet the mind. When you get rid of the distractions of the materiel world and the buzz of thoughts and reasoning in your head it becomes easier to realize the existence of such intangibles as ki.
I would not be too concerned about it. As your training progresses it will come clear when the time is right for you to understand it.