Psychokinesis is by its very definition not invisible. It is a tangible thing and in fact very easy to test. Just ask somebody to state their intention with regards to some remote physical action and then see if that action occurs.

Psi wheels move by themselves. All you have to do is set one without a human nearby for a long time and see if it moves. Convection currents are one of the main reasons, why don't you think they are?

If it doesn't move after a long time, then it's safe to see if you can move it and see if you get results. This is clearly a vital part of the testing process, in science known as a 'control'. Yet nobody has ever been able to make a psi wheel move in these necessary conditions. They can only ever do it with wheels which move by themselves, or are not actually isolated.

Unless of course you have some evidence to the contrary.