for example what is the differences between them? Are there different strengths of them? What would happen if a physic power was used to say throw a projectile at them from out of their blank range?
According to the short story, The Voice
an untouchable's gift can manifest in different ways, and yes there are different strengths. According to The Inquisition
- anyone with a psi-rating below pi is a blunt, an individual who is oblivious to psychic activity or probing. Their ability is graded too, for example an individual with a rating of upsilon might just be affected by a severe psychic approach but is otherwise inert. Omega rating indicates the far extreme, the so called untouchables who are so 'blunt' as to have a measurable anti-psychic effect. As for the last question - I can't remember a source, but I'm pretty sure if the projectile is already moving and has sufficient momenteum when it reaches the edge of the untouchable's field of effect, then it will continue on and hit them.