ok, i read them when i have more time (i mean not tonight).
Just want to say another thing i think is right.
In the world of low speed (= our world) a particular force which is exercised on a free moving object during a fixed, short time, causes a defined increase of the speed of that object (in the direction of the force). But when the object moves superfast (in special relativity), then it's not like that. The higher the speed of the object, the less that speed will increase. The rest of the energy which is used by the force demonstrates itself as an increase of the mass of the moving object. The energy changes into mass, into matter.
(That's what i believe on this moment, but promise will have a look at the site you say).
(Thanks for the hint).
Greetings,
David.