I have not yet studied all that relativity stuff. I have a couple of question about it all. First. I have often heard it said that continually increasing your velocity, in spaceflight for example, requires an ever-larger supply of energy. That the amount of energy required increases the faster you go. However, what science has so far acheived, in repeatable experiments and real-life applications, demonstrates clearly that such is not the case. The Deep Space One spacecraft has been accelerating for about two year, with an ever-diminishing supply of energy. It is only logical. If there is no resistence, and thrust is continually applied, then the spacecraft will continually accelerate. While velocity continually increases, the energy requirements do NOT increase. So why on Earth do people often claim otherwise? Second. As that Deep Space One probe accelerates, it's mass is NOT increasing. In fact its total mass is decreasing, due to its slow fuel consumption. There is only ONE thing about that spacecraft which is increasing: it's potential kinetic energy. And that only matters if it hits something or thrust is applied in another direction. So, real-life applications and repeatable work demonstrate quite clearly that mass DOES NOT increase as things go faster. So why do people say otherwise? As I've mentioned many times, I am a beginner at all this. But this particular matter has bothered me for a while.