Hello, I am quite new to this forum, but have been lurking around reading your posts for some time now. I have one question that has bothered me for some time. Scientists have been observing the universe with advanced technology, and seem quite certain that their observations indicate the age of the universe is approximately 13.73 billion years old, and that the "diameter" of the observable universe is 93 billion light years. My question is how is this possible if supposedly nothing can move faster than the speed of light? I've read somewhere that the universe itself expands with a speed greater than c, and I've also stumbled upon tachyons. Which also supposedly moves faster than light. I was wondering which "things" are limited to the speed c, and why is it this way? This does not make any sense to me. I've watched numerous documentaries where physicists say that nothing can move faster than light. Have they not studied the universe's expansion, or is this just a matter of course? I hope some of you can shed some light on this topic for me, I haven't found any good explanation to this yet..