If you have read my other threads, i am having trouble understanding special relativity. The issue seems to be my understanding of space-time. Space-time infers to me that two events are not separated by only a length in three dimensions, but also time, with time being essentially indistinguishable from a length. This concept can be explained by considering a supernova occurring several thousand light years away and it being observed looking up at the sky. To the observer looking up in the sky, the event of looking up in the sky coincides with the supernova and are to the observer simultaneous. But in fact this occurred several thousand years ago and the event can only be recognised as occurring, once the information has travelled the distance. It might turn out in fact that the supernova wasn't a supernova, but a plane in the sky that has turned on a light. These events are not separated by a massive distance and so it can be considered that the fact that they are simultaneous according to the observer, means that the light only turned on a marginally before it was recognised. This has been developed into a quantitative concept of four vector space (x,y,z,t) where time is indifferent to length. The resultant formula for space time is: S^2 = X^2 + Y^2 + Z^2 -(CT)^2 S: the resultant distance between event A and event B X: the difference between the x coordinates of event A and event B or (Xb-Xa) Y: the difference between the Y coordinates of event A and event B or (Yb-Ya) Z: the difference between the Z coordinates of event A and event B or (Zb-Za) C: the speed of light in a vacuum (converts the time units into the length units used) T: the difference in when event A occurs and when event B occurs, if they were in the same position (Ta-Tb) Lets consider the supernova situation. Consider event A to be recognition of event B the supernova, the position of event A to be (0,0,0) and event B (100,0,0) units in light years. If in the same position then event A would occur 100 years after event B. As event A is the recognition of event B we know that the resultant distance in 4 vector space is zero and so a result for S must be zero. S^2 = (100 light years)^2 + 0^2+ 0^2 -(C*100 years)^2 = 10,000-10,000 = 0 their for S = 0 This formula works perfectly in this situation, but in the next situation, something in my logic goes wrong. Event A is a bunch of 2012 believers looking to the sky expecting the end of the world and event B is a supernova, that emits massive amounts radiation, which when this radiation hits earth, will kill the majority of life. If event A and event B are in the same position then event B would occur 10,000 years later. event A has a position of (0,0,0) and event B a position of (10000,0,0). A prediction of what S will equal is based on my logic that (1) event A will happen (2) 10,000 years will pass (3) the supernova occurs and (4) 10,000 years pass before the radiation hits earth. My conclusion is that S=20,000 light years but the math gives a different result. S^2 = (10,000 light years)^2 + 0^2+ 0^2 -(C*-10,000 years)^2 = 1,000,000 - 1,000,000 = 0 their for S = 0 According to the result found using the formula, the 2012 believers were right. My problem with space-time seems to be a difficulty in recognising time behaves the same as a dimension such as x,y,z as my logic seems to consider time behave the same as S or the resultant. My logic would have the formula for S as: S = (X^2+Y^2+Z^2)^0.5 -CT This is causing me huge confusion and i can not put my finger on what i have done wrong. please help.