How old is our Universe?

Are scientist just to proud to admit, or can anyone exact tell me how old our Universe is?
When You calculate the known beginning and the known end, then measure the movingspeed, afterwhich You take a fixed point like earth to calculate how long our Universe exist. Do you also use the "speeding up"from it, and did it speed up from the beginning or was there first a "big bang" then slow movement that speed up? Or... Is it speeding up as in gaining momentum, after an explosion??? If our planet is already 4 billion years is 13 billion years the even enough to gain this size of our current Universe??? Tell tell tell me, what is Your vision? Include other ideas like how long will it exist? Is gravity related to our relative speed in the milky way, and/or our Universe??