This is not known, its a possibility but there has been no experiment done that confirms or denies it.In actuallity time is dimensional -- WHA?? Thats right boys and girls the time line branches...
It branches at every significant and insignificant event of time - infinatly
It is essentially the quantum multiple universe hypothesis that Adrian mentioned earlier, though it should be noted that "time lines" do not split off at a specific time (if you are going by reltavistic block-time there is no passing of time, time is stationary), they start off that way.