设 S'相对S系的速度为 v,则 t1'=(t1-vx1/c2)/√[1-(v/c)2] t2'=(t2-vx2/c2)/√[1-(v/c)2] 所以 (t2'-t1') = [(t2-t1) -v(x2-x1)]/√[1-(v/c)2] 由题意 x1=x2 t2-t1= 4 t2'-t1'=5 所以 √[1-(v/c)2] = 4/5 v=3c/5 x1'=(x1-vt1)/√[1-(v/c)2] x2'=(x2-vt2)/√[1-(v/c)2] 则 (x2'-x1')= [(x2-x1)-v(t2-t1)]/√[1-(v/c)2] = -3c 即 |△x'|= 3c=9X10^8 m