a1     a
thinking of a parallax vector >d….,d1
me(d) is determined by positions a and b,,,one of these being constant,say(b)..the ratio of Me(d)/me(d1),is same as the ratio of a/a1…as d is observed a can be any position determined by position and momentum of observer within system ,,,since b is constant,,d is predetermined by a,,and its velocity,and momentum (p) relative to vp of c(which is unchanging)
that determines a system of positive mass e+positive vp,,,,
massless system,,has an unobserved a,and therefore(a/b)=1,,can only be observed at the rate of constant,,therefore is never observed as =,or >1…because d,has no intersecting points of ab so line is infinite
now if you reverse the parallax b1 a1….the system is still
d 1< d1<

observed at d,,,b is still constant,but a has a ratio of >1 relative to (b)….so while a and b determined the vector,,,and both a,and b are of same coordinates,,the velocity of a relative to b, is greater therefore (a) is observed as b,while the ratio of b1/c is <1 ,, sum of b1,and d1 observed as d1….the ratio of d/d1=the ratio (a1/c) to(b1/c)….since a1 is unobserved,the a1=0,,,and d1 is observed as the ratio of b1/d1 wich must always =>0…
in this case a particle of mass at high speed >c…is measured at =,or <c,,,and me=,or >.00000000000000000~1…..and observed as d1 where the ratio of b1/d1=ratio a1/b1…therefore a1=b1 d1>0<a1-b1…any gmeasure other than zero,,,is down to innaccuracy,,,any >o is due constant bbeing observed as the ratio of (b1>c)/c-(d1<c)….