The foreshortening of B
     The distances set along the x axis of frame B when frame B was at rest in the qm have decreased due to B's .6 ca absolute velocity, but the observers on B cannot detect the change. The distance from the origin of B to the 1 ls location on the x axis is now only .8 LS, but radar ranging by the automatic positioning systems and by observers(c) tells them this distance is still 1 ls. They are correct that a radar signal still takes 2 s on their clocks to make a round trip to the x=1 ls location, but their 1 ls along the x axis is now only .8 times as long as before. Radar photons, traveling along the x axis with relative velocity cr=.4 ca, take 2 sa to travel the .8 LS distance to the 1 ls location. And they take another .5 sa to return with a relative velocity of cr=1.6 ca. During the 2.5 sa round-trip travel time, the origin clock advances 2 s because its rate is only .8 times the at-rest rate.

     The foreshortening of everything in frame B (spaceships, occupants, instruments, etc.) along lines parallel to va occurs because, as B's absolute velocity increases, the rate of round-trip energy exchange would decrease more in the direction of va than in directions perpendicular to va unless B's atoms adjust (like the automatic positioning systems adjust frame B) to maintain equal rates in all directions. As the absolute velocity of B increases, the time required for photons to make a round trip over a distance of D LS along the x axis of B is [D/(1−va)]+[D/(1+va)] = 2·D/(1−va) sa, and the time required for photons to make a round trip over the same absolute distance in a direction perpendicular to va is 2·D/(1−va) sa because, as we determined earlier, the speed of light along the y axis is (1−va) ca. Therefore, whether D is 3E8 ma (the size of frames A or B), or whether D is 1E−10 ma (the size of an atom), the rate of round-trip energy exchange in a system decreases as va increases, and the rate decreases more along lines parallel to va than along lines perpendicular to va unless the system maintains the same balanced, isotropic rate by contracting by a factor of (1−va) along lines parallel to va.

      Due to the foreshortening of the atomic structure throughout B, the interactions between the constituents of the atoms appear to the constituents no different than before. The rate of interaction is slower than before, but it appears the same, just as the observers(c) and instruments aboard frame B do not detect the foreshortening and the slower rates of mechanical, biological, chemical, and atomic processes throughout B.