  We consider the effect of gluon radiation on the energy of top/antitop quarks
and on the anticollinearity of top-antitop quark pairs produced in $e^+e^-$
annihilation. Our results are presented in terms of the $E_q$-dependence of the
$t\bar tg$ cross section and the dependence on the cosine of the opening angle
$\theta_{12}$ between top and antitop for a center of mass energy of
$\sqrt{q^2}=500 GeV$. We then go on to determine mean values for the top
quark's energy as well as its longitudinal and transverse projections, and for
the deviation of $\sin\theta_{12}$ and $\cos\theta_{12}$ from the
anticollinearity limits $\sin\theta_{12}=0$ and $\cos\theta_{12}=-1$. For a
center of mass energy of $500 GeV$ we obtain $<E_q>=248.22 GeV$, $<E_L>=247.24
GeV$ and $<E_T>=4.70 GeV$. Thus, at this energy gluon radiation causes a total
average energy loss of 0.71% of the top quark's energy. The average energy loss
in the longitudinal direction is 1.06% and the average energy gain in the
transverse direction is 1.88%. These percentage figures go up to 3.77%, 5.19%
and 6.06%, respectively, at $1000\GeV$. For the mean of the acollinearity angle
$\bar\theta_{12}=180^0-\theta_{12}$ we obtain $<\bar\theta_{12}>=1.25^0$ at
$500 GeV$, the value of which goes up to $4.62^0$ at $1000 GeV$. From an
analysis of the transverse momentum of the top we find that the mean transverse
momentum of the top stays close to the mean total momentum of the gluon in the
energy range from threshold to $1000 GeV$ showing that the gluon momentum has a
large mean transverse component in this energy range.
