At time zero, the first vacuum condensation occurred; giving the reality of the big bang singularity of the universal accelerated expansion of the space-time continuum. It could not happen if thermal gradient was zero, which can be expressed as the change in absolute temperature with respect to time ����/����. In the limit as ���� approaches zero ����/���� also approaches zero and the total or partial time derivative is ����/����=0. This implies the unreachableness of absolute zero as the third law of thermodynamics. Moreover, it implies �� is a positive constant not equal to zero, representing the first set of quantum thermal conditions: ����>0 and ����/����=0, which imply irreversibility, positive entropy and the second law of thermodynamics. However, ��<0 and ����/����=0 represent the second set for negative entropy, reversibility, negative energy, and time reversal if and only if the first law of total energy conservation is expressed as the square of total relativistic energy: ��²=��²��²+��²��⁴ and introducing its space-time symmetry as -��²=-��²��²+��²��⁴=(����+����²)(-����+����²)=(��+��)(-��+��)=-��²+��² where �� is the total kinetic energy of the space-time continuum and �� is the total potential energy such that (��+��) is equivalent to the Hamiltonian energy function and (-��+��) is the negative of the Lagrangian energy function. Then ��²-��²=2��²��⁴=0 implies the existence of zero rest masses for photons, gluons, and gravitons but without giving a proof for mass quantization. Fortunately, mass quantization is realized by the spontaneous broken symmetry of the quantized space-time continuum, whose physical existence can be validated by experiments of quantum vacuum condensation analogous to the first big bang condensation of the quark-gluon plasmas into mass and energy for all elementary particles of Planck energy physics.