  Time-domain Astrophysics (TDA), a foundation of Astronomy, has become a major
part of current and projected (2020s) astrophysics. While much has been derived
from temporal measures of flux and color, the real physics comes from
spectroscopy. With LSST coming on line in 2022, with TDA as one of its original
drivers, the deluge of Transients and new types of variables will be truly
astronomical. With multi-wavelength targeted EM surveys and multi-messenger
(e.g. LIGO-international and advanced ICECUBE), and the possibility of full-sky
and full-time X-ray imagers, the discovery of new Transients and Variables will
flood telescopes on the ground and in space, and this just for multi-band
imaging without spectroscopy. In this White Paper we briefly summarize several
long-standing major science objectives that can be realized with TDA imaging
and spectroscopy (near UV to mid IR) from space. We provide a brief description
of how these can be achieved with the Time-domain Spectroscopic Observatory
(TSO), a Probe-Class mission concept that ELTs on the ground and Flagship
missions in space can not achieve on their own.
