  The question "How did we get here and what will the future bring?" captures
the human imagination and the attention of the National Academy of Science's
Astronomy and Astrophysics Survey Commitee (AASC). Fulfillment of this
"fundamental goal" requires astronomers to have sensitive, high angular and
spectral resolution observations in the far-infrared/submillimeter
(far-IR/sub-mm) spectral region. With half the luminosity of the universe and
vital information about galaxy, star and planet formation, observations in this
spectral region require capabilities similar to those currently available or
planned at shorter wavelengths. In this paper we summarize the scientific
motivation, some mission concepts and technology requirements for far-IR/sub-mm
space interferometers that can be developed in the 2010-2020 timeframe.
