The far-infrared (FIR) regime is one of the wavelength ranges where no astronomical data with sub-arcsecond spatial resolution exist. None of the medium-term satellite projects like SPICA, Millimetron, or the Origins Space Telescope will resolve this malady. For many research areas, however, information at high spatial and spectral resolution in the FIR, taken from atomic fine-structure lines, from highly excited carbon monoxide (CO), light hydrides, and especially from water lines would open the door for transformative science. A main theme will be to trace the role of water in proto-planetary discs, to observationally advance our understanding of the planet formation process and, intimately related to that, the pathways to habitable planets and the emergence of life. Furthermore, key observations will zoom into the physics and chemistry of the star-formation process in our own Galaxy, as well as in external galaxies. The FIR provides unique tools to investigate in particular the energetics of heating, cooling, and shocks. The velocity-resolved data in these tracers will reveal the detailed dynamics engrained in these processes in a spatially resolved fashion, and will deliver the perfect synergy with ground-based molecular line data for the colder dense gas.

远红外 (FIR) 区域是不存在具有亚弧秒空间分辨率的天文数据的波长范围之一。SPICA、Millimetron 或起源太空望远镜等中期卫星项目都无法解决这一问题。然而，对于许多研究领域而言，从原子精细结构线、高度激发的一氧化碳 (CO)、轻氢化物，尤其是水线获取的 FIR 中高空间和光谱分辨率的信息将为变革性科学打开大门. 一个主题将是追踪水在原行星盘中的作用，以观察方式推进我们对行星形成过程的理解，以及与此密切相关的可居住行星的途径和生命的出现。此外，关键观测将放大我们银河系以及外部星系中恒星形成过程的物理和化学。FIR 提供了独特的工具来研究特别是加热、冷却和冲击的能量学。这些示踪剂中的速度分辨数据将以空间分辨的方式揭示这些过程中根深蒂固的详细动力学，并将与较冷稠密气体的地面分子线数据提供完美的协同作用。