|one billion years|
|the magnitude of a star as it would appear to a hypothetical observer at a distance of 10 parsecs or 32.6 light-years|
immersion im·mer·sion (ĭ-mûr'zhən, -shən)
The placing of a body under water or other liquid.
The use of a fluid on a microscope slide in order to exclude air from between the glass slide and the bottom lens.