The match was evident when the hydrogen density
in interstellar space was of the order of magnitude of one atom per cubic centimeter.
This is particularly due to the gravimetric and volumetric hydrogen density
requirements in order to achieve a 300 mile cruising range.
(4) to within 0.01 % from 220 K to 1000 K with pressures up to 70 MPa, and from 255 K to 1000 K with pressures up to 120 MPa, although the estimated uncertainty of the resulting hydrogen density
The telescope called the Canadian Hydrogen Intensity Mapping Experiment, or CHIME, uses the digitized signals it collects to create a three dimensional map of hydrogen density
to measure the expansion of the universe, (https://chime-experiment.ca/location) according to the CHIME website.