When the 300 - foot telescope observed galaxies, it saw invisible gas extending farther out than the visible galaxy — the galaxy was much larger than it appeared to optical telescopes. (public.nrao.edu)
Human brains are wired to detect threats such as tigers in the bush and are not well equipped for odorless invisible gases coming out our own tailpipes and pie holes. (commonwealthclub.org)
A carbon monoxide detector can guard against invisible gas leaks, so keep one in every bedroom and the nursery. (babycenter.com)