There’s no such thing as a complete vacuum. Even in the cosmic void between galaxies, there’s an estimated density of about one hydrogen or helium atom per cubic meter. But these estimates are largely theoretical—no one has yet launched a sensor into intergalactic space and beamed back the result. On top of that, we have no means of measuring vacuums that low.
At least, not yet.
Researchers are now developing a new vacuum-measurement tool that may be able to detect lower densities than any existing…
