I have read the following excerpt over and over and still cannot wrap my head around how this was accomplished. They [physicists] are talking about measuring something.... ‘on the order of a billionth of a billionth the diameter of an atom.’ Just how and when did we [humanity] create something that can be measured that precisely! Even the proxy method described below couldn’t possibly be fine tuned down to billionth of an atom. Are we now able to measure down to the Planck length?

Can anyone elaborate on how this was measured so exactly?

“But the first generation LIGO experiment, which ran for eight years, wasn’t sensitive enough. Which is understandable. Gravitational waves are minuscule— the atomic jitters that pass through our world when two black holes bash together in a distant galaxy are on the order of a billionth of a billionth the diameter of an atom. LIGO detects them by proxy, using high powered lasers to measure tiny changes in the distance between two objects positioned thousands of miles apart. A million things can screw this up, including a rumbling freight train, a tremor in the Earth, and the inconvenient reality that all objects with a temperature above absolute zero are vibrating all the time.”