Detection of gravity waves used interferometry for observing the result. This means two light waves interfere with each other to create an effect with light. When the waves precisely overlap, they cancel each other and become dark. Any change in the alignment, and some light appears. Change in distance the light travels will misalign the waves and create some light. The amount of light depends upon the amount of change in alignment.
The measurement is in the misalignment of two waves. A variation of 0.1 atto meter is said to be detected. The actual distance that the waves travel is of no relevance. It is not measured or analyzed. Only the offset of waves is detected.
The light waves are produced by laser beams which have a wavelength of approximately one micron (one micro meter). The change in distance said to be detected is 0.1 atto meter. That's 10 trillion times as much distance in one wave as the detected distance change. The laser beam is reflected 280 times, which increases the detection distance change to 28 atto meters. That's still 36 billion times less detection distance than the size of one wave of the laser beam. Such a miniscule influence over the laser beam would not really be detectable.
One problem is diffusion of light. Light cannot be created perfect or made perfect after it is created. The imperfections create diffusion. Then the reflection off imperfect mirrors 280 times adds more diffusion. Beam splitters would require heterogeneity of matter and light to spit a light wave.
The light detector is said to be a photo diode. I have used silicone based photo diodes, and they are nothing but crap. Cadmium sulfide detectors from the nineteenth century work better, but they wouldn't be controllable enough. The problem with silicone based devices is that they produce a lot of current noise, thermal noise, popcorn noise and drift. The silicone has to be spiked with dopants to create a diode, which creates a lot of variations.
Since obfuscation is the standard, a vacuum tube detector, called a photomultiplier, might be used. These puppies create super amplifaction, which should be good for a lot of contrived magic, except that the more the amplification, the less the resolution, while the degree of resolution is the problem in picking the signal out of 10 trillion times as much background light.
Interferometry is not a realistic procedure for highly demanding measurements due to the crudeness of light waves. At the macro scale, telescopes gathering light create the impression of high precision, but this is due to the accumulation of a large number of waves. At the micro scale, individual waves are used, and they are too diffuse and imperfect for high precision. But physicists exploit the vagaries to create the desired obfuscation and ability to contrive without accountability.
Physicists do not account for all of the factors which influence their results. In fact, they reduce their calculations to one factor, in part because math cannot handling the increased complexity of interacting factors, and in part because physicists cannot relate one reality to another well enough to understand the complexities. Examples of this are in every element of global warming science. In calculating temperature change in the oceans, climatologists didn't notice that air does not have enough heat capacity to influence ocean temperatures.
I proved the definition of energy to be wrong using simple math. The error corrupts ninety pecent of physics. Physicists won't touch the subject, because they used more contrivance than the Mafia to get the erroneous result. They go for errors for the same reason they go for relativity, which was totally contrived with no relationship to the rest of science, because falsehoods allow them to contrive without accountability. Falsehoods are "nonfalsifiable", which means force overwhelms opponents in the absence of real science.