Question

Why is it not possible that both arms of ligo's interferometer

Answer 1

Although much more sophisticated, at their cores, LIGO's interferometers are fundamentally Michelson Interferometers, a device invented in the 1880's. We can say this because both Michelson and LIGO interferometers share these traits:

• They are both are L-shaped (not all interferometers are this shape)

• They both have mirrors at the ends of the arms to reflect light in order to combine light beams and create an interference pattern

• They both measure patterns and intensity of a resulting light beam after two beams have been superimposed or forced to 'interfere'

But this is where the similarities end. The size and added complexity of LIGO's interferometers are far beyond anything Michelson could have envisioned or that his original interferometer could have achieved.