Relax wrote:
Your aligned LIGO..... Can only do so at one temperature, one stress level. Why they have to try and do real time inferometry as even someone walking close by will stretch/move a material at the photon level meters away.
Why accelerometer labs are built on fine dry silica sand 10 meters deep with 1 meter thick concrete "tub" to try and zone out cars/trucks driving several hundred meters away. They still can't.
It is all about calibration on the fly. This is where the magic comes from.
NOTHING is rigid. NOTHING
For instance, light based RING laser gyros are the pinnacle of position internal navigation systems. So, we have light... moving at 300,000km/s racing around, mirrors, optical fibers in a circle and we are measuring tiny fractions of spin angular velocity in 3 dimensions by measuring how much "slower" said light beam moves around this ~4(10cm)inch circle. I'll let you do the math on how many revolutions the light "spun" going around that circle and what its delay is. This must be kept at constant temperature because if the temp changes by even 0.01C(it is calibrated much better than this), the circle changes diameter throwing off the calculations.
SO, the fact is EVERY SENSOR MOVES massively compared to how sensitive its accuracy must be. It does not matter that the sensor MOVES. They all do. What DOES matter is how you, the design engineer, constantly calibrate said moving, flexing, twisting, stretching, vibrating, sensor. IN REAL TIME. Folding a sensor when launching, a one time occurrence is beyond trivial in comparison.
Its the difference between lighting a match, and exploding a nuclear bomb
Ummh, no. And I am a research physicist, and have done interferometry of a type for close to 50 years, until I retired. I was a research student for Rai Weiss, the fellow who invented LIGO, and was at the student seminar at which he first proposed the device.
Sand tubs are obsolete, and have been for half a century. Readers interested in modern tech should investigate
https://www.newport.com/ .
Second, the core vibration at LIGO starts with massive objects hung from very weak springs. There is then a vast amount of compensation, as described above. LIGO runs as the outside-the-building temperature changes, for reasonably long periods of time. The extremely long optical paths are cryogenically pumped vacua.