Comment by kragen
2 days ago
"Vast" really shouldn't have been eliminated from the title, because interferometers have been measuring distances with nanometer precision since even before there were lasers, and lasers have been used in interferometers since the first laser in 01960. Victorian-era interferometers, commonly used for grinding telescope mirrors, could only measure distances of a few meters with precision in the hundreds of nanometers.
However, laser interferometers were already quite good; LIGO, most famously, detected gravitational waves by measuring strains of around 10⁻²⁰ over a distance of 1120 km, which works out to a change in distance of less than 0.000012 nanometers, much less than the width of a proton.
The news here actually seems to be that "A new way to gauge distance using lasers can measure lengths of more than 100 kilometres ... To continue reading, subscribe today with our January sale." So, uh, I don't know, maybe the reporter wasn't familiar with LIGO and thought that nanometer-precision interferometry over kilometers was new? Sitkack, you say there's a paper somewhere?
I skipped the article, went directly to the paper https://arxiv.org/abs/2412.05542
It is very readable. This measures absolute distance.
LIGO was its own thing https://en.wikipedia.org/wiki/LIGO many people, big vacuum.
Two sites, one by Hanford the other in a swamp https://www.ligo.caltech.edu/WA https://www.ligo.caltech.edu/LA
Thank you! I'll check it out.
LIGO can accurately measure small (1/2 wavelength) changes in distance, but it does not measure absolute distance.
Absolute is a lot harder to do with interferometers vs. relative measurements.
Aha! Yes, very much harder.
Oooh it's the guy with octal years!
Noticed that too, but it has a '9' in it.
Best guess is, he's not about to let the Y10K problem catch him napping.
It's kind of silly, but I do like the philosophy behind it: https://longnow.org/ideas/long-now-years-five-digit-dates-an...
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