[HN Gopher] Laser technique measures distances with nanometre pr...
       ___________________________________________________________________
        
       Laser technique measures distances with nanometre precision
        
       Author : westurner
       Score  : 16 points
       Date   : 2025-01-14 03:32 UTC (2 days ago)
        
 (HTM) web link (www.newscientist.com)
 (TXT) w3m dump (www.newscientist.com)
        
       | westurner wrote:
       | > _optical frequency comb_
       | 
       | "113 km absolute ranging with nanometer precision" (2024)
       | https://arxiv.org/abs/2412.05542 :
       | 
       | > _two-way dual-comb ranging (TWDCR) approach_
       | 
       | > _The advanced long-distance ranging technology is expected to
       | have immediate implications for space research initiatives, such
       | as the space telescope array and the satellite gravimetry_
        
       | sitkack wrote:
       | I am only two pages in, but I want to say this paper is very well
       | written. People should give reading it a try reading (with LLM
       | assistance).
       | 
       | If this technique could be adapted to existing optical fiber
       | infrastructure, we could see the effects of fiber optic cable
       | stretch and deformation in realtime.
        
       | kragen wrote:
       | "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?
        
         | stavros wrote:
         | Oooh it's the guy with octal years!
        
       ___________________________________________________________________
       (page generated 2025-01-16 23:00 UTC)