🚀 go-pugleaf

In article <1992Oct5.154211.21663@ecrc.de>, micha@ecrc.de writes...
>In article 24242@access.usask.ca, choy@skorpio.usask.ca (I am a terminator.) writes:
>>How do you know that the line you draw is really straight? What
>>defines straightness?
> 
>This is something I've been wondering about since a long time. Although we can
>make a circle as precise as we want, I think we cannot make a really
>precise straight line - every straight line is made from another one or from a tool
>that has been made using some older straight lines - so it all comes down to
>copying a line that has been made thousands years ago. Although we have precise
> 
ahem... This isnt my area of expertise,
but many surveys these days are based on straight lines defined by lasers.
Could someone from a national standards institution tell us
if there is a straight line standard based on laser light?

On another note, the gravitational wave researchers at my institution
(Glasgow University) and at other places can measure
changes in DISTANCE to quite mind--boggling accuracy using laser
light stored in cavities.
Don't have the exact number to hand, but could find out if need be.