There is no magic "6ft apart". It's just the maximum that seemed reasonable to demand. It's about the width of a supermarket aisle or a typical business hallway. Metric countries surely don't use that distance. Nothing is said about length of exposure or ventilation quality either.

There is no such thing as a perfectly safe distance but there is a "you're really risking common spread in most situations if less than" and that's where the 6 feet/ 2 meter number somes from and why it's relevant not because the virus counts out 6 feet and drops dead. I don't think anyone here is claiming that by referencing it either and you always want more distance if it's reasonably possible.

I believe there are several qualifiers on that number, though. For example, the CDC "close contact" guidelines say that a close contact is "someone who was within 6 feet of an infected person for a cumulative total of 15 minutes or more over a 24-hour period".

Passing someone on a sidewalk means you're within 6 feet for maybe 5 seconds, which would constitude about 0.5% of such a "close contact" exposure.

They also say that several factors with insufficient data mean that it's unclear how things like ventilation, indoor vs outdoor, mask vs no mask, etc, affect the exposure assessment.

https://www.cdc.gov/coronavirus/2019-ncov/php/contact-tracin...

The Netherlands and maybe other European countries use 1.5 meters (~ 5 feet) as their guideline.

Metric countries use 2 meters, and it's determined by how far droplets fly when you talk/cough/sneeze. If covid were only transmitted via droplets, 6 feet/2 meters of distance would be enough. Alas.

Indeed, I've seen anything between 1-2 meters and a small moose (SI unit of distance in the local zoo)..