If your finger was the size of the Earth, you could feel the difference between houses from cars
I think it would be easier to visualize this way:
If the Earth was the size of an orange, your finger could feel the difference between houses from cars
So, perhaps an even better analogy would be:
If the Earth was the size of an orange, your finger could feel the difference between cities and forests.
This puts more emphasis on the distinct patterns the objects form as a group, rather than the individual objects.
2 nm Diameter of a DNA Alpha helix
4 nm Globular Protein
6 nm microfilaments
7 nm thickness cell membranes
20 nm Ribosome
25 nm Microtubule
30 nm Small virus (Picornaviruses)
30 nm Rhinoviruses
50 nm Nuclear pore
100 nm HIV
I make telescope mirrors. The error I'm allowed is 100 nm. I would love to just drag my fingers over the glass and tell if something is not quite right with the optical surface. In reality, I need a pretty elaborate optical setup to amplify the errors about 1/2 million times, in order to see them.
I'm guessing the spatial frequency of the pattern in that experiment is on the same size scale like the vertical amplitude of it.
http://en.wikipedia.org/wiki/Bernhard_Schmidt#Mittweida_year...
"The researchers found that the emission of only 90 photons could elicit visual experience. However, only 45 of these actually entered the retina, due to absorption by the optical media. Furthermore, 80% of these did not reach the fovea. Therefore, the human eye can detect as few as nine photons."