












Comments     Threshold


By HilbertSpace on 1/19/2007 10:52:41 AM , Rating: 3
I don't think we've quite reached the point where we're using picometer sized objects for practical applications. An atom is roughly an order of magnitude larger than a picometer! Unless you're referring to quantum dots (which use electrons) but even then the overall structure is much larger than a picometer.

RE: picometer?
By Some1ne on 1/19/2007 8:42:13 PM , Rating: 1
"Picometer sized" doesn't necessarily mean that the size ~= 1 picometer. Generally speaking, and considering the context of the article, it's safe to assume that "picometer sized" in this case means "so small that picometers make for the most convenient units when describing the size". For example, transistors have been nanometer sized for quite some time now, but they are all still quite larger thana single nanometer. Something .7 nanometers in size might as well be considered picometer sized, because it's more convenient and descriptive to say 700 picometers than .7 nanometers.

Besides, the way atomic radii are computed, it's not really meaningful to say that an atom is an order of magnitude larger than a picometer, as they measure all the way out to the farthest available electron orbital, so the lion's share of that measurement is simply empty space. Really they ought to just measure the radius of the nucleus, but physicists never learn.

RE: picometer?
By masher2 (blog) on 1/19/2007 11:26:07 PM , Rating: 2

"Picometer sized" implies within one order of magnitude of a picometer. In other words, somewhere in the range 10 - 0.1 pm.

> "Really they ought to just measure the radius of the nucleus, but physicists never learn. "

Physicists have good reason for distinguishing the atomic radius from the nuclear radius (both are measured, and useful for different purposes). The atomic radius gives us the spacing between nuclei while covalently bonded, for instance.

