Comments on: American Metric

By: Calla Cofield

Calla Cofield — Mon, 22 Mar 2010 14:07:14 +0000

Thank you for spotting that – it has been corrected.

By: erikbergren

erikbergren — Thu, 18 Mar 2010 23:51:47 +0000

There was a typo:
“299.19 million miles from the Sun is…
twice the distance from the Earth to the Sun (2 AU). ”
2 AU is 299.19 million kilometers not miles.
It is 186 million miles (the first three digits
happen to be the same as the speed of light “c”.

By: David Harris

David Harris — Thu, 10 Jul 2008 14:38:06 +0000

The kilogram is still defined by a physical artifact but there are many plans afoot to change the definition to something based on fundamental constants.

There are various suggestions for how this might be done but one involves fixing the Avogadro constant and then basing the kilogram on the definition of length by creating an ultra-pure sphere of silicon of a given diameter, as a practical realization.

Other techniques would involve electrical measurements that essentially act as scales for a sample mass.

By: Uncle Al

Uncle Al — Tue, 08 Jul 2008 17:09:39 +0000

The SI Brochure states that the eV is not accepted officially by SI because it has to be obtained experimentally and can only be expressed approximately in terms of SI units.

Has SI redefined the kilogram from fundamental constants, outside physical artifacts that empirically drift in value over time?

By: Blake Stacey

Blake Stacey — Mon, 07 Jul 2008 16:07:10 +0000

In six years living around Cambridge, Mass., I’ve never heard anyone (even an MIT student) use the smoot to measure anything other than positions on the Harvard Bridge.

I did, however, set up my computer to report weather conditions in kelvins.