Planck's constant is wrong by 10 orders of magnitude

[svenberkvens2]

Planck's constant is defined as 6.6260755 × 10^-24 J.s in the UCUM technical document, but that value is wrong. It is actually 6.6260755 × 10^-34 J.s (10 orders of magnitude less).

The source that is cited in the UCUM specification document (​http://physics.nist.gov/cuu/Constants/index.html) also says so, I guess somebody made a typo when copying the value.

[Christof Gessner]

I agree. Should be fixed in next update.

The numerical value given in the cited reference is 6.626 070 040 x 10-34 J s.

Note that this error has no effect on using the UCUM codes as unit symbols in expressions. However, if conversion factors are employed for converting between units, such an error is of course significant.

[Gunther Schadow]

This is a major error, yes.

The dighits have also been updated, as Christof says, but the digits change with the passage of time.

​1986	6.626 075 5(40)	×	10−34	J.s
​1998	6.626 068 76(52)	×	10−34	J.s
​2002	6.626 0693(11)	×	10−34	J.s
​2006	6.626 068 96(33)	×	10−34	J.s
​2010	6.626 069 57(29)	×	10−34	J.s
​today	6.626 070 040(81)	×	10−34	J.s

So we see that the original value was from the 1986 publication. This part has not been updated since 1997/8 so the new values of 1998 had just been released when the data compilation was finished.

I will fix this wrong exponent immediately and apply it as an immediate correction, but will not change the digits yet.

We will have to consider what to do with the updating of digits for these natural constants over time. This would be a new ticket.

[Gunther Schadow]

See new ticket #178 for follow up questions to the issue of the changing digits.

[Gunther Schadow]

I am adopting this ticket because of the need for an immediate correction.

[Gunther Schadow]

Fixed with [437] and immediately published release 2.0.1 [438].