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MathGroup Archive 2005

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Re: Get numbers out of PhysicalConstants?

  • To: mathgroup at
  • Subject: [mg62616] Re: Get numbers out of PhysicalConstants?
  • From: dh <dh at>
  • Date: Tue, 29 Nov 2005 06:43:19 -0500 (EST)
  • References: <dme8l6$inj$>
  • Sender: owner-wri-mathgroup at

Hi Wonseok,
One way to achieve what you want is to replace all the units by 1.
Toward this aim you may use a function from Miscellaneous`Units`Private` 
called UniqueCasesUnit:


that gives you the units of an expression.

With this we can extract the numerical part of an expression by e.g. 

<< Miscellaneous`PhysicalConstants`
  << Miscellaneous`Units`
(t = VacuumPermeability) /. ((# -> 1) & /@ \


Wonseok Shin wrote:
> Hello,
> Is there any way to get numbers out of the constants defined in
> Miscellaneous`PhysicalConstants` package?  Carrying units all the time
> is inconvenient in calculation.
> For example,
> In[1]:= << Miscellaneous`PhysicalConstants`
> In[2]:= VacuumPermeability
> Out[2]= \!\(\(p\ Second\ Volt\)\/\(2500000\ Ampere\ Meter\)\)
> I want to get the number p/2500000 out of VacuumPermeability, without
> units.  How can I do this?

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