[QUANTITY] The quandary

[Niall Gaffney]

One more to consider.  Air vs Vacuum wavelengths which, historically, 
are used depending on the area of the EM spectrum being observed (many 
optical spectra are measured in air wavelenghts).  So we may find that 
in some cases (ground based compared to space based optical data) 550 nm 
 > 550 nm should return true!

Niall

Ivo Busko wrote:

>David Berry wrote:
><snip>
>  
>
>>the operation. This potentially has many aspects. The simplest aspect is
>>the issue of Units: obviously if you are comparing a frequency in Hz with
>>another frequency in GHz, the Quantity class needs to transform them into
>>the same units before comparing them - simple enough. But as I mentioned last
>>week, there are many Quantities which are not completely defined simply
>>by a Units string. Continuing with the above example, a frequency is not
>>    
>>
><snip>
>
>Another example where this happens is with flux units. To convert a measurement
>expressed in, say, Flambda units, to Fnu units, one needs to know the
>wavelength or frequency at which the measurement took place. 
>
>-Ivo
>  
>