Hi Jim,

Here's my understanding of how the speed of light can vary: You can think of the speed of a particular light wave as being fixed by the relationship between its wavelength and its frequency: (speed) = (wavelength) * (frequency) . So in the scenario Lieu et al are talking about, both the frequency and the wavelength of the light can vary independently by a tiny amount (set by the Planck scale) because of the discreteness of space and time. Thus the speed of that light wave will also vary. It's worth noting that these experiments put limits on any such variation - the speed of light is constant to within about one
part in 10^32.

Todd

On Thursday, April 3, 2003, at 03:27 PM, Jim McClellan wrote:
> We can measure the Planck time, reasoned Ragazzoni and Lieu, by
> looking at
> distant objects. As a beam of starlight hops towards us through
> countless
> Planck times, its speed varies. This would smear the beam out so that
> different parts arrive at different times and distort our picture of
> where
> it came from. The longer the journey, the bigger the distortion.
>
> Todd:
> Why does the speed of light vary?
> ----- Original Message -----
> From: "Todd Duncan" <duncan@scienceintegration.org>
> To: "SII listserv post" <science@lists.pdx.edu>
> Sent: Monday, March 31, 2003 11:01 PM
> Subject: graininess of the universe
>
>
>> Does anyone have any insights about this recent Nature news update on
>> observations related to the "graininess" of spacetime?
>>
>> "Sharp images blur universal picture - Hubble measurements suggests
>> Universe isn't as lumpy as it should be."
>>
>> http://www.nature.com/nsu/030324/030324-13.html
>>
>> Are the results really as big a concern as they make it sound in the
>> article?
>>
>> Thanks,
>> Todd
>>
>> "We must be the change we wish to see in the world." - Gandhi