sci.physics.relativity

On Mon, 24 Sep 2007 08:26:49 -0700, mluttgens@ wrote:

>On Sep 23, 11:44 pm, Eric Gisse < ...@ >
>wrote:
>> On Sun, 23 Sep 2007 07:05:01 -0700, mluttg...@ wrote:
>>
>> [...]
>>
>>
>>
>> >> >I said "if", which doesn't mean it is allowed. Your exemple of a
>> >> >z of 10 simply shows that Hubble law is only valid for small z
>> >> >values.
>>
>> >> Except that it isn't. Hubble's law is valid for all z values to a
>> >> large degree. It isn't valid in the sense that the expansion is
>> >> accelerating [oh, didn't you hear about that?] but that expansion is
>> >> small so the linear fit works fine.
>>
>> >For small z values.
>>
>> Nope.
>>
>> Hubble's linear fit pretty much exactly valid except for an
>> exceedingly small acceleration that has been observed in supernova
>> data.
>>
>>
>>
>> >> Oh, and making the d = (c/H) * z/(1+z) ~ (c/H) * z approximation is
>> >> only valid for z >> 1.
>>
>> >No, another gross misunderstanding of you:
>> >d = (c/H) * z is only valid for z << 1 !
>>
>> Posting at 5 am is bad juju. One of these days I'll not only recognize
>> the lesson but accept it.
>>
>> The condition z << 1 means Hubble's law is valid for z ~ or
>> there-abouts. Hubble's law remains valid for z ~ 1 and z > 1.
>>
>> [...]
>
>Please compare the Hubble law results with those
>obtained with Ned Wright's calculator
>( /~wright/ ),
>when hypothetizing a flat universe, c/H0 = Gly
>and Omega M = .
>
> z Light travel
> time in Gy
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>Marcel Luttgens

Why?