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hackenslash wrote:Nice article. Can't see any obvious issues (except the missing 't' in 'thought' in the third paragraph).
Greyman wrote:You obtain equation (6) by approximating under the assumption: d_1 << R_{source}
That is, you assert that the distance from earth's surface to the emitter galaxy is much less than the radius of the earth.
twistor59 wrote:Not sure exactly what the OP is saying.
Pulsar wrote:What a pile of garbage
You start with the weak-field approximation of gravitational redshift, and you showed that it is linear with distance. Well duh,
z ~ Δϕ/c2 = gh/c2
Not only is your little exercise trivial, it has absolutely nothing to do with Hubble's Law.
zaybu wrote:Greyman wrote:You obtain equation (6) by approximating under the assumption: d_1 << R_{source}
That is, you assert that the distance from earth's surface to the emitter galaxy is much less than the radius of the earth.
Assume the universe is infinite, Rsource → ∞.
Then for any galaxy at a distance d1,
d1 << Rsource
This is always true.
Thommo wrote:zaybu wrote:Greyman wrote:You obtain equation (6) by approximating under the assumption: d_1 << R_{source}
That is, you assert that the distance from earth's surface to the emitter galaxy is much less than the radius of the earth.
Assume the universe is infinite, Rsource → ∞.
Then for any galaxy at a distance d1,
d1 << Rsource
This is always true.
eh? Rsource is described as the radius of the Earth in the text, isn't it?
Scarlett and Ironclad wrote:Campermon,...a middle aged, middle class, Guardian reading, dad of four, knackered hippy, woolly jumper wearing wino and science teacher.
campermon wrote:This bit has confused me too.
Scarlett and Ironclad wrote:Campermon,...a middle aged, middle class, Guardian reading, dad of four, knackered hippy, woolly jumper wearing wino and science teacher.
Scarlett and Ironclad wrote:Campermon,...a middle aged, middle class, Guardian reading, dad of four, knackered hippy, woolly jumper wearing wino and science teacher.
A common belief about big-bang cosmology is that the cosmological redshift cannot be properly viewed as a Doppler shift (that is, as evidence for a recession velocity), but must be viewed in terms of the stretching of space. We argue that, contrary to this view, the most natural interpretation of the redshift is as a Doppler shift, or rather as the accumulation of many infinitesimal Doppler shifts. The stretching-of-space interpretation obscures a central idea of relativity, namely that it is always valid to choose a coordinate system that is locally Minkowskian. We show that an observed frequency shift in any spacetime can be interpreted either as a kinematic (Doppler) shift or a gravitational shift by imagining a suitable family of observers along the photon's path. In the context of the expanding universe the kinematic interpretation corresponds to a family of comoving observers and hence is more natural.
twistor59 wrote:I still think the essence of what zaybu is trying to put across is what's discussed in the Ted Bunn link I gave above
twistor59 wrote:I still think the essence of what zaybu is trying to put across is what's discussed in the Ted Bunn link I gave above:
http://arxiv.org/abs/0808.1081A common belief about big-bang cosmology is that the cosmological redshift cannot be properly viewed as a Doppler shift (that is, as evidence for a recession velocity), but must be viewed in terms of the stretching of space. We argue that, contrary to this view, the most natural interpretation of the redshift is as a Doppler shift, or rather as the accumulation of many infinitesimal Doppler shifts. The stretching-of-space interpretation obscures a central idea of relativity, namely that it is always valid to choose a coordinate system that is locally Minkowskian. We show that an observed frequency shift in any spacetime can be interpreted either as a kinematic (Doppler) shift or a gravitational shift by imagining a suitable family of observers along the photon's path. In the context of the expanding universe the kinematic interpretation corresponds to a family of comoving observers and hence is more natural.
I've only ever skimmed this paper, but it looked kind of OK.
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