[guest39538]

Is the red-shift we observe simply a change in vision?

[Atomic-S]

No, it is detected also by instruments having nothing to do with anyone's eyesight.

[guest39538]

No, it is detected also by instruments having nothing to do with anyone's eyesight.

What do you mean it is detected by instruments?   

How would an instrument know it was the ''colour'' red?


Isn't Hubble a telescope that uses vision?

Do we not see through the ''eye'' of Hubble and visually observe the red-shift?

[Colin2B]

How would an instrument know it was the ''colour'' red?

Measure the frequency

Isn't Hubble a telescope that uses vision?

There isn't a human eye looking down the end.

I think you need to be clearer what you mean by "change in vision"
Also, you might want to consider what might cause such a change, unless you are suggesting it is all in the imagination!

[guest39538]

Measure the frequency

How do you measure the frequency of something that is very far away?   

Have you got ''probes'' out there?

There isn't a human eye looking down the end.

I think you need to be clearer what you mean by "change in vision"
Also, you might want to consider what might cause such a change, unless you are suggesting it is all in the imagination!

Obviously the Hubble does not have a human eye, but at the end of the ''line'' it is a human eye that observes the ''view''.

A change in vision is that the redshift is different to the ''surrounding'' light passing through space, my constant-'constant and the invisible light .

[alancalverd]

How do you measure the frequency of something that is very far away?   

You wait until it arrives, then measure it, using a spectrometer.

[guest39538]

You wait until it arrives, then measure it, using a spectrometer.

Hmm you wait for  it to arrive, but is light not continuously arriving and also continuously being emitted from the observation ''point'' , how do you know the light that is arriving is the light from a distant ''object' , do you directly aim your spectrometer at the ''object''? 


Relative to the observer how do you  know the light is not red shifting this ''end''?   

Relativity states that if two observers  are in motion, neither observer can tell who is moving,  it all sounds a bit hmmmm to me.

[alancalverd]

Hmm you wait for  it to arrive, but is light not continuously arriving and also continuously being emitted from the observation ''point'' , how do you know the light that is arriving is the light from a distant ''object' , do you directly aim your spectrometer at the ''object''? 

We can estimate distance by astronomical parallax - worth a google!

Relative to the observer how do you  know the light is not red shifting this ''end''?

because we also observe blue shifts, and red shifts vary from object to object, so it seems more likely that the shift is connected with the source rather than the receiver.   

Relativity states that if two observers  are in motion, neither observer can tell who is moving,  it all sounds a bit hmmmm to me.

Nothing clever about it - just common observation. If you are in a train moving at constant speed, and you pass another train, you can't tell by looking at it which of you is moving at what speed - all you can measure is your relative speed. Same thing applies to converging aircraft in the absence of any other reference points: your air-to-air radar can only measure your speed relative to each other. That's the basis of relativity. It gets interesting when you discover that there is no fixed interstellar medium: all astronomical movement is relative. It's really very simple.


Incidentally "red" and "blue" don't just refer to perceived color. All photons are subject to frequency shift due to source movement (Doppler shift) or gravitational field gradient.

[jeffreyH]

Alan's last post sums it up nicely. You need to take these things in to make positive progress.

[guest39538]

 because we also observe blue shifts, and red shifts vary from object to object, so it seems more likely that the shift is connected with the source rather than the receiver. 

Are you saying that the blue-shift or red-shift is observed at/of the observed point source?