Is there an answer?

Can anybody explain why the frequency of an observed source of EM radiation
cannot be proportional to the distance the radiation has travelled to the
observer?

L

"Lionel" lionel wrote in message
...
Can anybody explain why the frequency of an observed source of EM
radiation cannot be proportional to the distance the radiation has
travelled to the observer?

L

The frequency is inversely proportional to distance. Red-shifting means an
increase in wavelength toward the red end of the spectrum. Since frequency
is inversely proportional to wavelength, that yields an inverse relationship
between frequency and distance. Hubble realised the cosmological red-shift
of light due to the metric expansion of space-time. The greatest red-shift
we observe comes from the most distant source, namely the cosmic background
radiation. One way of visualising the effect is to consider photons
travelling through a space-time continuum which is slowly expanding, thereby
stretching them and increasing their wavelength. (Fold a piece of paper,
concertina fashion to simulate waves, then slowly stretch it). Recent
observation suggests that the universe is not only expanding, but doing so
at an increasing rate, i.e literally accelerating apart. If that proves to
be correct, we will have a non-linear (but still inverse) relationship.

The red-shift due to metric expansion is not to be confused with Doppler
red/blue shift due to sources receeding/approaching, nor with gravitational
red-shift due to light passing through the gravity fields of massive
objects. For objects relatively close to us, those effects dominate. The
cosmological shift due to space-time expansion only becomes noticeable for
very distant objects.

This is my understanding, but there are hopefully some here present who can
refine it.

Wasn't it Lionel who wrote:
Can anybody explain why the frequency of an observed source of EM radiation
cannot be proportional to the distance the radiation has travelled to the
observer?

http://en.wikipedia.org/wiki/Tired_light#Criticisms

--
Mike Williams
Gentleman of Leisure

As you well know, you can't prove a negative. If you're a supporter of tired
light, you've got to prove why it can.
"Mike Williams" wrote in message
...
Wasn't it Lionel who wrote:
Can anybody explain why the frequency of an observed source of EM
radiation
cannot be proportional to the distance the radiation has travelled to the
observer?

http://en.wikipedia.org/wiki/Tired_light#Criticisms

--
Mike Williams
Gentleman of Leisure

"Mark Dunn" wrote in message
...
As you well know, you can't prove a negative. If you're a supporter of
tired
light, you've got to prove why it can.

But the tired light theory (photons losing energy as they propagate over
great distances) is only a whacky alternative to Hubble expansion - both
lead to red-shift (frequency inversely proportional to distance); it is only
the cause of the red-shift which is questioned.

TeaTime wrote:
"Mark Dunn" wrote in message
...
As you well know, you can't prove a negative. If you're a supporter of
tired
light, you've got to prove why it can.

But the tired light theory (photons losing energy as they propagate over
great distances) is only a whacky alternative to Hubble expansion - both
lead to red-shift (frequency inversely proportional to distance); it is only
the cause of the red-shift which is questioned.

But tired light theory implies effects that are contradicted by
empirical evidence. Hubble expansion and tired light are not
equivalent.

http://www.astro.ucla.edu/~wright/tiredlit.htm

Bill

wrote in message
ups.com...
But tired light theory implies effects that are contradicted by
empirical evidence. Hubble expansion and tired light are not
equivalent.

http://www.astro.ucla.edu/~wright/tiredlit.htm

Bill

I agree, but the point I made was that they both attempt to explain
red-shift over long distances. Like the great majority of prominent
physicists, I do not support the tired light theory (I used the words
'whacky alternative'). I did not state that the two theories are
equivalent. The OP's question was why the frequency of an observed source
of EM radiation cannot be proportional to the distance the radiation has
travelled. I explained that it is in fact inversely proportional and
another poster suspected that the OP subscribed to the tired light idea. I
merely pointed out that whichever theory one subscribes to, the relationship
of frequency with distance is due to red-shift. If you are trying to score
a point off me, you might read what I have posted first.

OK, teatime is over, back to work.

the gaffer wrote:
wrote in message
ups.com...
But tired light theory implies effects that are contradicted by
empirical evidence. Hubble expansion and tired light are not
equivalent.

http://www.astro.ucla.edu/~wright/tiredlit.htm

Bill

I agree, but the point I made was that they both attempt to explain
red-shift over long distances. Like the great majority of prominent
physicists, I do not support the tired light theory (I used the words
'whacky alternative'). I did not state that the two theories are
equivalent. The OP's question was why the frequency of an observed source
of EM radiation cannot be proportional to the distance the radiation has
travelled. I explained that it is in fact inversely proportional and
another poster suspected that the OP subscribed to the tired light idea. I
merely pointed out that whichever theory one subscribes to, the relationship
of frequency with distance is due to red-shift. If you are trying to score
a point off me, you might read what I have posted first.

No problem but you must admit your post was open to misinterpretation.

Bill

wrote in message
oups.com...
No problem but you must admit your post was open to misinterpretation.

Bill

Fair enough - there are two posts from me above - if you read them in order
I think they make sense.