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Nuradnan
2005-Apr-09, 07:39 PM
Light will be redshifted if the source is moving away from the observer. Otherwise, light will be blueshifted. Physically, what cause the wavelength stretch? Some books explain it by pulse analogy. Well, actually, what is, physically, the relation between pulse and wave? How could pulse can be used to explain a wave phenomenon?

My friend tried to explain redshift phenomenon by photon term. While moving, photon will lost its energy. Less energy means less frequency. But then, we realized that wave phenomenon can't be explained by particle phenomenon.

So, in short, how, physically, does moving source affect wavelength?



Thanks before,

Adnan

Littlemews
2005-Apr-10, 02:08 AM
what cause the wavelength stretch?
I.e. your cellphone signal : if you are taking Bart, can you see an signal bar on the screen? If someone ask you to describe what is the signal line would look like, how would you draw that line? Perhaps, just a straight line right? In order word, when "distance" and "energy" together on the stage, you can see many out of many shapes of wavelength on your detector.

and your rest of the questions, you can visit this site below and I hope you can find your answer there :
Click here (http://www.spectrogon.com/gratappl.html) :)

Garvs
2005-Apr-10, 07:05 AM
With regards to redhsift and the expansion of the universe, you have to remember that it's space itself that is expanding, and the objects within that space are moving along for the ride. Think about it this way. Cut a wide rubber band so it's now a strip. Draw a wave on it. Now grab both ends and stretch the band and lo and behold, the wave stretches with it. Think of the expanding band as expanding space, and the objects within it are naturally moving apart as a result. This is the sort of redshift used on the cosmological scale to determine the distances to galaxies on the edge of the observable universe, and I think is used (mathematically) in conjunction with to Hubbles Constant.

Doppler related shift in the traditional sense, as you get with sound waves, or the light from two binary stars in orbit is a bit different. If a stationary object is emitting "waves", you will receive the waves at even intervals. If the object is moving away from you, each time the object emits a wave, the object is further away from you, so you receive each successive wave later and later.

Hope this makes sense.

Cheers,
Andrew.

filrabat
2005-Apr-10, 08:28 PM
Garves is correct on "universal" scales, particularly with regard to receding galaxies. Space is expanding, and therefore wavelengths are expanding. The longer the wavelengths, the redder they are.

To bring in other perspective though, I'd like to talk about "blueshifting". This is what happens when bodies move toward you. The faster them move toward you, the bluer the light gets. The reason this is so is that (from our perspective), the speed of light is fixed. Since the speed of light is fixed, it follows that the wavelengths moving toward you will get shorter. Correspondingly, the wavelengths of light from an object moving away from you will get longer.

It's best to think of this as sound (it also is subject to the Doppler Effect because the speed of sound is fixed within the substance through which it travels (sound travels faster in water than in air, and even faster through steel than through either of these0.

Whenever a train moves toward you, the whistle has a higher pitch (the equivalent of a blueshift). When it passes you by and starts moving away from you, the whistle drops to a lower pitch (the equivalent of a redshift).

So while the expansion of the universe does lengthen the wavelength of light, that by itself does not completely explain redshifts. After all, I understand the Andromeda galaxy is actually blueshifted (moving toward us) rather than redshifted (moving away from us). The expansion of space between us and that galaxy is not enough to overcome our mutual galaxies gravitational attraction.

Svemir
2005-Apr-11, 06:04 AM
Well, I think Nuradnan is aware of all these explanations.
What he wanted is physicall explanation of frequency shift phenomenon.
It might be that some physicist can explain it in the terms of physics, what I'v been taught is geometrical representation of the waves and the frequency shift.
The wave is usually represented by some sinusoidal function i.e.
y=Acos(x+t)
where A is amplitude and t is phase. The interesting term in this equation is A (amplitude) which represents the energy of the wave.
In Doppler effect, when you strech the wave (i.e. sound wave) the amplitude get smaller (geometrical representation), the wave loses it's energy (to medium, to the air, this could be physical explanation).
In the current picture of Universe, space-time, the medium which through light waves propagate, has no physical characteristics.
Light wave can't lose energy to the space-time, and yet you have redshift overall.
Bing Bang theory, uses Einstein's General Relativity Theory and it's represantation of the space-time as pure geometry. In BBT space-time can be streched/curved (by gravity, cosmological constant or simply have instrinct curvature), so the cosmological redshift is explained, as others on this topic mentioned, by expanding universe.
Now, when light wave is redshifted, the distance between the pitches is lengthened,
the amplitude is lowered, how do you explain the energy loss since you have no medium you can transfer the energy to (and you don't believe in "tired light" model)?
Yet, you must not destroy the energy since that is fundamental law.
There are 2 answers to this:
1.The unit of space-time is streched in that manner that light wave's energy per unit of space-time is not the subject to the change. The energy is preserved.
2. Conservation of energy does not apply to Universe.

Nuradnan
2005-Apr-16, 08:51 AM
Thanks for you all. :D

By the way, would you like to give me some information about experts working on this subject?

Now, I'm working on a paper about Doppler redshift and cosmological redshift. I'm curious in how we can distinguish between Doppler redshift and cosmological redshift. Well, how could we distinguish them, merely from spectral data?

Nereid
2005-Apr-16, 02:34 PM
By the way, would you like to give me some information about experts working on this subject?

Now, I'm working on a paper about Doppler redshift and cosmological redshift. I'm curious in how we can distinguish between Doppler redshift and cosmological redshift. Well, how could we distinguish them, merely from spectral data?
This (http://www.physicsforums.com/forumdisplay.php?f=71) might be a good place for you to start.

imported_Thomas
2005-Apr-19, 05:49 PM
Originally posted by Nuradnan@Apr 9 2005, 07:39 PM
Light will be redshifted if the source is moving away from the observer. Otherwise, light will be blueshifted. Physically, what cause the wavelength stretch? Some books explain it by pulse analogy. Well, actually, what is, physically, the relation between pulse and wave? How could pulse can be used to explain a wave phenomenon?

My friend tried to explain redshift phenomenon by photon term. While moving, photon will lost its energy. Less energy means less frequency. But then, we realized that wave phenomenon can't be explained by particle phenomenon.

So, in short, how, physically, does moving source affect wavelength?



Thanks before,

Adnan
The reason for the Doppler red/blue shift is the circumstance that the distance to the light source increases/decreases between two points of equal phase of the light wave. I have explained this in terms of a pulsed signal on my webpage http://www.physicsmyths.org.uk/discussions...relativity1.htm (http://www.physicsmyths.org.uk/discussions/relativity1.htm) (see discussion with M.B. towards the bottom). The pulses just signify points of equal phase (e.g. maxima) of the wave.

Regarding the 'cosmological' redshift, you may also be interested in my page http://www.physicsmyths.org.uk/redshift.htm .

Plautus
2005-Apr-20, 12:22 AM
Originally posted by Nuradnan@Apr 9 2005, 07:39 PM
Light will be redshifted if the source is moving away from the observer. Otherwise, light will be blueshifted.
[...]
So, in short, how, physically, does moving source affect wavelength?
Thanks before,
Adnan

Actually this idea has been falsified by observation. Also falsified is the notion that the velocity of light is affected in any way by the motion of the emitter. This so-called "redshift" has been proven to be an intrinsic property of objects themselves, and not a result of velocity or distance, therefore this "redshift" can not be used to calculate either velocity, or distance, and it can not be used to support big bang myths.

Plautus
2005-Apr-20, 12:31 AM
Originally posted by Garvs@Apr 10 2005, 07:05 AM
With regards to redhsift and the expansion of the universe, you have to remember that it's space itself that is expanding, and the objects within that space are moving along for the ride.
[...]
Hope this makes sense.
Cheers,
Andrew.

The universe is not expanding. This is another fictional prop holding up big bang myths. The primary reason for this "redshift", which, by the way, is quantitized (not at all what we should expect from big bang predictions), is spontaneous amplification of light. For those unfamiliar, amplification of light is generally known as "lasing". In other words the increased "redshift" is caused by a natural and spontaneous amplification of light, a well-known effect of high-energy plasmas.

The universe is NOT a rubber band.

Plautus
2005-Apr-20, 12:41 AM
Originally posted by filrabat@Apr 10 2005, 08:28 PM
Garves is correct on "universal" scales, particularly with regard to receding galaxies. Space is expanding, and therefore wavelengths are expanding. The longer the wavelengths, the redder they are.
[...]

This idea and other tenents of big bang myths have been falsified by observations. Halton Arp and others have shown many objects in space with drastically different "redshifts" are in physical contact with one another, falsifying the notion that "redshift" equals velocity equals distance equals age, falsifying big bang itself. There have even been observed "blushifted" objects IN FRONT OF highly "redshifted" objects.

The obvious implication is that "redshift" and "blueshift" are not shifts away from an ASSUMED IDEAL, but are merely properties of certain classes of objects, typically defined by the electric current density at their surface. Cosmological "redshift" is bunk, big bang is falsified, time and space are hypothetical coordinate systems that can not be bent or folded or warped or manipulated in any physical way.

Toc
2005-Apr-20, 01:31 AM
Think of the frequency of the light as a clock. When the source of the light is moving away from you, between one tick of the clock and the next it has moved slightly away from you so the time distance between successive ticks is lengthened (for you the observer). So the frequency of the light is diminished, ie the wavelenght is lengthened and the light is redshifted. This by the way is not a relativistic effect. When the light source is moving towards you the ticks are compressed because when the next tick comes it is slightly closer to you. So the frequency is increased and the light is blue shifted.
There is relativistic effects as well, but they are not doppler shift. There is also redshifting due to gravity, but that is also not doppler shift.
As for Andromeda, our galaxy and Andromeda are heading toward each other, (hence there is a doppler blue shift), and will merge in about 2 billion years. We are far too close for the expansion of the universe to have any significant effect on the distance between us.
Cheers,
Toc

Garvs
2005-Apr-20, 02:19 AM
falsified is the notion that the velocity of light is affected in any way by the motion of the emitter.

No one has said that it is, so what's your point? We've known since Einstiens Special Theory of Relativity that the velocity of light is constant.


This so-called "redshift" has been proven to be an intrinsic property of objects themselves.

You've certainly pegged my curiosity. Please provide a reference to accepted research results proving this.


The universe is not expanding.

Once again, I'd be happy to read the results of any accepted research proving this.


"redshift", which, by the way, is quantitized

Quantisized redshift? Please explain.


For those unfamiliar, amplification of light is generally known as "lasing". In other words the increased "redshift" is caused by a natural and spontaneous amplification of light, a well-known effect of high-energy plasmas.


Amplification of electromagnetic radiation increases it's amplitude, not it's wavelength, or the shift of emmisions lines in a spectra. What on earth does this have to do do with redshift?


...big bang is falsified, time and space are hypothetical coordinate systems that can not be bent or folded or warped or manipulated in any physical way.

What?

mas_to
2005-Apr-20, 04:24 AM
garvs, I believe Plautus is one of Electric Universe Model fans club member, if you want to understand what he's saying you must read tread about EU in Alternative theory.
also some link about EU model but I forgot those link but I think there is some in that tread above
Be prepared to reconstruct your understanding of Universe, it totally different from what yours now. but anton and others trusted source could give you the right oppinion base on current accepted theory

Garvs
2005-Apr-20, 05:18 AM
mas_to, I think you've hit the nail on the head with the term "current accepted theory". I've just been doing a bit of research into quantized redshift, and while there is observational evidence pointing to redshift occuring in multiples of certain quantities, it is a very contentious issue that is not at all accepted but by a few. One of the biggies seems to be that it implies a prefered frame of reference (ie, our frame of reference) which contradicts special relativity. It does pose a conundrum though and I'm certainly going to look into it further.

I'm all for alternative theories, it's how we learn and continually refine our understanding ... but until it becomes accepted physics, making blanket statements like "the universe is not expanding" is just plain stupid. While quantized redshift does contradict expansion, there appears to more observed issues that contradict quantized redshift, relativity being one.

mas_to
2005-Apr-20, 09:06 AM
well, I ask for forgiveness if my previous post caused my nail to hit on their head. I mean no harm. maybe my gramar is a bit rude, I learn english from movie etc. that almost all had rude gramar

in my oppinion a theory always dynamic it won't be accepted entirely if it hasn't proofed entirely by fact
for your information, I'm no scientist with no scientific background thou so all scientific word from me had no scientific meaning

Edwin
2005-Apr-20, 09:16 AM
I would like to throw Gravity into the discussion.

We know from gravitational lensing that gravity has an effect upon light. If it can 'bend' light then surely if it is present at the point of origin then it will have an effect upon any light emitted from it.

If the speed of light in a vacuum is constant then gravity would have to effect some other part of the equation ie wavelength. I belive that if the gravity of the emitting object is increased then the wavelength of light escaping from it will also increase.

An example of this would be quasars which we can see are linked to galaxies having a much longer wavelength than their 'parent' galaxy and therefore appearing to be much further away.

Guest_mike
2005-Apr-21, 07:15 PM
hi

just an idea to throw into the discussion on the 'expanding universe'

there's no evidence that the universe is finite and therefore no evidence that it's expanding

I'll accept that the visible (and probably the less visible as well) population is moving apart at the grand end of the scale of objects but it's doing so within 'the universe' - one cannot guess at the size of the universe, it's infinite - if you want to guess at something, then try and get yr mind round how much space there is between the leading edge of the expanding population and the infinite space beyond that

there's no reason to think that there's something at the edge of infinity that's making it expand

comments??

Nereid
2005-Apr-21, 07:48 PM
Is there a question here Guest_mike?

Perhaps you are asking "If the universe were infinite, in what sense could it be said to be expanding?" If so, then may I recommend a good cosmology website (such as Ned Wright's), and (if you're sufficiently interested) taking a course in General Relativity? There are many, many things which seem counter-intuitive if you stick to plain (English) words; when you understand the math and theory more deeply, it becomes easier to see how intuition can mislead you.

Or, you may be confused about 'expanding', and your question may be "If the universe is expanding, where is its 'edge'?". If so, then {see above}.

Guest
2005-Apr-24, 12:58 AM
Originally posted by Toc@Apr 20 2005, 01:31 AM
Think of the frequency of the light as a clock. When the source of the light is moving away from you, between one tick of the clock and the next it has moved slightly away from you so the time distance between successive ticks is lengthened (for you the observer). ... ...
Yup, thanks for the explanation.

But I'm still confused. You explained redshift by pulse analogy. By the way, pulse means alternating condition between, let say, "on" and "off". With this pulse analogy, redshift (and blueshift of course :rolleyes: ) can be explained. Meanwhile, wave is coming contonuously, with range from maximum to minimum, not alternating between "on" and "off".

So the question is, how is (again, physically) the relation between wave and pulse (to explain redshift)? :blink:

Well, to much asking, right? Sorry. And thank you so much for your patient and for the "illumination", all of you. :D

Nuradnan
2005-Apr-24, 01:04 AM
Argh, sorry. The last post, with heart post-icon, is from me, Nuradnan. I forgot to log in. Sorry for the inconvenience ...

Nereid
2005-Apr-27, 10:56 PM
Originally posted by Ed J@Apr 20 2005, 09:16 AM
I would like to throw Gravity into the discussion.

We know from gravitational lensing that gravity has an effect upon light. If it can 'bend' light then surely if it is present at the point of origin then it will have an effect upon any light emitted from it.

If the speed of light in a vacuum is constant then gravity would have to effect some other part of the equation ie wavelength. I belive that if the gravity of the emitting object is increased then the wavelength of light escaping from it will also increase.

An example of this would be quasars which we can see are linked to galaxies having a much longer wavelength than their 'parent' galaxy and therefore appearing to be much further away.
You're talking about the gravitational redshift, I think.

This was predicted in GR, and observed here on Earth in a rather ingenious experiment done over a vertical distance of ~20m (here (http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/gratim.html#c2) is a brief description); it's since been observed in the (optical) spectra of certain white dwarfs, and the line profiles of certain Fe X-ray emission from SMBH (such as at the heart of an active galaxy).

While it could, in principle, account for the redshifts observed in quasars, there is no physical model of how such redshifts could arise (esp when you add in all the other observational data on quasars).

(BTW, observations of quasars being 'linked to' a parent galaxy should be examined carefully - the sky is essentially flat to astronomers, so the problem of disentangling objects that are merely 'close' because they have very similar lines of sight is an acute one)

molly's kid
2008-Apr-19, 09:32 PM
I posted this under another heading on this site but it seem to fit in here... comments?

Over looked is the density of light in the inter galactic space. When the theories of light we are now believing our understanding of light was more limited than it is now.

Our theorests did not know that light bent with the density of gravity, demonstrated by the occlusion of stars.

This is "The Molly principal of light"

Since light is effected with gravity then we may surmise that light will also effect light, Not much but some... Over the millions of years and more of travel the only thing we know is between the stars is light. Light is energy, and or particles traveling fast and thru proximity the light absorbs some of the energy from light coming the other direction. This loss of energy is noticed as a red shift in spectral signature of the light (in both directions)... thou we can only measure one.

From some article on stellar occlusion I remember some formula that if gravity effects mass at 1, gravity effects light at the power of negative26. I contend that light may effect light at the power of negative676.. Thats a small number, but remember that the light has been traveling a long time and the light is in very close contact with the light from the other direction.

Molly was my Great grandmother, she was a small woman but if she wanted to move the mountain she started pushing, The mountain moved!

Doug