Redshift.

[too-open-minded]

Can cosmological red-shift have any effect on the physical properties of light? I mean the "redshifted" light we see has a different frequency, wavelength, etc, so could this have any effect on individual photons?

[Janus]

Er, it's the wavelength and frequency of the individual photons that is undergoing the red-shift.

[too-open-minded]

Yes but what can this difference in wavelength and frequency do to light other than make it appear on the red end of the spectrum?

[alpha2cen]

Can cosmological red-shift have any effect on the physical properties of light? I mean the "redshifted" light we see has a different frequency, wavelength, etc, so could this have any effect on individual photons?

 

Redshift is only depend on two object's relative speed and direction.

But, some doubt remain.

Redshift exposure time gives no effect to redshift value? Does 10000yr redshift have no difference than 10yr redshift, if moving condition is the same?

[too-open-minded]

So speed and direction are what change the properties of the wave?

 

I'm guessing the redshift light and blueshift light are mostly a directional difference relatively to our own?

[alpha2cen]

So speed and direction are what change the properties of the wave?

 

I'm guessing the redshift light and blueshift light are mostly a directional difference relatively to our own?

 

Short time Doppler theory fits perfectly. But I have not found any reference about the very long time Doppler effect.

[too-open-minded]

What would time have to do with it? I mean theoretically light can travel forever if their isn't things to absorb and dissipate it, right?

[MigL]

All EM radiation emitted by stars is actually produced in the interior, close to the centre. On the way to the surface it travels through the stellar medium, abour all Hydrogen plasma, but there is also some atomic Hydrogen, which absorbs and re-emits this light at certain frequencies. These absorption frequencies show up as dark lines in the continuous spectrum of EM radiation emitted by the star. We know exactly where these lines are and at what frequencies they are found, we have even named them, Balmer series, Lyman series, etc.

If these characteristic absorption lines appear at any other frequency, then we have a blue or red shift. The shifting of the EM radiation can be easily pictured by having a simple sine wave travel between two objects as the space between them expands. The only assumptiom made is that elemental absorption lines are the same in the distant and past universe. which seems lvery likely.

[swansont]

!

Moderator Note

The plasma discussion stated by EMField has been moved http://www.scienceforums.net/topic/68611-plasma-is-the-cause-of-redshift/
Do not bring it up again in this thread

[too-open-minded]

Ok so basically redshifted waves are just spread out while blue waves are still closer together.

 

We know their farther away because the wave is "more drawn own" and appears red. Well I get that and i'm guessing the photons are still the under the same behavior?

 

On a side note, how do we know things are moving away faster the farther they are away from us? How does redshift indicate this?

[imatfaal]

.../

On a side note, how do we know things are moving away faster the farther they are away from us? How does redshift indicate this?

 

This was Hubble's discovery through observation; there was a correlation between the distance we calculated of the galaxy and the observed red-shift. The further away a galaxy the greater the redshift - everything was moving away from us and the further distant the greater the speed.

 

Redshift indicates this through a fairly simple doppler effect. Just like a siren of an ambulance is higher pitched when approaching and lower pitched when receding - light from a moving source is red-shifted if the galaxy is moving away and (rarely) blue shifted if it is closing in. There are other factors that mean the calculation is a little more complicated than the old idea of Doppler Shift - but these are well known and accounted for in the Relativistic Doppler Shift

[too-open-minded]

I understand now. Thankyou very much.

 

So is this happening in all directions? Unless I misunderstood The blueshifted galaxies are mostly in our local cluster but are kind of in a line?

[imatfaal]

I understand now. Thankyou very much.

 

So is this happening in all directions? Unless I misunderstood The blueshifted galaxies are mostly in our local cluster but are kind of in a line?

"So is this happening in all directions?" - Yep - that's what blew their minds. And yes the blue shifted galaxies are in the local group.

[too-open-minded]

Well are their any galaxies we see blueshift from that arent in our local group?

[ACG52]

No.

[too-open-minded]

Okay well this thread has really helped me get this concept down.

 

Also is really helping me shape this hypothesis I previously had, I thought blueshifted galaxies were more than just in our local group. this actually helps my idea.

 

Thankyou, I might have a few more questions to ask in the next few days.

[IM Egdall]

This was Hubble's discovery through observation; there was a correlation between the distance we calculated of the galaxy and the observed red-shift. The further away a galaxy the greater the redshift - everything was moving away from us and the further distant the greater the speed.

 

 

Georges Lemaitre discovered the galaxy distance-redshift relationship several years before Hubble. Using Einstein's field eqautions of general relativity, Lemaitre predicted the expansion of space. He said the frequency of light from distant galaxies is stretched by the expansion of space as it makes its way to us on Earth.

 

The further away the galaxy, the more time its light takes to reach Earth. Thus the more space has expanded during this time. So the greater the distance to the galaxy, the greater the expansion and the greater its light's redshift. See link:

 

http://decodedscience.com/georges-lemaitre-discovered-the-expansion-of-the-universe/5588

[imatfaal]

Mark - I didn't realize, like many others seemingly, that Lemaitre had precedence in this area. Thanks

[too-open-minded]

So the galaxies moving towards us, why do we think they are blueshifted? Is the gravity strong enough to overpower dark-energy?

[ACG52]

We see the blueshift in the spectrum of the galaxy. Gravity is easily strong enough to overpower dark energy until we reach distances of over 200 million light years between galaxies.

[pantheory]

So the galaxies moving towards us, why do we think they are blueshifted? Is the gravity strong enough to overpower dark-energy?

There are between a 100 to maybe over 7,000 blue shifted galaxies depending upon the interpretation of galactic spectra/ redshifts. If there are 7,000 + they are mostly all just barely blueshifted. The greatest blueshifts are some of the closest galaxies in the local group. All the other possible blueshifted galaxies are part of the local super-cluster Virgo. Galaxies in these galaxy groups and super-clusters orbit their center of gravity therefore some can be moving in our direction and have blueshifted spectra. The farthest possibly slightly blueshifted galaxies in our super-cluster are no more than 70 million light years distant. The expansion of the universe and dark energy cannot be observed in the local group and it is debatable whether it can be observed in the local super-cluster. The consensus opinion is that gravity compensates for expanding space and dark energy (if it exists) in galaxy clusters.

 

Another type of galaxy blueshift is when a galaxy has a relative motion toward us but the supposed expansion of space is thought to be greater than the motion of the galaxy toward us. Although these galaxies display an overall redshift the spectra has also been blueshifted because of relative motion in our direction. Some of this may be due to the relative motion of the solar system around our galaxy, our galaxy orbiting within the local group, our local group orbiting within the local super-cluster, as well as our local super-clusters relative motion supposedly within the "dark flow" toward the "great attractor." The galaxies we are observing also have similar types of multi-orbital motions.

 

http://fittedplane.blogspot.com/

 

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Edited September 5, 2012 by pantheory

[JohnStu]

Topic: redshift

 

 

 

Two influencers in redshift: doppler effect and expansion of space-time

 

One result: redshifted or blueshifted

[too-open-minded]

Nobody has really answered my question yet lol

[pantheory]

Nobody has really answered my question yet lol

Yes, when light is redshifted it loses energy. Longer redshifted wavelengths are of lower frequency and energy and so the associated photons have proportionally less energy.

//

Edited September 14, 2012 by pantheory

[too-open-minded]

Thankyou man.

 

So being that they have less energy, are the photons more spread out?