In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and simultaneous increase in frequency and energy, is known as a negative redshift, or blueshift. The terms derive from the colours red and blue which form the extremes of the visible light spectrum.
In astronomy and cosmology, the three main causes of electromagnetic redshift are
The radiation travels between objects which are moving apart ("relativistic" redshift, an example of the relativistic Doppler effect)
The radiation travels towards an object in a weaker gravitational potential, i.e. towards an object in less strongly curved (flatter) spacetime (gravitational redshift)
The radiation travels through expanding space (cosmological redshift). The observation that all sufficiently distant light sources show redshift corresponding to their distance from Earth is known as Hubble's law.Relativistic, gravitational, and cosmological redshifts can be understood under the umbrella of frame transformation laws. Gravitational waves, which also travel at the speed of light, are subject to the same redshift phenomena.
Examples of strong redshifting are a gamma ray perceived as an X-ray, or initially visible light perceived as radio waves. Subtler redshifts are seen in the spectroscopic observations of astronomical objects, and are used in terrestrial technologies such as Doppler radar and radar guns.
Other physical processes exist that can lead to a shift in the frequency of electromagnetic radiation, including scattering and optical effects; however, the resulting changes are distinguishable from (astronomical) redshift and are not generally referred to as such (see section on physical optics and radiative transfer).
The value of a redshift is often denoted by the letter z, corresponding to the fractional change in wavelength (positive for redshifts, negative for blueshifts), and by the wavelength ratio 1 + z (which is >1 for redshifts, <1 for blueshifts).
Hello,
The reason for the shifting of freqeuncies of all types of waves in response to relative motion away or towards the center of propagation, is caused by a corresponding stretching or compressing of the medium, correct? I mean for sound, if one moves toward the place where the sound...
This might be a stupid question, but it came to me the other day while reading. Since the speed of light is the same in all frames what would happen if you were chasing a light beam at .999% c, so you were heading right for it (but could never catch it) and it is ahead of you traveling at c. If...
A 14.4 KeV photon from 57 Fe is red shifted as it rises from a sourceat ground level to an absorber placed at the top of a tower of a height of 20 m because it has to expend energy to climb the gravitational potential. Derive an expression for thered shift as a fraction of the energy of the...
Hi! I'm new here and I have a question I hope you can help me with.
I'm curious about the conclusion that our Universe is expanding and ask if the evidence of Red Shift is reliable enough - or, could the apparent Red Shift be caused by interference from Dark Energy/Matter distorting our...
Pardon me if i am not grasping something. but!
Tell me if this very short presentation does not give a good argument that red shift occurs between two stationary light sources where gravity is at 90 degrees.
http://creativefamily.net/science/Lecture0601.pps
This lecture is from a...
Hi,
We often say, an observer near the horizon of a BH finds the light traveling from far outside the horizon blue shifted, or an observer away from the BH finds the red shift of light from near the horizon. We get a conclusion that a clock near the horizon goes faster than a clocker far...
Are there any tables for the distance against red shift of stars. I've heard that for stars close enough so you can measure the distance by triangulation it is correlated but not as strongly as the "almost perfect correlation" that I have been taught.
Why does the frequency of a photon emitted from the surface of a star decrease as it moves away from the star?
if hf`=hf(1-GM/(R*c^2)
then as the distance becomes larger, R becomes larger, so f`becomes smaller?
http://arxiv.org/PS_cache/astro-ph/pdf/0506/0506115.pdf
Title: On quasar host galaxies as tests of non-cosmological redshifts
Authors: E. Zackrisson
Comments: 9 pages, 4 figures
Journal-ref: MNRAS 359 (2005), 1193
Despite a general consensus in the astronomical community that all...
http://arxiv.org/PS_cache/astro-ph/pdf/0506/0506040.pdf
Title: Rapid growth of high redshift black holes
Authors: Marta Volonteri, Martin J. Rees
Comments: Submitted to ApJ letters. AASTeX format. 11 pages, 1 colour figure
We discuss a model for the early assembly of supermassive black...
General Relativity is assuming the existence of a metric everywhere, in someway depending directly or not on the repartition of the energy. Must I understand this assumption as equivalent to the existence of a background geometric field ?
The satellite Gravity Probe B is actually testing the...
http://www.setterfield.org/Redshift.htm
This paper may be controversial, It discuses red shift quanta, i notice
reference is given to H Arp, but i leave the reader to form an opinion.
What is the cosmological red shift? I've seen it before and couldn't figure out what exactly it was. All I know is that it has something to do with the effects of gravity and how it relates to photon frequency.
HELP red shift dilemna
is it at all possible that the apparent red shift of distant stellar light sources is not actually as a result of expansion?? For example, the whole distance is a mess of gravity wells that could cause red-shift, as well as the emitting characteristics of Hydrogen which...
"Red Shift" caused by space itself ??
Perhaps the distant objects are not receding at all.
If "space" is not empty, but rather is a complex structure,
probably containing energy which can be released (wouldn't
we just love to know how), then as light "waves" - I prefer
to call them...
Question #1; Here are a few points on this topic. The proposal is many years old. I want to comment on the 4th point
A thought experiment: Suppose 2 photons of identical energy and momentum (wavelength & momentum?) leave a distant source and utimately get individually detected by our...
http://www.setterfield.org/Redshift.htm
Further data came in supporting z quantisation, but the astronomical community could not generally accept the data because the prevailing interpretation of z was that it represented universal expansion, and it would be difficult to find a reason for...
Can someone tell me if these statements are right/wrong, and if wrong, why they are wrong?
Lets say you have a light (or more generally, EM) source a distance r from a black hole's core, with r > event horizon radius.
As you move closer towards the black hole, since the energy of a...
when light hits a object,its image is tranfered from the object it hit until it hits something else.when the light hits our eyes the last image encoded on the light or photons is whatwe see.so light from other stars travels through space until it hits us,that it why we see them because the light...