Can any one tell me what "Red Shift" is?

Question

Can any one explain me what "Red Shift" is in Astronomy?

Answer 1

In physics and astronomy, redshift occurs when the electromagnetic radiation, usually visible light, that is emitted from or reflected off an object is shifted toward the (less energetic) red end of the electromagnetic spectrum. More generally, redshift is defined as an increase in the wavelength of electromagnetic radiation received by a detector compared with the wavelength emitted by the source. This increase in wavelength corresponds to a decrease in the frequency of the electromagnetic radiation. Conversely, a decrease in wavelength is called blue shift.

Any increase in wavelength is called "redshift", even if it occurs in electromagnetic radiation of non-optical wavelengths, such as gamma rays, x-rays and ultraviolet. This nomenclature might be confusing since, at wavelengths longer than red (e.g., infrared, microwaves, and radio waves), redshifts shift the radiation away from the red wavelengths.

An observed redshift due to the Doppler effect occurs whenever a light source moves away from the observer, corresponding to the Doppler shift that changes the perceived frequency of sound waves. Although observing such redshifts, or complementary blue shifts, has several terrestrial applications (e.g., Doppler radar and radar guns),[1] spectroscopic astrophysics uses Doppler redshifts to determine the movement of distant astronomical objects.[2] This phenomenon was first predicted and observed in the 19th century as scientists began to consider the dynamical implications of the wave-nature of light.

Answer 2

The Radiation spectrum list a wide range of radiation flux frequencies.
The Visible range that we see as a rain bow in the prism dispersion of light show colors as having different frequencies. Red is the lower frequency indicating minimum radiation power. Violet being the higher frequency indicates the maximum radiation power , in the visible range.

Thery are two ways of observing how fast an object is moving if its emiting a light signal.
One is called the Doppler effect and the other is called Wave dispersion effect. Both effects indicate changes of frequencies of light radiating from moving object such as stars.
If Star is moving away from the observer (in this case on Earth) a shift in frequency toward the red results. If the Star is moving towards the earth a shift in frequency toward the red results.This is what is called the red shift.

Therefore atronomers are able to determine whether a celstial body is moving towards or away from the Earth by observing the color spectum of light radiating from the star.. And by applying the doppler effect formuta the Veloctiy of the Star is calculated.

Answer 3

It has to do with the Doppler effect: Objects that are moving away from us appear to have their light "shifted" towards the red end of the spectrum. Using this one can calculate the speed of that object. If the object is moving toward us than there is a blue shift.

Answer 4

When a light emitting object (star) speeds away from earth its light waves are stretched due to the Doppler effect and seem more red (longer) than they are. The same effect causes the whistle of a steam locomotive to increase frequency while approaching and reduce frequency after it has gone by.

Answer 5

If a boxer is moving backwards his punches have less energy than if you get punched as he moves towards you. Red light has less punch than violet light and we get a shift towards redder stars if they are moving away from us. This is red shift.

E.g. For the sake of argument assume we live near the center of our galaxy. If we were looking at stars in the milky way further on the outside than us we would see some spinning towards us looking more purple and others moving away looking redder.
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Light from a distant star moving away from you has less energy than a closer star that seems to be standing fairly still. Red light has the weakest energy in the visual spectrum thus stars that appear to move away from us seem redder because the punch of the light is weaker.

The colors of light are like pitches of sound or waves on the sea.

If you move towards waves on the beach they might seem to be rushing towards you, and will hit you harder. Likewise if you run from them they are slower in catching you, and hit you softer. waves that hit you faster or more frequently have more energy. Sound waves that rush towards you sound higher in pitch and ones that move away sound lower in pitch.

Presumably some dude named Dopler noticed this when a train rushed past him.

The expansion of the universe is like an ant sitting on a balloon covered in nickel coins. No matter where the ant is on the outside of the balloon the coins will seem to be moving away as the balloon expands.

I think it also turns out that the further away the coins are the faster outwards they seem to be moving.

If we replace the coins with stars, the light from more distant stars will ( or appear to) be moving away from us faster. Thus the farer away a light source is the less energy it will appear to have from our perspective. When light is separated into more energetic and less energetic colors we get a rainbow effect with red violet (or purple) colors having more energy and red colors having less energy.

To further complicate stuff light from distant stars has taken longer to reach us thus if we look at a star 1000 light years from us we see what the star looked like 1000 years ago.

If we assume the universe is expanding at an accelerated rate more distant stars will appear younger and be moving away from us faster. The faster they are moving away the redder they will appear. Thus distant stars will appear younger and redder until we look into distant pace longer in light years than the universe is old. If we look deep enough into space we might see the birth of the universe.

I am not sure if I got all this stuff right but light that moves away has less energy and looks redder. This is red shift.