When astronomers see redshift in the light from a galaxy, they know that the galaxy is moving away from Earth. What astronomers are noticing is that all the galaxies have a redshift, strongly indicating that all galaxies are moving away from each other causing the Universe to expand.

Redshift is defined as the change in the wavelength of the light divided by the wavelength that the light would have if the source was not moving — called the rest wavelength: Click here for more Space.com videos…

Red shift is a way astronomers use to tell the distance of any object that is very far away in the Universe. The red shift is one example of the Doppler effect. This is where red shift got its name, since the colors are shifted towards the red end of the spectrum.

In physics and astronomy, redshift occurs when the visible light from an object is shifted towards the red end of the 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.

Bottom line: A redshift reveals how an object in space (star/planet/galaxy) is moving compared to us. It lets astronomers measure a distance for the most distant (and therefore oldest) objects in our universe.

Astronomers have discovered that, in general, the further away a galaxy is, the more red-shifted its light is. This means that the further away the galaxies are, the faster they are moving. Red-shift data provides evidence that the Universe, including space itself, is expanding.

Galaxy Colors: The various colors in a galaxy (red bulge, blue disks) is due to the types of stars found in those galaxy regions, called its stellar population. Thus, they are bright and hot = blue. Low mass stars, although more numerous, are cool in surface temperature (= red) and much fainter.

The redshift, symbolized by z, is defined as: 1 + z = l observed / l rest. z = 0.1. Note that if the observed wavelength were less than the rest wavelength, the value of z would be negative – that would tell us that we have a blueshift, and the galaxy is approaching us.

Evidence from red-shift Astronomers have discovered that, in general, the further away a galaxy is, the more red-shifted its light is. This means that the further away the galaxies are, the faster they are moving. Red-shift data provides evidence that the Universe, including space itself, is expanding.

The redshift (or blueshift) of a galaxy is the shifting of its spectral features to longer (or shorter) wavelengths primarily due to the combination of Doppler motions and the general expansion of the Universe.

(Image credit: NASA.) Redshift and blueshift describe how light shifts toward shorter or longer wavelengths as objects in space (such as stars or galaxies) move closer or farther away from us. The concept is key to charting the universe’s expansion. Visible light is a spectrum of colors, which is clear to anyone who has looked at a rainbow.

a shift in the lines of the spectrum of an astronomical object towards a longer wavelength (the red end of an optical spectrum), relative to the wavelength of these lines in the terrestrial spectrum, usually as a result of the Doppler effect caused by the recession of the objectCompare: blueshift.

Rather, the redshift tells us the size of the universe at the time the light left the galaxy. Because the universe is billions of light-years across, it takes billions of years for light from distant galaxies to reach us. Suppose the distance to galaxy 587731512071880746 was