The Concept of Red-Shift

• Red-shift is an important concept in astronomy, referring to the increase in wavelength, and subsequent decrease in frequency, of light from distant objects as perceived from an observer's point of view.
• This phenomenon is a direct application of the Doppler effect, which states that the observed frequency of a wave depends on the relative motion of the source and the observer.
• When an object moves away from the observer, the light waves from the object get stretched, which means they move towards the red end of the spectrum, hence the name 'Red-shift'.

Interpreting the Red-Shift

• High-redshift objects in the universe are typically further away. The greater the red-shift, the faster the object is moving away from us. This measurement gives astronomers a way to gauge the speed and direction of distant galaxies.
• Study of red-shift patterns provide strong evidence for the expansion of the universe, known as Hubble's Law. The law states that the recessional velocity of a galaxy increases with its distance from us, meaning the further away a galaxy is, the faster it is moving away from us.
• By observing how much the light from an object is red-shifted, astronomers can also estimate the distance of far-flung objects such as galaxies and quasars.

Red-Shift in the Context of the Big Bang Theory

• The observation of red-shifts in light from distant galaxies is significant evidence in support of the Big Bang theory, which proposes that the universe began from a very high density and high temperature state and has been expanding ever since.
• The cosmic microwave background radiation - the afterglow of the Big Bang detected in all directions of the universe - also exhibits a red-shift, which corresponds to very high temperatures, as expected from the theory.
• However, the causes and implications of red-shift along with the age and size of the Universe are continually being researched, as our understanding of the universe continues to refine.

Dangers of Misinterpreting Red-Shift

• Astronomers must be careful not to mistake red-shift for other forms of light stretching, such as gravitational red-shift, which occurs when light has to 'fight against' gravity to escape an object.
• An object's motion within a galaxy can also lead to red-shift or blue-shift. This intrinsic shift, as it is known, must be accounted for before the cosmic red-shift can be correctly determined.
• Red-shift measurements can contain errors, such as those arising from equipment limitations or incorrect assumptions. Validation of red-shift interpretations therefore generally requires other supportive astronomical observations.