Redshifts




EM radiation, such as light, is traveling through space. It loses a part of its energy due to various reasons before striking earth, hence its frequency decreases. Frequency decrease implies an increase in wavelength. 


Red has the highest wavelength of any colour, which means the given light is shifting its wavelength towards the red end of the spectrum--- Redshift.


This energy loss could happen due to a number of reasons.

1. Doppler Effect: Relativistic Redshift; The light is travelling between objects that are in relative motion, the wave crests (peaks) are either compressed or in this case, spread out, and redshift occurs.

2. Gravitational Potential: Gravitational Redshift; Space is a fabric. Imagine two depressions in it, one quite deep and one shallow. Light travelling from the deep one to the flat one loses energy to overcome gravity and redshift occurs.

3. Hubble–LemaĆ®tre Law: Cosmological Redshift; The universe is expanding. As the light travels from far away objects, space expands and the wave crests spread out, leading to redshift. For some distant galaxies, it even shifts to the infrared spectrum. 

Redshift has applications in finding cosmic distances, measuring energies, measuring the expansion of the universe, giving evidence for the big bang theory and forming the basics of all astronomy.

That's it, enjoy.

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