Question

PART A) What are the observational evidences of Big Bang theory? Write a precise description on cosmic microwave background radiation.

PART B) State Hubble’s law. What are the significances of Hubble’s constant? Comment on the age of our universe.

Answer 1

The earliest and most direct observational evidence of the validity of the theory are the expansion of the universe according to Hubble's law (as indicated by the redshifts of galaxies), discovery and measurement of the cosmic microwave background and the relative abundances of light elements produced by BBN.

The Cosmic Microwave Background radiation, or CMB for short, is a faint glow of light that fills the universe, falling on Earth from every direction with nearly uniform intensity. It is the residual heat of creation--the afterglow of the big bang--streaming through space these last 14 billion years like the heat from a sun-warmed rock, reradiated at night.The CMB is the oldest light we can see--the farthest back both in time and space that we can look. This light set out on its journey more than 14 billion years ago, long before the Earth or even our galaxy existed. It is a relic of the universe's infancy, a time when it was not the cold dark place it is now, but was instead a firestorm of radiation and elementary particles. The familiar objects that surround us today--stars, planets, galaxies and the like--eventually coalesced from these particles as the universe expanded and cooled.

Ans 2.

Hubble's law is a statement of a direct correlation between the distance to a galaxy and its recessional velocity as determined by the red shift. It can be stated as

The Hubble Constant (H_o) is one of the most important numbers in cosmology because it is needed to estimate the size and age of the universe. This long-sought number indicates the rate at which the universe is expanding, from the primordial "Big Bang.", the hubble constant is a unit that describes how fast the universe is expanding at different distances from a particular point in space.

The age of the universe is approximately 13.77 billion years. This age is calculated by measuring the distances and radial velocities of other galaxies, most of which are flying away from our own at speeds proportional to their distances. Using the current expansion rate of the universe, we can imagine “rewinding” the universe to the point where everything was contained in a singularity, and calculate how much time must have passed between that moment (the Big Bang) and the present.