Gravity and Special Relativity
Einstein's Special Relativity Theory and the related effect on Newton's explanation of gravity led in 1922 to a theoretical study of the cosmological implications by Alexandr Friedmann [2, 704]. Friedmann's study modeled the density of the universe as a uniform distribution of galaxies on a large scale based on a 'pressureless fluid' or dust. [2, 717].
Numerous experiments have collected values for gravity and for the speed of light required for the model. Once a model was proposed, collected data was tested its accuracy.
Isomorphic and Homogenous
Several projects documented that the universe was isomorphic and homogenous including the data collected by the Cosmic Background Explorer (COBE) of background radiation[1, 456-459], WMAP, and BOOMERANG at 2.73K.
Age of the Universe
When astronomers take pictures of the universe at different times, they are able to calculate the likely distance/age of the objects including:
* 300,000 years after the Big Bang the Universe became transparent [1, 420-422].
* WMAP provided the timing of epoch when the first stars began to shine; about 400 million years after the Big Bang .
* NASA's Spitzer and Hubble Space Telescopes spotted a universe about 650 million years after the Big Bang known as Abell2744 Y1
* Observations by WMAP of distant quasars explain that the first stars 30-300 times larger than our sun exploded as supernovae when the Universe was almost a billion years old.
Other dates use artifacts found on Earth and via a number of sampling missions within the solar system including:
* Earth’s age is dated by a meteorite as 4.53-4.58 billion years old
* Moon’s age is dated by Moon rocks tungsten decay to hafnium at 4.527 billion years old
* Chondrites are made up of varying types of elements that establish likely regions i.e. interplanetary, interstellar with the implication of likely distance.
These dates are used to help validate the model is consistent according to age.
The studies of proton decay and element ignition using particle accelerators provided the model for nucleosynthesis which explains how the different elements are produced by the stars[8, 45]. An estimate of hydrogen atoms versus helium atoms calculated from diffraction studies show a 10 hydrogen:1 helium as predicted by the Big Bang theory. [1, 367-369].
Tests of the Big Bang Model using photographs of the universe, calculations for distance/time, predicted effects like gravity lenses, continue with new telescopes like the NASA James Webb Space Telescope.
 Brian May, Patrick Moore, Chris Lintott, "Bang! The Complete History of the Universe", Carlton Books, 2009, [Note: all references refer to Kindle Locations instead of pages]
 Roger Penrose, "The Road to Reality: A Complete Guide to the Laws of the Universe", Vintage Books, 2004
 Armand Delsemme , "Our Cosmic Origins: From the Big Bang to the Emergence of Life and Intelligence", Cambridge University Press, 1998