Cosmology

Cosmology is the branch of astronomy that deals with the universe. 

NASA defines cosmology as "The study of the structure and changes in the present universe". Another definition of cosmology is "the study of the universe, and humanity's place in it".

Modern cosmology is dominated by the Big Bang theory, which brings together observational astronomy and particle physics.

Though the word cosmology is recent (first used in 1730 in Christian Wolff's Cosmologia Generalis), the study of the universe has a long history.

History
Until the Renaissance people thought the universe was only the planets up to Saturn, and stars. With the invention of the telescope, we could see more of the universe. Early in the 20th century, astronomers thought the Milky Way was the entire universe. Later, with astrophotography and spectroscopy, astronomers (for example Edwin Hubble) showed that the Milky Way was only one of many galaxies. 

Modern cosmology is considered to have started in 1917 with the final paper of Albert Einstein's theory of general relativity. This made physicists realize that the universe changed. When a scientific discipline begins to change an idea that is believed by many people, it is known as a paradigm shift. Many scientists debated if there were other galaxies. The debate ended when Edwin Hubble found Cepheid Variables in the Andromeda Galaxy in 1926.

The Big Bang model was then proposed by Belgian priest, Georges Lemaître in 1927. This was supported by Edwin Hubble's discovery of the redshift in 1929. Later the discovery of cosmic microwave background radiation was made. This was found by Arno Penzias and Robert Woodrow Wilson in 1964. 

All of these discoveries have been supported in the 21st century. Some more observations of the cosmic microwave background radiation were found by the COBE, WMAP, and Planck satellites. Some more observations of the redshift were found by the 2dfGRS and SDSS. An astronomical survey looks at a place in space. A redshift survey is a survey that looks for redshifts.

On 1 December 2014, at the Planck 2014 meeting in Ferrara, Italy, astronomers reported that the universe is 13.8 billion years old and is composed of 4.9% regular matter, 26.6% dark matter and 68.5% dark energy.

According to Dr Robert Massey, deputy director of the Royal Astronomical Society, the evidence for a rethink of what has been a central plank of astronomy is growing.

"This is the seventh large structure discovered in the universe that contradicts the idea that the cosmos is smooth on the largest scales. If these structures are real, then it's definitely food for thought for cosmologists and the accepted thinking on how the universe has evolved over time," he said.

 Key terms 
 Mass 
 Gravity 
 Electromagnetic radiation 
 Dark matter 
 Dark energy 
 Speed of light 
 Age of the Universe 

 Related pages 
String theory
Earth science
Inflation

 References 

Category:Astrophysics