Penguin Book: book research

Some of the theories presented in A Brief History of Time: 

• planets/stars - orbits, patterns, 
• time - time moving forward, Einstein and relativity
• light - red/blue shift, lightwaves, colour
• black holes - look at the way things get sucked in, shape, distortion
• Big Bang and expansion of the universe

Black Holes
https://www.theguardian.com/news/video/2013/sep/19/stephen-hawking-history-time-simple-video
If you were able to travel to the centre of a black hole you would find a singularity, where a lot of mass is condensed into a small space, which makes the force of gravity infinite. Nothing can escape it, even light is pulled in.
Particles pop in and out of existence, and can be found in pairs. When this happens on the edge of a black hole, one of the particles is pulled in, but one escapes. These particles are known as Hawking radiation. 


The Big Bang 
The Big Bang is responsible for the creation of our universe, with everything in it once being a singularity. The particles mentioned earlier that have fallen in have a negative mass, which means the black hole gets smaller and smaller, eventually exploding with the force of a million nuclear bombs. 
George Lemaitre first noted in 1927 that the idea of an expanding universe could be traced back to a single point. The idea of cosmic expansion has been built upon by other scientists, notably by Edward Hubble who concluded that galaxies are drifting apart by observation of redshift. Proving that galaxies are moving apart from eachother proves the that before cosmological expansion, the universe was denser and hotter.


Red and Blue Shift
Redshift happens when the light from an object is increased in wavelength, or shifted to the red end of the spectrum. A redshift occurs whenever a light source moves away from an observer, a significant instance of this is in cosmological expansion, where the universe is expanding and so objects are moving away from the observer. They have a redshift.
The opposite is true for blueshift, where the light from an object decreases in wavelength, or shows that the object is moving towards the observer.