The document discusses the origins of the universe according to the Big Bang theory. It describes how Einstein identified the equivalence of energy and mass, while Friedmann predicted expanding universe models of closed and open forms. Hubble then observed redshift in nebulae and used this to propose an expanding universe model, developing the Hubble constant to estimate expansion rates. This evidence supports the Big Bang theory of an exploding, expanding universe originating from a hot dense point.
3. Syllabus references Outline the discovery of the expansion of the Universe by Hubble, following its earlier prediction by Friedmann Identify that Einstein described the equivalence of energy and mass Identify data sources and gather secondary information to describe the probable origins of the Universe
5. The Big Bang theory The expanding universe Cosmic background radiation
6. The expanding universe Scientists who have contributed to the expanding universe Albert Einstein AleksandrFriedmann Edwin Hubble
7. Albert Einstein Special theory of relativity The speed of light Equivalence of energy & mass Energy can be converted into mass Mass can be converted into energy E = mc2
8. Evidence for Einstein’s theory Predicted that light rays can be warped by space-time and should curl around stars (gravitational lensing) Gravitational lensing of distant quasars has been studied by astronomers using the Hubble telescope Predicts that time should run slower near an object as large as a planet Tested and verified in 1962 Predicted that the universe is expanding but Einstein believed in static universe so he put a cosmological constant in the equation to make the universe static
9. AleksandrFriedmann Read Einstein’s work but thought his cosmological constant was wrong, so he tried to solve Einstein’s equations Assumed that the universe is the same no matter where we look Friedmann’s maths proposed two models: (1) closed universe and (2) open universe
10. Closed universe Time and space have a beginning and an end Time and space both began with a big bang and will end when gravity stops the universe and pulls everything back into one point – “ the big squeeze” The universe is finite and the expanding universe is due to space expanding
11. Open universe Universe began with a big bang and will continue to expand forever Time and space has no end
12. How do we know the universe is expanding? In 1912, VestoSlipher examined the spectrum of light produced from a nebulae Found that the light from the nebulae had frequencies lower than normal light The light from the nebulae was more shifted towards the red end of the spectrum – red shift
13. What is redshift? Remember: light travels at the same speed regardless of how fast you are travelling Light is made up of different colours; red has the lowest frequency and blue/purple has the highest frequency Redshift is when light moves towards the red end of the visible light spectrum
16. Redshift in the universe The left spectrum is the transmitted frequency of light from a star The right spectrum is the observed frequency of the star from Earth The spectral lines are shifted towards the red end Shows star is moving away from us
17. Edwin Hubble Hubble used the redshift idea to propose his expanding universe model where the universe is like an exploding bomb He also came up with the Hubble constant (Ho) Rate at which universe is expanding Used to estimate the size of the universe
18. Summary The big bang theory proposes that the universe exploded out of a hot dense point. The big bang theory is supported by the expanding universe model which various scientists have contributed to Einstein – equivalence of energy and mass (E = mc2) Friedmann – closed and open universe Hubble – spectral lines and Hubble constant
