THE EXPANSION OF THE UNIVERSE!

Einstein The discovery of the expansion of the

universe was first found by Einstein -Disagreed with this point- as he

believed the earth was static and unchanging.

- In his equation he created what is called the ‘cosmological constant’

- Which proved the universe was static and unchanging

Friedmann

Considered Einstein made an error, set out to prove the universe was expanding based on the theory of relativity.

Assumed 1. Universe appears the same in every

direction you look 2. This is true for whatever your

viewpoint in the universe is

Friedmann Equation

Radius of curvature of space increases with time

finding were verified by Belgian astronomer Georges Lemaitre in 1927

Three models that satisfy his assumptions

1. ‘Closed’ Universe’-(by Friedmann) mutual gravitation of universe is able to stop expansion, then pulling matter back- contracting it again.

“Flat Universe’-(Dutch astronomer Willem de Sitter in 1912) universe is just faster enough to balance the force of gravity, the expansion will slow but not stop.

“Open universe”- universe is expanding so fast gravity cannot stop it.

Models

Hubble

Hubble is accredited with the discovery of the expansion of the universe; this is because in 1924 he discovered Andromeda was not as star, but in fact a galaxy.

800,000 light years it was further than most stars

Measured the red shift of the light- which is finding specific wavelengths of the light. This similar to the Doppler Effect (relationship between speed and wavelength)

measuring the degree of the red shift it possible to calculate how fast it is moving away

measured more galaxies were mostly moving away from earth- he also found that the further the object was from earth, the faster it was moving.

explanation for the expanding Universe is that it is the space between the galaxies

Hubble’s Law

ν=H0D ν = velocity of recession (km s-1 ) D= Distance from us (megapacsecs, Mpc) H0 = Hubble’s constant aprrox. Equal to 70 km S-1

Mpc-1

1 megaparsec is 3.26 million light years

I.e. If a galaxy 1 megaparsec away will be moving away from us at a speed of about 70 km/sec

Hubble was also able to find the approximant age of the universe which is 12-14 billion years ago.

Issues

As technology has improved we have able to more accurately calculate the expansion of the universe.

As technology advances people will be able even more accurately find the distance of objects which will define more clearly Hubble’s constant.

However this is also a problem as Hubble constant, will change- this will mean everything else must be readjusted to new constant and may cause major problems

Friedmann made two assumptions they are

1. Universe appears the same in every direction you look

2. This is true for whatever your viewpoint in the universe is.

the accepted models are based entirely on these assumptions, if they were found to be incorrect or untrue this would completely change the view of the universe as we would have no model of the universe and how it works

As these are assumptions they are not known. This means people do not have enough information to make definitions on universe the universe works

evidence against the expansion of the universe tired-light theory- this theory suggests that lost

energy disappears from the universe completely-even tho it goes against the First Law of Thermodynamics;

Paul LaViolette was one of the first people to disprove the expanding universe theory some of his work suggested cosmological red shift- which would indicate that the universe was static

also tested four different techniques which mainly fitted with his theory where as it was found that scientist’s regularly change the expanding universe models to fit their data.

Evidence for the expansion of the universe much more evidence for the expansion of the

universe which does suggest that the universe is expanding, and not static.

the observation of a 1a supernova, two scientists in America found that the remnants of the star were found to be 15% further away than the standard model predicts.

evidence that the universe is expanding as an open universe, and the expansion rate is increasing.

Bibliography

Unknown (1998) Evidence mounts that the expansion of the Universe is accelerating [internet]. Unknown; Institute of Physics and IOP Publishing. Available From: http://physicsworld.com/cws/article/news/3137 [accessed 22/8/09]

Unknown (2008) Evidence Against the Expanding Universe Hypothesis [internet].Unknown; unknown. Available from: http://www.etheric.com/Cosmology/redshift.html [accessed 22/8/09]

Wu F. (2009) The Big Bang [internet] Unknown; Unknown Available From: http://highered.mcgraw-hill.com/sites/dl/free/0070138354/676284/Chapter_18_TheUniverseBegins.pdf [accessed 23/8/09]

White M (unknown). The Hubble Expansion [internet] USA; UC Berkeley Available From: http://astro.berkeley.edu/~mwhite/darkmatter/hubble.html [accessed 23/8/09]

Hawking S. (2001). The Universe in a Nutshell London: The Random House Group Ltd.

  Andriessen M. Lofts G. Morante R. Barry Mott J. (2009) Physic 1: Preliminary course

Australia; John Wiley & Sons Australia Ltd.