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Astrophysics

Astrophysics. Tan Yang Jie. Density of the Universe.

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Astrophysics

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  1. Astrophysics Tan Yang Jie

  2. Density of the Universe • In order to find the density of the Universe, we need to find the Mass and Volume of the Universe. To find that, it is deem as inaccurate as the mass and volume are very hard to determine, due to the Universe expanding. So scientist use the expansion speed to determine the density, based on the formula to derive the density of the Universe: Ω = 2q0 =  Λ • where … • Ω = densityq0 = Deceleration ParameterΛ = Cosmological Constantc = speed of lightH = Hubble Constant • As shown above in the formula, there are 4 constants: Deceleration Parameter, Cosmological Constant, Speed of Light and Hubble Constant. Out of all the 4 constant, only the Speed of light is known, whereas the Deceleration Parameter and Cosmological Constant are unknown and there are still disagreements over Hubble Constant. • The main substance that we are measuring is the matter of the Universe. The age of the Universe or matters is about 13.7 Billion years, which means our scopes can view up to 13.7 Billion years before spotting the horizon.

  3. Dark Matter • The Universe is made up of mass-energy, consisting of Dark Energy, Dark Matter and atoms. • 95% of the mass-density is dark, which is to say does not emit electromagnetic radiation. • Dark matter takes up 23% of the mass-energy density of the Universe. • Dark Matter is needed for gravity to increase the view on small changes in the Cosmic Microwave Background, to form a view on the Universe.

  4. Dark Matter

  5. Why is it so hard to measure density? • Dark matter is dark, does not emit light for us to see. It is also very far away so reflecting light from stars nearby takes a long time. • Dark matter is made up of MACHOs (20%), which locating and to determine the mass is very difficult. As MACHOs have gravitational pull, they warp the space around them, causing light to bend and magnify out, making it seem to move and grow. • WIMPs (Weakly Interacting Massive Particles) are invisible and very hard to detect. It passes through solids easily, and it is still unsure if it really exists. Cosmic Rays also make it hard for WIMPs to be detected as it is very high in energy. • Neutrinos are very small and difficult to locate. It carries energy which a very small mass. There are many of the Neutrinos, and it is estimated to make up 25% mass of the Universe.

  6. The Large hadron collider • A gigantic circular equipment that spans through at least 2 countries, France and Switzerland, being about 100m underground. • It is used by physicist to simulate the Big Bang to find out about the Universe. • E.g. • The fundamental blocks of all things. • New Laws of Nature. • What is Mass? • Mass of the Universe • Birth and development of the Universe • There are 2 subatomic beams called ‘Hadron’, either protons or lead ions, will travel at/ close to speed of light before colliding into each other.

  7. The Large hadron collider : ATLAS • There are 6 main experiments to be done using the LHC. These are mainly: • ALICE • ATLAS • CMS • LHCb • TOTEM • LHCf • ATLAS is the one that we are mainly looking at, as it deals with the questions of Dark Matter and Mass.

  8. The Large hadron collider • Recently, the LHC managed to trap antimatter for a few fragment of a second. • They managed to trap 38 Anti-Hydrogen Atoms individually, long enough for them to study it.

  9. Appendix • Dark Matter. (n.d.) Retrieved on 24/11/2010, from astronomy.swin.edu.au: http://astronomy.swin.edu.au/cms/astro/cosmos/D/Dark+Matter • CERN. (2008). ATLAS. Retrieved on 24/11/2010, from public.web.cern.ch: http://public.web.cern.ch/public/en/lhc/ATLAS-en.html • Science and Technology Facilities Council. (2010). What is the LHC? Retrieved on 24/11/2010, from www.lhc.ac.uk: http://www.lhc.ac.uk/About+the+LHC/11795.aspx • Science & Nature. (n.d). Neutrinos. Retrieved on 24/11/2010, from www.bbc.co.uk: http://www.bbc.co.uk/science/space/deepspace/darkmatter/neutrinos.shtml • Science & Nature. (n.d). WIMPs. Retrieved on 24/11/2010, from www.bbc.co.uk: http://www.bbc.co.uk/science/space/deepspace/darkmatter/wimps.shtml • Science & Nature. (n.d). MACHOs. Retrieved on 24/11/2010, from www.bbc.co.uk: http://www.bbc.co.uk/science/space/deepspace/darkmatter/machos.shtml • Griswold, B. , Dr. Hinshaw, G.F. (16/04/2010). What is the Universe made off? Retrieved on 24/11/2010, from map.gsfc.nasa.gov: http://map.gsfc.nasa.gov/universe/uni_matter.html • Hangst, J. (18/07/2007). Keeping antihydrogen-the ALPHA trap. Retrieved on 24/11/2010, from cerncourier.com: http://cerncourier.com/cws/article/cern/30577 • Brice, M. (10/11/2010). ALPHA experiment facility and Prof. Jeffrey Hangst. Retrieved on 24/11/2010, from cdsweb.cern.ch: http://cdsweb.cern.ch/record/1307522 • Xscience.info (18/10/2006). Antimatter Chemistry. Retrieved on 24/11/2010, from www.xscience.info: http://www.xscience.info/news/physics-and-astronomy/antimatter-chemistry-51.html

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