To do Run through the ppt on Big

To do: • Run through the ppt on Big Bang and Cosmology (resources. faulkes-telescope. com > GCSE Astronomy > Class Exercises > Cosmology • Complete the following worksheets: – Expansion of the Universe – Cosmic Microwave Background Radiation – Hubble Trouble – Galaxies Wordsearch

Age of the Universe • Hubbleʼs Law is given by: v = H 0 d (1) If a galaxy has travelled at a speed v for a time t since the Universe began, it will have travelled a distance d given by: d=vt (2) Putting (2) into (1) gives: v=H 0 vt Cancelling out the vʼs gives: t=1/H 0 (3)

The Big Bang

What was the Big Bang? • Big Bang theory says… • Universe started from an explosion

Evidence? • A glow - Cosmic Microwave Background

Echoes of the Big Bang • Penzias & Wilson found a faint background ‘hiss’ • Leftover radiation from Big Bang! • Universe was originally filled with very high energy blackbody radiation • As Universe expanded, the radiation cooled, and predicted to be at microwavelengths – with T approx. 3 K

WMAP • Studied the whole sky and mapped the microwave emissions to very accurate levels. • WMAP has: Confirmed the age of the Universe as 13. 7 billion years Shown the existence of dark energy Limited the effects of dark matter Defined the stages of development of the Universe more accurately – Produced data on events of the first fraction of a second of the Universe – –

Expansion of the Universe • What is the Universe expanding into? • Not an expansion into space, but an expansion of space itself. Matter is more or less fixed. We are not expanding, nor is the Earth, the solar system, galaxy, or local group of galaxies. These are all held together by gravitational and chemical (i. e. electrical) forces.

Evidence? • Galaxies are rushing away from each other • Observations from HST have found extremely high redshifted galaxies and quasars – shows they are moving away from us faster and faster….

The future of the Universe • An analogy: • Balance between kinetic energy and gravitational energy

The future of the Universe • As with the rocket, so with the Universe Open Universe: kinetic energy wins Closed Universe: gravitational energy wins

Fate of the Universe • The future depends on the density of the Universe • High density : gravity wins : Universe is ‘closed’ • Low density : expansion wins : Universe is ‘open’ • Dividing line = critical density • Critical density = where the average density of matter is just high enough so the galaxies come to a halt in an infinite time when they’re infinitely far apart

• Universe can be ‘open’, ‘flat’ or ‘closed’ depending on its density

The bit we think we probably know a bit about…

Dark Matter • Matter that is invisible to us (doesn’t emit EM radiation) • We can only ‘see’ it due to its gravitational influence • Evidence: – galaxy rotation curves – gravitational lensing • Could be: black holes, neutrinos, WIMPs (exotic particles)

Dark Energy • In 1998, astronomers found evidence that the expansion of the Universe was accelerating • Repulsive force of negative gravity – dark energy • Look at: http: //science. nasa. gov/astrophysics/focusareas/what-is-dark-energy/

Summary • Observations suggest the Universe began ~13. 7 billion years ago • It is expanding faster now than in the past…Dark Energy? • Most of the mass of the Universe is not “normal matter”…