Origin of Universe - Big Bang Dr. Charles Ophardt EDU 370

Expanding Universe Big Bang Theory Universe began 15 billion years ago Began as a huge expansion known as the Big Bang Space and Time came into existence All matter started to expand

Big Bang Big Bang Event created space and time No time before and no space outside of it Explosion occurred everywhere filling all space from the beginning with energy. At instant of Big Bang, universe was infinitely dense and hot

Big Bang II Immediately after Big Bang: Universe consisted of primarily radiation with some matter From extremely dense and hot beginning, universe expands and the matter begins to cool As it expands matter dominates within 1,000 years of the beginning

Big Bang III First few seconds: Photons of radiation collide and convert energy into mass Protons, electrons, and neutrons formed Universe cooled from 100 million trillion trillion degrees to 10 billion degrees

Big Bang IV After three minutes: Temperature falls to one billion degrees Protons and neutrons combine to form the nuclei of helium, deutrium, and a few other light nuclei. Temperatures were too high for other elements to form

Big Bang V After 300,000 years: Universe cooled to 3000 degrees Electrons combine with atomic nuclei to form neutral atoms Proton + electron = H atom 2 p + 2 n + 2 electron = He atom From this time radiation is unable to interact with gas. Background microwave radiation now at 3 degrees Kelvin

Big Bang VI Stars and Galaxies: After one billion years: Small perturbations in the matter resulted in condensation Stars formed from condensation of matter Stars have conditions to form the rest of the elements.

Big Bang is a Testable Model Basic Assumptions are plausible Empirical support Reasonable sound physical basis Real test Does the Big Bang Model explain and make predictions that can be tested against observations?

Evidence for Big Bang 1. Universe is expanding and cooling 2. Theory predicts 25 % of total mass should be helium 3. Cosmic Background Radiation 4. Collapse of matter to form galaxies and stars

Universe is Expanding Hubble Expansion Law 1929 - almost all galaxies appeared to moving away from us Observation - red shift in spectrum Red shift larger in faint galaxies (further away and moving faster)

Universe is Expanding II Hubble Law H = v / d H = Hubble Constant V = velocity D = distance Hard to measure the Hubble Constant need velocity from red shift and distance from earth

Red Shift or Doppler Effect If object moving away-light waves are stretched toward red spectrum If object moving toward -waves are compressed toward blue spectrum

Doppler Shift Lines in spectra move left for blue shift and move right for red shift Blue shorter wavelength, red longer

Red Shift or Doppler Effect II Amount of shift depends on speed The faster an object moves, the greater the doppler shift Example: an emission line of hydrogen is shifted less by close galaxies than faraway ones. This means faraway galaxies are moving faster than nearby ones. Sound of train whistle works the same

Abundance of Light Elements Observed abundances of: Hydrogen Deuterium, helium, and lithium Formed in first 3 minutes of big bang Helium calculated to be 25% and observed in that amount These elements are not produced in required quantities in observed stellar fusion

Cosmic Microwave Background The thermal spectrum of CMB was predicted before its observation Expansion caused the hot universe to cool as it spread out Radiation thinly spread to its present temperature of 2.7 degrees Kelvin Observed as uniform background microwave radiation at peak wavelength of 1 mm- detected with a RadioTelescope

Formation of Galaxies At 10,000 years, temperatures fall so that massive particles begin to dominate Gravitational forces begin to dominate Stars form from the increasing density of matter Clusters of stars form galaxies

Other Theories Steady State Model Postulate no origin to universe Large scale features are constant Maintain an average density of galaxies Whole new galaxies must be popping into existence between old ones

Steady State II To explain Cosmic Background Radiation A whole new class of weak microwave emitting sources must exist (about 100,000 times the total visible galaxies) Lacks supporting evidence

Conclusion The Big Bang theory is one of the most strongly supported theories in all of science. It explains the observed facts It has made successful predictions; It has stood the test of time; There is no alternate theory that the professional scientific community deems valid.

Questions I Describe the universe as a system. Which statement is false? A. The universe consists of all matter and energy that exists. B. The universe is that it is mostly empty space C. The matter of the universe tends to occur in clumps D. The empty space is small compared to the size of the objects themselves.

Questions II Which statement about the evidence for the Big Bang Theory is false? A. Universe is expanding and cooling B. Theory predicts 25 % of total mass of universe should be helium C. Cosmic Background Radiation is a measure of the background infrared light D. Matter collapsed to form galaxies and stars

Questions III Which statement about the Big Bang Theory is false? A. Photons of radiation collide and convert energy into mass B. Protons combine with electrons to form neutrons C. A proton combines with an electron to form a hydrogen atom D. A helium atom is formed from 2 p + 2 n + 2 electron

Questions IV Which statement about the Hubble Law is false? A. Almost all galaxies appeared to moving away from us B. Hubble Law is based upon the observation of a red shift in spectrum of galaxies and stars C. The red shift is smaller in faint galaxies since they are further away and moving faster D. The most inaccurate term in the Hubble Constant is the distance to the object.

Questions V Which statement about the Red Shift is false? A. If object is moving away the light waves are compressed toward the red spectrum B. If object is moving toward you the light waves are shifted toward blue spectrum C. Amount of red shift depends on speed D. The faster an object moves, the greater the doppler shift

Questions VI Which statement about the CMB is false? A. The thermal spectrum of CMB was not predicted before its observation B. Expansion caused the hot universe to cool as it spread out C. Radiation thinly spread to its present temperature of 2.7 degrees Kelvin D. CMB is observed as uniform background microwave radiation at peak wavelength of 1 mm

References http://www.astronomynotes.com http://www.pparc.ac.uk/Ed/Notes/Bbwebpage.asp