How the universe has changed… Begin at the Beginning…

“Big Bang” Theory 13.7 billion years ago, an event occured when all matter in the universe (originally in a single dense speck) began to rapidly expand. This is currently the prevailing theory of how our universe began and evolved.

Origins  How and when did the:  universe form?  solar system / Earth form?  Moon form?  What were early Earth conditions? How Do We Know?

Origin of the Universe  Big Bang  occurred 13.7 billion years ago  It is a model for the beginning of the universe

- infinitely dense point not governed by our physical laws or time - all matter and energy contained in one point Building a Universe

Ancient Ideas… People have wondered about the universe from the moment they raised their eyes to the heavens. Based on observation of sun, moon, and stars moving across sky, ancient cultures had the idea that the Earth was the center of the universe. WRONG!!

Copernicus ( ) Johannes Kepler (1600) Galileo ( ) Newton ( ) Einstein (1900) LeMaitre(1927)

Nicolas Copernicus: Polish the SUN was the center of solar system Kepler: German math, astronomy – concluded that planets move in elliptical orbits around the sun Galileo Galilei : Italian “Father of modern science” Dialogue Concerning Two Chief World Systems: He used three characters to discuss the merits of sun-centered vs earth-centered universe. He showed Jupiter has moons (so not all objects orbit EARTH!), sun has spots, moon has phases

Newton: Formula for gravity explained that objects will orbit more massive objects (earth goes around sun, not sun around earth) Lemaitre: Used Einsteins equations to hypothesize a moment of creation and expanding universe. Henrietta Leavitt: She used variable stars to determine distances to other objects in the universe. Edwin Hubble: Distant galaxies give off a red shift to their light – they are MOVING AWAY FROM US!

 Red-Shift  Cosmic Background Radiation  Proportion of Hydrogen and Helium

Evidence for Big Bang  Red shift - as light from distant galaxies approach earth there is an increase of space between earth and the galaxy, which leads to wavelengths being stretched  In 1964, Arno Penzias and Robert Wilson, discovered a noise of extraterrestrial origin that came from all directions at once - radiation left over from the Big Bang  In June 1995, scientists detected primordial helium in the far reaches of the universe - consistent with an important aspect of the Big Bang theory that a mixture of hydrogen and helium was created at the beginning of the universe

 Henrietta Leavitt – relative distance of stars  Edwin Hubble – Measured distances of stars and the wavelengths of light  Hubble determined that galaxies were moving away at increasing speeds!

Edwin Hubble  Used his telescope at Mount Observatory. He saw that there were lots of galaxies, not just the Milky Way.  He also noted that the galaxies were MOVING AWAY from one another! The universe is continuously expanding!!!  Galaxy ’ s velocity is proportional to its distance (galaxies that are twice as far from us move twice as fast)  taken every galaxy the same amount of time to move from a common starting position to its current position

Hubble ’ s Evidence  Doppler shifting - wavelength emitted by something moving away from us is shifted to a lower frequency  Sound of a fire truck siren - pitch of the siren is higher as the fire truck moves towards you, and lower as it moves away from you  Visible wavelengths emitted by objects moving away from us are shifted towards the red part of the visible spectrum  The faster they move away from us, the more they are redshifted. Thus, redshift is a reasonable way to measure the speed of an object (this, by the way, is the principal by which radar guns measure the speed of a car or baseball)  When we observe the redshift of galaxies outside our local group, every galaxy appears to be moving away from us - universe is expanding.

Stationary bug producing waves. Both A and B observes get the same observation. A bug moving to the right. A and B get different observations, due to the shift in the wavelength.

The Doppler Effect: the effect produced by a moving source of waves in which there is an apparent shift in frequency for observes towards whom the source is approaching.

Abundance of Light Elements If a rapid expansion occurred, from a very hot dense point, we should see a certain amount of H and He according to when the universe began cooling. Researches have found that the ratio of elements in the universe supports this hypothesis.

 If the universe was incredibly hot, there should be a remnant of the heat.  1965 – Penzias & Wilson found radiation that permeates the universe

Building a Universe s - gravity separates from other forces centimeters to s - fundamental particles - quarks and electrons - softball s - quarks combine into protons and neutrons - solar system 1 s - electromagnetic and weak nuclear forces separate 3 minutes - protons and neutrons combine into atomic nuclei 10 5 years - electrons join nuclei to make atoms; light is emitted years - matter collapses into clouds, making galaxies and stars Orion Nebula -

When Did the Universe Form?  10 to 20 billion years ago (15)  How do we know?  spreading (Red Shift)  know distances, rates of retreat, relative positions  pervasive background radiation of 2.7°C above absolute zero  afterglow of the Big Bang Orion Nebula -

How old is the universe?  Speed x time = distance  (distance of a particular galaxy) / (that galaxy ’ s velocity) = (time)  or  4.6 x 10^26 cm / 1 x 10^9 cm/sec = 4.6 x 10^17 sec  ~ 15 billion years