Origin of the Universe Have you ever heard of a little thing called the “Big Bang?”

A long, long time ago…. (About 14 billion years!) The entire universe was confined to a dense, hot, super massive dense ball smaller than an atom. Then a cataclysmic explosion occurred that hurled material in all directions. The Big Bang!.

Origin of the Universe The ejected masses of energy collided, cooled and condensed, forming the galaxies, suns and planets we now observe. E=mc 2

Is Big bang for real? Must assume: Time and energy didn’t exist before the Big Bang All matter, energy, space and time were created in the big bang. The universe is still expanding today

Observed phenomenon offered as proof of BB 1. Abundance of light weight elements in the universe 2. Hubble’s Red Shift 3. Cosmic Background Radiation

Light weight elements Most stars are made up of hydrogen and helium The most abundant gases in the universe today are H, He and, to a lesser extent, Li. Assumption: Majority of atoms produced by the BB were hydrogen, helium and small amounts of lithium, which eventually coalesed through gravity to form starts and eventually galaxies.

Any elements heavier than these must be made during nuclear fusion on the sun OR through supernova explosions.

Hubble evidence for the universe expanding Discovered by Edwin Hubble in 1929 Not all matter is traveling at the same velocity. Galaxy’s velocity is proportional to its distance (galaxies that are twice as far from us move twice as fast, galaxies 5x as far from us move 5x as fast)

Let’s try this! If you have a balloon… Using your permanent marker and your balloon, draw 10 dots on your balloon…. OK, now blow it up! Stop before it pops Now look at your balloon. How has the placement of the dots changed? Are they closer together or further apart?

Red shift V0

Hubble’s Evidence of Expanding Universe Used the electromagnetic spectrum wavelengths

Electromagnetic spectrum Energy & Frequency Increases

Hubble & Red Shift Doppler shifting - wavelength emitted by something moving away from us is shifted to a lower frequency Visible wavelengths emitted by objects moving away from us are shifted towards the red part of the visible spectrum

So the proof is in the color we observe. The faster other galaxies move away from us, the more they are red shifted, or appear RED to us redshift is a reasonable way to measure the speed of an object When we observe the redshift of galaxies outside our local group, almost every galaxy appears to be moving away from us – so, the universe is expanding!

Cosmic Microwave background CMB is heat radiation that fills the universe and can be detected in every direction CMB created shortly after big bang & earliest radiation possible to detect Invisible to the naked eye, and only seen with instruments

tiny temperature fluctuations correspond to regions of slightly different densities, representing the seeds of all future structure: the stars and galaxies of today

Nebular Hypothesis – formation of galaxies As H, He and Lithium expanded out they eventually began to condense due to gravity & form solar systems.

A. The solar system begins to form as a rotating cloud and collapses due to gravity.

B. The dust particles accrete into billions of planetesimals. They collide and form protoplanets The protosun becomes massive and hot enough to "turn on" by fusing hydrogen.

C. The Sun begins to radiate energy and vaporize dust in the inner part of the Solar System. The remaining gas is blown away by solar winds. Protoplanets will collide until their orbits are cleared allowing planets to orbit the sun freely.

So how long ago did this occur in the Milky Way? Big Bang -14 bya Milky Way Formed- 5 bya Earth Formed bya

Other theories? Steady State asserts that although the universe is expanding, it nevertheless does not change its appearance over time (the perfect cosmological principle) new matter is continuously created as the universe expands it has no beginning and no end.