Chapter 19 – Formation of the Universe Why do scientists think the universe is expanding?
I. The singularity – The theorized beginning of the universe. A. All particles of matter in the universe was compressed into a unimaginably dense object about the size of a dime. B. Suddenly this single atom imploded and with a great release of energy all matter began expanding with tremendous speed to create our universe
<ul><li>II. The Big Bang Theory </li></ul><ul><li>A. The first minute </li></ul><ul><li>98% of all matter in the universe was formed. First particles formed were quarks (make up protons and neutrons), electrons, photons, neutrons. </li></ul><ul><li>2. The first elements formed were hydrogen, helium and deuterium (isotope of hydrogen) </li></ul><ul><li>3. Our universe is 1 million billion miles across and 10 billion degrees Kelvin . </li></ul>
B. Inflation Theory 1. For a very short period of time (10 –30 sec) the universe doubled itself every 10 –34 sec. 2. This theory was proposed in 1979 by Alan Guth . 3. This period of great expansion helped establish the law of gravity (All objects have a gravitational force , the larger the object the greater the force, ex. the earth vs. your pen.) other laws of physics were established between subatomic particles. This theory also helps explain how the force of gravity began to condense clumps of matter into objects that would eventually form stars and galaxies.
C. Size and organization of our universe. 1. There is no end to the universe, due to the nature of space, it curves . a. Thought to be 90 billion trillion miles “across”, this is as far out as we can see. b. At this distance, quasars (star like objects) are observed. Quasars give off more energy than 100’s of galaxies combined, thought to represent the earliest stages of the universe formation
2. The universe is composed of around 100 billion galaxies, of which the Milky Way (our home) is one. a. Galaxies are composed of 100’s of billions of stars
b. There are 3 general shapes: - Elliptical : older galaxies, more disc shaped
- Spiral : looks like a pin wheel, Milky Way is one.
c. Galaxies are rushing away from each other, space is expanding
3. Formation of heavier elements may be found in supernovae. a. Supernovae occur when giant stars (much bigger than our sun) explode and immense energy is released (equal to a trillion hydrogen bombs detonating)
b. 10 million degree temperatures are adequate to create heavier elements necessary for life (carbon, nitrogen, oxygen, sulfur, and phosphorous).
4. Our galaxy the Milky Way (“milky circle”) is about 100,000 light years across and 15,000 light years long.
D. Future of our universe – Scientists are measuring the density (amount of mass per unit of area) of our universe, to predict what will happen. A density unit is called an omega is used to refer to the density of our universe. Scientists cannot yet measure dark matter (ex. Black holes, neutrinos).
1. Open / Eternal Universe ( The Big Rip) If galaxies continue to move away from each other, eventually all stars will die and the universe will fizzle out.
2. Closed Universe ( Big Crunch ) The gravitational attraction between stars will overcome the energy that resulted from the “ Big Bang”. The galaxies will begin to come toward each other, eventually the universe would condense again into another singularity.
3. Flat / Critical Density- Momentum will be lost, galaxies will stop moving from each other, the universe will not expand , but not contract. Momentum will eventually die and the stars will fizzle out.
<ul><li>III Evidence to Support the Big Bang </li></ul><ul><li>The Doppler Effect – The universe is currently expanding </li></ul><ul><li>1. Every object in universe is moving (earth </li></ul><ul><li>rotating, sun around the Milky Way, galaxies </li></ul><ul><li>move away from each other). </li></ul>
2. Direction of this movement is measured by a spectroscope which breaks up white light into individual colors (like a prism).
3. Light, like sound, travels in the form of waves , light just travels A LOT faster ( 186,000 miles a second ). These waves are measured in wavelength (different wavelengths of light appear as different color s)
4. Light waves when approaching an object are shorter with a higher frequency (Just as with sound - ex. train whistle sounds high when approaching you). In light, blue /violet are the visible colors with shorte r wavelength. Therefore objects moving toward the earth and giving off light, have a blue shift / color to them when measured with a spectroscope
5. Light waves when moving away from an object are longe r with a lower frequency (i.e. train whistle sounds lower when moving away from you) – red is the visible color with longer wavelengths. Therefore objects that are moving away from earth have a red shift when measured with spectroscope
6. All galaxies observed in the universe have a red shift , so they are moving away from our galaxy. 7. The degree of the shift (how blue or red) gives information on the speed at which the object is moving
B. Detection of uniformly distributed cosmic background radiation (CBR), left over energy from the Big Bang , is found in the form of radio waves . 1% of static on TV is this background radiation from the big bang.
C. Chemical Composition: The big bang model predicts that the universe is about 75% hydrogen and about 25% helium with small amounts of heavier elements. This is supported by measurements of observable universe.
<ul><li>IV. Important milestones in modern cosmology (study of the origins of the universe): </li></ul><ul><li>1927 – Georges Lamaitre, hypothesized that the universe began from an explosion of a “primitive atom”. </li></ul>
B. 1929 – Edwin Hubble, hypothesized approximate size of the universe and observed “red shift” of neighboring galaxies
C. 1948 – George Gamow, speculated that such a Big Bang explosion would have left behind uniformly distributed background radiation throughout the universe
D. 1964 – Arno Penzias and Robert Wilson, discovered the background radiation coming from all directions
E. 1970’s – Alan Guth, Inflation Theory explaining laws of physics and formation of galaxies. F. 1992 – George Smoot, measured temperature fluctuations of space at 2.7 Kelvin, evidence of structure of universe
<ul><li>V. Formation of our Solar System – Solar Nebular Theory </li></ul><ul><li>Gas and dust (Nebular cloud) began to collapse due to the force of gravity . Usually initiated by a shockwave of neighboring supernova. This cloud may have been seeded with heavier elements by a neighboring supernova. </li></ul>
B. Particles in the center of the cloud, coalesce (come together) faster and become more dense , increasing temperature causing nuclear fusion , gives off heat and light (2 hydrogen atoms fuse and form helium)- this is called a protostar (our sun). 99.9% of all the mass in our solar system is contained in our sun.
C. In the outer portions of the cloud, colliding dust grains begin to stick together until they are big enough to produce their own gravitational field, attracting even more matter, forming protoplanets .
<ul><ul><li>1. Inner planets (Mercury, Venus, Earth, and Mars) are so close to the sun that their gases burn off and tend to be rocky and metal. </li></ul></ul>
2. Outer planets (Jupiter, Saturn, Uranus and Neptune) are far enough from the sun that gases do not burn off and they tend to be very large planets.
3. Asteroid belts are thought to be created from clumps of matter that were not assimilated into the protoplanets.
There is an asteroid belt between Mars and Jupiter termed the “main belt”, and another on the outer edge of the solar system called the “Kuiper belt”. The “Oort Cloud” is on the outermost edges of our universe and contains a collection of comet-like objects.
D. The forming protoplanets of the outer portion of the cloud begin to swirl around the center (sun). Our solar system formed about 4.5 billion years ago
E. It takes our sun 200 million years to rotate around the core of the Milky Way galaxy.