Origins of the Universe

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Johnathan Scott
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a simultaneous expansion from all places 13.7 billion years ago EVIDENCE 1.

1 Cosmology Origins of the Universe The study of the universe, its current nature, its origin, and evolution 1 2 The Theory Theory Expansion indicates a denser, hotter past uniform, hot gas that cools as it expands NOT an explosion from a point, but a simultaneous expansion from all places 13.7 billion years ago EVIDENCE 1. Cosmic microwave background radiation noise, same in all directions Scientists sense energy from the explosion, and it is everywhere in space Arno Penzias and Robert Wilson 1

2 EVIDENCE 2. Expansion measured by Hubble constant Distant galaxies are redshifted (based on electromagnetic spectrum) This is the doppler effect being applied to light 1929 Edwin Hubble Doppler Effect: Red Shift: slower, moving away Wavelength is longer thus the color appears red. 8 Doppler Effect: Blue Shift: faster, moving toward Wavelength is shorter, thus the color appears blue. EVIDENCE 3. most elements in universe are H and He (light elements) Created during first moments of when stars reach the end of their life cycle, they distribute C, O, and Fe into the universe if the universe was older, there would be more C, O, and Fe 9 Age of the materials Oldest material should be furthest away. Quasars at the edge of the universe are 12 billion lightyears away. Expanding Universe All distant galaxies are redshifted. What does this mean about their distance from us? Hubble s Law further away a galaxy is, the faster it is speeding away If we can determine how fast the universe is expanding (aka Hubble constant), we can determine the AGE OF THE UNIVERSE! 11 2

Beginnings http://www.youtube.com/watch?

3 Beginnings Steady State Theory The universe looks the same to all observers, everywhere, and it has always looked that way. Types of Universes Open Universe Closed Universe Universe will expand forever At some point the universe will stop expanding and collapse inward (continuous)

Visible Light Telescopes, spectroscopes (ROY G

Invisible Light UV, Infrared, X-Ray, and Space

These measure energy waves beyond the Visible

Historical Perspective Characters in the great

Nicolaus Copernicus (1473-1543) Tycho Brahe

4 Visible Light Telescopes, spectroscopes (ROY G BIV) How we study the universe Radio, Invisible Light UV, Infrared, X-Ray, and Space telescopes. These measure energy waves beyond the Visible Light Spectrum A little drama Astronomy A Historical Perspective Characters in the great drama Aristotle (350 BC) Claudius Ptolemy (140) Nicolaus Copernicus ( ) Tycho Brahe ( ) Johannes Kepler ( ) Galileo Galilei ( ) Isaac Newton ( ) 4

The Earth is spherical. It seems natural that our first hypothesis regarding the structure of the Solar System would be geocentric.

Aristotle s shoes Then came Ptolemy A good theory should explain what is observed and be able to make predictions. Planets move in circles called epicycles.

The test of all knowledge is measurement Ptolemy s theory explained the retrograde motion of the planets Predicted future locations of the planets Geocentric Model C.

He believed the heavens were perfect and that everything moved in a perfect circle and at a constant speed.

5 The Earth is spherical. It seems natural that our first hypothesis regarding the structure of the Solar System would be geocentric. Being more philosophical and less empirical, we would hope to see harmony and perfection in the heavens that fit our philosophy--thus, the motions of bodies are perfect circles. Aristotle s shoes Then came Ptolemy A good theory should explain what is observed and be able to make predictions. Planets move in circles called epicycles. The center of the epicycle moves in a circle called a deferent. To make theory match prediction, Earth isn t exactly at the center of the deferent. The test of all knowledge is measurement Ptolemy s theory explained the retrograde motion of the planets Predicted future locations of the planets Geocentric Model C : Ptolemy places Earth at the center of the universe with everything (including the sun and the seven planets) revolving around Earth. He believed the heavens were perfect and that everything moved in a perfect circle and at a constant speed. His biggest challenge was explaining the planet s retrograde motion and apparent changing speeds. Observed throughout a year, the stars always go in one direction, but not so for the planets years later -heliocentric idea Copernicus, for philosophical reasons, sought to explain the retrograde motion of planets using a heliocentric solar system. He still assumed perfect circles for the orbits of planets (with the Sun at the center of the orbits). He could calculate the relative distances to the planets the orbital periods of the planets Predictions of the future positions of planets were not much better than those from the Ptolemaic model We need better data! Tycho Brahe had ideas for a new model but recognized the need for more precise measurements. He devoted his life to making more precise measurements of the positions of stars and planets. He built the first modern observatory 5

Heliocentric vs Geocentric Model Finding a needle in a haystack Kepler believed the Copernican model and sought to prove that it was correct using Brahe s data for the positions of the planets.

6 Heliocentric vs Geocentric Model Finding a needle in a haystack Kepler believed the Copernican model and sought to prove that it was correct using Brahe s data for the positions of the planets. He found that Planets orbit in elliptical paths (not circles!) with the Sun at one focus of the ellipse. A line from the Sun to a planet will sweep out the same area in a certain time interval, regardless of where the planet is in its path. The ratio of the (period) 2 to (semi-major axis) 3 was the same for every planet. Finding a needle in a haystack He described the planets orbits, but could they be explained? Kepler answered the What?, but didn t know Why? Kepler s Laws 1 st Law: planet s orbit the Sun in ellipses, with the Sun at one focus. 2 nd Law: The line joining the Sun and a planet sweeps out equal areas in equal time intervals. As a result, planets move fastest when they are near the Sun (perihelion) and slowest when they are far from the Sun (aphelion). 3 rd Law: The larger the orbit of a planet, the slower its speed in orbit and the longer its orbital period. Standing On The Shoulders Of Giants Isaac Newton formulated three laws of motion and a law of gravitation. This model for understanding motion (how motion is related to forces) and gravitation explained Kepler s three laws. When Why? matches What? (theory matches observation), we must reexamine our dearly held beliefs. Standing On The Shoulders Of Giants This happened again in 1911 with Einstein s publication of the General Theory of Relativity an entirely different explanation of gravity explained phenomena that Newton s law of gravitation could not explain. has been verified by experiment to this day 6

Cosmology is the study of the universe. What is it s structure? How did it originate? How is it evolving? What is its eventual fate?

Cosmology Cosmology is the study of the universe. What is it s structure? How did it originate? How is it evolving? What is its eventual fate? ANCIENT COSMOLOGIES The Ptolemaic Universe Claudius Ptolemy