Origin of Our Universe

Transcription

1 Origin of Our Universe

2 Before the Big Bang? As cosmologists begin to understand what happened just after the Big Bang, many are questioning what led up to the Big Bang (4 possibilities) 1. No previous era: matter, space, and time began abruptly with the bang 2. Quantum emergence: ordinary space and time develop out of a primeval state described by a quantum theory of gravity 3. Multiverse: our universe and others bud off from eternal space 4. Cyclic universe: the big bang is the latest stage in an eternal cycle of expansion, collapse, and renewed expansion

3 Formation of the Universe The Big Bang Theory: The theory that the universe began as a point (singularity) and has been expanding ever since 1. The universe was originally packed into one dense sphere of hydrogen about the size of a pearl! 2. The sphere exploded forming a gigantic, hot expanding cloud 3. As the cloud moved, parts condensed and formed billions of galaxies

4 Formation of the Universe The Big Bang Theory: The theory that the universe began as a point (singularity) and has been expanding ever since 4. The galaxies continue to move outward today 5. Most commonly accepted theory of universe formation

5 Formation of the Universe: previous ideas The Steady State Theory: the belief that the universe doesn t change with time but more matter is added as it expands Popular during the 50 s and 60 s The universe had no beginning and has no end (no big bang)

6 Formation of the Universe: recent developments The Inflationary Theory: predicts that there was a sudden expansion when the universe was very young, more extreme than predicted by the big bang Considered to be a revised Big Band Theory universe expanded until about seconds after the big bang when it became so cool that the forces of nature caused the universe to inflate tremendously

7 Evidence for Big Bang/Inflation 1965 Panzias and Wilson discovered background radiation interfering with radio antennae, causing a hiss in phone lines That radiation is called cosmic background radiation and thought to be from the big bang (extreme red-shift into microwaves, we see a wall of microwave radiation filling the sky) Provides a glimpse of the universe at only 380,000 years old (when atoms formed) can be detected by common radio and TV antennae (snow) 1980, Nasa discovered that the CMB

8 Evidence for Big Bang/Inflation Astronomers also observe red shifts throughout universe This Red shift, or a Doppler shift toward the red end of the spectrum, occurs because the light waves are stretched, which shows that Earth and the source are moving away from each other.

9 Formation of galaxies 1. Galaxies begin as a spherical cloud (called a nebula)in space 2. the cloud collapses under the force of it s s own gravity, forming galaxies of a variety of shapes 3. Our galaxy, the Milky Way, is a spiral galaxy consisting of a nucleus surrounded by arms that rotate in a clockwise fashion 4. Solar systems similar to ours move around in this galaxy in a regular pattern

10 Shape of Galaxies QuickTime and a decompressor are needed to see this picture. 1. Spiral (like the Milky Way) background pic some are Barred Spirals Our solar system is here 2. Elliptical 3. Irregular QuickTime and a decompressor are needed to see this picture. QuickTime and a decompressor are needed to see this picture.

11 Formation of a Solar system Within each galaxy are many nebulae (plural of nebula). A nebula is a cloud of interstellar dust and gas from which stars and eventually solar systems are formed. A nebula is a cloud of interstellar dust and gas from which stars and eventually solar systems are formed. Nebula can be many colors depending on the chemical makeup of the gas.

12 How a Nebula becomes a Solar System - The Solar Nebula Hypothesis: Just as an ice-skater s spin speeds up when she pulls her arms in, so does a cloud of dust in space. As the cloud spins faster, enough pressure is created to produce fusion in the center of the disk, forming a star like our sun. Planets are formed from the rings left behind as the dust disk formed.

13 Formation of OUR solar system: Our sun was the center of that cloud of dust and gas. As the planets formed, the more dense ones were pulled closest to the sun. They are called Terrestrial Planets (Mercury, Venus, Earth, and Mars). The less dense planets moved toward the outer portion of the solar system. They are called Jovian Planets, or Gas Giants. (Jupiter, Saturn, Uranus, and Neptune) Pluto is now thought to be a minor planet, most likely a captured comet who was drawn in by the gravity of the sun and placed in an orbit around it (similar to asteroids)

14 Planetary Development Terrestrial planets (like Earth) go through the same 4 stages of development: 1. DIFFERENTIATION - heavier materials move to the center of the planet, lighter materials move to the outer portion while it is still molten (liquid) 2. BOMBARDMENT - planets receive surface features due to cratering from space debris (there was much more debris in the early universe!) 3. FLOODING - planets were covered with molten rock or water, filling in lower areas 4. SURFACE EVOLUTION - planets continue to change their look from impacts, erosion, or plate tectonics.

15 Planetary Development Gas Giants Jovian planets (gas giants) all went through differentiation, but we are unsure about development after that. We DO know that they are constantly influenced by storms that move through their thick atmospheres.

16 Formation of moons and rings Planets have moons for 2 different reasons: 1. A large object in space hit the planet, throwing out debris that collected into a moon (ex: Earth s s moon) 2. Asteroids have been captured by the planet when the came too close, getting trapped by the gravitational pull of the planet (ex: the moons of Mars) All planets have moons except Mercury and Venus

17 Formation of moons and rings Some planets also have rings: Rings are either debris blown away from the planet but trapped in it s s gravitational field OR they are rings of debris from captured space debris. Only the Gas Giants have rings