Chapter 3: The Universal Context of Life
Chapter 3: The Universal Context of Life ASTR 115
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Date Created: 10/11/15
Chapter 3 The Universal Context of Life Vocab Terrestrial Planets Rocky planets with small or no moons Jovian Planets quotGas Giantsquot Large gas planets mad mostly of hydrogen and hydrogen compounds 0 They have tons of moons and some have rings made of countless small particles 0 The pressure is so high that the gases are condensed down into liquid forms Impossible to land a craft on the surface Hydrogen Compounds Hydrogen based compounds 0 Water Methane and Ammonia Asteroids Small bodies of metal and rock Comets Small bodies of rock and ice Asteroid Belt An area where tons of asteroids rotate around the Sun together Kuiper Belt A group of asteroids rotating on the outside of our solar system The Law of Conservation of Energy Energy can not be created or destroyed but only transformed from one form to another Conservation of Angular Momentum The total amount of circling motion of an object must be conserved Condensation The process of a gas or liquid condensing to a solid Accretion The process when particles stick together and grow Planetesimals Boulder sized particles that have grown through accretion of 110 km Solar Wind A stream of charged particles that is blown away from the Sun Modern Astronomy The universe is massive and extremely old giving there plenty of opportunity for life in other places to evolve The elements necessary for life are located everywhere in the universe The same physical laws on Earth operate everywhere in the universe We are not the center of the universe Our Cosmic Address Earth is a planet in our solar system We are part of the Milky Way Galaxy 0 Galaxy A group of hundreds of millions of stars The Milky Way is part of a Local Group 0 Local Group A group of galaxies close together 0 Superclusters Groups of galaxies with more than a few dozen galaxies Together all of this forms the universes Sizes of the Universe The majority of space is empty The next closest star to our Sun is 44 lightyears away 0 Lightyear Distance light travels in one year 10 trillion kilometers We can t actually see things in deep space in the present because it takes time for the light to travel Content in the Universe Stars planets and asteroids make up very little of the universe Most mass in the universe is unknown and called dark matter 0 We have never been able to detect light coming from this dark matter The universe also has an unknown form of energy called dark energy o It pushes galaxies apart even though gravity is trying to bring them together Dark matter and dark energy make up the majority of the universe History of the Universe The Universe began to expand in an event called the Big Bang 14 billion years ago 0 Two major pieces of evidence support the Big Bang 1 Radiation left over from the big bang This radiation is called the cosmic microwave background 2 The chemical compound of the universe 0 Universe has always been expanding since the Big Bang Clusters of galaxies get closer but the clusters get further from each other Stars are born when gravity compresses material until the center becomes hot enough to generate energy through the process of nuclear fusion 0 Nuclear Fusion Lightweight atomic nuclei smash together and stick to make heavier atoms 0 The fusion of hydrogen to helium gives the Sun the energy to shine The spin of the forming Sun causes planets and other objects to atten out into a disk Stars die by blowing their matter back into space Figuring Out What the Universe is Made of Evidence for stars forming larger mass 0 Stars of different ages exhibit the expected patterns of elements heavier than helium 0 We study the overall abundance of chemical elements in the universe 0 Studied star and gas explosions and analyzed the make up of the debds We need these larger atoms for life to exist Implications for Life in the universe We believe that other galaxies will have a similar composition to our own The Scale of Time Life of the Universe in 1 Year Every month is a little less than a billion years each day is about 40 million years and each second is about 400 years January 1 The Big Bang occurs Early February The Milky Way has formed Early September Our solar system and planets formed Late September Life is on Earth created but most are microscopic Mid December Recognizable animals walk on Earth December 26th Dinosaurs appear December 30th Dinosaurs wiped out and mammals begin to rule December 31st 90000pm Early hominids begin to walk December 31st 115959 Galileo proved Earth orbits the Sun The Observable Universe Observable Universe The portion of the universe that we can see We can t observe anything more than 14 billion light years away To us we are the center of the universe because we can only see light coming to Earth so we don t actually know where the center of the universe is Impossible to know the exact number of galaxies because some are too faint o 100 billion galaxies 100 billion stars per galaxy Because there are so many stars in the universe we only look for life in the Milky Way Fine Tuned Universe Anthropic Principle Humans are here to study the universe and its basic properties however if any of those properties were different then we wouldn t have been able to study them in the rst place The expansion of the universe couldn t have been too fast or too slow for life to exist The Nature of Worlds Inner planets all have a relatively small and circular orbit o All planets orbit in the same direction 0 Similar circumstances for large moons orbiting planets Two Major Types of Planets 1 Terrestrial Planets Rocky planets with small or no moons 2 Jovian Planets quotGas Giantsquot Large gas planets mad mostly of hydrogen and hydrogen compounds 0 They have tons of moons and some have rings made of countless small particles 0 The pressure is so high that the gases are condensed down into liquid forms Impossible to land a craft on the surface 0 Hydrogen Compounds Hydrogen based compounds Water Methane and Ammonia Terrestrial planets are much more likely to hold life because we assume life needs land to live on Kuiper Belt Kuiper Belt A group of asteroids rotating on the outside of our solar system Oort Cloud A spherically shaped region lled with trillions of comets o Pluto and other similar sized comets are referred to as Kuiper Belt Objects Moons Asteroids and comets can also have moons Some moons are planetlike 0 They orbit large gas giants like Jupiter and Saturn 0 These moons are similar in every way but their orbit 0 Made of ice and are because of the heat from the gas giants they have the potential to hold life Different Worlds Nebular Theory Our solar system was created by the gravitational collapse of an interstellar cloud Solar Nebula The particular cloud that birthed our solar system Forming the Solar System Once the cloud collapses on itself it begins to heat up and spin faster creating a at disk 0 Heating occurs due to the gas particles moving faster 0 The center becomes the hottest gt Sun forms in the middle 0 Gravitational potential energy transformed into heat Because of the conservation of angular momentum as the cloud gets smaller it spins faster 0 The spinning attens the solar system out into a disk Planet Formation Planets required seeds or large bits of solid matter to attract other mass to form a planet These seeds probably formed from particles condensing Accretion is the process when particles stick together and grow 0 The rst particles stuck together through electrostatic forces 0 Once the seed got big enough gravity would attract surrounding particles 0 Planetesimals formed from accretion Condensann 0 Solar Nebula 98 by mass of H and He 2 other 0 Tiny solid particles condense during cooling 0 Higher temperatures only metal and rock can condense o Lowe temperatures almost everything condense Except H2 and He which stay as gases Volatile elements condense at low temperatures Water Methane Ammonia O o Refractory elements have higher temperatures Minerals lron Nickel Aluminum 0 This explains why inner planets are made of rock and metal while outer planets are made of gas Near the Sun the temperature is to high for the gases to condense and form the seeds necessary to form planets Asteroids and Comets They are leftover planetesimals that didn t pull in other material Asteroids tend to be in the asteroid belt because Jupiter s gravity keeps them from crashing into each other 0 There were probably other asteroids earlier in time but they all crashed into each other or into other planets Comets are located in two main areas Kuiper Belt and Oort Cloud Kuiper Belt comets still orbit in the general area in which they were created 0 Outside of Neptune relatively low density of objects Oort cloud is thought to have comets that originated near the jovian planets 0 When one of these comets passed near a jovian planet it was ung out by the planet s gravity Once the gas was cleared from the universe the planets were set o If the gas had been blown out earlier the planets could have been swept away with them Are Habitable Worlds Common Because of how solar systems form we should expect other planets like Earth Some solar systems are laid out differently than our own and would not be suitable for holding life Matter and Energy All matter is made up of atoms 0 Different kinds of atoms are called elements Eg Oxygen lron Carbon 0 Atoms are made up of protons electrons and neutrons o Protons and neutrons form the core of the atom called the nucleus 0 Electrons orbit the nucleus in a cloud not similar to planet orbits Properties of atoms depend on the electrical charge in its nucleus 0 Electrical charge is how strongly it can attract other particles 0 Written as 1 or 1 etc o Electrons have a 1 charge while protons have a 1 charge 0 Most atoms have an equal number of protons and electrons so they are neutral Charged atoms are called ions ions have one less electron O ions have one more electron Atomic Terminology 0 Atomic Number The number of protons an atom contains makes up its element 0 Periodic Table of the Elements Complete table of over 100 known elements 0 Atomic Mass Number The sum of the number of protons and neutrons o lsotopes When two atoms are the same element same number of protons but they have a different number of neutrons Molecules are groups of atoms that stick together and act as one 0 Eg H20 02 C02 Molecules with 2 or more elements are called compounds Compounds containing carbon are called organic compounds Phases of Matter Almost everything exists in 3 phases solid liquid or gas Chemical bond the interactions between atoms that hold the molecule together Changes in temperature or pressure can change the phases 0 Ex At low temperatures water becomes ice but when heated it can phase change from ice to liquid water into water vapor Melting point 0 degrees Celsius is the temperature where ice begins to melt to water Boiling point 100 degrees Celsius is the temperature when liquid water evaporates into water vapor Molecules are always bouncing around no matter what phase they are in and sometimes a molecule with have enough energy to leave the object Sublimation The process by which some molecules escape a solid Evaporation The process by which some molecules escape a liquid Energy Energy is what makes matter move but there are many types of energy Kinetic Energy Energy of motion 0 Falling rocks running anything that is moving Radiative Energy Energy carried by light 0 All energy carried by light waves Potential Energy Stored Energy 0 A rock held over a tall building could be converted to kinetic energy if dropped Energy can not be created our destroyed but it can change phases Light Light travels at a nite speed 0 The speed of light constant c is 3 x 10quot8 ms The speed of light is only this fast in a vacuum Learni 0 When traveling through a medium such as air it is slower Light acts like a wave but also as a particle Light doesn t require a medium to move The speed of the wave can be found by multiplying the frequency by the wavelength Light is made up of particles called photons that travel at the speed of light 0 A photon of light is quantized The higher the frequency of the light wave the more energy the photon is carrying Energy h x frequency 0 h Planck s Constant or 663 x 10quot34 Highenergy light is blue lowenergy light is red Electromagnetic Spectrum Light can have waves that are longer and shorter than our eyes can see Electromagnetic waves are considered light waves because light is related to electricity and magnetism The entire range of different wavelengths of light is called the electromagnetic spectrum Shortest wavelengths are gamma rays or gamma radiation 0 Very high energy and penetrates matter easily Next shortest wavelength are Xrays Ultraviolet UV radiation has a slightly longer wavelength than Xrays Visible Light has the next shortest wave length and these are colors visible to the eye 0 Shortest wavelengths in violet and longest in red Infrared IR radiation has longer wavelengths than the color red 0 Often felt as heat Microwave Radiation is the second longest wavelength Radio waves are the longest wave in the electromagnetic spectrum Seen in the form of FM AM and TV signals ng from Light Spectroscopy Collecting light in a telescope and then dispersing it out into a spectrum 3 Basic types of spectra 0 1 Continuous Spectrum Smooth light with a variety of wavelengths o 2 Emission Line Spectrum Bright lines on a dark background 0 3 Absorption Line Spectrum Dark lines on a continuous background Thermal Radiation An object s surface temperature These help us determine what lights planets re ect and also what may lie on the surface Different isotopes also have different radiation Studying spectral lines allows us to know temperature rotation pressure density and magnetic eld strength Changing Ideas about the Formation of the Solar System Today we know that the solar system was born from a gravitational collapse of an interstellar cloud Immanuel Kant and PierreSimmon Laplace came up with the interstellar cloud idea and it became known as the nebular hypothesis 0 They had little evidence so the idea was buried Properties of Our Solar System Explained by the Nebular Theory 1 Orderly Motions of Large Bodies The theory should explain the orbits and rotations of large objects in our solar system All planets orbit the same way counterclockwise and rotate in the same direction 2 Two Types of Planets There are terrestrial planets and gas giants 3 Small Bodies Asteroids and comets largely outnumber planets 4 Exceptions to the Rules There are exceptions to how solar systems are 0 Eg Earth has a uniquely large moon for being an inner planet Nebular Model Didn t explain Laplace s idea of how planets formed successive rings of gas Close Encounter Hypothesis Two stars almost had a collision and blobs of gas were pulled out of the sun and formed the planets 0 Didn t account for the orbits so it lost favor Laplace s idea was replaced by the idea of condensation and accretion Late 20th C the nebular hypothesis was accepted as a theory Not set in stone because 0 1 There are extrasolar planets in other solar systems that are gas giants rotate closer to the sun than terrestrial planets o 2 Young star systems being viewed as they are create
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