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Life Beyond Earth.docx

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York University
Natural Science
NATS 1880
Paul Delaney

Life Beyond Earth Chapter 3 (The Universal Context of Life) Since Newton … • the universe is wast and old! implying a lot of real estate for life to develop upon and the time for it to evolve • the elements of life are widespread: carbon and long chain organic molecules (raw material) have been detected through the galaxy. • Physical laws seem universal : the process that evolved life on earth could occur anywhere. Key Concept *where are we in the universe and how did it all begin? • astronomy has defined where earth is in relation to other major components in the universe • the big bang theory has defined a possible evolutionary path and timeline for these components *How big is big? Our "cosmic address" is • planet in our solar system • solar system in our galaxy, milt way • our galaxy in local group • the local group is in the local supercluster • all a part of the universe A sense of scale: Planet distances • many ways to visualize the size of our Solar System • recall, the earth is 1 A(astronomical) U(nit) from the sun, 150 million Beyond the Solar System: to the stars! • a light year (ly) is the distance a photon of light will travel in a year • the scones in a year: -60 x 60 x 24 x 365. 25 =~ 3.156x10 power of 7 • the speed of light: 300,000 km per second • thus the distance light would travel in a year is 60 x 60 x 24 x 365. 25 x 300, 000 or 9. 46 x 10 power of 12 km!!! Alphas Centauri: our closest star system • 4.3 light year to alpha centauri (a ken) • if 1 AU = 1 metre, then a ken =271 km • our fastest spacecraft leaving the solar system,, voyager 1(50, 000 km per hour) would take about 100,00 years to get there • our technology is far too primitive to consider tips to the stars at this time A trip to a stellar nursery • the orion nebula (M42) is ~1500 ly away. Thus we are seeing the nebula as it was 1500 years ago. Our galaxy: the milky way • 100,000 ly across and home to ~200 billio stars and a lot of dark matter The universe contains • the universe contains all of the matter and energy in existence • matter that you would recognize (planets, stars, etc) so called baryonic matter: 4% • dark matter cannot be seen but does have a gravitational influence: 28% • dark energy (vacuum energy) cannot be seen but manifests itself as a "repulsive force": 68% The big bang: 13.8 billion years ago -observational evidence supports strongly that the universe was once compressed into a very hot, very dense point and that since that time the universe has continued to expand -galaxy motion is (by and large) away from the milky way • the cosmic microwave background radiation is the left over "echo" of the universe's hot beginnings • the distribution of the chemical elements has changed with time notably H and He initially and now many more elements Galaxies act as cosmic recycling plants • stars are created in galaxies by the collapse of clouds of hydrogen and helium • stars release energy as a result of nuclear fusion. For example, the formation of helium from hydrogen. Some mass "lost" becomes energy (E = m x c squared Further reflection on the age of the universe • the cosmic calendar equates 14 billion years to a 12 month calendar time span Andromeda, our galactic neighbour • we see andormeda today as it wazs 2.5 millii years ago. It will collide with us in ~4= billion years The Observable universe • the further away an object is from us the further back in time we are looking • we can only observe as far as light has travelled in the age of the universe, namely 13.8 billion light years The Hubble Deep Field • within the observable universe, based upon the HST Deep Field, lie at least 100 billion galaxies Terrestial (earth-like) planets • relatively small diameters • relatively high densities, rock and metals composition • orbit close to the sun (warmer surfaces) • thin (if any) atmosphere (carbon dioxide, oxygen, water vapour, etc) • few (if any) satellites (moons) • no ring systems Jovian or Gas-giants planets • relatively large diameters • relatively low densities, mostly gaseous composition (hydrogen, helium, hydrogen, compounds) • orbit further from the sun (colder surfaces) • thick ,substantial atmospheres • many satellites (moons) • ring systems Other bits and pieces • dwarf planets, asteroids (minor planets) and comets are also very common components in the Solar System. All "resemble" very small terrestrial planets with comets having a higher "volatile material " (gases) content that allow them to develop beautiful tails Medium and Large Moons • enough self-gravity to be spherical • have substantial amounts of ice • formed in orbit around Jovian planets • circular orbits in same direction as planet rotation Formation of the Solar System • small, rocky planets form close to sun and large gas planets grow in cooler regions further out • the sun starts to "shine" & the solar wind clears out remaining dust and gas Chapter 3 Alterntives to the Nebula Theory • nebula theory not the only hypothesis developed to explain our own solar systems formation (e.g. collision or catastrophic theories) but it is the theory that explains most observations • the variety of explanatory systems found to date have forced revision and flexibility into the Nebula Theory, the scientific method in action! atoms, the building blocks of matter • atoms are compromised of a positively charged nucleus containing protons and neutrons surrounded by a negatively charged electron cloud. ( classical model) • most atoms around you are electrically neutral. If they gain or lose electrons, they become charged and are referred to as ions. • as the nucleus is very small most atomic interactions arise through the electron cloud. atomic number = number of protons atoms mass number = number of protons + neutrons (a neutral atom has the same number of electrons as protons.) Terminology • 92 naturally occurring elements. Each element has a different number of protons in the nucleus, the atomic number for that element. • atoms can have a differs….. More terminology • atoms can combine to form molecules. if 2 or more elements combine, it is called a compound. h2o is the chemical formula for water and it is a compound. • molecules stay together because of the strength of the bonds between atoms. further the molecules stay close to each other by bonds swell. temperature can change the phase of the molecules. What makes matter move : energy • energy comes in different forms • kinetic energy is the energy of motion • radiants energy is the energy carried by light • potential energy is stored energy awaiting a use (as in to m ove or fall) • energy can transform from one type to another but it can neither be created nor destroyed (always conserved) Light: the carrier of information • light carries energy at a speed of 3x10 to the power of 8 m/sec (in a vacuum), the speed of light • it is essentially a combination of oscillating electric ad magnetic fields, hence the term electromagnetic radiation • it is characterised by a wavelength and thus a frequency. lIGHT DISPLAYS WAVE- LIKE PROPERTIES BUT CARRIES ENERGY IN DISTINCT PACKETS CALLED PHOTONS, a particle - like property Properties of light • the higher the frequency of light, the shorter the wavelength • the higher the frequency, the more energy is carried by the photons • theoretically, electromagnetic… Our atmosphere • not all light reaches the earths surface. Fortunately the most energetic frequencies are absorbed by the gasses in the atmosphere (e.g. ozone absorbs ultraviolet radiation). our atmosphere is not transparent to all frequencies • earths atmosphere absorbs light at most wavelengths Why is the sky blue? • atmosphere scatters blue light from the sun, making it appear to come from different directions • sunsets are red because less of the red light from the sun is scattered Information from light • distant objects emit light which we can receive and "decode" • the intensity of light gives some information but analyzing the lights " fundamental characteristics" or its spectrum revrelas a great deal more information • 3 types of spectrum exists: continuous, emission and absorption and all relate to different physical processes Chapter 3 Lighting at home - soft white ( color temperature t = 2700K) - bright white (colour temperature t = 3500 = 4100K) - daylight (colour temperature t = 5000 – 6500K) - all 3 relate to the plot of intensity as a function of wavelength and where each “temperature curve peaks” Doppler effect The apparent change in wavelength (or frequency) of a wave as experienced by an observer that arises from the relative motion of the source of the wave with respect to the receiver 4. The Habitability of earth What is a planet? The basic requirements to be deemed a planet according to the IAU are - it orbits the sun - it has sufficient mass to be spherical in shape (this is due to gravity) - it has “cleared: its planetary orbit of other objects The big picture - the complex interactions of the organisms in these different ecologies results in the integrated system of life on earth (the terrestrial biosphere0 Characteristics of a planet - position in the solar system - physical body and lithosphere of the planet (the geology of the planet) - magnetic field - atmosphere (air) and hydrosphere (water : oceans, lakes, rivers) Position – earth is the 3 planet from the sun in our solar system. At this distance water can exist in a liquid state. Only a narrow range of distances from a star allows this to occur – these distances are referred to as the habitable zone (existence of liquid water is the key actor in determining a habitable zone) – the seasons result from the fact that earth is tilted 23.5 degrees on its axis – earth also has a single moon. Compared to the size of earth our moon is very large. This causes the tides – the moon may also provide some protection from asteroid impacts Physical body Geology is the study of the earth and the processes which shape our planet. Geology on long time scales intertwines with life and its development. - earth has changed over time. As earth evolves the life that exists on it must evolve with it. - By extension, geology often means the study of other planetary surfaces Volcanoes Volcanoes are important since they allow material to escape from earths interior. This includes carbon dioxide and water vapour. They emerge as hot gasses… Spreading Zones - at spreading zones new land, usually seafloor, is being created. When a spreading zone first forms it can be on land but because they tnd tobe at lower elavations, eventually they are flooded and end up underwater. Subduction Zone - regions where one plate us sliding un der another. Near these zones there tend to be strong earthquakes and explosive volcanic activity - where the plates are moving into one another one plate slides under the other- this is called subduction zone. This collision of plates creates a mountain range Plate movement - this movement of the plates used to be referred to as continental drift but is now called plate tec tonics since
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