NSCI 314LIFE IN THE COSMOS1- INTRODUCTION MATTER, LIGHT, AND THE UNIVERSEDr. Karen KolehmainenDepartment of PhysicsCSUSBCOURSE WEBPAGE:http://physics.csusb.edu/~karenARGUMENTS FOR THE EXISTENCE OF EXTRATERRESTRIAL LIFEWE DON’T THINK THERE IS ANYTHING UNUSUAL ABOUT THE EARTH OR THE CONDITIONS THAT ALLOWED LIFE TO TO DEVELOP HERE.–THE SUN IS AN ORDINARY STAR, ONE OF ABOUT 400 BILLION IN THE MILKY WAY GALAXY.–THE MILKY WAY GALAXY IS AN ORDINARY GALAXY, ONE OF AT LEAST A TRILLION IN THE UNIVERSE.–PLANETS ARE KNOWN TO ORBIT MOST STARS, SO THE EARTH IS PROBABLY NOT UNIQUE.–THE ORIGIN OF LIFE IS THOUGHT TO INVOLVE ORDINARY AND COMMON MATERIALS AND PROCESSES.LIFE DEVELOPED VERY EARLY IN THE HISTORY OF THE EARTH. THEREFORE, IT WOULD PROBABLY ALSO DO SO ANYWHERE ELSE WITH SIMILAR CONDITIONS.ARGUMENTS AGAINST THE EXISTENCE OF EXTRATERRESTRIAL LIFEMAYBE THE EARTH IS UNUSUAL IN WAYS THAT WE DON’T FULLY APPRECIATE.WE HAVE DISCOVERED NO REAL EVIDENCE FOR EXTRATERRESTRIAL LIFE.–THERE IS NO GOOD EVIDENCE THAT EXTRATERRESTRIALS HAVE EVER VISITED EARTH.–WE HAVE NOT RECEIVED ANY RADIO OR OTHER SIGNALS THAT ARE OBVIOUSLY THE RESULT OF AN EXTRATERRESTRIAL CIVILIZATION.–SPACECRAFT VISITING SEVERAL OTHER BODIES IN OUR SOLAR SYSTEM HAVE FOUND NO LIFE.OUR APPROACHSTUDY ASTRONOMY TO FIND OUT HOW COMMON SUITABLE ENVIRONMENTS FOR LIFE ARE LIKELY TO BE.STUDY BIOLOGY TO LEARN ABOUT THE ORIGIN AND EVOLUTION OF LIFE ON THE EARTH – OUR SINGLE EXAMPLE.USE THIS KNOWLEDGE TO ESTIMATE HOW LIKELY WE ARE TO SUCCEED IN FINDING EXTRATERRESTRIAL LIFE. STUDY TECHNOLOGICAL ALTERNATIVES FOR DISCOVERING EXTRATERRESTRIAL LIFE AND/OR COMMUNICATING WITH EXTRRATERRESTRIAL CIVILIZATIONS.THINGS TO KEEP IN MIND…REMEMBER THAT OUR ESTIMATES OF HOW COMMON LIFE MIGHT BE WILL BE MOST VALID WHEN APPLIED TO LIFE SIMILAR TO OUR OWN. THE EXISTENCE OF EXOTIC AND UNFAMILIAR LIFE FORMS WILL BE MORE DIFFICULT TO PREDICT.HOWEVER, THIS DOESN’T MEAN THAT “ANYTHING GOES.” THE LAWS OF PHYSICS ARE UNIVERSAL.APPLY CRITICAL THINKING SKILLS AT ALL STAGES. BE SKEPTICAL OF OUTRAGEOUS CLAIMS.THE SCIENTIFIC METHOD1. MAKE A HYPOTHESIS (A CONCEPTUAL AND/OR MATHEMATICAL FRAMEWORK FOR UNDERSTANDING) THAT IS CONSISTENT WITH THE KNOWN FACTS.2. USE THE HYPOTHESIS TO PREDICT THE RESULTS OF EXPERIMENTS.3. CONDUCT THE EXPERIMENTS.4. IF EXPERIMENTAL RESULTS DISAGREE WITH THE HYPOTHESIS, REPLACE OR MODIFY THE HYPOTHESIS AND REPEAT THE PROCESS.5. IF EXPERIMENTAL RESULTS AGREE WITH THE HYPOTHESIS, CONTINUE WITH MORE EXPERIMENTS TO DOUBLE-CHECK, UNTIL EVENTUALLY HYPOTHESIS BECOMES A “LAW.”THE SCIENTIFIC METHODA SINGLE EXPERIMENTAL FACT THAT DISAGREES WITH THE PREDICTIONS OF A THEORY OR HYPOTHESIS WILL DISPROVE THAT HYPOTHESIS.IN CONTRAST, A HYPOTHESIS CAN NEVER BE PROVEN. IT IS ALWAYS POSSIBLE THAT AN ALTERNATIVE HYPOTHESIS CAN EXPLAIN THE SAME EXPERIMENTAL FACTS. THE BEST WE CAN DO IS TO ACCUMULATE MORE AND MORE EVIDENCE THAT IS CONSISTENT WITH THE HYPOTHESIS.LARGE NUMBERS1 THOUSAND = 1,000 = 103 = 10 x 10 x 10103 SECONDS IS ABOUT 17 MINUTESLECTURE LASTS 6600 SECONDS1 MILLION = 1,000,000 = 106 = 10x10x10x10x10x10106 SECONDS IS ABOUT 12 DAYS1 BILLION = 1,000,000,000 = 109109 SECONDS IS ABOUT 32 YEARSAVERAGE HUMAN LIFETIME IS ABOUT 2.5 BILLION SECONDS1 TRILLION = 1,000,000,000,000 = 10121012 SECONDS IS ABOUT 32,000 YEARSMETRIC UNITSDistance/Length: measured in meters (m) or kilometers (km) 1 km = 1000 m1 m = a little over 3 feet1 km = about 0.62 milesMass: measured in grams (g) or kilograms (kg)1 kg = 1000 g1 kg corresponds to about 2.2 poundsTime: measured in seconds (s)MATTERELEMENT: A FUNDAMENTAL TYPE OF SUBSTANCE. EXAMPLES ARE HYDROGEN, HELIUM, CARBON, OXYGEN, AND IRON. THERE ARE 92 NATURALLY OCCURRING ELEMENTS, AND ABOUT 110 ELEMENTS TOTAL (INCLUDING THOSE PRODUCED IN THE LABORATORY). ELEMENTS ARE OFTEN ARRANGED ON A CHART CALLED THE PERIODIC TABLE. (SEE APPENDIX C OF TEXTBOOK.) THE SMALLEST PARTICLE OF A GIVEN ELEMENT IS AN ATOM.ATOM: COMPOSED OF PROTONS AND NEUTRONS IN A NUCLEUS, WITH ELECTRONS ORBITING AROUND IT. AN ATOM IS HELD TOGETHER BY THE ELECTRICAL FORCE BETWEEN THE POSITIVELY CHARGED NUCLEUS AND THE NEGATIVELY CHARGED ELECTRONS.PROTON: POSITIVELY CHARGED PARTICLE IN THE NUCLEUS OF AN ATOM. THE NUMBER OF PROTONS SPECIFIES THE IDENTITY OF ELEMENT, e.g. 1 IS HYDROGEN, 2 IS HELIUM, 6 IS CARBON, 8 IS OXYGEN, 26 IS IRON.MATTERELECTRON: NEGATIVELY CHARGED PARTICLE ORBITING AROUND THE NUCLEUS. IN A NEUTRAL ATOM, NUMBER OF ELECTRONS = NUMBER OF PROTONS.NEUTRON: NEUTRAL (NO CHARGE) PARTICLE IN THE NUCLEUS, ADDS MASS TO NUCLEUS, DETERMINES THE ISOTOPE.ISOTOPE: VARIETY OF AN ELEMENT WITH A SPECIFIC NUMBER OF NEUTRONS; e.g. THE ISOTOPES OF CARBON ARE 12C (6p + 6n), 13C (6p + 7n), 14C (6p + 8n). FOR EACH ELEMENT, USUALLY ONE ISOTOPE IS COMMON AND THE OTHERS ARE RARE.ION: AN ATOM IN WHICH THE NUMBER OF ELECTRONS DOES NOT EQUAL THE NUMBER OF PROTONS, i.e., ELECTRONS HAVE BEEN ADDED OR REMOVED. THE IDENTITY OF THE ELEMENT IS RETAINED (SINCE THE NUMBER OF PROTONS IS UNCHANGED)MATTERMOLECULE: SEVERAL ATOMS BOUND TOGETHER. THE ATOMS CAN BE OF THE SAME ELEMENT, e.g. O2 AND N2; OR DIFFERENT ELEMENTS, e.g. CO2 AND H2OCOMPOUND: A SUBSTANCE WHOSE MOLECULES CONSIST OF ATOMS OF TWO OR MORE DIFFERENT ELEMENTS, e.g., CO2 (CARBON DIOXIDE) AND H2O (WATER).SPEED, DISTANCE, AND TIMESPEED = DISTANCE TIMEExample: An object that travels a distance of 6 meters (m) in a time of 3 seconds (s) has an average speed of 2 meters per second (m/s).Note that speed has units of distance/time, e.g., m/s, km/hr, mi/hr.DISTANCE = SPEED x TIMETIME = DISTANCE SPEEDSPEED OF LIGHTLight always travels at the same speed (c) through a vacuum (empty space).c = 300,000 km/s = 3 x 105 km/sLight travels 300,000 km in 1 second!How far does light travel in a year?(300,000 km/s) X (60 s/min) X (60 min/hr) X (24 hr/day) X (365 days/year)= 9,500,000,000,000 km = 9.5 X 1012 kmSPEED OF LIGHT9,500,000,000,000 km = 9.5 x 1012 km= ONE LIGHT YEAR (LY)SPEED OF LIGHT = 1 LIGHT YEAR 1 YEAREXAMPLE: How long a time does it take light to reach us from a star located 200 LY away?ANSWER: 200 yearsTHE DUAL NATURE OF LIGHT: PARTICLES AND WAVESSOMETIMES LIGHT BEHAVES LIKE A WAVE (AN OSCILLATING ELECTROMAGNETIC FIELD).SOMETIMES LIGHT BEHAVES LIKE A STREAM OF PARTICLES.WHICH IS IT? NEITHER, BUT BOTH ARE USEFUL WAYS TO THINK