1. NSCI 314 LIFE IN THE COSMOS 1- INTRODUCTION MATTER, LIGHT, AND THE UNIVERSE Dr. Karen Kolehmainen Department of Physics CSUSB COURSE WEBPAGE: http://physics.csusb.edu/~karen

2. ARGUMENTS 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.

3. 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.

4. 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.

5. 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.

6. THE SCIENTIFIC METHOD 1. 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.”

7. THE SCIENTIFIC METHOD A 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.

8. LARGE NUMBERS 1 THOUSAND = 1,000 = 10 3 = 10 x 10 x 10 10 3 SECONDS IS ABOUT 17 MINUTES LECTURE LASTS 6600 SECONDS 1 MILLION = 1,000,000 = 10 6 = 10x10x10x10x10x10 10 6 SECONDS IS ABOUT 12 DAYS 1 BILLION = 1,000,000,000 = 10 9 10 9 SECONDS IS ABOUT 32 YEARS AVERAGE HUMAN LIFETIME IS ABOUT 2.5 BILLION SECONDS 1 TRILLION = 1,000,000,000,000 = 10 12 10 12 SECONDS IS ABOUT 32,000 YEARS

9. METRIC UNITS Distance/Length: measured in meters (m) or kilometers (km) 1 km = 1000 m 1 m = a little over 3 feet 1 km = about 0.62 miles Mass: measured in grams (g) or kilograms (kg) 1 kg = 1000 g 1 kg corresponds to about 2.2 pounds Time: measured in seconds (s)

10. 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.

11. 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 12 C (6p + 6n), 13 C (6p + 7n), 14 C (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)

12. MATTER MOLECULE: SEVERAL ATOMS BOUND TOGETHER. THE ATOMS CAN BE OF THE SAME ELEMENT, e.g. O 2 AND N 2 ; OR DIFFERENT ELEMENTS, e.g. CO 2 AND H 2 O COMPOUND: A SUBSTANCE WHOSE MOLECULES CONSIST OF ATOMS OF TWO OR MORE DIFFERENT ELEMENTS, e.g., CO 2 (CARBON DIOXIDE) AND H 2 O (WATER).

13. SPEED, DISTANCE, AND TIME SPEED = DISTANCE TIME Example: 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 TIME TIME = DISTANCE SPEED

14. SPEED OF LIGHT Light always travels at the same speed (c) through a vacuum (empty space). c = 300,000 km/s = 3 x 10 5 km/s Light 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 10 12 km

15. SPEED OF LIGHT 9,500,000,000,000 km = 9.5 x 10 12 km = ONE LIGHT YEAR (LY) SPEED OF LIGHT = 1 LIGHT YEAR 1 YEAR EXAMPLE: How long a time does it take light to reach us from a star located 200 LY away? ANSWER: 200 years

16. THE 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 ABOUT IT.

17. IF THIS SKETCH REPRESENTS A WATER WAVE, THE HEIGHT OF THE WATER CHANGES AS YOU MOVE TO THE RIGHT OR LEFT. FOR A LIGHT WAVE, THE STRENGTH OF AN ELECTROMAGNETIC FIELD CHANGES AS YOU MOVE TO THE RIGHT OR LEFT. THE WAVE TRAVELS EITHER TO THE RIGHT OR LEFT AT THE SPEED OF LIGHT. SPEED OF LIGHT: c = 300,000 km/s c = 1 light year / year (SAME SPEED FOR ALL LIGHT WAVES IN A VACUUM) THE WAVE NATURE OF LIGHT

18. WAVELENGTH = DISTANCE BETWEEN TWO ADJACENT PEAKS FREQUENCY = NUMBER OF WAVES OR PEAKS PASSING BY A GIVEN LOCATION PER SECOND 1 Hertz = 1 wave per second passing by 1 kHz = 1,000 Hz 1 MHz = 1,000 kHz = 1,000,000 Hz WAVELENGTH x FREQUENCY = SPEED OF WAVE THE WAVE NATURE OF LIGHT

19. WAVELENGTH x FREQUENCY = SPEED OF WAVE SINCE THE SPEED IS THE SAME FOR ALL LIGHT WAVES (c), BIGGER FREQUENCY MEANS SMALLER WAVELENGTH, AND VICE VERSA. FOR LIGHT WAVES, FREQUENCY AND WAVELENGTH ARE RELATED TO COLOR. -THE SMALLER THE WAVELENGTH, THE LARGER (OR HIGHER) THE FREQUENCY, AND THE BLUER THE COLOR. -THE LARGER THE WAVELENGTH, THE SMALLER (OR LOWER) THE FREQUENCY, AND THE REDDER THE COLOR. THE WAVE NATURE OF LIGHT

20. AMPLITUDE = HEIGHT OF THE WAVE (TECHNICALLY, IT'S DEFINED AS HALF OF THE TOTAL HEIGHT) THE LARGER THE AMPLITUDE, THE BRIGHTER THE LIGHT. THE SMALLER THE AMPLITUDE, THE FAINTER THE LIGHT. THE WAVE NATURE OF LIGHT

21. THE PARTICLE NATURE OF LIGHT PHOTON = A PARTICLE OF LIGHT. A PHOTON CARRIES ENERGY. THE AMOUNT OF ENERGY THAT EACH PHOTON HAS IS RELATED TO THE COLOR OF THE LIGHT (AND THEREFORE ALSO TO WAVELENGTH AND FREQUENCY OF THE CORRRESPONDING WAVE). THE LARGER THE ENERGY PER PHOTON – THE SHORTER THE WAVELENGTH – THE HIGHER THE FREQUENCY – THE BLUER THE COLOR THE SMALLER THE ENERGY PER PHOTON – THE LONGER THE WAVELENGTH – THE LOWER THE FREQUENCY – THE REDDER THE COLOR

22. LONG WAVELENGTH LOW FREQUENCY LOW ENERGY PER PHOTON SHORT WAVELENGTH HIGH FREQUENCY HIGH ENERGY PER PHOTON ELECTROMAGNETIC SPECTRUM TYPE GAMMA RAYS X- RAYS ULTRAVIOLET VISIBLE LIGHT INFRARED MICROWAVE TV & FM RADIO AM RADIO WAVELENGTH SIZE OF ATOM VIRUS BACTERIA DUST 1 cm 1 m 100 m FREQUENCY VERY HIGH HIGH BILLION MHz MILLION MHz 1000 MHz 100MHz 1000 kHz

23. SOME BASIC ASTRONOMY STAR: A VERY LARGE, HOT BALL OF GAS THAT EMITS LARGE AMOUNTS OF LIGHT. THE LIGHT AND HEAT (BOTH OF THESE ARE FORMS OF ENERGY) ARE PRODUCED BY NUCLEAR FUSION (i.e., SMALL NUCLEI COMBINING TO PRODUCE LARGER NUCLEI) OCCURRING IN THE CENTER. PLANET: A FAIRLY LARGE OBJECT (BUT MUCH SMALLER THAN A STAR) THAT ORBITS AROUND A STAR. IT CAN BE ROCKY OR GASEOUS. THERE IS NO NUCLEAR FUSION OCCURRING INSIDE. MOON: A SMALLER OBJECT THAT ORBITS AROUND A PLANET.

24. SOME BASIC ASTRONOMY EARTH: THE PLANET UPON WHICH WE LIVE. SUN: THE STAR AROUND WHICH THE EARTH ORBITS. SOLAR SYSTEM: OUR SUN, THE 8 PLANETS AND SMALLER BODIES (COMETS, ASTEROIDS, ETC.) THAT ORBIT IT, AND THE MOONS THAT ORBIT THE PLANETS. GALAXY: A LARGE CLUSTER OF STARS (1 MILLION TO 1 TRILLION STARS). MANY OF THESE STARS HAVE THEIR OWN SOLAR SYSTEMS. THE MILKY WAY: THE GALAXY IN WHICH OUR SOLAR SYSTEM IS LOCATED. IT CONTAINS ABOUT 400 BILLION STARS, PLUS ANY OTHER PLANETS AND SMALLER BODIES ORBITING THESE STARS.

25. SOME BASIC ASTRONOMY UNIVERSE: EVERYTHING THAT EXISTS. WITH POWERFUL TELESCOPES, WE CAN SEE ABOUT 100 BILLION OBSERVABLE GALAXIES. THE TOTAL NUMBER OF GALAXIES IN THE UNIVERSE IS LIKELY TO BE MUCH HIGHER, PROBABLY AT LEAST 1 TRILLION. BIG BANG: AN EXPLOSION THAT STARTED THE UNIVERSE APPROXIMATELY 13.7 BILLION YEARS AGO. ALL OF THE MATTER IN THE UNIVERSE WAS EXPELLED OUTWARD FROM THE EXPLOSION. GALAXIES ARE STILL MOVING APART FROM EACH OTHER AS A RESULT. (BY COMPARISON, OUR SOLAR SYSTEM IS ONLY 4.6 BILLION YEARS OLD.)

26. MOTIONS IN THE SOLAR SYSTEM EACH PLANET SPINS OR ROTATES ON ITS OWN AXIS, PRODUCING DAY AND NIGHT. THE EARTH SPINS ONCE EVERY DAY, OR 24 HOURS. EACH PLANET ORBITS OR REVOLVES AROUND THE SUN. THE EARTH COMPLETES ONE ORBIT IN A YEAR, OR 365 DAYS. THE FARTHER A PLANET IS FROM THE SUN, THE LONGER IT TAKES TO COMPLETE ONE ORBIT (i.e., THE LONGER ITS YEAR). MOONS ORBIT OR REVOLVE AROUND PLANETS. THE EARTH'S MOON TAKES ABOUT A MONTH TO COMPLETE ONE ORBIT AROUND THE EARTH. SEASONS ARE CAUSED BY THE FACT THAT THE EARTH'S ROTATIONAL AXIS (THE LINE IT ROTATES AROUND) IS TIPPED.

27. UNITS FOR MEASURING DISTANCES ASTRONOMICAL UNIT (AU) –THE AVERAGE DISTANCE BETWEEN THE EARTH AND THE SUN –ABOUT 150,000,000 KM –A UNIT OF DISTANCE USED WITHIN THE SOLAR SYSTEM LIGHT YEAR (LY) –THE DISTANCE LIGHT TRAVELS IN ONE YEAR –ABOUT 9.5 x 10 12 KM OR 6333 AU –A UNIT OF DISTANCE USED FOR STARS PARSEC (PC) –ABOUT 3.26 LIGHT YEARS –ANOTHER UNIT OF DISTANCE USED FOR STARS

28. NAMEDistance From Sun MERCURY0.4 AU VENUS0.7 EARTH1.0 MARS1.5 JUPITER5.2 SATURN9.5 URANUS19 NEPTUNE30 ALL PLANETS ORBIT THE SUN IN THE SAME DIRECTION, AND THEIR ORBITS ARE NEARLY IN THE SAME PLANE. THUS, THE SOLAR SYSTEM IS SHAPED LIKE A FLATTENED DISK. PLANETS IN OUR SOLAR SYSTEM

29. SHAPEFLATTENED DISK DIAMETER100,000 LY THICKNESS2,000 LY NUMBER OF STARS400 BILLION ROTATION PERIOD250 MILLION YEARS SUN’S DISTANCE FROM CENTER30,000 LY AVERAGE DISTANCE BETWEEN STARS 5 LY TYPICAL STAR0.5 SOLAR MASSES MILKY WAY GALAXY

32. ACROSS UNITED STATES0.02 SECONDS EARTH TO MOON1.3 SECONDS EARTH TO SUN8 MINUTES ACROSS SOLAR SYSTEMFEW HOURS NEAREST STAR (BEYOND SUN)4 YEARS ACROSS MILKY WAY GALAXY100,000 YEARS NEAREST OTHER GALAXY2 MILLION YRS FARTHEST GALAXIES10 BILLION YRS LIGHT TRAVEL TIMES