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. EXTRATERRESTRIAL LIFE Defined as life beyond the earth –“earth” includes on the surface, below the surface, in oceans and lakes, and in the atmosphere This could be life on another planet, or perhaps some other body: –a moon (smaller object that orbits around a planet)‏ –some other small object, like an asteroid or comet –a star –some other object (a neutron star?)‏ –out in space (not on any object)‏

3. EXTRATERRESTRIAL LIFE Level of advancement or complexity? –Could be technologically advanced (like aliens in science fiction)‏ –Could be intelligent, but not technologically advanced –Could be complex, but not very intelligent (like terrestrial animals or plants)‏ –Could be very simple, something like terrestrial bacteria Similarity to life on earth –Almost certainly won't be identical –May be VERY different –Need a definition of life

4. ARGUMENTS FOR THE EXISTENCE OF EXTRATERRESTRIAL LIFE WE DON’T THINK THERE IS ANYTHING UNUSUAL ABOUT THE EARTH. –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. –SOME OF THESE PLANETS ARE PROBABLY SIMILAR TO THE EARTH. WE THINK LIFE CAN GET STARTED EASILY IF THE CONDITIONS ARE RIGHT. –LIFE ON EARTH CAN SURVIVE UNDER A WIDE VARIETY OF CONDITIONS. –EXPERIMENTS SHOW THAT THE MATERIALS FROM WHICH LIVING THINGS ARE MADE FORM EASILY. –LIFE DEVELOPED VERY EARLY IN THE HISTORY OF THE EARTH. THEREFORE, IT WOULD PROBABLY ALSO DO SO ANYWHERE ELSE WITH SIMILAR CONDITIONS.

5. 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.

6. OUR APPROACH STUDY ASTRONOMY TO FIND OUT WHAT TYPES OF OBJECTS MIGHT PROVIDE SUITABLE ENVIRONMENTS FOR LIFE, AND HOW COMMON THESE SUITABLE ENVIRONMENTS FOR LIFE ARE LIKELY TO BE. STUDY BIOLOGY TO LEARN ABOUT THE ORIGIN AND EVOLUTION OF LIFE ON THE EARTH – THE ONLY EXAMPLE OF LIFE WE KNOW ABOUT. USE THIS KNOWLEDGE TO ESTIMATE HOW LIKELY WE ARE TO SUCCEED IN FINDING EXTRATERRESTRIAL LIFE. STUDY TECHNOLOGICAL POSSIBILITIES FOR DISCOVERING EXTRATERRESTRIAL LIFE AND/OR COMMUNICATING WITH EXTRRATERRESTRIAL CIVILIZATIONS.

7. 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.” WE HAVE STRONG EVIDENCE THAT THE LAWS OF PHYSICS ARE UNIVERSAL. APPLY CRITICAL THINKING SKILLS AT ALL STAGES. BE SKEPTICAL OF OUTRAGEOUS CLAIMS.

8. THE SCIENTIFIC METHOD 1. MAKE OBSERVATIONS. 2. ASK A QUESTION. 3. MAKE A HYPOTHESIS (A CONCEPTUAL AND/OR MATHEMATICAL FRAMEWORK FOR UNDERSTANDING) THAT IS CONSISTENT WITH THE KNOWN FACTS. 4. USE THE HYPOTHESIS TO PREDICT THE RESULTS OF EXPERIMENTS. 5. CONDUCT THE EXPERIMENTS. 6. IF EXPERIMENTAL RESULTS DISAGREE WITH THE HYPOTHESIS, REPLACE OR MODIFY THE HYPOTHESIS AND REPEAT THE PROCESS. 7. IF EXPERIMENTAL RESULTS AGREE WITH THE HYPOTHESIS, CONTINUE WITH MORE EXPERIMENTS TO DOUBLE-CHECK THE HYPOTHESIS.

9. THE SCIENTIFIC METHOD A SINGLE EXPERIMENTAL FACT THAT DISAGREES WITH THE PREDICTIONS OF A THEORY OR HYPOTHESIS WILL DISPROVE THAT HYPOTHESIS. (THIS DISTINGUISHES SCIENCE FROM PSEUDOSCIENCE.)‏ IN CONTRAST, A HYPOTHESIS CAN NEVER BE PROVEN BEYOND A SHADOW OF DOUBT. IT IS POSSIBLE THAT SOME FUTURE EXPERIMENT WILL DISPROVE THE HYPOTHESIS, OR THAT ANOTHER HYPOTHESIS (THE “RIGHT” ONE) CAN EXPLAIN THE SAME EXPERIMENTAL FACTS. THE BEST WE CAN DO IS TO ACCUMULATE MORE AND MORE EVIDENCE THAT IS CONSISTENT WITH THE HYPOTHESIS, IN WHICH CASE IT EVENTUALLY BECOMES A “THEORY,” THEN A “LAW.” IF TWO HYPOTHESES CAN EXPLAIN THE SAME EXPERIMENTAL FACTS, WE PREFER THE SIMPLER HYPOTHESIS (“OCCAM'S RAZOR”)‏

10. 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

11. 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)‏

12. 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

13. 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

14. 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

15. 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 D 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 (ATOMIC NUMBER) SPECIFIES THE IDENTITY OF ELEMENT. EXAMPLES: 1 IS HYDROGEN, 2 IS HELIUM, 6 IS CARBON, 8 IS OXYGEN, 26 IS IRON.

16. MATTER ELECTRON: NEGATIVELY CHARGED PARTICLE ORBITING AROUND THE NUCLEUS. IN A NEUTRAL ATOM, NUMBER OF ELECTRONS = NUMBER OF PROTONS. NEUTRON: NEUTRAL (NO ELECTRIC CHARGE) PARTICLE IN THE NUCLEUS, ADDS MASS TO NUCLEUS, DETERMINES THE ISOTOPE. ISOTOPE: VARIETY OF AN ELEMENT WITH A SPECIFIC NUMBER OF NEUTRONS. EXAMPLE: 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)‏

17. 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. THE ATOMS ARE HELD TOGETHER BY CHEMICAL BONDS. 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). THE PROPERTIES OF A COMPOUND ARE VERY DIFFERENT FROM THE PROPERTIES OF THE ELEMENTS THAT MAKE IT UP. FOR EXAMPLE, WATER IS QUITE DIFFERENT FROM HYDROGEN AND OXYGEN. CHEMISTRY: THE STUDY OF HOW ATOMS CAN COMBINE TO FORM MOLECULES HOW MOLECULES CAN BE BROKEN APART INTO ATOMS HOW MOLECULES CAN INTERACT WITH EACHOTHER, SWAPPING ATOMS TO FORM DIFFERENT MOLECULES.

18. MATTER SIZES: AN ATOM IS APPROXIMATELY (DEPENDING ON THE ELEMENT) 10 -10 METERS (0.0000000001 m) IN DIAMETER. THE NUCLEUS OF THE ATOM IS APPROXIMATELY 10 -15 METERS (0.000000000000001 m) IN DIAMETER. THIS MEANS THAT THE DIAMETER OF THE NUCLEUS IS ONLY ABOUT 1/100,000 OF THE DIAMETER OF THE ATOM. THUS AN ATOM IS MOSTLY EMPTY SPACE (BETWEEN THE NUCLEUS AND THE ELECTRONS). MASSES: EVEN THOUGH THE NUCLEUS IS MUCH SMALLER THAN THE ENTIRE ATOM, THE NUCLEUS CONTAINS MOST OF THE MASS OF THE ATOM. THE ELECTRONS ARE MUCH LIGHTER. THE MASS OF A PROTON IS CLOSE TO THE SAME AS THE MASS OF A NEUTRON. THE MASS OF AN ELECTRON IS ONLY ABOUT 1/2000 OF THE MASS OF A PROTON OR NEUTRON.

19. PHASES OF MATTER EVERY SUBSTANCE (ELEMENT OR COMPOUND) CAN BE FOUND IN THREE PHASES: –SOLID -- MOLECULES ARE HELD CLOSE TOGETHER IN A RIGID GEOMETRICAL ARRANGEMENT. –LIQUID – MOLECULES ARE CLOSE TOGETHER, BUT CAN MOVE RELATIVE TO EACH OTHER. –GAS – MOLECULES ARE FARTHER APART AND CAN FLY AROUND INDEPENDENTLY OF EACH OTHER. AS TEMPERATURE INCREASES, A SOLID MELTS TO BECOME A LIQUID, THEN BOILS TO BECOME A GAS. AS TEMPERATURE DECREASES, A GAS CONDENSES TO BECOME A LIQUID, THEN FREEZES TO BECOME A SOLID. THE BOILING POINT (TEMPERATURE AT WHICH A LIQUID BOILS OR A GAS CONDENSES) AND MELTING POINT (TEMPERATURE AT WHICH A SOLID MELTS OR A LIQUID FREEZES) DEPENDS ON THE SUBSTANCE (AND THE PRESSURE). –EXAMPLE: WATER AT “NORMAL” ATMOSPHERIC PRESSURE BOILS AT 100 O C (212 O F) AND FREEZES AT 0 O C (32 O F)‏

20. TEMPERATURE MOLECULES ARE ALWAYS IN MOTION. THE DIRECTIONS OF MOTION ARE RANDOM. DIFFERENT MOLECULES MOVE IN DIFFERENT DIRECTIONS. THE HIGHER THE TEMPERATURE OF AN OBJECT, THE FASTER THE MOLECULES INSIDE IT ARE MOVING, ON THE AVERAGE. AT A GIVEN TEMPERATURE, NOT ALL MOLECULES MOVE AT THE SAME SPEED. SOME MOVE FASTER THAN AVERAGE, AND SOME MOVE SLOWER THAN AVERAGE. IMAGINE A COLLECTION OF MOLECULES, SOME LIGHTER AND SOME HEAVIER, ALL AT THE SAME TEMPERATURE. THE LIGHTER MOLECULES ARE FASTER AND THE HEAVIER MOLECULES ARE SLOWER, ON THE AVERAGE.

21. 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.

22. 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 ORLEFT 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

23. 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

24. 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

25. 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

26. 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

27. 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

28. FORMS OF ENERGY KINETIC ENERGY – ENERGY OF MOTION POTENTIAL (STORED) ENERGY –ELASTIC (LIKE A STRETCHED OR COMPRESSED SPRING)‏ –GRAVITATIONAL –ELECTRICAL –CHEMICAL –NUCLEAR LIGHT SOUND THERMAL (HEAT) ENERGY – KINETIC ENERGY OF RANDOM MOTION OF MOLECULES MASS (E = m c 2 )‏

29. CONSERVATION OF ENERGY ENERGY CANNOT BE CREATED OR DESTROYED. ENERGY CAN BE CHANGED FROM ONE FORM TO ANOTHER. ENERGY CAN BE TRANSFERRED FROM ONE OBJECT TO ANOTHER.

30. FUNDAMENTAL FORCES GRAVITATIONAL FORCE –OCCURS BETWEEN MASSES –THE LARGER EITHER MASS IS, THE STRONGER THE FORCE –THE LARGER THE DISTANCE BETWEEN THE MASSES, THE WEAKER THE FORCE –ALWAYS ATTRACTIVE (PULLS MASSES TOGETHER)‏ –THE GRAVITATIONAL FORCE OF THE EARTH ON ORDINARY OBJECTS HOLDS THE OBJECTS ON THE EARTH'S SURFACE –THE GRAVITATIONAL FORCE OF THE SUN ON THE EARTH KEEPS THE EARTH IN ORBIT AROUND THE SUN –THE GRAVITATIONAL FORCE OF THE EARTH ON THE MOON KEEPS THE MOON IN ORBIT AROUND THE EARTH

31. FUNDAMENTAL FORCES ELECTRICAL FORCE –OCCURS BETWEEN ELECTRIC CHARGES –THE LARGER THE EITHER CHARGE IS, THE STRONGER THE FORCE –THE LARGER THE DISTANCE BETWEEN THE CHARGES, THE WEAKER THE FORCE – ATTRACTIVE (PULLS CHARGES TOGETHER) IF ONE CHARGE IS POSITIVE AND THE OTHER CHARGE IS NEGATIVE –REPULSIVE (PUSHES CHARGES APART) IF BOTH CHARGES ARE POSITIVE OR IF BOTH CHARGES ARE NEGATIVE –THE ELECTRICAL FORCE OF THE NUCLEUS OF AN ATOM (POSITIVELY CHARGED) ON THE ELECTRONS (NEGATIVELY CHARGED) KEEPS THE ELECTRONS IN ORBIT AROUND THE NUCLEUS

32. INVERSE SQUARE LAW BOTH GRAVITY AND THE ELECTRICAL FORCE OBEY AN “INVERSE SQUARE LAW.” THIS MEANS THAT THE STRENGTH OF THE FORCE IS PROPORTIONAL TO 1/D 2, WHERE D = DISTANCE BETWEEN INTERACTING OBJECTS (MASSES OR CHARGES). –IF THE DISTANCE BETWEEN THE OBJECTS IS DOUBLED, THE FORCE BECOMES 1/4 AS STRONG. –IF THE DISTANCE BETWEEN THE OBJECTS IS TRIPLED, THE FORCE BECOMES 1/9 AS STRONG. –OF THE DISTANCE BETWEEN THE ONJECTS IS CUT IN HALF, THE FORCE BECOMES 4 TIMES STRONGER. THE BRIGHTNESS OF A LIGHT SOURCE (LIKE A STAR) ALSO OBEYS AN INVERSE SQUARE LAW. –IF YOUR DISTANCE FROM THE STAR IS DOUBLED, THE BRIGHTNESS BECOMES 1/4 AS MUCH. –IF YOUR DISTANCE FROM THE STAR IS TRIPLED, THE BRIGHTNESS BECOMES 1/9 AS MUCH. –IF YOUR DISTANCE FROM THE STAR IS CUT IN HALF, THE BRIGHTNESS BECOMES 4 TIMES AS MUCH.