19 - LIFETIMES OF TECHNOLOGICAL CIVILIZATIONS

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1 NSCI 314 LIFE IN THE COSMOS 19 - LIFETIMES OF TECHNOLOGICAL CIVILIZATIONS Dr. Karen Kolehmainen Department of Physics, CSUSB

2 THE FERMI PARADOX THE DRAKE EQUATION LEADS US TO BELIEVE THAT THERE IS LIKELY TO BE A LARGE NUMBER OF TECHNOLOGICALLY ADVANCED CIVILIZATIONS IN OUR GALAXY (AND EVEN MORE IN THE UNIVERSE AS A WHOLE). BUT WE HAVE RECEIVED NO SIGNALS FROM THEM NOR HAD ANY KNOWN VISITS BY THEM. THEREFORE WHERE ARE THEY? (ASKED BY ENRICO FERMI, 1950)

3 SO, WHERE ARE THEY? WE DON'T KNOW, BUT LET'S EXAMINE SOME POSSIBLE ANSWERS. SOME OF THESE ANSWERS ARE UNLIKELY, WHEREAS OTHERS ARE PLAUSIBLE.

4 RESPONSES TO WHERE ARE THEY? THERE IS NO EXTRATERRESTRIAL LIFE AT ALL. THIS SEEMS UNLIKELY. WE THINK SUITABLE PLANETS ARE RELATIVELY COMMON, AND THAT LIFE ARISES EASILY WHEN THE CONDITIONS ARE APPROPRIATE. IT DID SO QUICKLY ON THE EARTH.

5 RESPONSES TO WHERE ARE THEY? ALTHOUGH THERE MAY BE EXTRATERRESTRIAL LIFE, THERE ARE NO ALIEN CIVILIZATIONS. THE FACTORS ALLOWING COMPLEX, INTELLIGENT, OR TECHNOLOGICALLY- DEVELOPED LIFE FORMS TO EVOLVE ARE UNIQUE TO EARTH. MAYBE. SUPPORTING ARGUMENTS: COMPLEX AND INTELLIGENT LIFE TOOK A LONG TIME TO EVOLVE ON EARTH. SPECIAL FEATURES OF EARTH (PRESENCE OF A LARGE MOON, SPECIFIC CLIMATE CHANGES, ETC.) MAY HAVE BEEN CRUCIAL IN STIMULATING THE EVOLUTION OF COMPLEX AND/OR INTELLIGENT LIFE FORMS ON EARTH.

6 RESPONSES TO WHERE ARE THEY? ALIEN CIVILIZATIONS HAVE DEVELOPED, BUT THEY TEND TO DESTROY THEMSELVES (OR ARE DESTROYED BY NATURAL DISASTERS) BEFORE DEVELOPING INTERSTELLAR SPACE TRAVEL OR COMMUNICATION. EVEN IF L IS VERY SHORT, REMEMBER THAT L IS THE AVERAGE LIFETIME OF A TECHNOLOGICAL CIVILIZATION. SOME CIVILIZATIONS WILL BE SHORTER-LIVED THAN THE AVERAGE, AND SOME WILL BE LONGER-LIVED. IF THERE ARE AS MANY CIVILIZATIONS AS THE DRAKE EQUATION LEADS US TO BELIEVE, THERE SHOULD BE A FEW OF THEM THAT ARE SUFFICIENTLY LONG-LIVED TO EXPLORE THE UNIVERSE AND VISIT THE EARTH.

7 RESPONSES TO WHERE ARE THEY? ALIEN CIVILIZATIONS EXIST, BUT THEY ARE ALL LESS TECHNOLOGICALLY ADVANCED THAN WE ARE. SEE REFUGES FOR LIFE IN A HOSTILE UNIVERSE IN SCIENTIFIC AMERICAN, OCTOBER MAYBE! ON THE ONE HAND, THIS SEEMS UNLIKELY GIVEN THAT THERE ARE OTHER APPARENTLY SUITABLE STARS SEVERAL BILLION YEARS OLDER THAN OUR SUN. BUT ON THE OTHER HAND, PERHAPS LIFE ON EARTH DEVELOPED UNUSUALLY QUICKLY. OR PERHAPS THE THRESHOLD ABUNDANCES OF HEAVY ELEMENTS NEEDED FOR PLANETARY FORMATION AND/OR FOR LIFE IS HIGHER THAN WE THINK, AND STARS THAT FORMED TOO MUCH EARLIER THAN OUR SUN DON'T HAVE ENOUGH HEAVY ELEMENTS TO SUPPORT LIFE.

8 RESPONSES TO WHERE ARE THEY? ALIEN CIVILIZATIONS EXIST, BUT THEY VE DECIDED THAT INTERSTELLAR TRAVEL IS NOT WORTH THE EXPENDITURE OF TIME AND RESOURCES. THIS SEEMS UNLIKELY. IF THERE ARE AS MANY CIVILIZATIONS AS WE THINK, IT SEEMS UNLIKELY THAT THEY WOULD ALL DECIDE THIS. CURIOSITY IS LIKELY TO BE A COMMON FEATURE OF ALL INTELLIGENT LIFE FORMS. SUCH AN ATTITUDE WOULD DOOM THEM TO EXTINCTION WHEN THEIR STAR DIES.

9 RESPONSES TO WHERE ARE THEY? ALIENS ARE ENGAGING IN INTERSTELLAR EXPLORATION, BUT THEY HAVEN T DISCOVERED US YET. THIS SEEMS UNLIKELY. RECALL THAT A CIVILIZATION COULD THOROUGHLY EXPLORE OUR MW GALAXY IN A FEW MILLION YEARS TO A FEW HUNDRED MILLION YEARS. IF THERE ARE AS MANY CIVILIZATIONS AS THE DRAKE EQUATION LEADS US TO BELIEVE, THERE SHOULD BE CIVILIZATIONS WITH HEAD STARTS OF A FEW BILLION YEARS ON US, SO THEY WOULD HAVE HAD PLENTY OF TIME TO FIND US.

10 RESPONSES TO WHERE ARE THEY? THEY KNOW WE RE HERE, BUT THEY DON T CARE. IF THEY ARE SO MUCH MORE ADVANCED THAN US, WE MAY NOT SEEM PARTICULARLY INTERESTING. THIS IS POSSIBLE, ESPECIALLY IF COMPLEX LIFE FORMS ARE VERY COMMON IN THE UNIVERSE. WE MAY NOT SEEM LIKE ANYTHING SPECIAL. HOWEVER, IF COMPLEX LIFE FORMS ARE NOT COMMON, WE'RE PROBABLY UNUSUAL ENOUGH TO BE INTERESTING.

11 RESPONSES TO WHERE ARE THEY? THEY HAVE VISITED EARTH, BUT THEIR VISITS ARE VERY INFREQUENT AND THEY HAVEN T BEEN HERE FOR A LONG TIME. THIS IS POSSIBLE. THE UNIVERSE IS A BIG PLACE, AND INTERSTELLAR SPACE TRAVEL IS DIFFICULT, COSTLY, AND TIME- CONSUMING. MAYBE THEY HAVE IDENTIFIED THE EARTH AS A POTENTIALLY INTERESTING PLANET, AND SO THEY CHECK UP ON IT EVERY FEW MILLIONS OF YEARS. MAYBE THE LAST TIME THEY WERE HERE, HUMANS HADN'T EVOLVED YET.

12 RESPONSES TO WHERE ARE THEY? THEY ARE HERE, BASED ON UFO EVIDENCE. - THIS SEEMS UNLIKELY. - THE ARGUMENTS THAT UFOs ARE ALIEN SPACESHIPS ARE NOT PARTICULARLY COMPELLING. - IF THEY WANTED TO CONTACT US, WHY WOULDN'T THEY DO SO MORE DIRECTLY?

13 RESPONSES TO WHERE ARE THEY? ZOO HYPOTHESIS - THEY ARE HERE, SECRETLY OBSERVING US (OR MAYBE EVEN CONTROLLING US). WE ARE LIKE ANIMALS IN A ZOO. - MAYBE, ALTHOUGH IT SOUNDS A BIT PARANOID AND EXAGGERATES OUR LIKELY IMPORTANCE. - WHAT MAKES US SO WORTHY OF OBSERVATION? THIS WOULD MAKE SENSE ONLY IF CIVILIZATIONS ARE RARE. - WHY BOTHER CONTROLLING US? WHAT DO THEY HAVE TO GAIN BY DOING SO?

14 RESPONSES TO WHERE ARE THEY? GALACTIC QUARANTINE HYPOTHESIS - THEY ARE HERE, OR HAVE BEEN HERE, BUT THEY HAVE CHOSEN NOT TO MAKE THEIR PRESENCE KNOWN TO US. - MAYBE THEY'VE DECIDED THAT WE'RE TOO VIOLENT AND DANGEROUS. - MAYBE WE MUST ACHIEVE A CERTAIN LEVEL OF TECHNOLOGY OR PASS SOME OTHER TYPE OF TEST BEFORE THEY ARE WILLING TO MAKE THEIR PRESENCE KNOWN TO US (E.G., PRIME DIRECTIVE ON STAR TREK TV SERIES). - NOTE: THIS IS THE ANSWER THAT I'D LIKE TO BELIEVE! - HOWEVER, IF THERE ARE AS MANY CIVILIZATIONS AS WE THINK, IT MAY BE UNLIKELY THAT THEY WOULD ALL FEEL THIS WAY. - ON THE OTHER HAND, MAYBE A SUFFICIENTLY ADVANCED CIVILIZATION WILL INEVITABLY DEVELOP THE WISDOM TO FEEL THIS WAY.

15 RECALL THAT THE LEAST WELL-KNOWN FACTOR IN THE DRAKE EQUATION IS L = AVERAGE LIFETIME OF A TECHNOLOGICAL CIVILIZATION

16 ESTIMATING L IS IMPORTANT BECAUSE: 1. IT ALLOWS US TO USE THE DRAKE EQUATION TO ESTIMATE HOW COMMON EXTRATERRESTRIAL CIVILIZATIONS ARE, AND, 2. EVEN MORE IMPORTANTLY, WE WOULD LIKE TO KNOW HOW LONG WE CAN EXPECT THE HUMAN RACE TO SURVIVE!

17 FACTORS THAT MAY LIMIT THE LIFETIME OF TECHNOLOGICAL CIVILIZATIONS IMPACTS BY ASTEROIDS, COMETS, OR LARGE METEORITES POPULATION GROWTH POLLUTION DISEASE WAR LOSS OF INTEREST IN COMMUNICATION

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20 FACTS ABOUT THIS IMPACT MOVING AT 10 to 30 km/sec PASSES THROUGH HOUSE IN 0.01 Sec at 10 km/sec ENERGY RELEASE = 1 KILOTON BOMB CRATER DIAMETER = 120 FEET (TYPICALLY AT LEAST 10x THE DIAMETER OF THE IMPACTING OBJECT!)

21 CRETACEOUS-TERTIARY BOUNDARY RECOVERY, AS DOCUMENTED IN THE FOSSIL RECORD, TOOK AT LEAST 5,000 YEARS BOUNDARY BETWEEN TWO GEOLOGICAL PERIODS 65 MILLION YEARS AGO ROCKS DEPOSITED BEFORE THE BOUNDARY CONTAIN DINOSAUR FOSSILS ROCKS DEPOSITED AFTER THE BOUNDARY CONTAIN NO DINOSAUR FOSSILS BOUNDARY MARKED BY THE EXTINCTION OF 80% OF LAND AND MARINE ORGANISMS (NOT JUST DINOSAURS)

22 EXTINCTION OF THE DINOSAURS LUIS & WALTER ALVAREZ DISCOVERED (1980): LARGE EXCESS OF IRIDIUM, A RARE-EARTH ELEMENT, LOCATED IN ROCKS DEPOSITED AT THE CRETACEOUS-TERTIARY BOUNDARY. THIS LAYER HAS BEEN FOUND WORLD-WIDE. IRIDIUM IS KNOWN TO BE PRESENT IN METEORITES AT MUCH HIGHER ABUNDANCES THAN IN EARTH ROCKS. TO SUPPLY THE ESTIMATED AMOUNT OF IRIDIUM WOULD REQUIRE A METEORITE 10 km ACROSS.

23 METEORITE ESTIMATED TO BE 10 km ACROSS (SOMETHING THIS SIZE IS USUALLY THOUGHT OF AS AN ASTEROID) CRATER ESTIMATED TO BE km ACROSS PEMEX DISCOVERED A BROAD SUBTERRANEAN ARC OFFSHORE YUCATAN PENINSULA (1978) SUBSEQUENT DISCOVERY OF 180 km CRATER AT CHICXULUB (STRUCTURE IS BURIED) CRATER HAS BEEN DATED AND IS 65 MILLION YEARS OLD

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25 99% of Atmosphere Below This Level Asteroid 10 km across moving at 30 km/sec Mt. Everest 8.7 km Ocean Floor 3 km

26 ENERGY OF A MOVING BODY DEPENDS ONLY ON THE MASS (M) AND VELOCITY (V) (BELOW EQUATION CORRECT ONLY IF V<< c) KINETIC ENERGY = (1/2) MV² FOR A 10 km DIAMETER ASTEROID M = 2 TRILLION METRIC TONS = 2,000,000,000,000,000 kg V = 30 km/s = 30,000 m/s KE = JOULES OF ENERGY = ONE TRILLION TRILLION JOULES (EQUIVALENT OF 95 DAYS OF SOLAR RADIATION ABSORBED OVER ENTIRE EARTH)

27 ENERGY RELEASE ON IMPACT UPON IMPACT, ALL ENERGY EVENTUALLY TURNS TO HEAT. IMPACT PRODUCED A FIREBALL 200 km ACROSS AND WITH A TEMPERATURE OF 100,000 K RESULTS: GLOBAL EFFECTS FIRES POSSIBLE TRIGGERING OF EARTHQUAKES POSSIBLE TRIGGERING OF VOLCANIC ERUPTIONS CLIMATE CHANGES EXTINCTION OF MANY LIFE FORMS

28 EFFECTS OF LARGE IMPACT FIRESTORMS ~ DAYS TO WEEKS FIREBALL INDUCED FIRES UP TO SEVERAL THOUSAND KILOMETERS FROM IMPACT SITE GLOBAL FIRES DUE TO SECONDARY IMPACTS IMPACT WINTER ~ 1 YEAR GLOBAL CLOUD COVER, ACID RAIN, SALT RAIN, HIGH LEVEL OF DUST, REDUCED TEMPERATURE EXTINCTION OF NUMEROUS LIFE FORMS, ESPECIALLY LARGE ONES MANY PLANTS DIE DUE TO FIRES AND DARKNESS MANY ANIMALS DIE DUE TO INTERRUPTION OF THE FOOD CHAIN UTRAVIOLET SPRING ~ 1 -? YEARS DESTRUCTION OF OZONE LAYER UV INTERRUPTS PHOTOSYNTHESIS UV INCREASES MUTATION RATES, EVEN IN OCEANS FURTHER EXTINCTIONS

29 MASS EXTINCTIONS MAN-MADE DINOSURS ETC. SMALLER ASTEROID? MOST LAND & SEA MOST FISHES MANY INVERT. MARINE SPECIES MILLIONS OF YEARS AGO

30 ASTEROID IMPACTS EARTH-CROSSING ASTEROIDS ASTEROID S ORBIT INTERSECTS EARTH S ORBIT. ONE OF THEM HITS EARTH EVERY 50 TO 100 MILLION YEARS ON THE AVERAGE. ORBITS ARE NOW BEING MAPPED, SHOULD BE DONE IN 10 YEARS. THEN WE WILL BE ABLE TO PREDICT FUTURE IMPACTS. HUMANS MUST THINK ABOUT PROTECTION FROM IMPACTS! BEST METHOD USE EXPLOSIONS NEAR ASTEROID TO ALTER ITS ORBIT SLIGHTLY. DON T BLOW IT UP!

31 POPULATION GROWTH THERE ARE CURRENTLY 6.6 BILLION HUMAN BEINGS ON EARTH. HUMAN POPULATION IS GROWING AT A RATE OF: 1.4% PER YEAR 88 MILLION PER YEAR 7 MILLION PER MONTH 240,000 PER DAY 18,000 DURING OUR CLASS PERIOD TODAY IF YOU ARE 20 YEARS OLD, THE WORLD S POPULATION HAS GROWN BY 1.8 BILLION SINCE YOU WERE BORN. THE MAJORITY OF ALL HUMAN BEINGS WHO HAVE EVER LIVED ARE ALIVE TODAY!

32 HOW WILL WE FEED EVERYONE? THE EARTH IS NOT INFINITE! IF GROWTH CONTINUES, AT SOME POINT IT WILL BECOME IMPOSSIBLE TO FEED EVERYONE, EVEN IF FOOD IS DISTRIBUTED EQUALLY TO EVERYONE. IN ADDITION TO FEEDING HUMANS, WE MUST ALSO FEED: 4.3 BILLION LARGE DOMESTICATED ANIMALS 17 MILLION CHICKENS THEY EAT 40% OF THE WORLD S GRAIN HUMANS CONTROL ABOUT 90% OF ALL LARGE ANIMALS BY MORE SENSIBLE USE OF EXISTING RESOURCES (BETTER LAND USE, VEGETARIAN DIETS, DEVELOPMENT OF NEW CROPS), WE CAN DELAY THE PROBLEM, BUT NOT SOLVE IT!

33 POPULATION GROWTH GOVERNED APPROXIMATELY BY EXPONENTIAL GROWTH THIS TERM HAS A PRECISE MATHEMATICAL MEANING. EXPONENTIAL GROWTH OCCURS WHENEVER THE RATE OF GROWTH DEPENDS ON HOW MANY ARE ALREADY THERE - THE MORE PEOPLE ARE ALIVE, THE MORE OF THEM THERE ARE TO REPRODUCE. EXPONENTIAL GROWTH IS CHARACTERIZED BY A DOUBLING TIME, i.e., THE TIME NEEDED FOR THE NUMBER TO DOUBLE ALWAYS REMAINS THE SAME.

34 DOUBLING TIMES DOUBLING TIME ~ 70 % GROWTH RATE Example: You have $5,000 in savings earning 5% per year. You will have $10,000 in 14 years. Example: Inflation is running at 1.5% annually. In 47 years, the average cost of products will have doubled Example: The world s human population is growing at a rate of 1.4% per year. The current population is 6.6 billion. In 50 years the world population will be 13.2 billion.

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36 HISTORY OF HUMAN POPULATION YEAR 200AD POP. 200 M 400 M 800 M 1.6 B 3.2 B 6.0 B ANNUAL GROWTH 0.06% 0.16% 0.47% 0.93% 1.4% IT TOOK ABOUT 1 MILLION YEARS FOR EARTH S HUMAN POPULATION TO REACH 1 BILLION. DOUBLING TIME (YRS) THE NEXT BILLION TOOK ONLY 100 YEARS. THE LAST BILLION TOOK ONLY 12 YEARS.

37 POPULATION GROWTH DOUBLING TIME IS NOT CONSTANT, BUT RATHER DECREASES WITH TIME! THEREFORE, POPULATION GROWTH IS EVEN FASTER THAN EXPONENTIAL GROWTH!

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41 PAST AND FUTURE? YEAR 200AD POP. 200 M 400 M 800 M 1.6 B 3.2 B 6.0 B 12 B 24 B 48 B 96 B WHAT IS EARTH S CAPACITY? ASSUMING A 50 YEAR DOUBLING TIME FROM 2000 ONWARD

42 SOLUTIONS TO POPULATION GROWTH POPULATION GROWTH WILL BE HALTED. THE ONLY QUESTION IS HOW WILL IT BE HALTED. BY OUR INTENTIONAL ACTIONS (i.e., BIRTH CONTROL), OR BY EVENTS BEYOND OUR CONTROL (FAMINE, POLLUTION, DISEASE, WAR). THESE HAVE BEEN THE TRADITIONAL METHODS OF POPULATION CONTROL THROUGHOUT MOST OF HUMAN HISTORY. THE ANSWER IS UP TO US!

43 ARGUMENTS FOR SHORT L ASTEROID IMPACTS OCCUR REGULARLY. HUMAN POPULATION CONTINUES TO GROW RAPIDLY, BUT THE RESOURCES OF THE PLANET ARE LIMITED. HUMANS CONTINUE TO POLLUTE THE PLANET AND POISON OUR OWN ENVIRONMENT. OVERPOPULATION AND POLLUTION INTRODUCE NEW DISEASES AND MAKE EXISTING ONES WORSE. HUMANS CONTINUE TO KILL EACH OTHER IN WARS AND VIA OTHER POLITICAL AND ECONOMIC DECISIONS. EXISTING NUCLEAR WEAPONS COULD DESTROY THE HUMAN POPULATION MANY TIMES OVER. MANY IMPORTANT WORLD DECISIONS ARE MADE BY POLITICAL, BUSINESS, AND RELIGIOUS LEADERS WHO DON T TAKE THESE PROBLEMS SERIOUSLY.

44 ARGUMENTS FOR LONG L WE ALMOST HAVE THE TECHNOLOGY NOW TO PROTECT OURSELVES AGAINST ASTEROID IMPACTS. EDUCATION CAN HELP CONVINCE PEOPLE OF THE DANGERS OF OVERPOPULATION AND POLLUTION. SCIENCE AND TECHNOLOGY CAN HELP US CLEAN UP POLLUTION AND CURE & PREVENT DISEASE. INTERNATIONAL PRESSURE MAY HELP PREVENT WARS, OR AT LEAST LIMIT THE NUMBER OF DEATHS. WE HAVE ALREADY DECREASED THE NUMBER OF NUCLEAR WEAPONS ON THE PLANET THROUGH TREATIES, SO THIS CAN BE DONE. IF WE COMMUNICATE WITH ALIEN CIVILIZATIONS, WE MAY LEARN FROM THEM HOW TO SOLVE SOME OF THESE PROBLEMS.

45 CLOSING COMMENTS EITHER N = 1, AND HUMANS ARE THE ONLY INTELLIGENT CIVILIZATION IN OUR GALAXY, OR N > 1, AND OTHER (MAYBE MANY OTHER) CIVILIZATIONS EXIST. IN EITHER CASE, HUMANS ARE UNIQUE. IF LIFE DOES EXIST ELSEWHERE, IT WILL BE VERY DIFFERENT FROM US. THEREFORE WE ARE WORTH PRESERVING! WE WILL NEVER FIND OUT IF EXTRATERRESTRIAL LIFE EXISTS IF WE DESTROY OURSELVES (OR ALLOW OURSELVES TO BE DESTROYED) FIRST! BY OUR ACTIONS, WE DETERMINE OUR OWN LIFETIME AS A TECHNOLOGICAL CIVILIZATION, AND OUR CONTRIBUTION TO THE VALUE OF L. LET S CHOOSE TO MAKE THE LIFETIME OF HUMAN CIVILIZATION AS LARGE AS POSSIBLE!