Average Lifetime ofTechnological CivilizationAverage Lifetime ofTechnological CivilizationL = ?• End of Communication Efforts(Civilization Survives)(Decades?)• Civilization Evolves away from interest orcapability (Post-technological Civilization)(Centuries - Millenia)• Civilization Collapses(Reversion to Pre-technological Culture) Exhaustion of resources Population explosion ( ~ 100 yrs - 1000 yrs)• Sudden, Catastrophic End of Civilization or Extinction of our Species Nuclear War leads to Nuclear Winter (10’s - 100’s of years) Natural Catastrophes (> 105 yr for most)Resource DepletionMetals, Drinkable Water, Arable Land, …Energy is most fundamentalEnergy is conserved“Depletion” = conversion to less usable forms (entropy increases)Resource DepletionFossil Fuels (Stored Solar Energy)will eventually run out~ 500 years for coal 200?Nuclear Power? Stopgap…Ultimately Solar PowerLittle Attempt to Plan AheadWorld Energy UsageWorld 380 “Quads”Per year Quad = 1015 BTU ~ 3 × 1011 kw - H ~ 1018 Joules (one exajoule) 13 × 106 MW Avg. powerU.S. uses 26% of thisEnergy per capita ~ 6 metric tonnes of oil equivalent~ 2 × Europe ~ 5 × World avg.History of Energy Use in USARegional Primary Energy Consumption PatternFossil Fuel R/P ratiosEnergy Consumption per capitaSide Effects• General Pollution of Air, Water, LandMakes resources less usableAir pollution, respiratory problemsUndrinkable waterDesertification of farm-lands• Ozone Layer Destruction⇒ UV reaches surfaceSkin Cancer, Cataracts, …Crop DamageCaused by CFC’s (refrigeration, styrofoam,…)other chemicalsStratosphere is very sensitive andpoorly understoodCatalytic reactions: One CFC moleculeleads to the destruction of many ozone moleculesO3 O2Ozone overSouth PoleGrowth of ozone holeSide Effects (cont.)• Fossil fuels CO2 Greenhouse(any chemical fuel) Global warming and warmer waterRise in Melting iceSea level (50 - 100 yrs)Climate changes: (40 - 100 yrs)Increased desertificationCrop yields?Runaway greenhouse?(Earth become like Venus?)Not likely to go this farCarbon Dioxide IncreaseCO2 ProductionCarbon production (12/44 of CO2)3.66 tons CO2Update on CO2 leading to Global Warming• New models include Sulfateemission leads to haze which leads toincrease in albedo• Cooling tends to balance warming fromGreenhouse CO2Less temperature rise in short termIce core analysis shows strong correlationof temperature and astronomical cycles -rotation axis, orbital variations, solar cycleAlso - we are still in last stages of “little ice age”In climate behavior, but not temperatureGreenland ice cores Nature, 15 July 1993Study temperature, climate… over 150,000 yrLast interglacial (Eemian)115,000 - 130,000 yr agowarmer3 temp. states: like present colderVery rapid switches (up to 10º C)Our current stable climate may not be typicalof interglacialsPopulation Explosion(The revenge of Malthus?)Agriculture - Population Growth - DiseasePopulation Growth leads to more rapid depletion ofresourcesMore pollutionMore conflict?Two “events” (transitions)10,000 yrs ago Agriculture250 yrs ago Disease lessened(demographic transition)Time Total Pop. Growth Rate (per thousand per year)0.0150.360.564.417.1~ 18~ 8 × 106 (??)~ 3 × 108~ 8 × 108~ 1 × 109 4 × 109 6 × 109Before Agriculture~ 8000 B.C. - 1 A.D.1 AD - 1750 A.D.1750-18001950 - 19752000…Population Doubling in 55 yearsPopulation MathematicsRate of increase ∝ Number × (Birth - Death)leads to exponential growth if (Birth - Death) constantPop (t) = Pop (Now) 2(t/td)td = doubling time ~ 55 yearsSo doubles in 55 yrsQuadruples (22) in 110 yrs, …990 yr (18 td ) Pop = 1.3 × 1015~ fills land area2530 yr (46 td ) Mass > M(earth) !12, 375 yr (225 td ) Mass expands at c !!Current population growth is NOT sustainableWorld Vital Events Per Time Unit: 2005 (Figures may not add to totals due to rounding)------------------------------------------------- NaturalTime unit Births Deaths increase-------------------------------------------------Year 129,908,352 56,622,744 73,285,608Month 10,825,696 4,718,562 6,107,134Day 355,913 155,131 200,782Hour 14,830 6,464 8,366Minute 247 108 139Second 4.1 1.8 2.3-------------------------------------------------http://www.census.gov/main/www/popclock.htmlProjected World Population GrowthChanges in PopulationDoes negative effect on population growthBeat positive effect on resource depletion?Can we get to sustainable economy beforeWe exhaust resources?Nuclear WarTotal arsenal world-wide ~ 10,000 megatonsGlobal effects of all-out war• Depletion of ozone• Radioactive fallout• Dust and smoke in atmosphere would blocksunlight and lead to cooling of the Earth“Nuclear Winter”The World’s Nuclear Arsenals40035060+200+24-481200???25035060100-20024-48ChinaFranceIndiaIsraelPakistanSuspectedTotal NuclearWeaponsSuspectedNon-StrategicNuclearWeaponsSuspectedStrategicNuclearWeaponsCountryThe World’s Nuclear Arsenals~ 10,000 185 10,656~ 4,000 5 2,010~ 6,000 180 8,646RussiaUnitedKingdomUnitedStatesSuspectedTotal NuclearWeaponsSuspectedNon-StrategicNuclearWeaponsSuspectedStrategicNuclearWeaponsCountryNatural CatastrophesCollisionsStars? NegligibleMolecular Clouds? t ~ 108 yrLikely, but the effects are unclearAsteroids and other debris(comets, meteoroids, …)Effect of Asteroid Impact:e.g. 1/4 km radiusV = 30 km s–1(65,000 miles/hour)Ek = 1/2 Mv2 ~ 7200 megatons of TNT ~ all-out nuclear warCrater ~ 10 km across, few km deep1012 tons of debris released into atmosphereIf covers globe, leads to temperature drop and“asteroid winter”How Often do Large Asteroids Strike the Earth?1937 Hermes ~ 500,000 miles1989FC Similar1991BA 170,000 km (5 - 10 m diameter)How often might we expect global catastrophe?“Substantial” Impacts (1 km or larger) t ~ 105 yr - 106 yrMajor Extinctions t ~ 30 × 106 yrMass Extinctions t ~ 100 × 106 yr ?More massive asteroids more destructive,but also more rare, so collisions are less likelyPreventable by advanced civilization?1991 BA ~ 40 kilotons TNT (3 × Hiroshima) 50 meter objects - once per centuryApril 1992 - proposal for project to search andidentify - space
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