Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34NSCI 314LIFE IN THE COSMOS18 – INTERSTELLAR SPACE TRAVEL (CONTINUED), AND UNIDENTIFIED FLYING OBJECTS (UFOs)Dr. Karen Kolehmainen Department of Physics, CSUSBhttp://physics.csusb.edu/~karen/THE PROBLEM WITH INTERSTELLAR SPACE TRAVELSTARS ARE VERY VERY FAR AWAY!–THE NEAREST STAR BEYOND THE SUN (ALPHA CENTAURI) IS ABOUT 4 LIGHT YEARS AWAY (100 MILLION TIMES FARTHER AWAY THAN THE MOON). THIS MEANS THAT IT WOULD TAKE 4 YEARS TO GET THERE IF YOU COULD TRAVEL AT THE SPEED OF LIGHT.A SPACESHIP CAN’T TRAVEL FASTER THAN THE SPEED OF LIGHT (c = 300,000 km/sec), OR EVEN AT THE SPEED OF LIGHT. IN FACT, NOTHING CAN TRAVEL FASTER THAN c. THIS IS AN ISSUE OF FUNDAMENTAL PHYSICS, NOT TECHNOLOGY!THE BASIC LAWS OF PHYSICS DON’T MAKE IT IMPOSSIBLE, BUT THEY MAKE IT VERY DIFFICULT. CURRENT TECHNOLOGY IS NOWHERE NEAR ADEQUATE. EVEN WITH THE BEST TECHNOLOGY WE CAN IMAGINE BEING ABLE TO BUILD IN THE DISTANT FUTURE (MATTER-ANTIMATTER ANNIHILATION):- WE CAN’T GO FASTER THAN THE SPEED OF LIGHT (c)- IT WOULD TAKE YEARS TO REACH EVEN THE NEAREST STAR BEYOND THE SUN- FUEL REQUIREMENTS ARE ENORMOUS-INTERSTELLAR GAS, DUST, AND PHOTONS WOULD BE HAZARDOUSINTERSTELLAR SPACE TRAVELINTERSTELLAR TRAVELBECAUSE OF GENERAL RELATIVITY AND THE TWIN “PARADOX,” A TRAVELER IN A SHIP CAN ACCELERATE TO NEAR THE SPEED OF LIGHT AND MAKE A ROUND TRIP VOYAGE TO A DISTANT DESTINATION IN A REASONABLE TIME (A FEW YEARS FOR A NEARBY STAR), BUT…UPON HER RETURN, MORE TIME WILL HAVE ELAPSED ON EARTH THAN FOR HER. THE FASTER HER AVERAGE SPEED RELATIVE TO THE EARTH, THE BIGGER THE TIME DIFFERENCE WILL BE.METHODS OF PROPULSION(IN ORDER OF INCREASING EFFICIENCY)CHEMICAL ROCKETSION ROCKETS NUCLEAR-POWERED SPACECRAFTMATTER-ANTIMATTER ANNIHILATIONNOTE: ALL OF THESE ARE “ACTIVE” PROPULSION METHODS, i.e., THE SPACECRAFT CARRIES ITS FUEL WITH ITFUEL REQUIREMENTSFOR 10 LY ROUND TRIP DESCRIBED LAST TIME: EVEN WITH PROPULSION VIA MATTER-ANTIMATTER ANNIHILATION (MOST EFFICIENT METHOD),WE NEED 400 POUNDS OF FUELFOR EACH POUND OF PAYLOAD.THIS IS 30 TONS OF FUEL PER HUMAN(ENVIRONMENT NOT INCLUDED).THE PROBLEM IS EVEN WORSE FOR LESS EFFICIENT METHODS OF PROPULSION!WE'D NEED 1000 TIMES MORE FUEL FOR NUCLEAR PROPULSION, AND 1,000,000 TIMES MORE FUEL FOR CHEMICAL ROCKETSPASSIVE PROPULSION METHODS ADVANTAGE: NO NEED TO CARRY FUELLIGHT SAIL OR SOLAR SAIL–LARGE “SAIL” PROPELS SHIP VIA PRESSURE EXERTED BY PHOTONS FROM STAR –SAIL MUST BE VERY LIGHT, THUS FRAGILE–ACCELERATION IS VERY SMALL–WORKS BEST (LARGEST ACCELERATION) NEAR A STAR –COULD GET TO NEARBY STARS WITHIN A CENTURYPASSIVE PROPULSION METHODS VARIATION ON LIGHT SAIL–USE PHOTON PRESSURE OF LASER BEAM FROM EARTH (OR SPACE STATION) INSTEAD OF LIGHT FROM A STAR–COULD REACH NEARBY STARS IN A FEW DECADES–ACCELERATING A SHIP TO HALF THE SPEED OF LIGHT WOULD TAKE 1000 x AS MUCH POWER AS CURRENT TOTAL HUMAN POWER CONSUMPTION–SHIP WOULD BE DEPENDENT ON LASER BEAM FROM EARTH–HOW WOULD THE SHIP SLOW DOWN WHEN APPROACHING ITS DESTINATION? WOULD NEED A LASER BEAM FROM DESTINATION PUSHING BACK ON SHIP•POSSIBLE ANSWER: LASER IS USED TO HEAT PROPELLANT ON BOARD, PROPELLANT IS THEN EJECTED OUT IN FRONT OF THE SHIPPASSIVE PROPULSION METHODSBUSSARD RAMJET–COLLECT INTERSTELLAR GAS (HYDROGEN) FOR USE AS FUEL–HYDROGEN IS FUEL FOR NUCLEAR FUSION–WOULD HAVE TO COLLECT FUEL FROM A HUGE REGION OF SPACE–NEED HUGE “SCOOP” (SIZE OF A PLANET), OR USE MAGNETIC FIELDS TO COLLECT HYDROGEN (MORE LIKELY)–MUST HAVE ENOUGH ENERGY TO MAINTAIN MAGNETIC FIELDS–WAY BEYOND CURRENT TECHNOLOGYOTHER APPROACHESACCEPT THAT INTERSTELLAR TRAVEL WILL BE SLOW. ADVANTAGES:–DON'T NEED HUGE ENERGY REQUIREMENTS TO REACH HIGH SPEED–INTERSTELLAR HAZARDS NOT EXACERBATED BY HIGH SPEEDHOW DO WE DEAL WITH THE LONG TIMES NEEDED FOR VOYAGES?–PUT CREW INTO HIBERNATION•WE DON'T YET KNOW HOW TO DO THIS–HAVE GENERATIONS THAT ARE BORN AND DIE ON BOARD SHIP EN ROUTE TO DESTINATION •CREW MAY FIGHT AMONG THEMSELVES, LOSE INTEREST IN MISSION, OR LOSE TECHNICAL EXPERTISE TO COMPLETE MISSION. ALSO, IS IT MORALLY CORRECT TO REQUIRE PEOPLE TO SERVE IN THIS WAY IF THEY DIDN'T CHOOSE TO DO SO?WARP DRIVE??SCIENCE FICTION “TRICK” FOR GOING FASTER THAN SPEED OF LIGHT (c).THE IDEA IS TO BEND OR WARP SPACE SO AS TO MAKE A “SHORT CUT” BETWEEN DISTANT OBJECTS.WE KNOW THAT MASSIVE OBJECTS BEND SPACE AROUND THEM:–STARS DO THIS A LITTLE–BLACK HOLES DO IT A LOT (THEY WARP SPACE SUFFICIENTLY TO “PINCH OFF” THE INTERIOR OF THE BLACK HOLE FROM THE REST OF THE UNIVERSE)WARP DRIVE??HOWEVER, WE CAN’T VERY WELL CARRY ALONG A BLACK HOLE WITH OUR SPACESHIP.–THE NEAREST BLACK HOLES ARE HUNDREDS OF LIGHT YEARS AWAY. –THE BLACK HOLE WOULD BE MUCH MORE MASSIVE THAN THE SHIP ITSELF. –WE COULDN’T SURVIVE NEAR A BLACK HOLE. (TIDAL FORCES WOULD RIP US APART.)WORMHOLE: HYPOTHETICAL CONNECTION BETWEEN BLACK HOLES (“SHORT-CUT” TO PATH THROUGH NORMAL SPACE)–IF THESE EXIST, PERHAPS WE COULD USE EXISTING ONES.–GETTING TO AND FROM THEM WOULD STILL BE A PROBLEM (NEAREST ONES HUNDREDS OF LIGHT YEARS AWAY).–TIDAL FORCES WOULD STILL BE A PROBLEM.WARP DRIVE??IF WARP DRIVE IS POSSIBLE, IT WILL DEPEND ON BASIC LAWS OF PHYSICS THAT HAVEN'T BEEN DISCOVERED YET!–IT'S NOT JUST A MATTER OF IMPROVING TECHNOLOGY.–IT'S NOT ANALOGOUS TO “BREAKING THE SOUND BARRIER.”UNIDENTIFIED FLYING OBJECTSThousands are reported annually, in all parts of the world. The vast majority of scientists are not convinced that these objects are alien spacecraft. WHY?No physical evidence of an alien visit has even been produced.Photographs of alleged alien spaceships are either faked or else too vague (small, blurry, etc.) to be sure what the object isSightings of alleged alien spacecraft depend on eyewitness accounts, which are unverifiable.UNIDENTIFIED FLYING OBJECTSIf UFOs aren't alien spacecraft, how can so many people who claim to see them be wrong? (Many of these people are honest, sane, and intelligent.) •Most people spend most of their time indoors.•Air and light pollution prevent regular clear views of the sky.•People are increasingly unfamiliar with astronomical and other natural