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CSUSB NSCI 314 - UFOs and fermi paradox

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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 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Slide 45Slide 46Slide 47NSCI 314LIFE IN THE COSMOS18 – INTERSTELLAR SPACE TRAVEL (CONCLUSION), UFOs, AND THE FERMI PARADOXDr. Karen Kolehmainen Department of Physics, CSUSBhttp://physics.csusb.edu/~karen/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 ITPAYLOAD MASS RATIOFOR 5 LY TRIP DESCRIBED EARLIER (10 LY ROUND TRIP):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!PASSIVE PROPULSION METHODS ADVANTAGE: NO NEED TO CARRY FUELLIGHT SAIL– LARGE SAIL PROPELS SHIP VIA PRESSURE EXERTED BY PHOTONS FROM STAR –VERY SLOW–SAIL MUST BE VERY LIGHT, THUS FRAGILE–ONLY WORKS WELL NEAR A STAR VARIATION ON THIS–USE PHOTON PRESSURE OF LASER BEAM FROM EARTH (OR SPACE STATION)–SHIP WOULD BE DEPENDENT ON LASER BEAM FROM EARTH–PROBLEM: HOW WOULD THE SHIP SLOW DOWN WHEN APPROACHING ITS DESTINATION?PASSIVE 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 FIELDSWARP 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.”INTERSTELLAR HAZARDSBECAUSE OF THE RELATIVISTIC RELATIONSHIP BETWEEN SPEED AND KINETIC ENERGY, A 1 gm MASS MOVING AT 90% c HAS AN ENERGY EQUAL TO THAT OF A 30 KILOTON BOMB!(COMPARISON: HIROSHIMA BOMB WAS 12 KILOTONS AND NAGASAKI BOMB WAS 22 KILOTONS.)COLLISIONS WITH INTERSTELLAR GAS AND DUST WOULD BE SUFFICIENT TO HEAT A FAST-MOVING SPACECRAFT TO DANGEROUSLY HIGH TEMPERATURES AND PUNCH HOLES IN IT. COLLISIONS WITH HIGH ENERGY PHOTONS WOULD DAMAGE OCCUPANTS AND ELECTRONICS. “SHIELD” TECHNOLOGY IS NOWHERE GOOD ENOUGH TO PROTECT AGAINST THIS.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 (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 SPACE TRAVELINTERSTELLAR SPACE TRAVELPROCEDURE:- ACCELERATE AT 1 g UNTIL WE’RE HALFWAY TO OUR DESTINATION AND TRAVELING AT ALMOST THE SPEED OF LIGHT- THEN DECELERATE THE REST OF THE WAY THERE - THEN REPEAT THE ENTIRE PROCESS ON THE WAY BACKTHE FARTHER THE DESTINATION STAR, THE CLOSER TO c OUR MAXIMUM SPEED GETS, AND THE LARGER THE EFFECTS OF RELATIVITY BECOME.- THE ELAPSED TIME ON THE SHIP IS LESS THAN THE ELAPSED TIME ON THE EARTH (THE TWIN PARADOX).- HUGE FUEL REQUIREMENTS BECAUSE OF THE RELATIVISTIC RELATIONSHIP BETWEEN SPEED AND KINETIC ENERGY.- PHOTONS AND INTERSTELLAR DUST PARTICLES BECOME HAZARDOUS BECAUSE OF THE RELATIVISTIC RELATIONSHIP BETWEEN SPEED AND KINETIC ENERGY.ANOTHER WAY?WHAT IF WE TRAVEL AT SPEEDS MUCH LOWER THAN THE SPEED OF LIGHT?–ADVANTAGE: FUEL REQUIREMENTS ARE LESSIT WILL TAKE MANY YEARS TO COMPLETE THE TRIP, PROBABLY LONGER THAN A HUMAN LIFETIME.–GENERATIONS OF PEOPLE WILL BE BORN AND LIVE THEIR ENTIRE LIVES ON BOARD THE SHIP.–WE CAN'T BE SURE PEOPLE BORN ABOARD THE SHIP WILL BE INTERESTED IN CARRYING OUT THE MISSION. IS IT FAIR TO EXPECT THEM TO DO SO, GIVEN THAT THEY DIDN'T MAKE THE CHOICE TO DO SO?MOST UFO REPORTS INVOLVE:LIGHTS SEEN IN THE SKY AT NIGHT, ORDISKS (“FLYING SAUCERS”) USUALLY SEEN IN DAYTIME, ORUNIDENTIFIED RADAR SIGHTINGSOBJECTS OFTEN MISIDENTIFIED AS ALIEN SPACECRAFTNOCTURNAL LIGHTS–PLANETS OR BRIGHT STARS–METEORS–AIRPLANES–SATELLITES DISKS–CLOUDS–BLIMPS–WEATHER BALLOONSRADAR SIGHTINGS–FLOCKS OF BIRDS–DENSITY FLUCTUATIONS IN THE AIR–FALSE RADAR ECHOES ARE COMMONUNIDENTIFIED FLYING OBJECTSThousands are reported annually, in all parts of the world.Why are so many UFOs seen?•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 phenomena, and may therefore misidentify objects.UNIDENTIFIED FLYING OBJECTSCertain “facts” given in UFO reports are almost certainly erroneous.•Witnesses often claim large sizes and high speeds. However, to estimate the size and speed of an object, its distance must be known. It is very difficult to estimate the distance to an object seen in the sky.•Witnesses often report hearing a sound at the same moment that they see something happen (e.g., a sound from the engines at the same time there is a change in the object's motion).


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CSUSB NSCI 314 - UFOs and fermi paradox

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