NSCI 314

LIFE IN THE COSMOS

18 – INTERSTELLAR SPACE TRAVEL (CONTINUED),

AND UNIDENTIFIED FLYING OBJECTS (UFOs)

Dr. Karen Kolehmainen Department of Physics, CSUSB

http://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 HAZARDOUS

INTERSTELLAR SPACE TRAVEL

INTERSTELLAR 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 IT

FUEL REQUIREMENTS

FOR 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 ROCKETS

PASSIVE 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

CENTURY

PASSIVE 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 SHIP

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 FIELDS

– WAY BEYOND CURRENT TECHNOLOGY

OTHER 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 is

Sightings of alleged alien spacecraft depend on eyewitness accounts, which are unverifiable.

UNIDENTIFIED FLYING OBJECTS

If 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 phenomena, and may therefore misidentify objects.

MOST UFO REPORTS INVOLVE:

LIGHTS SEEN IN THE SKY AT NIGHT, OR

DISKS (“FLYING SAUCERS”) USUALLY SEEN IN DAYTIME

OBJECTS OFTEN MISIDENTIFIED AS ALIEN SPACECRAFT

NOCTURNAL LIGHTS– PLANETS – BRIGHT STARS– METEORS– AIRPLANES– SATELLITES

DISKS– CLOUDS– BLIMPS– WEATHER BALLOONS

UNIDENTIFIED FLYING OBJECTSCertain “facts” 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). However, sound travels much more slowly than light. Thus if a distant object makes a noise at the same time it visibly does something, you'll see the action before you'll hear the sound. (example: lightning and thunder)

UNIDENTIFIED FLYING OBJECTS

• VERY STRANGE CASES (SUCH AS ALLEGED ABDUCTIONS) ARE NEVER WELL DOCUMENTED (E.G., ONE WITNESS OF QUESTIONABLE RELIABILITY).

• WELL DOCUMENTED CASES (THOSE WITH NUMEROUS RELIABLE WITNESSES) ARE NEVER REALLY STRANGE (E.G., JUST AN UNEXPLAINED LIGHT IN THE SKY).

PSYCHOLOGICAL FACTORS• Whenever a case is publicized, there is an

increase in reports of similar cases soon afterwards. The more well-publicized the case is, the larger the number of similar subsequent reports.

• Descriptions of aliens do not reflect the expected biological and cultural diversity of life elsewhere, but they do reflect psychological biases of witnesses.

• Descriptions of aliens are almost always humanoid (human-like in appearance).• Descriptions of aliens are usually male. • Descriptions of aliens often reflect biases associated with the culture and time period of the witness.

PSYCHOLOGICAL FACTORS

• Eyewitness accounts are notoriously unreliable (especially years after the fact). This has been established by psychologists who study witnesses in legal cases.

• Humans seem to have a psychological need to believe in superior beings. (Some might argue that this leads to the existence of religion.)

UNIDENTIFIED FLYING OBJECTS

Some sightings of UFOs are difficult to explain.

• Sightings must be explained “after the fact” without complete information about what happened.

• Eyewitness reports are known to be unreliable.

• Many reports contain Inconsistencies (which are usually ignored by UFO enthusiasts).

• Failure to find a “normal” explanation is not evidence for alien visits.

UNIDENTIFIED FLYING OBJECTSThe high number of UFO sightings actually argues

against their being alien spacecraft.Remember the enormity of interstellar distances,

the extreme difficulties of interstellar space travel, and the number of planets to explore.

Why would there be so many alien spacecraft visiting the earth constantly? There are a lot of other planets to check out. What makes us so interesting? We should not overestimate our significance.

If every planet were visited as often as some people claim the earth is visited, there would have to be a huge number of spacecraft exploring the universe.

UFOSUNIDENTIFIED FLYING OBJECTS

Ideally, large numbers of experienced observers would watch the skies on a nightly basis and report true UFOs.

This is being done:

• Amateur astronomers• Automated asteroid searches• Automated nova and supernova searches

A UFO has never been seen in such circumstances!

ROSWELL “INCIDENT” A RANCHER FOUND DEBRIS FROM A

CRASHED OBJECT IN 1947 NEAR ROSWELL, NEW MEXICO.

MILITARY PERSONNEL CAME AND TOOK AWAY THE DEBRIS, AND TOLD REPORTERS THAT IT WAS FROM A “FLYING DISK.”

THE NEXT DAY, A MILITARY OFFICIAL SAID THAT THE DEBRIS WAS FROM A CRASHED WEATHER BALLOON.

NOTHING MORE HAPPENED FOR MORE THAN 30 YEARS.

ROSWELL “INCIDENT” IN 1978, A UFO ENTHUSIAST CLAIMED

THAT THE DEBRIS WAS FROM AN ALIEN SPACECRAFT, THAT ALIEN CORPSES WERE RECOVERED AS WELL, AND THAT THE GOVERNMENT WAS ENGAGED IN A COVER-UP.

HIS CLAIMS WERE PICKED UP BY OTHERS AND PUBLICIZED.

“EYEWITNESSES” WHO WERE THEN INTERVIEWED CONTRADICTED EACH OTHER.

NO PHYSICAL EVIDENCE HAS EVER BEEN PRODUCED.

ROSWELL “INCIDENT” DE-CLASSIFIED GOVERNMENT

DOCUMENTS SAY:– PROJECT MOGUL INVOLVED PUTTING

BALLOONS NEAR THE BORDER OF THE SOVIET UNION TO LISTEN FOR SECRET TESTS OF NUCLEAR WEAPONS.

– PROJECT MOGUL WAS BEING TESTED AT ROSWELL IN THE LATE 1940'S.

– THE CHIEF SCIENTIST FOR PROJECT MOGUL HAS VERIFIED THAT THE RECOVERED DEBRIS WAS FROM ONE OF THE PROJECT BALLOONS.

– PHOTOS OF THE ROSWELL DEBRIS LOOK LIKE THE PROJECT MOGUL BALLOONS.

UNIDENTIFIED FLYING OBJECTSIf UFOs are alien spacecraft, what would be the

motives of the aliens on board?

• If aliens wanted to observe us without being detected, we would not be able to detect them. Surely a civilization that is capable of interstellar space travel has the technology to avoid being detected by us.

• If aliens aren’t trying to keep their existence secret, why not meet us directly and openly? Why wouldn't they contact official bodies such as governments, or groups of scientists, or at least large groups of people all at once?

GOVERNMENT CONSPIRACY? IS THE GOVERNMENT COMPETENT ENOUGH TO

MASTERMIND SUCH AN EFFORT?

LOTS OF SCIENTISTS AND OTHERS WOULD HAVE TO BE IN ON THE SECRET. IS IT BELIEVABLE THAT THERE HAS NEVER BEEN A LEAK?

UNLESS THE ALIENS HAD CONTACTED ONLY THE U.S. GOVERNMENT, MANY GOVERNMENTS WORLDWIDE WOULD HAVE TO BE IN ON THE SECRET.– THIS SEEMS UNLIKELY, GIVEN THEIR

NUMEROUS DISAGREEMENTS ON OTHER MATTERS.

GOVERNMENT CONSPIRACY?

EVEN IF A “COVER-UP” EXISTS, THAT DOESN’T NECESSARILY MEAN THAT ALIENS ARE INVOLVED.– THE GOVERNMENT MAY BE TRYING TO

KEEP MILITARY PROJECTS SECRET (E.G., ROSWELL)

– GOVERNMENT OFFICIALS MAY BE MERELY COVERING UP FOR INCOMPETENCE OR LAZINESS

ALIEN INTERVENTION IN HUMAN HISTORY? Some people have suggested that

aliens have constructed artifacts on the earth or guided the development of human civilization.– Egyptian pyramids– Mayan pyramids– Stonehenge and similar structures– Nazca lines

ALIEN INTERVENTION IN HUMAN HISTORY? Such claims are an insult to human

ingenuity and creativity! Ancient humans are capable of impressive accomplishments without help.

Accomplishments such as the pyramids were possible with the human technology of the time. Archaeologists have provided explanations of the details.

SUMMARY THE VAST MAJORITY OF SCIENTISTS DO NOT

BELIEVE THAT UFOs ARE ALIEN SPACECRAFT.

HOWEVER, WE CAN'T PROVE THAT ALIEN SPACECRAFT NEVER HAVE VISITED THE EARTH.

IF THEY HAVE, MOST LIKELY THE VISITS HAVE BEEN– INFREQUENT (GIVEN THE DIFFICULTY OF

INTERSTELLAR SPACE TRAVEL AND THE NUMBER OF PLANETS TO EXPLORE)

– DONE IN SECRECY (IF ANY HAVE OCCURRED SINCE HUMANS HAVE BEEN AROUND)