The Allen Telescope Array in California, funded by Microsoft co-founder Paul Allen to search for signals from extraterrestrial civilizations (SETI Institute picture).
Lecture 11
The Allen Telescope Array in California, funded by Microsoft co-founder Paul Allen to search for signals from extraterrestrial civilizations (SETI Institute picture).
UFOs and SETI
Does life exist elsewhere in the universe? If it does, has it visited us already in UFOs? Or is it waiting to be discovered by ingenious surveillance methods (SETI)?
UFOs?
Unidentified Flying Objects... are they alien spacecraft? Or just a collection of mistakes, misperceptions and outright hoaxes? There are strong opinions on both sides. If all UFO reports are true, Earth must be constantly subjected to alien scrutiny. Could alien spacecraft really be so elusive that after fifty years we still have no hard and fast evidence? No crash, no fragment, no unmistakeable photo, no clear radar trace from air traffic control or military radar? Or is the evidence locked away in a gigantic conspiracy? Or are all reports capable of other explanations? I believe we have never been visited by aliens, but you don't have to take my word for it... see what others have said in these links:
UFO reports
More UFOs
Even more UFOs
A rare voice on the other side...
Another opposing view
Another opposing view
Well, it turns out that (who would have guessed?) the internet is full of UFO claims and vitriolic denouncements of people who don't believe in UFOs. So why do I not believe in them? This is like a lot of other topics - the Bermuda Triangle, Sasquatch, the Loch Ness Monster and so on. It isn't possible to prove that something doesn't exist. I can't prove that we have no alien visitors. But never, not once, has a solid bit of evidence been found. Look carefully at the evidence for a claim - is it really very good? Most claims are vague reports of lights in the sky, usually only by one person at a time. Where are the crowds of viewers at a sporting event or a busy city square, with thousands of smartphone videos? - that's what we should see if these are real events. Bring me real evidence and I'll admit I was wrong, but don't rely on fuzzy images, claims of a cover-up or unsupported stories.
Ancient Astronauts?
Modern UFO stories started in the middle of the last century, but there are people who have suggested there is older evidence as well. Various creation myths, Mayan carvings, the Nasca Lines, the Sphinx and pyramids, oblique references in the Bible and so on, have all been interpreted to support such ideas. But a critical reading makes it clear that there is no limit to our ability to overinterpret from vague texts.
von Daniken
Debunking von Daniken
Alien encounters
Abducted by aliens?
Historical references to UFOs?
Historical references to UFOs?
The Palenque (Mayan) 'astronaut'
The Face on Mars?
What can we say about this? A civilization living on Mars long ago, leaving city ruins and a hill carved or built in the shape of a face in a place we call Cydonia? But no amount of criticism is enough to end such ideas because it is not possible to disprove anything like this. As an exercise, consider what evidence you would need to prove the face is natural. And what would you need to prove it is artificial? Thinking about this problem is a much more important academic exercise than trying to debunk any specific claim. Let me go on record here, saying that I believe that the promoters of these ideas also do not believe them. Second-level believers may believe very strongly, but at the root of these stories is pure deception.
The Face
Face by NASA
Face again.
Cydonia mysteries
Cydonia again
... and again
Interplanetary travel and communication
If UFOs come here from other stars, interstellar flight must be possible. But could it really happen? The nearest star is 4.2 light years away - that's 260000 times as far as from the Sun to Earth, or about 6000 times further out than Pluto. We can send things to the stars - four of our spacecraft are already on the way - but they were only designed to study our outer planets and they will be dead long, looong before they pass another star. Could we design an interstellar probe? Yes, but it would take many decades or centuries to arrive, and at least 4 years to radio data back to us. Could we send people?. Presumably yes, at some point, but it would still take a long time to get there, maybe passing through several generations on the way - in other words, the great-grandchildren of the original crew might be the ones to arrive. Not a good situation for a teen-age rebellion! We are nowhere near understanding how to travel near the speed of light, and if we could the consequences of hitting a dust speck would be severe. The British Interplanetary Society, which pioneered serious studies for Lunar exploration before Apollo, has done similar pioneering work on a true interstellar mission called Daedalus.
Actually, we have already sent five spacecraft out from Earth on trajectories which will travel forever among the stars. Pioneer 10 and 11 flew past Jupiter in 1973 and 1974 respectively, and Pioneer 11 passed Saturn in 1979. After that they departed from the solar system, but their radio transmissions could no longer be picked up after 2003 and 1995 reaspectively. NASA's Voyager 1 and 2 spacecraft flew past Jupiter in 1979. Voyager 1 passed Saturn in 1980 and has now left the solar system, continuing to report on its environment. In November 2015 it was 20 billion km away from Earth. Voyager 2 passed all the outer planets, ending with Neptune in 1989, and is departing in a different direction. And New Horizons, which flew past Pluto in 2015, is also destined to float forever among the stars. Voyager 1 is the record-holder for distance. Its signals should be detectable for another 10 years before its power source is too depleted to operate any more.
NASA probe plan (but it doesn't really go to another star)
Laser-powered probe?
British Interplanetary Society probe plan
Bussard Ramjets as a way to go?
Voyager Interstellar Mission
The Search for Extraterrestrial Intelligence (SETI) and the Drake Equation
SETI is the search for extraterrestrial intelligence. SETI pioneer Frank Drake tried to quantify the number of civilizations in our galaxy which we might be able to detect. He devised the now-famous Drake Equation. It uses numbers such as 'the fraction of stars with planets' and 'the fraction of planets on which life appears' to try to calculate the number of civilizations currently broadcasting signals across the galaxy. Look at the link. When Drake thought of this nobody knew any of these numbers, but we are making progress. In the last few years over a thousand planets have been found orbiting other stars. But we are still a long way from knowing the solution to the equation.
The SETI Institute
Drake Equation - some answers?
Drake Equation
The Fermi Paradox
Physicist Enrico Fermi's response to optimistic SETI researchers was this paradox: If aliens are widespread, where are they? Why don't we see them or pick up signals on a regular basis? You can always come up with arguments why we might not be able to do this... we are in 'quarantine' (or a cosmic nature reserve) until we become less warlike, or so we can develop without interference, maybe. The problem is, these arguments have to work universally. No poachers in the reserve, no renegades, no aliens outside the pan-galactic culture that made the rules, no accidents...
Let's put it in perspective. If we could travel at 25% of the speed of light a trip to a star 10 light years away can be made in 40 years (50 if we allow time to speed up and slow down), which is a human working lifetime. A colonizing ship carrying multiple families could set up a colony on a planet, then take 100 years to build the colony, develop resources etc. Then it could move on again in the same way. At that rate the speed of travel across the galaxy would be 10 light years every 150 years. At that rate it would take only two million years to cross the galaxy and fill it with colonies. So if interstellar travel is feasible, a dynamic high-tech race could do it. Where are they? Is it impossible? Unsustainable? We don't know.
The Fermi Paradox
Maps of the sun's neighbourhood and the galaxy
Map of the sun's neighbourhood
Spacecraft carying messages
As mentioned above, four spacecraft have escaped from the solar system, Pioneer 10 and 11, and Voyager 1 and 2. All four were flung by Jupiter's gravity fast enough to escape the solar system, all in different directions. Another is on its way - New Horizons, the Pluto probe. They were designed only to study the planets they visited, and will be dead long before they approach any stars millions of years in the future. But the first four probes carry messages from Earth, in case they are found one day. Pioneers 10 and 11 carry the plaque shown above (see first link). Voyagers 1 and 2 carry disks a bit like a CD-ROM with graphical playing instructions. They carried sounds, music, images - information about us as a people, a race, a species. New Horizons, on its way to Pluto, does not carry a disk or message, but data may be uploaded to its computers after its science mission is over. Is this just trivial posturing? Consider this: these artifacts will outlast all other products of our culture. Something we made will be sailing through our galaxy long after humans themselves, and maybe life on Earth, have disappeared.
Pioneer plaques
Plaque history
The Voyager records
Lack of a New Horizons message
Adding a New Horizons message
Broadcasting our existence to the universe
Sending plaques on spacecraft is not the only way we announce our existence to the galaxy. We also broadcast radio signals. For 100 years weak radio signals have been spreading out from Earth like ripples on the cosmic ocean. For 50 years much stronger signals (television carrier signals, defensive radar) have also been broadcast. Aliens couldn't watch our TV (probably a good thing) but the strong carrier signal that is modulated to carry TV information could be detected. So all aliens within 50 light years of us could find us if they wanted to. Wait another 50 years, and all aliens within 100 light years will be able to detect us. This is not a planned communication - it's an uncontrolled experiment. Is it a good idea? What if we are alerting potential colonizers or slave-traders that we are here? Only time will tell. We have also made a few deliberate efforts to say "We are here" is that a good idea?
Project Ozma and the Arecibo message
Ozma
Interstellar broadcasting
Risks and benefits of interstellar transmission (PDF file)
Listening for other broadcasts
Rather than broadcasting that we are here, it might be safer to 'lurk', to listen in on broadcasts being sent by others. We have done a lot of that - see links below. But no obvious artificial signals have been detected. There are major problems: signals are weak and we make more interference all the time. There are billions of stars to monitor, and billions of potential "radio stations" - wavelengths - to listen to. And, how do you tell if a signal is artificial? Early radio astronomers were fooled by the rapid regular pulses coming from Pulsars until a natural explanation was accepted. Read Carl Sagan's novel 'Contact' (or see the movie) for a good story about this topic.
listening in...
listening in...
Optical SETI.
When will we find anything?
Will we find anything? A negative analysis.
Results so far...
... there are none. What does this mean? Are we alone? If so, are we alone because we are a unique creation? Many people believe this. Or are we alone because we are the first (at least in our corner of the galaxy) to evolve a technological civilization? Or is it just that we have not found our neighbours yet? SETI enthusiasts generally believe, or hope, this third answer is the explanation. Carl Sagan's discussion of this is very instructive - read the whole thing. If we really are alone in the galaxy, or extremely rare, should we be taking a bit more care of ourselves?
Pondering being alone...
More pondering...
Carl Sagan on SETI results
Putting Earth in perspective
Follow this link...
The Pale Blue Dot
The Allen Telescope Array in California, funded by Microsoft co-founder Paul Allen to search for signals from extraterrestrial civilizations (SETI Institute picture).