Posted on by Paul Scott Anderson

35 Years Later, the ‘Wow!’ Signal Still Tantalizes

The "Wow!" signal. Credit: Wikimedia Commons

Since the SETI program first began searching for possible alien radio signals a few decades ago, there have been many false alarms but also instances of fleeting signals of interest which disappeared again as quickly as they had appeared. If a potential signal doesn’t repeat itself so it can be more carefully observed, then it is virtually impossible to determine whether it is of truly cosmic origin. One such signal in particular caught astronomers’ interest on August 15, 1977. The famous “Wow!” signal was detected by the Big Ear Radio Observatory at Ohio State University; it was thirty times stronger than the background noise but lasted only 72 seconds and was never heard again despite repeated subsequent searches.

In a new book titled The Elusive Wow, amateur astronomer Robert Gray chronicles the quest for the answer to this enduring puzzle.

When the signal was first seen in the data, it was so pronounced that SETI scientist Jerry Ehman circled it on the computer printouts in red ink and wrote “Wow!” next to it. It appeared to fit the criteria for an extraterrestrial radio signal, but because it wasn’t heard again, the follow-up studies required to either confirm or deny this were not possible. So what was it about the signal that made it so interesting?

First, it did appear to be an artificial radio signal, rather than a natural radio emission such as a pulsar or quasar. The Big Ear telescope used a receiver with 50 radio channels; the signal was only heard on one frequency, with no other noise on any of the other channels. A natural emission would cause static to appear on all of the frequencies, and this was not the case. The signal was narrow and focused, as would be expected from an artificial source.

The Big Ear Radio Observatory. Credit: Big Ear Radio Observatory / North American AstroPhysical Observatory / Ohio State University

The signal also “rose and fell” during the 72 seconds, as would be expected from something originating in space. When the radio telescope is pointed at the sky, any such signal will appear to increase in intensity as it first moves across the observational beam of the telescope, then peak when the telescope is pointed straight at it and then decrease as it moves away from the telescope. This also makes a mere computer glitch a less likely explanation, although not impossible.

What about satellites? This would seem to be an obvious possible explanation, but as Gray notes, a satellite would have to be moving at just the right distance and at just the right speed, to mimic an alien signal. But then why wasn’t it observed again? An orbiting satellite will broadcast its signal repeatedly. The signal was observed near the 1420 MHz frequency, a “protected spectrum” in which terrestrial transmitters are forbidden to transmit as it is reserved for astronomical purposes.

There may be a bias in thinking that any alien signals will be like ours which leak out to space continuously, ie. all of our radio and TV broadcasts. That is, “normal” radio emissions from every-day type technologies which could easily be seen on an ongoing basis. But what if they were something more like beacons, sent out intentionally but only on a periodic basis? As Gray explains, radio searches to date have tended to look at many different spots in the sky, but they will only examine any particular spot for a few minutes or so before moving on to the next. A periodic signal could easily be missed completely, or if seen, it may be a long time before it is seen again.

Of course, it is also possible that any other civilizations out there might not even use radio at all, especially if they are more advanced than us (while other intelligent life might be behind us, as well). A newer branch of SETI is now searching for artificial sources of light, like laser beams, used as beacons.

So where does this leave us? The “Wow!” signal still hasn’t been adequately explained, although various theories have been proposed over the years. Perhaps one day it will be observed again, or another one like it, and we will be able to solve the mystery. Until then, it remains a curiosity, a tantalizing hint of what a definite signal from an extraterrestrial civilization might look like.

More information is available at the Big Ear Radio Observatory website.

Posted on by Paul Scott Anderson

Do Alien Civilizations Inevitably ‘Go Green’?

Beautiful view of our Milky Way Galaxy. If other alien civilizations are out there, can we find them? Credit: ESO/S. Guisard

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In the famous words of Arthur C. Clarke, “Any sufficiently advanced technology is indistinguishable from magic.” This phrase is often quoted to express the idea that an alien civilization which may be thousands or millions of years older than us would have technology so far ahead of ours that to us it would appear to be “magic.”

Now, a variation of that thought has come from Canadian science fiction writer Karl Schroeder, who posits that “any sufficiently advanced technology is indistinguishable from nature.” The reasoning is that if a civilization manages to exist that long, it would inevitably “go green” to such an extent that it would no longer leave any detectable waste products behind. Its artificial signatures would blend in with those of the natural universe, making it much more difficult to detect them by simply searching for artificial constructs versus natural ones.

The idea has been proposed as an explanation for why we haven’t found them yet, based on the premise that such advanced societies would have visited and colonized our entire galaxy by now (known as the Fermi Paradox). The question becomes more interesting in light of the fact that astronomers now estimate that there are billions of other planets in our galaxy alone. If a civilization reaches such a “balance with nature” as a natural progression, it may mean that traditional methods of searching for them, like SETI, will ultimately fail. Of course, it is possible, perhaps even likely, that civilizations much older than us would have advanced far beyond radio technology anyway. SETI itself is based on the assumption that some of them may still be using that technology. Another branch of SETI is searching for light pulses such as intentional beacons as opposed to radio signals.

But even other alternate searches, such as SETT (Search for Extraterrestrial Technology), may not pan out either, if this new scenario is correct. SETT looks for things like the spectral signature of nuclear fission waste being dumped into a star, or leaking tritium from alien fusion powerplants.

Another solution to the Fermi Paradox states that advanced civilizations will ultimately destroy themselves. Before they do though, they could have already sent out robotic probes to many places in the galaxy. If those probes were technologically savvy enough to self-replicate, they could have spread themselves widely across the cosmos. If there were any in our solar system, we could conceivably find them. Yet this idea could also come back around to the new hypothesis – if these probes were advanced enough to be truly “green” and not leave any environmental traces, they might be a lot harder to find, blending in with natural objects in the solar system.

It’s an intriguing new take on an old question. It can also be taken as a lesson – if we can learn to survive our own technological advances long enough, we can ultimately become more of a green civilization ourselves, co-existing comfortably with the natural universe around us.

Posted on by Paul Scott Anderson

Analysis of the First Kepler SETI Observations

Example of signals KOI 817 and KOI 812. Credit: The Search for Extra Terrestrial Intelligence at UC Berkeley

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As the Kepler space telescope begins finding its first Earth-sized exoplanets, with the ultimate goal of finding ones that are actually Earth-like, it would seem natural that the SETI (Search for Extraterrestrial Intelligence) program would take a look at them as well, in the continuing search for alien radio signals. That is exactly what SETI scientists are doing, and they’ve started releasing some of their preliminary results.

They are processing the data taken by Kepler since early 2011; some interesting signals have been found (a candidate signal is referred to as a Kepler Object of Interest or KOI), but as they are quick to point out, these signals so far can all be explained by terrestrial interference. If a single signal comes from multiple positions in the sky, as these ones do, it is most likely to be interference.

They do, however, also share characteristics which would be expected of alien artificial signals.

A couple of examples are from KOI 817 and KOI 812. They are of a very narrow frequency, as would be expected from a signal of artificial origin. They also change in frequency over time, due to the doppler effect – the motion of the alien signal source relative to the radio telescope on Earth. If a signal is found with these characteristics but also does not appear to be just interference, that would be a good candidate for an actual artificial signal of extraterrestrial origin.

These are only the results of the first observations and many more will come during the next weeks and months.

Looking for signals has always been like looking for a needle in the cosmic haystack; until now we were searching pretty much blind, starting even before we knew if there were any other planets out there or not. What if our solar system was the only one? Now we know that it is only one of many, with new estimates of billions of planets in our galaxy alone, based on early Kepler data. Plus the fact that the majority of those are thought to be smaller, rocky worlds like Earth, Mars, etc. How many of them are actually habitable is still an open question, but finding them narrows down the search, providing more probable actual targets to turn the radio telescopes toward instead of just trying to search billions of stars overall.

All twelve signal examples so far can be downloaded here (PDF).

Posted on by Tammy Plotner

Aliens Hanging Out in the Kuiper Belt? We Could See the Light from their Cities

Astronaut photograph ISS025-E-9858 was acquired on October 28, 2010, with a Nikon D3S digital camera using a 16 mm lens, and is provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Center. The image was taken by the Expedition 25 crew.

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When it comes to searching for ET, current efforts have been almost exclusively placed in picking up a radio signal – just a small portion of the electromagnetic spectrum. Consider for a moment just how much lighting we here on Earth produce and how our “night side” might appear as viewed from a telescope on another planet. If we can assume that alternate civilizations would evolve enjoying their natural lighting, wouldn’t it be plausible to also assume they might develop artificial lighting sources as well?

Is it possible for us to peer into space and spot artificially illuminated objects “out there?” According to a new study done by Abraham Loeb (Harvard), Edwin L. Turner (Princeton), the answer is yes.

For gathering light, the array of Earthly telescopes now at science’s disposal are able to confidently observe a light source comparable in overall brightness to a large city — up to a certain distance. Right now astronomers are able to measure the orbital parameters of Kuiper belt objects (KBOs) with the greatest of precision by their observed flux and computing their changing orbital distances.

However, is it possible to see light if it were to occur on the dark side? Loeb and Turner say that current optical telescopes and surveys would have the ability to see this amount of light at the edge of our Solar System and observations with large telescopes can measure a KBOs spectra to determine if they are illuminated by artificial lighting using a logarithmic slope (sunlit object would exhibit alpha=(dlogF/dlogD) = -4, whereas artificially-illuminated objects should exhibit alpha = -2.)

“Our civilization uses two basic classes of illumination: thermal (incandescent light bulbs) and quantum (light emitting diodes [LEDs] and fluorescent lamps)” Loeb and Turn write in their paper. “Such artificial light sources have different spectral properties than sunlight. The spectra of artificial lights on distant objects would likely distinguish them from natural illumination sources, since such emission would be exceptionally rare in the natural thermodynamic conditions present on the surface of relatively cold objects. Therefore, artificial illumination may serve as a lamppost which signals the existence of extraterrestrial technologies and thus civilizations.”

Spotting this illumination difference in the optical band would be tricky but by calculating the observed flux from solar illumination on Kuiper Belt Objects with a typical albedo, the team is confident that existing telescopes and surveys could detect the artificial light from a reasonably brightly illuminated region, roughly the size of a terrestrial city, located on a KBO. Even though the light signature would be weaker, it would still carry the dead give-away – the spectral signature.

However, we currently don’t expect there to be any civilizations thriving at the edge of our solar system, as it is dark and cold out there.

But Loeb has posed that possibly planets ejected from other parent stars in our galaxy may have traveled to the edge of our Solar System and ended up residing there. Whether a civilization would survive an ejection event from their parent system, and then put up lamposts is up for debate, however.

The team isn’t suggesting that any random light source detected where there should be darkness might be considered a sign of life, though. There are many factors which could contribute to illumination, such as viewing angle, backscattering, surface shadowing, outgassing, rotation, surface albedo variations and more. this is just a new suggestion and a new way of looking at things, as well as suggested exercises for future telescopes and studying exoplanets.

“City lights would be easier to detect on a planet which was left in the dark of a formerly-habitable zone after its host star turned into a faint white dwarf,” Loeb and Turner say. “The related civilization will need to survive the intermediate red giant phase of its star. If it does, separating its artificial light from the natural light of a white dwarf, would be much easier than for the original star, both spectroscopically and in total brightness.”

The next generation of optical and space-based telescopes could help to refine the search process when observing extra-solar planets and preliminary broad-band photometric detection could be improved through the use of narrow-band filters which are tuned to the spectral features of artificial light sources such as light emitting diodes. While such a scenario on a distant world would need to involve far more “light pollution” than even we produce – why rule it out?

“This method opens a new window in the search for extraterrestrial civilizations,” Loeb and Turner write. “The search can be extended beyond the Solar System with next generation telescopes on the ground and in space, which would be capable of detecting phase modulation due to very strong artificial illumination on the night-side of planets as they orbit their parent stars.”

Read Loeb and Turner’s paper: Detection Technique for Artificially-Illuminated Objects in the Outer Solar System and Beyond.

This article was inspired by a discussion on Google+.

Nancy Atkinson also contributed to this article.

Posted on by Ray Sanders

SETI to Resume Search for Extraterrestrial Intelligence; Will Target Kepler Data

The Allen Telescope Array. Image Credit: SETI Institute

After being shut down for over six months due to financial problems, The Allen Telescope Array (ATA) is once again searching other planetary systems for radio signals, looking for evidence of extraterrestrial intelligence.

Some of the first targets in SETI’s renewed search will be a selection of recently discovered exoplanet candidates by NASA’s Kepler mission.

“This is a superb opportunity for SETI observations,” said Dr. Jill Tarter, the Director of the Center for SETI Research at the SETI Institute. “For the first time, we can point our telescopes at stars, and know that those stars actually host planetary systems – including at least one that begins to approximate an Earth analog in the habitable zone around its host star. That’s the type of world that might be home to a civilization capable of building radio transmitters.”

What other studies will SETI be performing with the array, and how were they able to restart the Allen Telescope Array?

This past April, SETI was forced to place the ATA into hibernation mode, due to budget cuts of SETI’s former partner, U.C Berkeley. Since Berkeley operated Hat Creek Observatory where the ATA is located, their withdrawal from the program left SETI without a way to operate the ATA.

SETI has since acquired new funding to operate the ATA and can now resume observations where they left off – examining planetary candidates detected by the Kepler mission. The planetary candidates SETI will examine first will be those that are thought to be in their star’s habitable zone (the range of orbital distance from a planet’s host star which may allow for surface water). Many astrobiologists theorize that liquid water is essential for life to exist on a planet.

“In SETI, as with all research, preconceived notions such as habitable zones could be barriers to discovery.” Tarter added. “So, with sufficient future funding from our donors, it’s our intention to examine all of the planetary systems found by Kepler.”

SETI will spend the next two years observing the planetary systems detected by Kepler in the naturally-quiet 1 to 10 GHz terrestrial microwave window. Part of what makes this comprehensive study possible is that the ATA can provide ready access to tens of millions of channels at any one time.

Resuming ATA operations was made possible due to tremendous public support via SETI’s www.SETIStars.org web site. In addition to the funds raised by the public, the United States Air Force has also provided funding to SETI in order to assess the ATA’s capabilities for space situational awareness.

Tarter notes, “Kepler’s success has created an amazing opportunity to focus SETI research. While discovery of new exoplanets via Kepler is backed with government monies, the search for evidence that some of these worlds might be home to intelligence falls to SETI alone. And our SETI exploration depends entirely on private donations, for which we are deeply grateful to our donors.”

“The year-in and year-out fundraising challenge we tackle in order to conduct SETI research is an absolute human and organizational struggle,” said Tom Pierson, CEO of the SETI Institute, “yet it is well worth the hard work to help Jill’s team address what is one of humanity’s most profound research questions.”

Dr. Tarter will be presenting during the first Kepler Science Conference (at NASA Ames Research Center) from December 5 to 9, 2011. You can view the agenda for the meeting, along with the abstract for her talk on Earth analogs at: http://kepler.nasa.gov/Science/ForScientists/keplerconference/sessions/.

If you’d like to learn more about SETI, or would like to make a donation to help fund their efforts, visit: https://setistars.org/donations/new

Read more about SETI’s partnership with the United States Air Force at: http://www.seti.org/afspc

Source: SETI Institute press release

Posted on by Tammy Plotner

Alien Artifacts May Be Here… Just Hard To Find!

This image highlights the special cargo onboard NASA's Voyager spacecraft: the Golden Record. Each of the two Voyager spacecraft launched in 1977 carry a 12-inch gold-plated phonograph record with images and sounds from Earth. An artist's rendering of the Voyager spacecraft is shown at bottom right, with a yellow circle denoting the location of the Golden Record. The cover of the Golden Record, shown on upper right, carries directions explaining how to play the record, a diagram showing the location of our sun and the two lowest states of the hydrogen atom as a fundamental clock reference. The larger image to the left is a magnified picture of the record inside. Credit: NASA

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Greeting cards in space… We’ve certainly sent our share of them, haven’t we? So if humankind is foresighted enough to leave messages of our whereabouts – and our personalities – in space, then why haven’t other alien civilizations done the same? That’s a question a pair of postdoctoral researchers at Penn State are asking. By using mathematical equations, they’re showing us we simply haven’t looked in enough places… and would we recognize an alien artifact even if it were staring us in the face?

“The vastness of space, combined with our limited searches to date, implies that any remote unpiloted exploratory probes of extraterrestrial origin would likely remain unnoticed,” report Jacob Haqq-Misra, Rock Ethics Institute, and Ravi Kumar Kopparapu, Earth and Environmental Systems Institute, in a paper accepted by Acta Astronautica and posted online on ArXiv.

So far, we simply haven’t found any evidence of alien artifacts in our solar system – or anywhere else for that matter. According to the Penn State article, the Fermi paradox, originally formulated by Enrico Fermi, asks, if intelligent life is common, why have no technological civilizations been observed. Well, shucks… Maybe they’re shy – and maybe they’ve self-annihilated. There are hundreds of reasons “why” we haven’t found anything, but the most pertinent answer is we simply aren’t looking for the right thing in the right place at the right time. For example, have a look at just a few of the things we humans have sent into vastness of space to act as our ambassadors…

Duke Family Portrait: Apollo 16 Journal - Courtesy of Markus Mehring - Credit: NASA AS16-117-18841

Pioneer 10 and 11's famed Plaque features a design engraved into a gold-anodized aluminum plate, 152 by 229 millimeters (6 by 9 inches), attached to the spacecrafts' antenna support struts to help shield it from erosion by interstellar dust. Image Credit: NASA

Three LEGO figurines representing the Roman god Jupiter, his wife Juno and Galileo Galilei are shown here aboard the Juno spacecraft. Image credit: NASA/JPL-Caltech/KSC NASA's Jupiter-bound Juno spacecraft will carry the 1.5-inch likeness of Galileo Galilei, the Roman god Jupiter and his wife Juno to Jupiter when the spacecraft launches this Friday, Aug. 5. The inclusion of the three mini-statues, or figurines, is part of a joint outreach and educational program developed as part of the partnership between NASA and the LEGO Group to inspire children to explore science, technology, engineering and mathematics. Credit: NASA

And this is only just the tip of the human iceberg. How many of us have sent our name on missions to Mars, Pluto and more? There are footprints, plaques, flags, golf balls and an endless parade of human artifacts scattered far and wide. We might think they’re in plain sight, but would an alien culture see that? Would we comprehend what an alien culture might consider to be a greeting or sign or their presence? As far as we know, there could be unpiloted probes from alien civilizations out there right now, checking us out… But unless it were something the size of a proverbial school bus dropping itself on a house in Essex, our own arrogance would probably keep us from noticing it. And then again… it just might be hidden.

“Extraterrestrial artifacts may exist in the Solar System without our knowledge simply because we have not yet searched sufficiently,” said Haqq-Misra and Kopparapu. “Few if any of the attempts would be capable of detecting a 1 to 10 meter (3 to 33 foot) probe.”

Haqq-Misra and Kopparapu use a probabilistic method to determine the feasibility of aliens leaving us clues to their existence. Their work points to the Solar System as a fixed volume and then calculates the percentages of that volume that would need to be thoroughly searched to detect an alien probe or artifact. These searches would have to involve technology able to detect small, foreign objects and then apply it to a smaller portion of the volume to look for results. It’s a study which hasn’t been undertaken so far. We simply cannot say we’ve looked everywhere…

“The surface of the Earth is one of the few places in the Solar System that has been almost completely examined at a spatial resolution of less than 3 feet,” said Haqq-Misra and Kopparapu.

Sure. There are still a lot of nooks and crannies on Earth that haven’t been thoroughly explored – and our oceans are a good example. However, when it comes to searching elsewhere, it’s been a hit-or-miss proposition. While mapping the surface of the Moon, the Lunar Reconnaissance Orbiter is looking at the surface at a resolution of about 20 inches. It may take a few years, but perhaps something isn’t buried under the regolith. As for Mars, chances are slight – but new things seem to be discovered on Mars each day, don’t they? How about the LaGrange points, or the asteroid belt? Things could be hiding there, too.

“Searches to date of the Solar System are sufficiently incomplete that we cannot rule out the possibility that non terrestrial artifacts are present and may even be observing us,” said Haqq-Misra and Kopparapu. They add that “the completeness of our search for non terrestrial objects will inevitably increase as we continue to explore the Moon, Mars and other nearby regions of space.”

After all, what did we expect? E.T. to interrupt a prime time television program to announce their presence? A take-over of the Internet? Maybe each time a meteor makes it to Earth it’s a little calling card that life-possible organisms exists outside our own little sphere…

And maybe somebody needs to drop a bus on us.

Original Story Source: Penn State News Release.

Posted on by Nancy Atkinson

No Alien Visits or UFO Coverups, White House Says

Movie poster from 'Independence Day.' Credit: 20th Century Fox

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The White House has responded to two petitions asking the US government to formally acknowledge that aliens have visited Earth and to disclose to any intentional withholding of government interactions with extraterrestrial beings. “The U.S. government has no evidence that any life exists outside our planet, or that an extraterrestrial presence has contacted or engaged any member of the human race,” said Phil Larson from the White House Office of Science & Technology Policy, on the WhiteHouse.gov website. “In addition, there is no credible information to suggest that any evidence is being hidden from the public’s eye.”

5,387 people had signed the petition for immediately disclosing the government’s knowledge of and communications with extraterrestrial beings, and 12,078 signed the request for a formal acknowledgement from the White House that extraterrestrials have been engaging the human race.

“Hundreds of military and government agency witnesses have come forward with testimony confirming this extraterrestrial presence,” the second petition states. “Opinion polls now indicate more than 50% of the American people believe there is an extraterrestrial presence and more than 80% believe the government is not telling the truth about this phenomenon. The people have a right to know. The people can handle the truth.”

These petitions come from an Obama Administration initiative called ‘We the People’ which has White House staffers respond and consider taking action on any issue that receives at least 25,000 online signatures. Regarding these two petitions, the White House promised to respond if the petitions got 17,000 or more signatures by Oct. 22.

Larson stressed that the facts show that there is no credible evidence of extraterrestrial presence here on Earth. He pointed out that even though many scientists have come to the conclusion that the odds of life somewhere else in the Universe are fairly high, the chance that any of them are making contact with humans are extremely small, given the distances involved.

But that doesn’t mean we aren’t searching, there is just no evidence yet. Larson mentioned SETI (correctly noting that this at first was a NASA effort, but is now funded privately) keeping an “ear” out for signals from any intelligent extraterrestrials, with none found so far. He also added that the Kepler spacecraft is searching for Earth-like planets in the habitable zones around other stars, and that the Curiosity rover will launch to Mars this month to “assess what the Martian environment was like in the past to see if it could have harbored life.”

Regarding any evidence for alien life, all anyone has now is “statistics and speculation,” said Larson. “The fact is we have no credible evidence of extraterrestrial presence here on Earth.”

Whether or not this will appease or satisfy any conspiracy theorists or UFO believers is yet to be seen, but it is gratifying to see the White House respond in such a no-nonsense manner.

UPDATE: The Paradigm Research Group, one of the organizations sponsoring the petitions, has issued a statement saying, “As expected it was written by a low level staffer from the Office of Science and Technology Policy – research assistant Phil Larson. The response was unacceptable.”

See the petitions and the response at the WhiteHouse.gov website.

Hat Tip: NASA Watch

Posted on by Jason Rhian

Book Review: A Dictionary of the Space Age

A Dictionary of the Space Age covers most aspects of space flight but is somewhat lacking in detail. Image Credit: John Hopkins University & Alan Walters/awaltersphoto.com

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Writing a dictionary is not the same as writing a novel. While it might seem difficult to mess up a dictionary, even one with terminology that is as complicated as that used within the space industry – getting it right can be challenging. For those that follow space flight having such a dictionary can be invaluable. While A Dictionary of the Space Age does meet the basic requirements easily it fails somewhat in terms of its comprehensiveness.

When normal folks, even space enthusiasts watch launches and other space-related events (EVAs, dockings, landings and such) there are so many acronyms and jargon thrown about – that it is extremely hard to follow. With A Dictionary of the Space Age on hand, one can simply thumb through and find out exactly what is being said, making it both easier to follow along and making the endeavor being witnessed far more inclusive. That is as long if you are only looking for the most general of terms. The book is far from complete – but given the complex nature of the topic – this might not have been possible.

Crewed, unmanned, military space efforts and satellites – all have key terms addressed within the pages of this book.

The book is published by The Johns Hopkins University Press and was compiled and written by aerospace expert Paul Dickson. One can purchase the book on the secondary market (Amazon.com) for around $12 (new for around $25). The dictionary also has a Kindle edition which is available for $37.76. Dickson’s previous works on space flight is Sputnik: The Shock of the Century.

Weighing in at 288 pages, the book briefly covers the primary terms used within the space community. In short, if you are interested in learning more about space flight – or wish to do so – this is a good book for you.

Posted on by Nancy Atkinson

Now Available: 30 Free Lectures by Noted Astronomers

We just received a note from Andrew Franknoi and the Astronomical Society of the Pacific that they are making available, free of charge, 30 audio and video podcasts from talks given by distinguished astronomers on the latest ideas and discoveries in the field. Speakers include:

* Frank Drake, who began the experimental search for intelligent life among the stars,
* Mike Brown, who discovered most of the dwarf planets beyond Pluto (and whose humorous talk is entitled “How I Killed Pluto and Why it Had it Coming”),
* Natalie Batalha, project scientists on the Kepler Mission to find Earths around other stars,
* Alex Filippenko (national professor of the year) on finding black holes.

Recent topics added to the offerings include: multiple universes, Saturn’s moon Titan (with an atmosphere, rivers, and lakes), our explosive Sun, and whether we should expect doomsday in 2012.

The talks are part of the Silicon Valley Astronomy Lectures, jointly sponsored by NASA’s Ames Research Center, the Astronomical Society of the Pacific, the SETI Institute, and Foothill College.
They are available via the web and ITunes. For a complete list and to begin listening, go to:
http://www.astrosociety.org/education/podcast/

Posted on by Steve Nerlich

Astronomy Without A Telescope – The Unlikeliness Of Being

The Search for ExtraTerrestrial Intelligence could be a waste of time according to a recent statistical analysis of the likelihood of life arising spontaneously on habitable-zone exoplanets out there in the wider universe (and let's face it - when have predictive statistics ever got it wrong?) Credit: SETI Institute.

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History has proved time and again that mathematical modelling is no substitute for a telescope (or other data collection device). Nonetheless, some theoreticians have recently put forward a statistical analysis which suggests that life is probably very rare in the universe – despite the apparent prevalence of habitable-zone exoplanets, being found by the Kepler mission and other exoplanet search techniques.

You would be right to be skeptical, given the Bayesian analysis undertaken is based on our singular experience of abiogenesis – being the origin of life from non-life, here on Earth. Indeed, the seemingly rapid abiogenesis that occurred on Earth soon after its formation is suggested to be the clinching proof that abiogenesis on habitable-zone exoplanets must be rare. Hmm…

Bayes theorem provides a basis for estimating the likelihood that a prior assumption or hypothesis (e.g. that abiogenesis is common on habitable-zone exoplanets) is correct, using whatever evidence is available. Its usage is nicely demonstrated in solving the Monty Hall problem.

Go here for the detail, but in a nutshell:
There are three doors, one with a car behind it and the other two have goats. You announce which door you will pick – knowing that it carries a 1/3 probability of hiding the car. Then Monty Hall, who knows where the car is, opens another door to reveal a goat. So, now you know that door always had a zero probability of hiding the car. So, the likelihood of the remaining door hiding the car carries the remaining 2/3 probability of the system, since there was always an absolute 1/1 probability that the car was behind one of the three doors. So, it makes more sense for you to open that remaining door, instead of the first one you picked.

In this story, Monty Hall opening the door with a goat represents new data. It doesn’t allow you to definitively determine where the car is, but it does allow you to recalculate the likelihood that your prior hypothesis (that the car is behind the first door you picked) is correct.

Applying Bayesian analysis to the problem of abiogenesis on habitable-zone exoplanets is a bit of a stretch. Speigel and Turner argue that the evidence we have available to us – that life began quite soon after the Earth became habitable – contributes nothing to estimating the likelihood that life arises routinely on habitable-zone exoplanets.

They remind us that we need to acknowledge the anthropic nature of the observation we are making. We are here after 3.5 billion years of evolution – which has given us the capacity to gather together the evidence that life began here 3.5 billion years ago, shortly after the Earth first became habitable. But that is only because this is how things unfolded here on Earth. In the absence of more data, the apparent rapidity of abiogenesis here on Earth could just be a fluke.

Stromatolites - which were a fairly early form of life on Earth. Earth became inhabited by such early life shortly after it became habitable. This might seem suggestive that life is somewhat inevitable when the conditions are right. But a statistician is never going to buy such an argument when it's based on a single example.

This is a fair point, but a largely philosophical one. It informs the subsequent six pages of Spiegel and Turner’s Bayesian analysis, but it is not a conclusion of that analysis.

The authors seek to remind us that interviewing one person and finding that she or he likes baked beans does not allow us to conclude that all people like baked beans. Yes agree, but that’s just statistics – it’s not really Bayesian statistics.

If we are ever able to closely study an exoplanet that has been in a habitable state for 3.5 billion years and discover that either it has life, or that it does not – that will be equivalent to Monty Hall opening another door.

But for now, we might just be a fluke… or we might not be. What we need is more data.

Further reading: Spiegel and Turner. Life might be rare despite its early emergence on Earth: a Bayesian analysis of the probability of abiogenesis.