Remarkably, there are many new websites suggesting just that. For the moment, the cosmic conspiracy theorists are pushing aside the end of the world on 12/21/12 to make room for a more urgent threat from Comet Elenin, a faint long-period comet discovered in December. On Internet conspiracy sites, this comet is being blamed for the March 10 Japan earthquake and tsunami, and it is supposed to either hit the Earth or knock us off our axis in September. Many say it is not a comet at all but a black hole or brown dwarf star, or that it is a precursor of Nibiru, the 2012 death planet. Following are some questions and answers about Comet Elenin from the NASA “Ask an Astrobiologist” website.

Question: Please tell me about Comet Elenin; there does not seem to be much credible information. What is its size? I have heard it is twice the diameter of Earth. Some websites say that Elenin is 80,000 km in diameter including coma. Can you put something out there about what NASA knows about Comet Elenin, just to smooth things over before people get crazy? Some are claiming that the comet has disappeared or that there is a government plot to hide it.

Answer: I will be glad to tell you what I know about Comet Elenin. Most of the information comes from amateur astronomers, who have made hundreds of observations; see [http://www.aerith.net/comet/catalog/2010X1/2010X1.html]. Our knowledge of its orbit is constantly improving, with updates available from the Minor Planet Center [http://ubasti.cfa.harvard.edu/~cgi/ReturnPrepEph?d=c&o=CK10X010]. Elenin is estimated to have an orbital period of about 10,000 years.

There are many photos posted on the web, but be careful: the great majority of the images that come up in a Google search are not of Comet Elenin but of other comets or artist impressions (and some are fakes). For one good example see photos from Bernhard Hausler taken in early March [http://thewatchers.adorraeli.com/2011/03/11/new-approach-of-a-comet-with-an-asteroid-elenin/]. The comet is too faint to be seen or photographed with a small telescope; people who say the comet has disappeared or photos are being suppressed are lying.

To understand questions about the size of the comet, you must distinguish between the small solid nucleus of rock and ice and the large atmosphere (coma) and tail that develop as a comet approaches the Sun. The nucleus has not been measured but is probably about 4 km across. The coma was reported to be about 80,000 km across in early April, with a tail estimated at ten times that length. These are not unusual values for a comet, and both coma and tail are expected to grow as the comet approaches the Sun (it is still beyond the orbit of Mars at this writing on April 15). Some comets have developed atmospheres that can be more than a million kilometers across. But please remember that the atmosphere (coma and tail) is extremely tenuous—far less dense than the best vacuum that can be produced in the lab. This thin gas and dust can have no effect on the Earth or anything else.

Question: The photo of Comet Elenin that is usually shown is a fake image and it is actually comet 81P/Wild [http://www.suite101.com/view_image_articles.cfm/2683306]. NASA supposedly has limited info and no pictures. Oh, really? Not from the WISE satellite, designed specifically to look at low light objects (like dwarf stars) with high-sensitivity infrared? What about the South Pole telescope which has excellent IR detection capabilities? How about Hubble? Nothing! Is this really the dwarf star that would end all life on earth? Why doesn’t NASA ever say anything about it?

Answer: I am worried about the effects of the fear campaign about Comet Elenin that is being waged on the Internet. We all remember the Heaven's Gate cult that became so obsessed with Comet Hale-Bopp in 1997 that the members committed mass suicide [http://en.wikipedia.org/wiki/Heaven's_Gate_(religious_group)]. I don't want anything like that to happen again, so I will answer this and the following questions about Comet Elenin. Perhaps I can also promote some critical thinking about these claims.

(1) Yes, I know that this photo (which is not faked, just misidentified) is not of Comet Elenin. In fact, most of the images that come up when you Google "Elenin images" are not of Elenin. I don't know how this particular photo of Comet Wild became associated with Elenin, except that Elenin is so faint that perhaps some people wanted to substitute a picture of a brighter comet. (2) The WISE (Wide-field Infrared Survey Explorer) telescope ceased operations at about the time Elenin was discovered. This little comet, then in the asteroid belt, was probably too faint to be picked up by WISE. (3) I don't know much about the NSF telescopes at the South Pole, but in the five months since the discovery of Elenin, the South Pole has mostly been in continuous daylight. The South Pole would be one of the worst places to go to study this comet. (4) The Hubble Space Telescope will undoubtedly study Elenin when it is close to Earth, but I doubt that anyone has used it yet. Most astronomers will wait to study the comet when it is closer and brighter. (5) Do I need to remind my readers that a brown dwarf is billions (with a B) of times more massive than a comet? I suspect this brown dwarf rumor started when someone who is not familiar with the sky turned a small telescope on Jupiter with its four moons. (6) There is no reason that NASA (or the media) would be commenting on this small faint comet. The only people observing it now are amateur astronomers, who are tracking its orbit and its increasing brightness as it approaches the inner solar system. There is a lot of craziness circulating on the Internet, from people who either don't know much about astronomy or are intentionally making up stories to frighten gullible people. Shame on them!

Question: I read that a new calculation on Comet Elenin was posted on the NASA Buzzroom stating, "I've revised the 0.24 AUs down to 0.0004617 AUs on 16th Oct 2011" and that the Buzzroom forum was taken down due to that comment. I also read that "an inside source" from NASA is telling people that you guys are worried about the comet knocking the ISS out of orbit, which is why the space flights are being ended. I want to know if I am falling for the conspiracies trap. Where are these people getting their "updated calculations,” and who is this "inside source"? I truly dislike when people post these things in order to frighten others.

Answer: Those are indeed weird statements about Comet Elenin. Some of them come from an amateurish video that was posted anonymously on the NASA Buzzroom website in late February but is no longer available. There is no "inside source" from NASA. That is a standard technique of conspiracy websites: make up some story and then attribute it to a secret unnamed source so no one can check up on the claim. I don’t know details, but you are partly correct that the NASA Buzzroom website was taken down because of the video claiming that the comet orbit had changed. Also, other people had posted several offensive videos that had nothing to do with NASA or space. Because of these inappropriate postings, the entire Buzzroom website was taken down. I too get lots of offensive messages, but I don't post them. It is important that you be able to trust what you read on a government website.

NASA spaceflights are not ending, as anyone can tell by reading newspapers or looking at NASA websites. I am sure my readers realize that many people who are making comments on websites don’t know what they are talking about. Some think that the comet’s orbit will change suddenly and it may hit the Earth, whereas in reality it cannot come much closer than 100 times the distance to the Moon. Some question what mysterious force is pulling on it to bend its path; they seem to forget that this comet is in orbit around the Sun. Some think that we must know its mass to calculate its orbit; they have apparently forgotten the simple experiment credited to Galileo, who showed that objects of different mass behave the same way in response to gravity (for example, cannon balls of different mass fall at the same rate when dropped from a tower). One suggestion I saw was that perhaps Elenin is not a comet; the individual speculated that it might be a planet (perhaps Nibiru) or a brown dwarf or a massive black hole masquerading as a comet. Please think about what a comet is. By definition, a comet is a small object that sheds an extensive thin atmosphere of gas as it approaches the Sun. If it were massive (such as a planet, brown dwarf, or black hole), its gravity would hold on to the gas and it could not develop a coma or tail. Finally, there are the astrologers who seem to think that there are mysterious forces associated with alignments, but I am confident that no readers of this article would make such foolish errors.

Every month, as the Moon circles our planet in its elongated orbit, its distance from the Earth varies. At perigee (the Moon’s closest position to Earth), it is 14 percent closer than at apogee (the Moon’s farthest position from Earth) and therefore appears 14 percent larger. This change is too small to be noticed, unless you have some way to make a precise measurement of the Moon’s apparent size. In March 2011, the perigee happened within one hour of full phase.

The moment of full moon is also not easily apparent, and most people will call the Moon’s phase “full” over two or three days. So yes, the full moon was a little bit closer and brighter in March than usual, but if you missed it, it will be very nearly as close at the next full moon. The Moon’s perigee is nearly the same in every orbit, varying by less than 2 percent. Further, there is no evidence that the Moon is associated with anything on Earth except the tides. Neither earthquakes nor weather are correlated with the position or phases of the Moon. I received this question while attending the annual Lunar and Planetary Science Conference in Houston. About 1,500 scientists spent a week discussing fascinating new science, including spectacular high-resolution images from the NASA Lunar Orbiter, two space missions that have recently had close encounters with comets, and a flood of exciting new information about the planet Mars. Not one person mentioned 2012 doomsday or Nibiru, pole shifts, supermoons, or any of the other pseudoscience that circulates widely on the Internet. It is a jolt for me to shift attention from discussing exciting new scientific discoveries with my colleagues to answering questions I receive every day from people who fear imaginary threats like Nibiru or pole shifts or supermoons.

Question: There are reports and videos of two suns seen close together in the sky over China. What is in these videos; is it a second sun or planet? There was also a second sun seen in New Zealand at the time of the earthquake in Christchurch.

Answer: Let’s use common sense to analyze this question. (1) It is fascinating that people sit at their computer consoles and write to me about a second sun without stepping outside to see for themselves. If there really were a second sun in the sky close to the real sun, it would be equally visible everywhere to anyone who looked in the daytime. Since the image in the most popular video from China shows this “second sun” as being nearly as bright as the real sun, we would also be receiving nearly twice as much light and therefore be burning up. In other words, the idea of two suns in our sky is obviously untrue. (2) You mention that the second image could be a planet. Planets shine by reflected sunlight and are millions of times fainter than the sun. That is why it is so difficult for astronomers to photograph planets around distant stars. So we can easily reject that option. (3) Aren’t you concerned that the second sun images are being presented in videos, which are inherently low resolution? They are amateur videos at that with no accompanying documentation. These facts strongly suggest fakery. (4) A photo with two images of the same size side by side can be faked by shooting through double glass. The separation and relative brightness of the images depend on the spacing between the glass and the angle of the shot. (5) A few astronomers have suggested that this phenomenon could be produced under rare atmospheric conditions by a mirage. They may be right, and I would look seriously at these suggestions if I thought the double-sun photos were real. But scientists have been fooled in the past because they do not expect fake data. Professional magicians, who understand fakery, are often better skeptics than scientists.

Question: Everyone is freaking out about Comet Elenin, but no one has much real information. Has anyone determined its size and mass? If you don’t know its size and mass, how can you calculate its orbit? What are the chances that Elenin will either impact us or get close enough to cause a major catastrophe?

Answer: Comet C2012 X1 Elenin (to give its full name) is a small, long-period comet that takes about 10,000 years to complete one orbit around the Sun. Russian amateur astronomer Leonid Elenin discovered it with a robotic telescope in New Mexico on December 10, 2010. Astronomers have not measured its size because it is only a few kilometers across, and its solid nucleus is shrouded by the surrounding gas. The mass is too small to cause any change in the orbits of other objects, and so its mass is unlikely ever to be measured. However, we do not need to know either the size or the mass of a comet to calculate its orbit, as some readers may remember from their college physics or astronomy courses. It is precisely because Elenin is small and distant that journalists, and the public, have not shown much interest. Although there are still some uncertainties in its orbit, Elenin’s perihelion (when it will be closest to the Sun) is in early September 2011 at a distance from the Sun of forty to forty-five million miles. It will be closest to Earth on about October 16, 2011, at a distance of about twenty-one million miles, which is nearly a hundred times farther than the distance between the Earth and the Moon. It will probably be visible using binoculars during October.

Unfortunately, there is a rapidly growing list of conspiracy theory websites (apparently written by people who don’t know, or don’t care, what a comet is) making wild claims that Elenin will hit the Earth, disturb our orbit, cause changes to the tides, or interact with our magnetic field. Such claims are pure fiction. One of the worst examples is a video posted on March 1, 2011, claiming that the magnetic field of the comet would cause a large shift in the rotation axis of the Earth and produce mega-earthquakes on March 15, 2011. In reality, comets don’t have magnetic fields, and magnetic fields can’t change the rotation axis or cause earthquakes no matter how large they are. Unfortunately, the comet hysteria has grown since the tragic March 10 earthquake in Japan, which many pseudoscientific websites blame on this comet.

Question: Are you claiming that the March 10 earthquake in Japan and Comet Elenin are coincidences? Someone predicts an earthquake—basing it on Elenin orbit—and it happens. Isn’t it worth re-evaluating the prediction?

There is no connection between Comet Elenin and the March 10 earthquake. Scientific explanations depend on cause and effect. This comet can have no gravitational or electromagnetic effect on Earth. It is only a billionth of the mass of the Earth, and comets don’t have magnetic fields. Also remember that there was no large change (greater than 10 degrees was predicted) in the rotation axis of Earth, so there was no pole shift to trigger any earthquake. Equally important, earthquakes are not caused by external forces—not by gravity, electromagnetism, or pole shifts. Earthquakes are a product of the active geology associated with plate tectonics. The Japan earthquake was ordinary (although exceptionally large) and occurred on one of the most active subduction fault systems in the world. This is the same fault system that killed even more people in the great Yokohama quake and fire in 1923. Earth’s active geology caused this earthquake, not some poor little comet that is too faint to see without a telescope.

Question: NASA scientist Richard Hoover recently claimed to have found life in meteorites. Were these findings debunked or are they still inconclusive?

I have not yet met any astrobiologist who is convinced by Richard Hoover’s claims, which probably explains why you have not heard any updates on this story. One of the biggest problems is likely contamination by terrestrial microbes after the meteorite fell to Earth. It is also troubling that this result was not published in a real scientific journal but instead on an unreviewed online website. Over the past fifty years many scientists have investigated thousands of meteorites, and they have not seen anything that looks like life. Remember also that the meteorite parent objects are asteroids, not planets (except for the few meteorites we have from the Moon and Mars, which are in a special class). It would be unexpected to find life on a small, airless asteroid. This claim of fossil life is an example of an exceptional claim, and as Carl Sagan taught us, exceptional claims require exceptional evidence to be accepted. Hoover’s unreviewed paper is not exceptional evidence.

I am struck by the differences between this claim and the treatment given to the evidence for fossil life in a Mars meteorite reported in 1996. In that case, many scientists carefully reviewed the evidence, which was published in a prestigious scientific journal, yet it was presented at a NASA press conference as a tentative result with opportunity for critics to indicate their skepticism. Although the Mars claim is not generally accepted today, it stimulated a lot of excellent follow-up research. If Hoover wants to be taken seriously by the community of astrobiologists, he needs to publish his work in a real journal and respond to the criticisms from other scientists. That is the way science advances.

Question: If there is no problem coming in 2012 then why is the government of the United States in such a rush to build so many underground bunkers? On Jesse Ventura’s Conspiracy Theory on TV they showed the inside of bunkers and they also showed U.S. security forces. They stated they’d do what ever it takes to keep the bunkers secure in 2012.

There are no bunkers being built in anticipation of 2012, except possibly by some individuals who don’t realize that doomsday 2012 is a hoax. I expect that Jesse Ventura knows 2012 is just a hoax, but he is in show business. His show Conspiracy Theory is entertainment, not journalism. The name gives this away because “conspiracy theory” is a pejorative term that refers to any fringe idea that explains a historical or current event as the result of a secret plot by conspirators. Watch Ventura’s episode on 2012 carefully and you will see that he shows no actual government bunkers and interviews no one who claims to have seen them. It is all innuendo and speculation, with films of people (in the Denver airport for example) who are obviously confused by this guy asking weird questions and wanting access to “bunkers.” He does show one example where private developers are constructing homes inside an abandoned missile silo. Notice that Ventura did not contact the people who are planning to move into one of these underground homes to ask them why they are moving there. This show is for entertainment, so it is better to leave questions unresolved.

In reality, there are bombproof civil defense bunkers all around the U.S. that were built during the cold war, especially during the Eisenhower administration. These include the famous Cheyenne Mountain operations center of the Strategic Air Command and the large complex at Greenbrier, West Virginia, which was once the designated site for senior government officials in case of atomic attack on Washington. (There are good Wikipedia articles on both). Civil defense shelters are an old story, and they have nothing to do with 2012.

Question: Should we be worried about the gradual warming of the Sun?

No, but you should be worried about the rapid warming of the Earth that we are experiencing today. The Sun influences climate in two ways. First, there is the periodic variation in solar energy output related to the eleven-year sunspot (or solar activity) cycle. The temperature changes due to this variation have been carefully monitored from space for several decades, and they are very small—almost too small to be detected in global temperature measurements.

Second, there is the gradual warming that has taken place since the Sun was formed more than four billion years ago, which will continue for billions of years into the future. As it ages, the Sun brightens by about 7 percent per billion years, which is negligible on any timescale of less than tens of millions of years, although it will make Earth uninhabitable some two to three billion years in the future.

Our current climate crisis is not related to the Sun. It is the direct response of the Earth to the added carbon dioxide and methane and other greenhouse gases in the atmosphere. More than century ago, Nobel Prize-winning chemist Svante Arrhenius first predicted that the release of carbon dioxide from burning fossil fuels would cause additional greenhouse warming. Now we are seeing this as a dramatic climate change that places our entire civilization at risk.

There are interesting parallels between the campaign against climate science and the widespread efforts to deny biological evolution and block its inclusion in science classes. Both climate denialism and evolution denialism use pseudoscience to fight real science. They include founding of nonprofit institutes, publication of fake science in non-refereed journals, and sophisticated marketing in the halls of power. Apparently some scientists can be seduced by a strong ideological commitment to fight government environmental regulations, just as some creationists are much more interested in saving our souls (and theirs) than in addressing the science of biology. Like creationists, many of the climate contrarians are “merchants of doubt,” using pseudoscience to undercut real science and create a wedge for their nonscientific beliefs.

Question: If the world does not end in 2012, then when and how do you predict that it will end? Will it be a painful death?

The “end of the world” is a silly idea. For the first five years that I answered questions sent to “Ask an Astrobiologist,” I never encountered any questions about the end of the world. Now I receive at least one per week. My guess is that the people who ask these questions are not interested in the fact that the Sun will become a red giant and consume the Earth in about four billion years; no one expects the human race or human civilization to last for billions of years. These question askers seem to be fearful of something that will happen in their lifetimes or perhaps the lifetimes of their great-great grandchildren.

I promise you that there is nothing that could destroy the Earth. The only two possible global threats in the next few centuries or millennia are a collision with a large comet—which is extremely unlikely but possible—and the melting of the polar ice caps due to global warming, which is inevitable if we don’t dramatically alter our consumption of fossil fuels. Either global warming or a comet collision could lead to a mass extinction and perhaps the destruction of our civilization, but neither will be the end of the world or even of humanity. The problem with the question about the end of the world is that it raises needless fears and distracts us from dealing with the real problems we face.

Question: Lately there have been reports that the next solar maximum, or “solar tsunami,” is expected to be devastating to mankind. Meanwhile, it seems that the recent solar flare ejections are already starting to cause panic among some people, some of whom are saying NASA now expects the solar maximum to bring death. I’ve just watched a Discovery Channel show about solar storms. Looking at all that devastation still gives me goosebumps.

The Sun is not our enemy and will not hurt us. NASA has never suggested that the solar maximum could bring death. A lot of shows on the Discovery Channel exaggerate dangers; apparently such shows attract viewers and advertisers. The simple facts are that the Sun has an eleven-year activity cycle, but we cannot accurately predict individual events such as flares and coronal mass ejections (CMEs). In the case of the largest CMEs, it is possible to damage transformers in electrical grids, and NASA is currently planning to provide accurate warnings to electrical utilities so they can isolate any parts that are likely to be directly affected by solar particles.

Solar scientists expect that the next solar maximum will be in the spring of 2013 and will be unusually weak, but the Sun may have some surprises for us. However, there is nothing about this solar maximum that can hurt us or threaten devastation to mankind. There will be many solar flares between now and 2015, but there are no specific predictions. I think the use of such terms as “solar tsunami” or “solar storm” to describe solar activity is unfortunate. It makes people think of destructive tidal waves or storms on Earth—but the Sun is 150 million kilometers away! There is an especially confusing Fox News interview with cosmologist Michio Kaku that is popular on YouTube. Kaku states that at solar maximum the Sun’s magnetic field suddenly flips and a giant shock wave of radiation heads for Earth, which he warns could disable our civilization. This is not the way the solar cycle works, and it raises greatly exaggerated fears.

The current fear of the solar maximum reminds me of some of the stories that circulated around Y2K. In both cases there were legitimate concerns: to protect older computer systems from the “Y2K bug” and now to protect satellites from solar outbursts. But the dangers to individual people are hugely exaggerated. Assuming you were not killed or seriously hurt by the previous solar maxima in 2001 and 1990, you have nothing to fear from this one.

Question: I really want to believe Nibiru is not real. But why are people still talking about it on YouTube? Do you think the topic will die down? And if it grows, what can we do about it?

This 2012 hoax has been going strong for the past three years, and it shows no sign of dying down. Maybe a few people who post these crazy lies on the Internet and YouTube really believe it, but I suspect most of them are in it for the money. For the truth, I recommend the websites http://2012hoax.org and http://astrobiology.nasa.gov/ask-an-astrobiologist/intro/nibiru-and-doomsday-2012-questions-and-answers. I just returned from a meeting of professional science educators where we discussed at length how to respond to this doomsday hoax. Most of the educators I talked with plan to do more in their communities to inform people, especially to calm the fears that many children have about the end of the world. We are all concerned about the children who write that they are considering suicide before the world ends in 2012 and the mothers who have written that they intend to kill their children and themselves before the destruction begins.

Question: For many years, I have considered Planet X to be a myth. But in the past few weeks I have noticed a very bright “star” to the west, and it is very active. If it is Venus, it is much larger than usual. What do you think it is?

It is Venus. Others have written to me also suggesting it is Nibiru or Planet X, and similar claims were made last year about Jupiter. You can easily look up planet positions on the Internet, for example at www.skyandtelescope.com. I should add that while Venus is very bright, it is not large. All planets are so small that without a telescope they are seen as unresolved point sources. If Venus really looks large to you, you probably need new glasses or contacts. Within the next few months Jupiter (in the east) will displace Venus (in the west) as the brightest planet in the evening sky, and I anticipate that some people will also mistake it for Planet X. I wonder, though, how people can think they have discovered a brilliant planet that 100,000 astronomers have all missed.

Question: I have been told that in our night skies there were two moons visible on August 27, 2010, when Mars approached Earth at the nearest point in their orbits. Is this true?

This is a zombie question: dead a long time but still sure to pop up every summer. Everything you heard is wrong. This past summer Mars was very far from Earth, and it could not be seen even with a telescope. This silly rumor first surfaced in August 2003, when Mars was indeed very close to the Earth (about 55 million kilometers), but the claim about it being as large as the Moon is pure fiction. This is an example of how so much on the Internet is wrong and how difficult it is to get rid of such errors.

David Morrison is a planetary scientist and director of the NASA Lunar Science Institute. He is a Committee for Skeptical Inquiry fellow and a recipient of the American Astronomical Society’s Carl Sagan Award for science popularization. E-mail: david.morrison@nasa.gov. These (slightly edited) questions from the public were received through NASA’s Ask an Astrobiologist website (http://astrobiology.nasa.gov/ask-an-astrobiologist/0).

Question: I read that the solar storm is coming up in 2013, and it will be a big one, too. I understand that a solar storm doesn't kill us, but it says that certain technologies will be knocked out from the solar storm. Is this going to happen?

Answer: The article you refer to notes that “the Sun is about to get a lot more active, which could have ill effects on Earth. So to prepare, top sun scientists met Tuesday to discuss the best ways to protect Earth's satellites and other vital systems from the coming solar storms. The Sun is waking up from a deep slumber, and in the next few years we expect to see much higher levels of solar activity, said Richard Fisher, head of NASA's Heliophysics Division”. Note that there is nothing here that says “the solar storm is coming”. What it does say is that solar activity is increasing toward the expected solar maximum in 2013. The Sun has an 11-year activity cycle. There is more solar activity (or solar storms) in the years around the peak. This is not about one solar storm, and in any case solar storms are not predictable far in advance. For an analogy, think about hurricanes. Recently there was news about the annual Caribbean hurricane season, which is about to begin. We know there is a hurricane season, and we know there will be several hurricanes. We do not know when they will come, or how big they will be, or where they will hit land. People who operate satellites should (and will) take precautions to protect their systems against solar storms, but that should not worry you or me. The bottom line for the Sun is that if you weren’t hurt by the solar maxima in 1990, or 2001, you you are not likely be hurt by the one in 2013.

Question: Is is it possible to make DNA as we wish?

Answer: Some of the most important current issues in biology concern our ability to manipulate genetic information. Until recently, the discussions have concerned genetic engineering, the modification or insertion of one or more genes in an existing organism to achieve new capabilities, such as adding a disease-resistant gene to a crop. Often this means taking a gene from one organism and introducing it in the genome of another organism. This kind of genetic manipulation has already yielded many successes, with genetically modified crops now accounting for a substantial fraction of world agriculture. The new frontier is in genetic synthesis or synthetic biology -- the design and construction of new biological functions and systems not found in nature. The goal is to have a library of genes from which we can select parts to obtain a new, viable genome that allows us to make a new life-form. The synthesized genome is then inserted into a living cell, where it can (if properly constructed) take over the functions of the cell, and ultimately pass on the new genetic structure to subsequent generations. Recently Craig Venter achieved the first step in this process, constructing a new genome out of parts of other organisms and inserting it successfully in a microbial cell. He calls this new cell Mycoplasma laboratorium. An analogy might be the construction of a building, in which the builders don't make the construction materials (bricks, cut wood, steel rebar, cement etc.) but can combine them in a variety of ways to construct different buildings. This kind of work represents the frontiers of biology, and it raises multiple ethical issues as well as exciting scientific challenges.

Question: You say there is no evidence of aliens visiting earth... what about when humans suddenly appeared out of nowhere 250,000 years ago? Could that not be alien life arriving on earth?

Answer: Humans did not appear suddenly 250,000 years ago. We have a long and complex family history revealed by both the fossil record and genetic comparisons with other animals. See “timeline of human evolution” in Wikipedia for a summary . The great apes (Hominidae) appeared on Earth 15 million years ago, and about 6 million years ago the human lineage separated from that of the chimpanzees. By 2 million years ago our ancestor, Homo erectus, was living in Africa, giving rise to the first true humans (Homo sapiens) around 200,000 years ago. But even if we did not have this fossil record, we know that humans are genetically similar to other animals (with 98% identical genes with the chimpanzees). Genetic analysis is the clearest way to demonstrate the common evolutionary heritage of life on Earth. There is no way that humans could have come from elsewhere. We are a part of the history of life on this planet, not some weird transplant from beyond. ]]> Tue, 01 Jun 2010 09:19:00 EDT info@csicop.org () http://www.csicop.org/specialarticles/show/extraterrestrial_life http://www.csicop.org/specialarticles/show/extraterrestrial_life Questions from the public regarding extraterrestrial life.

Question: I would like to ask you about the SETI program and the radio signals we are transmitting every day...How exactly are humans or aliens supposed to translate the received signals?

SETI (the search for extraterrestrial intelligence) does not transmit, it receives. Sensitive radio telescopes and optical telescopes that look for ultra-short pulses are involved in the searches. We do not transmit for several reasons. We are a very young and immature technical civilization. With current technology, we could detect the “leakage” radio transmission from a planet like Earth only to the distance of Alpha Centauri, the nearest star. Therefore we are looking for powerful radio beacons that might be operated by more advanced civilizations. Also, as you note, we would not know what to transmit that could be understood (or would even interest) an advanced technical civilization. Thus it is a much better strategy for us to listen quietly. For more about SETI look it up in Wikipedia or check out the SETI Institute.

Question: Stephen Hawking said in a special on the Discovery Channel that aliens exist and are dangerous. Could you clarify it and perhaps calm my nerves.

Hawking's show was primarily about the science of astrobiology. He explained the likelihood of life beyond Earth and the value of searching for it, including missions to Mars and Europa. In the last few minutes of the show, he speculated about intelligent alien life and explained the value of doing a SETI radio search. He also briefly discussed his concerns about intentionally transmitting, including the possibility that there might be some advanced life forms that could be motivated to visit our solar system in search of resources. I have no problem with any of these statements. Since we have no evidence that aliens (intelligent or otherwise) exist, all such comments are speculations. While I don’t share Hawking’s concern, I note that these are the sort of reasons that are frequently given for why it is better for us to receive but not to transmit any interstellar radio beacons of our own.

Question: Does the Drake equation accurately predict alien civilizations?

The Drake Equation is a useful tool for organizing the unknowns that need to be filled in to estimate the number of communicating civilizations that might co-exist in our Galaxy. It was introduced in 1961 by Frank Drake as a list of discussion topics for a meeting about life in the universe held at the National Radio Astronomy Observatory. Like any equation, the quality of the answer depends on the quality of the input (the so-called "garbage-in, garbage-out" phenomenon). Several factors in the Drake equation are completely unknown, such as the probability that intelligent aliens will develop radio technology, or the lifetime of the transmitting stage of such a technical civilization. Therefore the equation makes no actual prediction of the number of alien technical civilizations.

Question: Is there any consideration given to, instead of simply looking for life on other planets, actually sending it there? Is it possible to send out probes teeming with bacteria to crash land on planets which could be habitable? Bacteria that could terraform planets for us perhaps?

A lot of serious consideration has been given to the issues of planetary contamination, planetary protection, and terraforming. There are three persuasive arguments against intentionally contaminating another planet with microbes from our planet. (1) We don’t know of any planet on which terrestrial microbes could grow (or equivalently we don’t know of any microbes that could grow on the other planets in our solar system). (2) It would be unethical to introduce terrestrial life-forms on another planet that may have its own indigenous life. (3) It would be foolish for scientists to contaminate anther planet and thus render it impossible for subsequent missions to distinguish transplanted terrestrial life from possible indigenous life.

Note: These are questions (slightly edited) from the public, received during April 2010 at NASA’s Ask an Astrobiologist.

Question: Why so many strong earthquakes all of a sudden? In no past years have we had so many earthquakes in so little time.

There has been no increase in numbers or intensity of earthquakes, but there has been increased news reporting, especially when earthquakes are “close to home” for U.S. audiences. The world-wide frequency of earthquakes has been tabulated by the U.S. Geological Survey based on historical data. For the largest earthquakes (magnitude 8 and higher) there is an average of about one per year. There was one in 2009 (Sept 29 in Samoa) and there has been one so far in 2010 (Feb 27 in Chile). For Earthquakes of magnitude 7.0 to 7.9 (sometimes called “major earthquakes”), the average frequency is about one every 3 weeks. Thus earthquakes like Haiti (Jan 12, at magnitude 7.0) and Baja (Apr 4, at magnitude 7.2) are not unusual. The earthquake in Tibet on April 14, at magnitude 6.9, does not even qualify officially as a “major earthquake”, although it caused extensive damage because of poor construction practices. As summarized by the USGS, “we expect about 17 major earthquakes and one great earthquake per year.” That is close to the rate we have experienced so far in 2010.

Question: Why have there been over double the number of 4.0 magnitude earthquakes so far this year (71 as of April 12, as opposed to 30 last year)...is this not proof that the earths crust is shifting more rapidly than anytime in recent recorded history?

I don't understand the numbers you give for magnitude 4 earthquakes. There are more than ten thousand magnitude 4 earthquakes every year, and probably additional thousands that are undetected. (Note that the energy released by a magnitude 4 earthquake is only about one millionth that of a magnitude 8 earthquake). At this small size, many of these earthquakes are not primary tectonic events but aftershocks from major earthquakes. People are sensitized to earthquakes right now because several have been in populated regions including Haiti (January 12), Chile (February 27), and Tibet (April 14). But tectonic activity on Earth has not increased, and the crust is not shifting. I regret that so many people write to me with unwarranted fears of nature -- including tectonic activity, solar outbursts, volcanic eruptions, planet alignments, black holes, changes in Earth's rotation or magnetic fields, and many other ordinary events in astronomy and geology. This fear of nature seems to be spread by irresponsible TV "documentaries" and a proliferation of pseudoscience and conspiracy theory websites. The Internet is a powerful source for education, and some websites like Wikipedia and the public webpages of NASA and USGS are excellent, but they compete with the "noise" of poorly informed and intentionally misleading websites. People need to learn, at an early age, how to distinguish reliable information from the misinformation and disinformation that are so widespread.

Question: Is the volcano that has been erupting in Iceland a supervolcano (such as Yellowstone)? Can a very large volcano explosion be the end of humans world wide?

No, the eruption of Eyjafjallajökull, which has produced some spectacular images and disrupted airline traffic across Europe for a week, is not a particularly large eruption. It will probably rate a 2 on the Volcanic Explosivity Index (VEI). Eruptions of this size happen somewhere on the planet every few weeks. In contrast, the 1980 eruption of Mt. St. Helens produced about 1 cubic km of ash, rating a VSE of 5. The Pinatubo eruption of 1991 (VSE 6) was the second largest in the twentieth century, and it created red sunsets around the world and produced measurable global cooling lasting at least a year. The eruption of a supervolcano like Yellowstone is more than a thousand times larger yet, but even an explosion of that magnitude would not produce a mass extinction or seriously threaten human civilization. What is happening in Iceland now is a routine geological event, important to us only became of its temporary effect on air travel.