Back in December 2004, there was some concern that the asteroid known as Apophis 99942 might strike the planet in 2029. However, further number-crunching ended up eliminating the remote (approximately 3%) possibility and, as a result, I was forced to convert my asteroid shelter into a curbside taco stand. Then came the suggestion that come 2029, Apophis 99942 would be passing through a gravitational keyhole that could put it on a collision course with Earth in 2036! Since then, however, the probability of an impact has been downgraded to a 1 in 45 000 chance, forcing me to transform my asteroid shelter yet again, this time converting it into a backyard recording studio where I laid down some tracks for my first hip hop album (PB and Jamz drops September 3^rd, G.).

Apophis 99942 ended up engendering a fair amount of discussion about what our governments should be doing to better identify, track and deal with near-impact asteroids. Amidst all the chatter, however, there some questions I found myself asking: Who discovered Apophis 99942? What was their story? And, most importantly – Could we hold them accountable for the actions of their little asteroid?

Sadly, the answer to the last one is no. The answer to the first one is astronomers (and Stargate fans) Dave Tholen and Roy Tucker. As for the answer to that middle question, read on…

 

 

 

Roy: We’re delighted to give your readers some insight into the mysterious realm of asteroid astronomy. Out of the world’s population of six billion people, there are probably only a couple of thousand who are so serious about the subject that they will spend significant time and effort pursuing their interest. Since Dave is a professional and I am an amateur, we can provide both perspectives.

Let me start with some prefatory information that might help with some of the questions. A lot of information about asteroids is available in astronomy books and on the web so I won’t cover the basics. A good website to visit is that of the Minor Planet Center, http://www.cfa.harvard.edu/iau/mpc.html. Until the 1990’s, asteroid research was the almost exclusive domain of professional astronomers. As a young amateur astronomer in the 1960’s, the idea of discovering an asteroid was a wild flight of fantasy. However, with the advent of CCD imaging technology, the advance in home computers, and the availability of precise star catalogs on CDROM, it became possible for amateurs with modest instrumentation to make valuable contributions to asteroid research. Indeed, amateurs often enjoy some advantages over professionals such as having a telescope available to them at any time. A 14-inch aperture amateur telescope with a CCD camera is equivalent to a 120-inch telescope in the days of photographic imaging. With such modest instrumentation, one may detect stars a million times fainter than the faintest star you can see with the unaided eye in a dark sky. Not bad for puttering around in the back yard.

When an asteroid is first discovered, it receives a provisional designation based upon the year and half-month of the year. This is detailed at http://www.cfa.harvard.edu/iau/info/OldDesDoc.html . At the time of discovery, the motion of an asteroid is very poorly known and only very crude estimates of the orbit may be made. As time goes by, the motion becomes better known and the orbit may be refined. When the orbit of an asteroid is known sufficiently well, it is given a permanent number and may then be named. In the early 1990’s, there were fewer than 10,000 numbered asteroids after almost two hundred years since the first discovery. Because of amateurs and large professional surveys, there are now over a quarter million numbered asteroids and hundreds of thousands of known objects as yet un-numbered.

Besides discovery and tracking, there is much that can be learned from carefully measuring brightness and color with the passage of time as the asteroid rotates and appears in other parts of its orbit. The color may be used to indicate mineralogical composition and the rotation rate and pole orientation can tell a story of how terribly tiny forces have acted upon the body over the four-and-a-half billion year history of the Solar System. In few other fields of scientific research can amateurs be such full partners with professionals.

Near-Earth Objects are asteroids and comets that can closely approach the earth. There are four general classes of Near-Earth Asteroids. Amor asteroids have orbits that lie entirely outside the orbit of the earth but can approach as closely to the sun as 1.3 Astronomical Units or AU. The AU is equal to the average distance between the earth and the sun, about 93 million miles. Apollo asteroids have average distances from the sun greater than that of the earth but may approach the sun more closely than the earth. As a result, the orbit of such an object crosses that of the earth and an impact is possible. Aten asteroids have average distances from the sun less than the earth but can also cross the earth’s orbit and pose a hazard. Finally, the Apohele asteroids have orbits entirely inside the orbit of the earth and are harmless. Long-period comets such as those depicted in “Armageddon” and “Deep Impact” are a special hazard since they cannot yet be detected at great distances from the sun and may suddenly appear and threaten impact with warning times of perhaps months or weeks.

As of this June, Dave and I will have been acquainted for thirty years, since the summer of 1979 when I was a summer student at Kitt Peak Observatory and he was a graduate student in planetary sciences at the University of Arizona. At that time, Dave was sharing an apartment with another planetary sciences graduate student who decided to go home for the summer. Realizing that I needed a place to stay in Tucson that summer and Dave needed a temporary replacement roommate to help with the rent, a mutual acquaintance introduced us. Due to our shared interests in classical music, Star Trek, and all things astronomical, we became fast friends.

Our first observing collaboration was making observations of David’s first asteroid discovery, 1981 VB, now numbered and named (3124) Kansas. He had discovered the object while making other observations but was not able to gain access to a telescope and follow up during a critical period some days later. I was working at the Multiple Mirror Telescope at the time and was able to obtain the needed observations there on an engineering night.

Upon completion of my backyard observatory in the fall of 1996, Dave encouraged me to begin a program of measuring asteroid positions to help in determining their orbits more precisely. In the course of twelve years of asteroid observations with this backyard facility, I have discovered several hundred Main Belt asteroids, six Near-Earth Asteroids (three Atens, two Apollos, and one Amor), and two comets. Dave has been very helpful with his advice and orbital computations.

The sequence of events that led to the discovery of Apophis began when I started working at the University of Arizona’s Imaging Technology Laboratory in the fall of 2002 as a CCD characterization engineer. One of the instruments under development at the time was a prime-focus mosaic camera for the Bok 90″ telescope called 90 Prime. I quickly realized that this camera would be an excellent asteroid search instrument because of its wide field of view and ability to record very faint objects.

Dave has had a continuing program of looking for Near-Earth Asteroids in regions of the sky relatively near the sun. This observing strategy enhances the chances of finding Aten-class objects and is necessary for asteroids whose orbits lie entirely inside that of the earth. When the 90 Prime instrument became available for use, we submitted an observing proposal in support of his program that would require about an hour at the beginning of the night and at the end. Since Dave and his research staff member, Fabrizio Bernardi, are University of Hawaii people, they were listed as collaborators and I, as the University of Arizona participant, was designated the Principal Investigator and the certified Instrument Operator. This was a bit unusual since, strictly speaking, I am an amateur astronomer, not a professional.

Because of conflicting obligations at observing facilities in Hawaii, Dave and Fabrizio were not able to be present until halfway through the third night. Before arriving, they had requested that I follow up on an object they had spotted in Hawaii. The next day we examined those images to find the object he was looking for. I spotted a fast-moving object that I thought was his but he quickly concluded it could not be. We reported it to the Minor Planet Center to be listed on the NEOCP (Near-Earth Object Confirmation Page). Strangely, they concluded it was not sufficiently unusual in motion to be listed. Upon reporting the second night’s observations, it was designated 2004 MN4 and posted on the NEOCP. Because of an interruption due to weather and another, incompatible, observing program, we were not able to recover the object and report further observations. Because of the difficulties of observing at small solar elongations, there was no follow up from its listing on the NEOCP. It was upon its recovery in December of 2004, with an observational interval of six months, that it became apparent that this object could perhaps impact the earth in 2029.

We began considering a good name for the object as soon as it was numbered. 2004 MN4 was an Aten asteroid and a name of Egyptian origin is customary. However, after encountering the earth in 2029, the orbit will be changed to that of an Apollo asteroid and an Egyptian name would not be so appropriate. We liked the name “Apophis” because that is the Greek name for the Egyptian god Apep, who in Egyptian mythology was the enemy of Ra and repeatedly threatened destruction of the earth. This name seemed appropriate since the orbital motion of 2004 MN4 permitted repeated close passages to the earth (repeated threats) and the orbital evolution from Aten to Apollo. And, yeah, we’re Stargate fans. We had a few jokes among ourselves about the “SpaceGuard SG-1 team” (as opposed to Stargate) defending the earth. Another reason the name was a good match is that in Egyptian mythology, Apophis was always thwarted in his efforts to destroy the earth. At this stage of our technology, the human race can do something to prevent an impact if it indeed threatens.

The QA:

Thornyrose writes: “First, what is your area of expertise in the field of astronomy?”

Dave:  My doctorate is in planetary sciences, and I specialize in observational studies of small bodies, including asteroids,vcomets, and planetary satellites.

Roy: My background is in physics and scientific instrumentation. Professionally, I enjoy supporting astronomical research. For three years I pursued a graduate degree in planetary sciences and this has helped direct my amateur endeavors.

“Which other objects have you discovered and named?”

Dave:  1981 VB was discovered by me in 1981 and named “Kansas” in 1985 in recognition of the centennial of observational astronomy at the University of Kansas (my undergraduate alma mater).  The University has a 6-inch Alvan Clark refractor with “Alvan Clark & Sons, Cambridgeport, Massachusetts, 1885” engraved on the brass baseplate.
1995 UU6 was discovered by me in 1995 and named “Almary” in 2002 in recognition of the golden wedding anniversary of my parents (Alfred and Mary).
1998 QM107 is one of our Centaur discoveries, so we needed to select a name from among the Centaurs to adhere to tradition, and “Pelion” was our selection.

Roy: As of the time of this writing, I am credited with 363 Main Belt asteroids, three Atens, two Apollos, and one Amor. I also have a couple of comet discoveries.

“Do you have any names you would like to bestow on a discovered object, and what type of object would you like to bestow those names?

Dave:  I’d love to bestow my name on a newly discovered comet!  But only one comet was discovered during our survey observations, and my postdoc Fabrizio Bernardi saw it first, so it’s known as Comet Bernardi.  At least it is a periodic comet.  I do have some other asteroid names in mind, and I have several unnamed asteroid discoveries available, but because all asteroid names need to be approved by a committee of the International Astronomical Union, it’s probably not a good idea to speculate here on what names I might be allowed to bestow on these asteroids.

Roy: I may only propose a name for an asteroid. Comets are named for their discoverers. I have only proposed a few names but for Main Belt asteroids I usually suggest names of amateur astronomers or notable scientists. Near-Earth Objects I have more fun with. Aten asteroids are usually given names of Egyptian deities or historical figures. I named my first Aten after Selqet, the goddess often depicted with a scorpion on her head and who provided protection against venomous insects. Since I live in the desert and occasionally find a scorpion in my house, I figured it couldn’t hurt to try and curry a little favor. My first Apollo was named for Thor’s hammer, Mjolnir. An object that seriously threatens a destructive impact should get a really good name such as Ragnarok from Norse mythology, defined in the Random House College dictionary as “The destruction of the gods and of all things in a final battle with evil powers; Twilight of the Gods”. Whew!

“Astronmer Phil Plaitt is known as the Bad Astronomer. What nom de’guerre would you choose for yourselves?”

Dave:  Spaceguard SG-1, of course!

Roy: My friends have sometimes called me Mr. Aten for my propensity of finding relatively rare Aten asteroids. Other than than that I haven’t even thought about a nickname

“Thanks for all the work you do and for helping us marvel at how much there is out there beyond our own little pretty blue mudball.”

Dave:  You’re very welcome.

Roy: No thanks are necessary. I do this for the fun of it and I am delighted to be able to share some of the excitement and experience.

Shawna writes: “Questions for the astronomers:
– What percentage of your time working do you spend doing math? (I ask because I thought about being an astronomer in high school, until I realized the amount of math involved, so I decided to become a writer instead. But I still wonder exactly how much math is involved.)”

Dave:  Almost all of my time involves math to one degree or another, but I write computer programs to handle most of the tedious number crunching.

Roy: A fine piece of wisdom I encountered along the way is that your options are defined more by the classes you don’t take than by the ones you do. In the field of science, one would be seriously limited by having little knowledge of math. I use math in my astronomy and engineering work occasionally in the course of a day, but it may be anything from simple arithmetic to differential equations. A student may be intimidated but it is important to remember that it is all simple stuff, one simple thing built upon another simple idea. It’s just that it can be an awful lot of simple stuff that just takes time and effort to learn.

” – If you discovered a new M-class planet (or, you know, Earth-like planet for the non-Trekkies) and had free rein to name it whatever you wanted, what would you name it?”

Dave:  I haven’t really given that one much thought.  I’d probably try to have it be consistent with some property of the planet.  For example, if the planet was close enough to its sun to have a high surface temperature, I might call it “Vulcan”.  If it’s far from its sun and very cold, maybe “Hoth”.  If it’s dry and desert-like, maybe “Tatooine”.  Makes them easier to remember that way.  If I were really good at making up names on my own, I might have become a science fiction writer instead!

Roy: I could not resist selecting some name from science fiction that suggests the nature of the planet discovered such as “Arrakis” or “Barsoom” for a desert world.

” – What do you think are the chances of their being intelligent, sentient life elsewhere in our galaxy?”

Dave:  The more we learn about planetary system formation, the higher the chances appear to go.

Roy: When I think about the likelihood of life on other worlds, I think of quartz crystals. A quartz crystal is a fine example of how matter can arrange itself into an organized form when the physical conditions are right and enough time elapses. So, too, will life arise on worlds where the conditions are conducive and enough time passes. Bacteria and algae are probably the most common forms of life in the universe. The question of intelligent life in the galaxy depends sensitively upon how long an intelligent species can survive the consequences of its own technology. Will an intelligent species destroy itself or retreat into a comfortable virtual reality, never to re-emerge? Or, will it seek to explore the universe and know all that is knowable?

“What do you think are the chances of there being non-sentient, animal life?”

Dave:  About the same as there being sentient life.

 ” – What do you think is the better term for people from Earth: Earthling? Terran? Something else?”

Dave:  That’s sort of like choosing whether “sports” or “deportes” is a better term for athletic activities.  “Earth” is, I believe, an English term, whereas “Terra” is derived from Latin.  Both work for me.  Or you could even use “hoo-man” (with a distinctly Ferengi-esque pronunciation), though if we ever have descendants born on extraterrestrial worlds, that might not be sufficiently distinctive anymore.

Roy: I’ve always preferred the term “Terran” derived from the astronomical name for the earth, although it is very rarely used.

Ytimyona writes: Questions for Dave and Roy: 1) How far away do you live from your primary telescope? (I live in Cleveland and the astronomers at my school have to travel to Tucson, Arizona to collect data!)”

Dave:  I’m about 200 miles from my primary telescope, but I only have to walk upstairs to our remote observing room to collect data with it.

Roy: Well, being an amateur who lives near Tucson, I only have to go out into my backyard. http://gpobs.home.mindspring.com/gpobs.htm

 “2) What inspired you to pursue astronomy?”

Dave:  I’d have to say that the first real impetus came from a particularly good high school teacher who taught the electronics, physics, and astronomy classes that I took.

Roy: In 1966, I read about something called the Zodiacal Light in a high school library astronomy book and decided to arise early the next morning to try to see it. I failed but I was captivated by the beauty and serenity of the morning twilight. It was as if I had the whole world to myself. It became my habit to rise early each morning to enjoy that experience. It was only a few weeks later that I accidentally witnessed the 1966 Leonid meteor storm as a result. I had quickly learned there is much beauty and wonderment in astronomy. I was addicted as if to a drug.

 “3) What is your favorite scifi novel?”

Dave:  That’s a tough one.  Taking a dart and throwing it at the dartboard,I think I’ll say “Rendezvous With Rama”.

Roy: I have read so many wonderful stories but I guess the winner is Arthur Clarke’s “Rendezvous With Rama” if I must pick just one.

 “4) What is your opinion on the possible existence of wormholes?”

Dave:  Until such time that science can prove that they don’t exist, I’ll accept the possibility that they can exist.

Roy: That is far outside my field of expertise but I am reminded of the wisdom of Wernher Von Braun, “Always use the word ‘impossible’ with the greatest of caution.” Always there is the possibility of new discovery, new physics. Consider the consequences that have cascaded from the observation by Henri Becquerel that a particular type of rock would fog a photographic plate. In the 1920’s it was asserted by noted physicists that rockets could not operate in a vacuum and interplanetary travel was impossible. Only about forty years later there were footprints on the surface of the moon. I will not say it is impossible.

EdgarDerby writes: “Questions for Drs. Tholen and Tucker: 1. Given the US refusal to go metric any time soon, couldn’t we keep an imperial list of planets that includes Pluto?”

Dave:  I guess that depends on who you consider to be “we”.  Over twenty years ago, I wrote a computer program to compute ephemerides of solar system objects, with separate categories for planets, asteroids, and comets.  My collection of planetary orbits includes eleven objects.  One of those eleven is Pluto.  I don’t intend on changing that.

Roy: People can’t even decide on the definition of a ‘continent’. Why are Asia and Europe considered to be two continents? Maybe Greenland is a ‘minor continent’? I’ll continue to call Pluto a planet.

“2. Are Nico Marquardt’s numbers really that ridiculous?”

Dave:  I have not seen Nico Marquardt’s numbers directly, and I don’t want to trust any of the numerous sources on the Internet, because so many of them are so unreliable.  It’s particularly amusing to read web pages that claim to have gotten the story right, only to find an error in their story.  Let it suffice to say that Apophis isn’t going to hit in 2029, and anybody’s calculations to the contrary must be in error.

“Was it a probability of impact issue or a negligible effect from a satellite impact that made his calculation so unlikely?”

Roy: Dave is the orbital mechanic, I’ll let him comment on that one.

Dave:  Again, I have not seen Marquardt’s numbers directly, so it’s hard to say where the supposed error occurred.

 “3. The largest of dwarf planets? Isn’t that like being the smartest guy in the dumb class? Seriously, guys, Tombaugh’d roll over in his grave if he hadn’t been cremated and shot into space (partially).”

Dave:  Pluto may not even be the largest of the dwarf planets.  Eris may the largest.  But let’s not go there.  I was one of hundreds of astronomers who signed a statement saying that we disagreed with the IAU decision and wouldn’t use their terminology.

Roy: I like to respond that Jupiter is too big to be a planet and it radiates more energy than it receives from the sun. It’s a small brown dwarf. Oh, you don’t like that? Fine, Pluto is a planet.

“4. Did you ever consider Anubis in naming (being fans, you likely know he once sent an asteroid on a collision course with Earth) or did you think it would be in rather poor taste if it turned out the thing would hit us after all?”

Dave:  Sorry, Anubis is already taken.  So is Hathor.

Roy: The name Anubis was assigned to asteroid 1912 a long time ago.

 “5. Who is your second favorite Beatle?”

Dave:  None of the above!  My tastes in music run more toward the classical, though as a hobbyist musician, I’ve performed a wide variety of music, including orchestral, wind, and musical theater.

Roy: Oh, gee… I can’t even name all four. I can tell you my second favorite Jovian satellite is Europa.

“6. Look, confound the entire criteria! If we find some rock way out in the boonies of the Oort cloud that’s twice the size of Pluto and they wanna call it a dwarf, so be it. Let’s just keep this one, man(s). Seriously, guys, Tombaugh’d roll over in his grave if he hadn’t been cremated and later shot into space.

Dave:  Whoa.  Did we just experience a time loop, sort of like when O’Neill kept eating Froot Loops for breakfast over and over?  According to the IAU’s ill-advised decision, an Earth-sized object discovered 500 AU from the Sun probably couldn’t be called a planet right away, because we probably won’t know whether it has cleared out its zone around the Sun.  That’s one of the problems with the IAU’s definition.

Roy: No argument from me.

DasNdanger writes: “Questions for Dave & Roy: What are your thoughts on the Hubble vs its proposed replacements, the JWST & ATLAS Telescope, and do you think the latter (ATLAS) is just a dream that will be made obsolete before it ever comes to be?”

Roy: Hubble has accomplished many things. The benefits from the later telescopes would be correspondingly greater. Will there be the funding and national will to make them a reality?

Dave:  JWST is an infrared optimized telescope, thus compromising performance at ultraviolet wavelengths where Hubble can make  significant contributions to astronomy.  As I understand it, ATLAS would come closer to matching the wavelength coverage of Hubble, but reality often differs rather substantially from design, so I’m going to take a wait and see attitude.

“Thank you for your time.”

Roy: You’re very welcome.

Michael A. Burstein writes: “My question for Dave Tholen and Roy Tucker is a simple one: what can we do to convince our governments across the world to do more to track Near Earth Objects? Last I checked, we weren’t putting enough resources into protecting this planet. (I can’t be the only one who worries about a Tunguska-level event taking place over a populated area.).  Anyone interested in the global threat of asteroids should check out http://www.space-explorers.org and the PDF they have called Asteroid Threats: A Call for Global Response.

Dave:  Keeping governments informed is part of the answer.  Finding more objects like 2008 TC3 (the small asteroid that hit the Earth’s atmosphere over the northern part of Sudan) could also help to demonstrate that it’s not just science fiction.

Roy: It’s all quite true. The consequences of a major impact could be terrible but the chances are remote. An insurance actuary would recommend that expenditures of many millions of dollars a year would be prudent. However, how many people drive around without car insurance? Politicians prefer to gamble and spend the money on things that will get them more votes.

BeckettsPatient writes: “Questions for Dave Tholen and Roy Tucker: What was first: Interest in Science or interest in Science-Fiction?”

Dave:  Hard to say.  Star Trek debuted in 1966 when I was just eleven years old, but by then I had been exposed to basic science in grade school and can recall reading books on subjects like weather.

Roy: My oldest sister turned me on to sci-fi when I was about ten years old. Stephen Barr’s “I Am A Nucleus” was the first story I read. Later, it was an episode of Twilight Zone that helped me decide to get my B.S. in physics. The description of scientific things in the stories led naturally to an interest in science.

“How many astroids of to the earth dangerous-size are running through the neighbourhood of earth?

Dave:  About a thousand are dangerous enough to wipe out civilization as we know it.  Many more can cause regional damage.

Roy: Really dangerous asteroids would be a kilometer or larger in size.Objects that large could potentially cause major climatic effects worldwide for a year or more. Effects would increase with the cube of the diameter. It is expected that there are about a thousand such objects in the earth’s vicinity and about 80% of those are known. None of these known objects currently pose a serious threat. More numerous are the “city-busters” with sizes on the order of a hundred meters. There may be a few hundred thousand such objects and very few of them are known. Impacts from such  “Tunguska”-sized objects are estimated to occur about once every two hundred years, usually in some remote place or over an ocean.

“Do you know them all or do new ones keep popping up?”

Dave:  We know of 80 to 90 percent of them and are actively working on finding the rest to the extent it’s practical to do so.

Roy: The smaller, hundred-meter objects are observable with current instrumentation for usually a few days or weeks when they get close to the earth. Such periods of observability may occur only at intervals of decades. The current surveys find a few hundred a year. Better instrumentation is needed for the smaller objects. More money is needed to fund these searches. It’s the old “No bucks, no Buck Rogers” thing.

“Are you going to name more of them after SG1 villains?”

Dave:  Possibly!  Near-Earth asteroids with orbits smaller than the Earth’s are traditionally named after Egyptian gods, and quite a few of them popped up in Stargate SG-1.

Roy: Generally, the names would come from mythology. Since SG1 villians also have names from the same origins, they may be shared. You will likely find that many SG1 villians already have their name on a rock. A list of asteroid names may be found at http://www.cfa.harvard.edu/iau/lists/MPNames.html. One of the rules of the asteroid-naming game is that names may not be pre-announced so I can’t reveal any names I might have in mind until the IAU (International Astronomical Union) naming committee approves the suggestion.

“What do you think about the end of SGA and the beginning of SGU?”

Dave:  It’s hard to comment on a series that hasn’t made it’s debut yet (SGU), but SGA probably ended prematurely, though perhaps another season might have revealed a decline that became evident in SG1 after Richard Dean Anderson stepped aside.

Roy: The Stargate stories are imaginative and the quality of the production is excellent. I’m glad the franchise continues.

David writes: “Question for Dr. Tholen and Tucker: if you had a faster than light ship which object in our sky would you like to visit first and why.”

Dave:  Pluto.  I’ve been studying that system for quite some time and really want to see it more detail without having to wait for New Horizons to get there in 2015.

Roy: It would be interesting to see the oceans of Titan. Actually, I’m pretty satisfied with a faster-than-light imagination. When thinking about visiting other worlds, I remember the words of the ship’s cook from the movie “Forbidden Planet”: “Another one of these brave, new worlds. No women, no beer, no pool halls. Nothing to do but throw rocks at tin cans and we have to bring our own tin cans.” It’s good to be able to stand on the surface of a planet without a pressure suit and feel the wind in my hair and the soft rain on my face. How many light-years would you have to travel to find another world where you can do that?

“If you could discover or prove anything in astronomy what would it be.”

Dave:  The existence of intelligent life elsewhere in the universe.

Roy: To prove the existence of life elsewhere in the universe would be the ultimate accomplishment, I think.

“What do you consider to be the most accurant use of science that you have seen use in an episode and what was the most inaccurate use of science you seen us in Stargate.”

Dave:  With over 200 episodes made, that’s a tough one.  Trying to recall all the uses of science and to identify the most and least accurate taxes my memory.  I’ll have to rewatch all 200-plus and get back to you.

Roy: Please pardon me for not expressing an opinion about the most accurate use of science. If they have the science right, I can’t really easily assign an assessment of its correctness. Having a background in physics, I can do a lot of nit-picking about things like conservation of momentum and such. Please bear in mind that good theatre involves a willing suspension of disbelief and that sci-fi invokes the notion of as-yet-undiscovered knowledge. I would say the main thing that has stretched my willingness to suspend disbelief has been those instances in which characters have been ‘shifted in phase’ and become invisible and are able to walk through walls. If they can walk through walls, why do they not fall through the floor and begin to orbit around the earth’s center of mass? If they are applying their weight to the floor, can they stand on someone’s toe and make their presence known? If they can see while they are invisible, this is because light passes through their eye lenses and strikes their retinas. Why can no one see the dark pupils of their eyes? How can their eye lenses focus light and permit them to see? I suppose one can assert that light is also phased and that is how they are seeing but would phased light reflect off of unphased objects permitting them to see it? Maybe a little more hand-waving needs to be applied to explaining the phasing phenomenon.

“Do you think we will discover lots of earth type planets out there or do you think they are rare. How do you think until the first one is discovered.”

Dave:  I see no reason to believe that Earth-type planets are rare.  Astronomers have been finding larger planets at an impressive rate in recent years.  The similar discovery of smaller planets simply awaits the technology.

Roy: I think earth-sized planets with liquid water on the surface and orbiting a dwarf K to F type star are very rare. Such planets with multicellular life forms and oxygen atmospheres are very few in number. It may very well be that at any given time there are only two or three intelligent races in the whole galaxy. Think about that. You are an example of the rarest and most precious thing in the universe. I would not be surprised if earth-sized planets are found in the next couple of decades but an earth-sized planet in the habitable zone of a suitable star is likely to be considerably more elusive.

“Which side if the debate are you on in argument over whether pluto planet or a dwarf planet. And if you agree it is a planet, should every object discovered be classed the same or should pluto be kept special and class differently from the rest.”

Dave:  It’s not like each object comes with a tag on it that says whether it’s a planet or a dwarf planet, so there is no right or wrong answer.  The debate has been over whether to change the existing labels.  Although Pluto has been the most commonly discussed “victim” of the IAU’s decision to change the definition of “planet”, the asteroids were also affected. Previously, the term “minor planet” could be used to refer to asteroids, but the IAU did away with that term as well.  When it became obvious in the 1990s that Pluto was one of many small bodies in solar orbits beyond Neptune, the debate started out over whether Pluto should be called a “minor planet”, just like the other Kuiper belt objects were being called.  That is, the debate was over whether Pluto is a “major” planet or a “minor” planet.  Somehow the debate morphed over the next decade to become whether Pluto is a “planet” or not.  Pluto’s physical and dynamical properties didn’t suddenly change overnight when the IAU made its decision.  It is still the same object in 2006 September as it was in 2006 July.

Roy: Most of my life, Pluto has been a planet. I’m very fond of the idea of Pluto being a planet. I could also argue the Jupiter is too big to be a planet and it radiates more energy than it receives from the sun, making it a self-luminous body. I’m also fond of having Jupiter called a planet. Let me continue pretending Pluto is a planet and I will continue pretending Europe and Asia are separate continents.

Crayonbaby writes: “I have questions. I just hope they’re not weird or stupid. 1) What university are the two of you associated? Do you teach or do research or both?”

Dave:  I am associated with the University of Hawaii.  Roy is associated with the University of Arizona.  In both cases, the association is via employment.  I am also associated with the University of Arizona as an alumnus (graduate school).  I both teach and do research.

Roy: I am a senior engineer at the University of Arizona’s Imaging Technology Laboratory. I am involved with the production of sensitive CCD imaging devices for research applications, usually in astronomy.

 “2) Do you ever watch a television show and groan at how bad the science is? I sincerely hope that Stargate isn’t one of them.”

Dave:  Oh yes.  Movies too.  One of my favorite groaners is “You haven’t heard of the Millennium Falcon?  It’s the ship that did the Kessel run in 12 parsecs.”  Another groaner is the reference to “one to the twentieth power wattumunits” (name that episode!).  And ion drive being so much more advanced than warp drive.  And phaser beams that travel so slow that a person can move out of the way if they’re in an “accelerated” state.  I can’t recall any specific groaners associated with Stargate, though the reason they call it science fiction is because a lot of the stuff is just that, namely fiction.  I don’t get bent out of shape by transporters and inertial dampeners, even though they’re clearly fictional and not real science.  I do get bent out of shape by logical inconsistencies, and one of my favorite Stargate moments is when they took Star Trek The Next Generation to task for one of their logical inconsistencies.  In the episode “Wormhole Xtreme”, the Carter wannabee talks to Marty about a problem she has with the script. It says she can pass through tables and walk through walls.  Marty says it’s because she’s “phased” (shades of Geordi and Ensign Ro).  She then asks “Well, if I can walk through walls, then why don’t I fall through the floor?”  There’s a full 15 seconds of dead air while Marty looks at the other guy and the Carter wannabee tries valiantly to suppress a smile before  Marty responds with “We’ll have to get back to you on that.”  Absolutely hilarious!

But that’s not to say that Stargate hasn’t had some questionable moments.  For example, in the series opener “Children of the Gods”, we see a breeze fluttering the cloth over the stargate before any sign that it has been activated.  And there’s a lot of vibration associated with the stargate’s activation that we don’t see in later episodes.  And exactly how does Apophis manage to activate the stargate to return home after he abducts the female?  There is no ancient dialing device.  He doesn’t know how to use the Air Force’s improvised dialing device.  Looks like he simply pushes a button on some wrist device and voila!

I do appreciate it when science fiction programs try to pay attention to certain details, however.  The way the Star Fury was maneuvered in Babylon 5 was particularly well done.

Roy: I actually enjoy “bad” sci-fi and some of the finer examples I’ve collected make “Plan 9 From Outer Space” look like an Oscar winner. Take as an example “The Creeping Terror” (http://www.imdb.com/title/tt0057970/) . In this story there are a couple of space monsters that go around eating people. However, the people must be very cooperative while they are being devoured. It’s hilarious! I object to things that are simply absurd, such as one movie that had Space Shuttles landing and being ready to launch again in a couple of hours.

“3) How do you spend your downtime? I hope it’s not to break out the telescope you have at home?”

Dave:  Sea level in Hawaii is a terrible place for a telescope.  I broke out my homemade six-inch telescope to monitor the expansion of comet Holmes, but I spend far more time working with the mountaintop research-grade telescopes.  Most of my downtime is spent in music performance, totaling hundreds of hours each year.

Roy: “Downtime” is when the skies are cloudy and I can’t observe. I catch up on my sleep then. When the skies are clear and the moon is dark, I’m looking at images. Each clear night yields about 600 images to search. 200 usable nights means about 100,000 to 120,000 images a year to look at. On week nights, it may be that I’ll only get five hours of sleep before I have to get up and go to work at my day job.

“4) I have many friends and family that are into that hobby. Do either one of you even have a telescope at home? It can’t compare to some of those monster telescopes on Mt. Wilson in California.”

Dave:  Actually, my homemade six-inch telescope is stored in my office. I often use it when teaching an introductory astronomy class, so it’s handier to keep it in my office.  And the biggest “monster telescope” on Mt. Wilson is only one-quarter the size of the biggest telescope on Mauna Kea!

Roy: I actually do most of my asteroid-searching from my backyard observatories. I have three different shelters housing five different telescopes. http://gpobs.home.mindspring.com/gpobs.htm

“Thanks so much!”

Roy: You’re very welcome!

Gaymede writes: Don’t know if he was before your time, but did either of you ever know Dr. Peter Millman? I used to deliver our library’s copy of Marsden’s Minor Planets Newsletter to him as soon as it arrived in the building [NRC/HIA-Ottawa]. He was a great guy!”

Dave:  I don’t recall ever meeting him.

Roy: I’m sorry but I never had the honor. Astronomy attracts some very wonderful people.

Michelle writes: “The asteroid being named after Stargate is the coolest thing ever! Questions for David and Roy: 1. You both appear (based on google anyway) to be observational astronomers. How do you and the theoreticals get along? Do mixed-astronomer cocktail parties quickly turn ugly over string theory etc?”

Dave:  Theoretically, I get along fine with the theoreticals.  But being a planetary astronomer, I know so little about string theory that I don’t get into any ugly debates about it at cocktail parties.

Roy: Not at all. Theoreticians provide “Big Picture” concepts that observers may then put to the test. For example, Einstein predicted that gravity would deflect starlight. At the time, that was a startling idea. Observers then used solar eclipses to prove the existence of the effect. Today, we have things like Dark Matter and Dark Energy. It’s very exciting!

“2. Do you think there’s any practical way to clear out all the space junk orbiting Earth?”

Dave:  Depends on what you consider to be practical.  It can be done, but it might be expensive.  Maybe we should have a student competition to see who can come up with the most cost effective way to clean up all the space debris.

Roy: A material called ‘aerogel’ has been used in spacecraft missions to capture high-speed dust particles (http://stardust.jpl.nasa.gov/tech/aerogel.html). If there was a method developed to produce huge masses of the material in orbit, repeated encounters of junk with the aerogel would reduce the orbital energy of space junk until these unwanted objects eventually fell out of orbit. Unfortunately, it is likely that all orbiting objects would be affected, including working satellites, and this is a solution that would best be applied to clean up near-earth space in preparation for the construction of space elevators when that technology matures.

“3. Do you think the US manned space program is worth the cost, discovery-wise, vs robotic exploration and science?”

Dave:  We clearly get more science for the buck from robotic space probes, but I still think the manned space program is worth the cost.  The manned program provides so much inspiration to the next generation of scientists, and the manned program is necessary if we’re ever to colonize beyond the Earth, which is necessary for the long-term survival of the human race.

Roy: A robotic spacecraft returns more science for the money than a manned mission and it doesn’t risk human lives. However, humans will spread beyond the earth and we need to learn how to make these voyages. That is engineering and it needs to be mastered. If a little science gets done along the way, so much the better.

“4. I wanted to be an astronomer coming out of high school but switched to ero engineering after I found out a) you have to get a PhD and b) even if you get a PhD, the odds of getting a job in astronomy are small. Is that still true? Did I make the wrong choice??”

Dave:  There are jobs for astronomers holding masters degrees, but they’re not as numerous as the jobs for astronomers holding doctorates.  The odds of getting a job in astronomy depends on how good you are at what you do.  The good ones will get jobs.  Whether you made the wrong choice depends on how well you might have been able to do.

Roy: Each person has to make a choice of what is important and satisfying to do as a career in the context of his or her life. I had an established career as an electronic instrumentation engineer but I loved astronomy and planetary sciences. I decided to enter a degree program in planetary sciences to pursue this love. After three years of classwork, I had the education that I wanted and decided that I didn’t want to make a career of it. I bailed out of the program and resumed my engineering work to support myself. I continue to follow my love of astronomy as an amateur, but with greater knowledge and capability. Sometimes I regret not finishing the program but I think things have worked out well as an engineer supporting astronomical research and enjoying astronomy as an amateur for my own satisfaction.

“5. Will you be looking at the results coming back from the new Kepler planet-finder? I have friends who work on the science data processing.”

Dave:  Probably not in any great detail.  I expect to be busy looking at the results coming back from the new WISE and Asteroid Finder spacecraft for the next few years.  And here in Hawaii we have the Pan-STARRS sky survey gearing up to deliver terabytes of data each night.

Roy: We had some involvement with the development of the CCD imaging devices where I work but that is the extent of my connection to Kepler. I am only a member of the general public with regard to its results. I hope the mission is successful and they find lots of planets.

“Airelle writes: Questions for David and Roy: If I was a wanna be look-at-the stars,kind of person, what brand/strength of telescope would you suggest?”

Dave:  There’s no easy answer to that question without greater detail.  Some people prefer looking at star clusters, comets, nebulae, and other extended objects, for which a wide field of view is a primary consideration.  Others want to track faint asteroids, for which a large aperture is a primary consideration.  Some people hate to go through the trouble of setting up a large, heavy telescope and letting it take the time to properly come to thermal equilibrium so that it delivers the best images. You really need to take a long, hard look at how you want to use a telescope and then optimize your purchase decision.

Roy: A beginner can be very happy with a good pair of binoculars. After one has learned a bit about astronomy and how to find things in the sky, an 8-inch Schmidt-Cassegrain telescope is an excellent general purpose instrument. Good used instruments can be found online on such sites as Astromart (http://www.astromart.com/) and Cloudy Nights (http://www.cloudynights.com/).

“Do you think we are alone in the universe?”

Roy: I think the universe is full of life but intelligent life is likely to be very rare.

Dave:  At the moment, there is no direct evidence either for or against the existence of intelligent life elsewhere in the universe.  Having said that, I’d be surprised if we’re alone.

“I love looking at the night sky, how cool!”

Roy: I completely agree.

“thank you for your time.”

Dave:  You’re welcome!

Roy: You’re absolutely welcome.

Juliet writes: To Dave and Roy – I cannot begin to express how cool it is that you even get to name asteroids, let alone the fact that you named it after a Stargate character! I read an interview of Peter Williams, who played Apophis, and he was beyond stoked that you had done that. He kept saying, Apophis may defeat Earth yet!  So, questions. How do you live with your overwhelming coolness?”

Dave:  I rent myself out to people whose air conditioning has broken down.  🙂

Roy: Ah, yes. It was difficult at first but I learned much from watching birds-of-prey, porpoises, and otters. Eventually, I reached an accommodation that worked for me.

“What is a typical day for you at work like?”

Dave:  Deal with email, answer questions from a student who has stopped by my office, deal with more email, fill out paperwork (amazing how our electronic world has increased the amount of paperwork that I need to do), deal with email, attend some meeting, deal with email, answer questions from another student who has stopped by my office, deal with more email.  I’m not joking!  The amount of email that I need to deal with has become oppressive.  I actually started keeping statistics.  Over the last five years, I’ve averaged 290 email messages every day.  Of course, 185 of those are filtered out as spam, but the other 105 wind up in my inbox, a few of which are also spam, but got by the spam filter.

Roy: Typical week day, clear skies, dark moon – Up at 5am to shut down the asteroid search instrument and begin transferring and archiving the image data. Eat breakfast and dress for work. Arrive at work at 7:30am , return home at 5pm. Begin calibrating and plate-solving the previous night’s images in preparation for looking for asteroids and comets. Have dinner while the software is working on the data. After dinner, I begin looking at images. Usually, I have music in the background while I work. The score to the movie “Transformers” is a current favorite. I am typically finished at about 11pm and I prepare for bed. I try to get to bed by about midnight.

“And this may have already been asked – If you were to discover something else to name (other than a mineral), what would you name it Stargate related or not?”

Roy: So far, I only get to name asteroids. Most commonly, I select names from mythology, history, scientists, and amateur astronomers.

Dave:  Actually, I have several asteroid discoveries awaiting name proposals, but the IAU committee frowns on making name proposals public because they feel like they’re having their hands tied.  Can you imagine serving on a committee that wants to disapprove of a name that has already been in common public use?  You might find a lot of discussion about “Sedna” along those lines.  So to avoid getting some of my colleagues upset with me, I prefer not to mention any possible names.  However, I can say that I have another asteroid ready for naming that falls into the category for which the names of Egyptian gods are traditional, so it would be easy to make it Stargate related.

“Btw, naming a mineral naquadah would be hilarious and awesome.”

Dave:  Wouldn’t that be fun!

Roy: Hmmm… Yes, it would. Not necessarily a mineral. Hmmm…

“Thanks for your time and I hope you get guest spots on Stargate Universe!”

Roy: You’re very welcome. I’m sure at some point they’ll need someone to portray an overwhelmingly cool character.  ;^)

“Silversi writes: Question(s) for Dave and Roy: http://www.ucsc.edu/currents/06-07/art/galaxies1.06-09-18.jpg > In the text along with this picture where you can see just tons of spirals to indicate galaxies, they indicate that what we see from these is like 13 billion year old-light. Do you think that our Universe really does still have so many galaxies in a single snapshot or that those galaxies might have since been destroyed (can a galaxy be destroyed? How would one cease to exist anymore?)? And with a slight Stargate twist do you think like all of them or like 3/4 or even 1/2 support some sort of life?”

Dave:  Most galaxies have so many stars in them that I’d be surprised if the majority of them didn’t have at least a few planets able to support some sort of life.  I suppose you could ultimately destroy a galaxy by using up all the atoms that can give off energy when fused to form a heavier atom.  But that would take a very long time.  Our own Sun can survive on its own hydrogen supply for over ten billion years.

Roy: Various lines of evidence suggest that it has been about thirteen billion years since the “Big Bang” or whatever event it was that marked the beginning of our universe. Galaxies are still occasionally forming in our current time. Some images were recently obtained that seem to show dwarf galaxies with active star-forming regions producing metal-poor stars, a sign of young galactic age. A young galaxy has mostly just hydrogen and helium and forms stars with those materials. As these stars age and eject much of their mass into space, they enrich the interstellar medium with heavier elements formed by nuclear reactions in the star’s interior. Later generations of stars formed from this material have greater abundances of these heavier elements or ‘metals’, indicative of advancing age.

Galaxies evolve principally by collisions with other galaxies. Galaxies may be torn apart or merge with the other galaxy. Our own Milky Way galaxy contains within it remnants of several absorbed galaxies, recognizable by the motion of groups of stars that is distinctively different from the neighboring stars.

I think we’ll eventually learn that life, at least simple forms such as bacteria and algae, is very common wherever conditions permit. Higher forms of life, including intelligent beings, are likely to be much rarer.

Silversi writes: Question(s) for Dave and Roy: If the milky way really does revolve around a black hole, like it’s theorized do you think that in say a hundred million years that our galaxy would be in danger of getting sucked in?  “How does it work for a galaxy to surround something like a black hole but to not move ever closer to eventually disappear inside it?”

Dave:  No; some mechanism would be required to dissipate energy, causing a star in a circular orbit around the center of the galaxy to spiral inward.  I don’t see that happening for most of the galaxy.

It’s just like the Earth not spiraling into the Sun.  The kinetic energy in the Earth’s orbit would have to be dissipated to cause it to spiral inward.  There are mechanisms that can do that for objects the size of dust grains, but not for objects the size of the Earth.

Roy: The stars of our galaxy are in orbit around the galaxy. They cannot be drawn to and consumed by the black hole at the center of our galaxy without transferring their angular momentum to other stars or massive objects such as clouds of dust and gas. Such events happen but only for objects very near the center of the galaxy. Some videos were recently released (http://www.eso.org/public/outreach/press-rel/pr-2008/phot-46-08.html) that show the motions of stars in the very close vicinity of the massive black hole at the center of our Milky Way galaxy over a sixteen year period. It can be seen that the stars are orbiting around something that is not visible. The rate of accretion of the matter in a galaxy is very slow compared to the lifetime of the universe. If you’re way out in the spiral arms like we are, it’s not something we ever have to worry about.

“One from Joe had me wondering as well What kind of instruments are used to detect extrasolar planets?”

Dave:  Mostly high-precision spectrometers that can measure tiny variations in radial velocity caused by a planet’s gravity pulling on a star as the planet orbits that star.  However, one extrasolar planet around the nearby star Fomalhaut has been directly imaged by the Hubble Space Telescope.

Roy: I think there are four methods currently used: photometric detection of planetary transits, radial velocity variations, proper motion variations, and direct imaging.

I believe the very first claim of the discovery of an extra-solar planet was by the amateur astronomer John Goodricke in 1783 when he offered an explanation for the changing brightness of the variable star Algol. Some planets reveal their presence by passing in front of the star that they orbit and blocking some of the light that would otherwise come to us. This event is called a transit and causes the star to decrease in brightness while the planet is between us and the star. Such transit events can be recorded with relatively small telescopes equipped with a CCD camera or photoelectric photometer.

We say that a planet orbits around a star but in reality the planet and the star both revolve around the common center of mass or barycenter. This orbital motion can be detected spectroscopically due to the Doppler shift that it produces in the stellar spectrum. We can only detect the radial component of such motion, that part of the motion that occurs along our line-of-sight. If we look down upon the pole of such a system, we would see no variation. The maximum variation would be measured if we see the orbit of the planet edge-on.

Stars are actually moving through space and the nearer stars can actually be seen to be moving among their neighbors over time spans of years. This is called ‘proper motion’ and is usually very slow. The high-speed champion is Barnard’s Star and is moving over ten arcseconds per year (an arcsecond is approximately equal to the thickness of a dime at a distance of two football field lengths). A star is expected to move along a straight line. If one is seen to be moving along a wavy line, then it might be due to the presence of an unseen planet orbiting around it. The system’s barycenter will move along a straight line and we would see the star’s orbital motion around the barycenter.

Recently, the first direct image of a planet was obtained of a body orbiting the star Fomalhaut by the Hubble Space Telescope (http://www.nasa.gov/mission_pages/hubble/science/fomalhaut.html). This is a monumental feat and the first of many such detections, I hope.

“When the rover was on Mars, I believe at one point they mentioned using the microphones to actually record sound do you know if anything ever came of that, or if they just dropped the idea entirely?”

Dave:  To my knowledge, neither of the Mars rovers had a microphone on board.  There was a microphone on the Mars Polar Lander, but that mission ended in failure.  The Mars Phoenix Lander has a microphone on board, and there were reports that NASA had given the go-ahead to turn it on, but I’ve not encountered any news reports about the results.

Roy: The Mars Microphone project is described at http://sprg.ssl.berkeley.edu/marsmic/. The first one was lost with the Polar Lander and no data came back. The second one is looking for a ride.

“And just for good measure. Who DO you think would win in a fist fight between Ronon and Teal’c?”

Dave:  I would guess Ronan.  He appears to have more experience in hand-to-hand combat, whereas Teal’c has more experience with a staff weapon and a zatnicatel.  But neither would go down easily.

Roy: I’m sure they are equally matched and it could only end in a draw. Translation: I wouldn’t want to have either one of them upset with me for doubting his martial prowess. (Teal’c cocks an eyebrow and comments, “Indeed.”)

“Silversi writes: (Another) Question for Dave and Roy: Say for some crazy reason that Apophis was actually on a direct collision course with earth just dead on. Do you think the antics that they used in “Armageddon” or “Deep Impact” would work to divert it away? By blowing it up in the middle and hoping that it splits off and goes on either side of Earth?”

Dave:  A lot of asteroids appear to have interior structures that  might be best described as “rubble piles”.  So I doubt that a single nuclear blast would cleanly cleave Apophis into two pieces that would miss Earth to either side.  Most likely we’d get a whole bunch of smaller pieces.  If Apophis were disrupted far enough in advance of the impact, most of the debris would miss the Earth, and the fraction that didn’t might not survive atmospheric entry.  I think disaster movies such as those have their place in calling the public’s attention to the possibility of an impact, but I wouldn’t want to use them to educate the public on the science portrayed (surface properties of asteroids and comets, for example).  I do wish that half the box office profits could go to near-Earth asteroid research!  They could fund NASA’s current program for a century at the current rate of spending.

Roy: In the scheme of things, Apophis is a relatively small body about 400 meters across and about ten to the eleventh kilograms in mass. Before earth encounter in 2029, we only need to nudge it a little to prevent it from passing through a “keyhole” in space (http://en.wikipedia.org/wiki/Gravitational_keyhole) about 600 meters across, a fairly easy job for our current level of technology. After earth encounter and a hypothetical passage through the keyhole, we would have only about six years to push it a distance equal to the radius of the earth,something that may be beyond our capability. We’d be a lot happier doing something before 2029 if we need to.

Long-period comets are the most dangerous threat since we would have warning times of only about a year at the most and perhaps as little as a few months. If we face the prospect of an impact by a large comet, the use of some sort of nuclear device is pretty much our only option other than hiding in a hole. That’s the way ‘Armageddon’ and ‘Deep Impact’ portrayed the situation but in reality it’s not so much a matter of trying to deflect the object as much as choosing whether to get hit by a rifle bullet or a shotgun blast. Fortunately, such comet impacts are likely to occur on time scales of 100 million years. I don’t worry too much about it.

“What are your take on Disaster movies such as those?’

Roy: Impacts by astronomical bodies have been used as a story element for a long time and for many purposes. I think the earliest depiction of an asteroid impact was probably in the Bela Lugosi movie “The Invisible Ray” in which a powerful substance was provided to a scientist who had to make choices between good and evil. Impacts are sometimes used to threaten an end to civilization, as was also done in the 1951 movie “When Worlds Collide”, in order to explore how characters respond to the coming end of everything. Nuclear war has been used for the same purpose as in “On The Beach”. Disaster movies portray the responses of ordinary people to extraordinary circumstances. It encourages us to ask ourselves how we would handle such a situation. If well done, I enjoy such movies.