A CIVILIZATION on MARS? 1B/200M Years Ago? (Pt. 5)

star_sirius · Jun 26, 2005

I thought comets with hyperbolic or parabolic orbits can become bounded orbits if they are interacted with a third body like Jupiter!!! <img src="/images/icons/tongue.gif" /> <div class="Discussion_UserSignature"> A dazzling bluish luminosity from A distant south pacific. <img id="cb51e87e-8221-424c-8ff2-78c95122196c" src="http://sitelife.livescience.com/ver1.0/Content/images/store/11/15/cb51e87e-8221-424c-8ff2-78c95122196c.Large.jpg" alt="blog post photo" /> </div>

yevaud · Jun 26, 2005

How? According to him, such orbits don't exist, are never seen. What the hell: I have already had... A business major insist to me Cold Fusion is a reality. Obviously his business studies trump my science majors. A housewife inform me that UFO's exist. Junior High students tell me that time travel exists. Some anonymous dude telling me that understanding QM is a snap, and Richard Feynman obviously had no clue what he was talking about. Sometimes debating science here is like lecturing a 15 year old on their curfew. Possibly I should have gone for a business major..then I would be taken serious...by other non-scientists. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

sinova · Jun 26, 2005

Yevaud, since astrophysics is not my field of expertise, I risk being a chump explaining this, but . . . I do believe MA is correct in a semantical sense. Circular orbits are very rare. Elliptical orbits in the shape of some dimension of oval are common. Hyperbolic and parabolic "orbits" are not orbits in the commonly used definition of the word. The smaller body (asteroid, comet, etc.) is indeed attracted by the gravity of the larger body. The smaller body comes and makes its pass, but because of the high velocity of the smaller body and angle of approach, it is a one-time shot. It never comes back, it meets or exceeds escape velocity at its angle of approach. Yes, these are technically called "orbits," but they aren't in the sense that there is no perpetual gravitational capture. That is what I remember from studies long ago, that is why I said Yevaud was right, and that is why I thought he was just splitting hairs to laugh at you. We all knew what you meant, even if in one sense or other it was incorrect. Now, if they changed the terms since I last reviewed the subject, or if I'm coming down with Alzheimer's, I apologize. But I think what I've just said is true.

sinova · Jun 26, 2005

I thought comets with hyperbolic or parabolic orbits can become bounded orbits if they are interacted with a third body like Jupiter!!! Right. But when they do, they are no longer in parabolic or hyperbolic orbits.

sinova · Jun 26, 2005

What the hell: I have already had... How about this one? I've met an extraterrestrial -- and he's living in my pants.

sinova · Jun 27, 2005

okay, you made me look it up. nobody take my word for it, go here: http://www.hq.nasa.gov/office/pao/History/conghand/traject.htm

yevaud · Jun 27, 2005

Huh. That's the exact same site I posted on the last page... <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

yevaud · Jun 27, 2005

***/ Never Mind / *** <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

sinova · Jun 27, 2005

Huh. That's the exact same site I posted on the last page... oops. Right you are. I feel kind of stupid, but I googled that site and checked it out totally independently. Good habit, checking things out for myself. Bad habit, not paying attention to your post as it deserved. I'm the pinhead on this one.

sinova · Jun 27, 2005

Lord knows I have no reluctance to napalm, but your comments didn't deserve that, whether they were technically right or wrong. Come on, Mental Avenger--don't you think you were just a little unfair?

JonClarke · Jun 27, 2005

Colin Ypou must constrain your ideas with facts and realism. There are so many ifs there. 1. We do not know that Mars has a lower impact rate than earth. This is a fact. 2. Not all mass extinctions are impact linked. This is a fact. 3. Mass extinctions may be good for evolutionary diversity in the long run. This has been widely suggested. Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

sinova · Jun 28, 2005

Mass extinctions may be good for evolutionary diversity in the long run. huh?

mental_avenger · Jun 28, 2005

OK, you hang onto semantics to extract yourself from your mistake, I was (obviously) referring to the traditional meaning of the word. It appears that the word “orbit” is being used rather carelessly by those folks. Perhaps it is laziness or simply a shortcut term. Traditionally, the term “orbit” has referred to an object that continues around another object for a complete revolution. My statement, By definition, a hyperbolic or parabolic trajectory would not be an orbit, but would be a one-time pass. was quite accurate, it would be a one-time pass. All parabolic or hyperbolic trajectories, unless further acted upon, would never come back. Remember that your initial comment was ”Not all infalling material [from the asteroid belt] approaches the sun in an elliptical orbit, by any means. Frequently, it just falls inwards.” I pointed out that In order for any object currently in orbit to plummet straight in towards the Sun, 100% of it’s orbital velocity (no more, no less) would have to be negated by some force, presumably an impact. I asked you for a mechanism for that, and you never supplied one. AFAIK, objects in the asteroid belt have very little velocity (relative to each other) , so internal impacts would not suffice. It would require either a comet or an extra-solar body to create enough delta-V to result in the body simply “fall inward”. I don’t believe Jupiter has enough influence on asteroid belt objects to put them into parabolic or hyperbolic trajectories. Even the site you reference indicates only 4% from the Asteroid belt, and even that is unconfirmed. They even hedge their conclusions by admitting that the reliability of the data is dependent on the accuracy of the radar data. IOW, they really don’t know, they are guessing. Bottom line, if you want to use the term “orbit” that loosely, there is really no need for the term “trajectory”. I am quite surprised that otherwise (apparently) conscienti <div class="Discussion_UserSignature"> Our Solar System must be passing through a Non Sequitur area of space. </div>

mental_avenger · Jun 28, 2005

I thought comets with hyperbolic or parabolic orbits can become bounded orbits if they are interacted with a third body like Jupiter!!! Of course. The same goes for passing near any of the other planets. I merely wouldn’t consider their trajectories to be actual “orbits” until then. However, the original discussion was essentially about asteroid belt objects. But, even very very long period comets are in elliptical orbits. Currently we don’t have enough history (or accurate enough measurements) to determine if the comets we do not see return are merely in very long eccentric orbits. That is one reason why I advocated comet and asteroid detection satellites out near the orbit of Mars, perhaps as many as 20 equally spaced. The triangulation measurements would allow much better tracking and prediction. <div class="Discussion_UserSignature"> Our Solar System must be passing through a Non Sequitur area of space. </div>

mental_avenger · Jun 28, 2005

How? According to him, such orbits don't exist, are never seen. It appears that you are going to ride this semantics horse until it dies of old age. Have a nice trip. <div class="Discussion_UserSignature"> Our Solar System must be passing through a Non Sequitur area of space. </div>

mental_avenger · Jun 28, 2005

MA's science posts are usually pretty good. Thank you, I work at it. I'd be curious if there are any parabolic orbits in the solar system known, beyond those of comets, I mean. ?? By definition, any such “orbit” would be a one-time event. As I pointed out, we still don’t have measurements accurate enough to tell the difference between a very long elliptical orbit and a parabolic or hyperbolic trajectory. At this point, it would probably be nearly impossible to make a definitive determination on long-period vs hyper/parabolic trajectories. <div class="Discussion_UserSignature"> Our Solar System must be passing through a Non Sequitur area of space. </div>

mental_avenger · Jun 28, 2005

So the truly parabolic orbit can continue as an elliptical orbit, or break out into an hyperbolic orbit. Not really. A parabolic trajectory, by definition, is an open figure. Remember, a parabola is a section of a cone, and a cone extends to infinity. All it takes is a bit of a kick out of an ellitpical orbit and bingo, very wide parabolic orbit, or hyperbolic. Very few of the asteroids are in such long-period elliptical orbits that it would only require a “bit of a kick”. Here’s a little bit of reality. Space is really big, and objects are really very far apart. Although the asteroid belt looks crowded on the map, it is really very sparsely populated. I blame the SciFi movies for creating an unrealistic view of ships passing through an asteroid belt. In reality, IIRC, the average distance between asteroids in the belt is further than from the Earth to the Moon. Since they are much smaller, a ship could pass through the asteroid belt and never even detect an asteroid. In fact, IIRC, Nasa doesn’t even use any special precautions for spacecraft passing through the belt. <div class="Discussion_UserSignature"> Our Solar System must be passing through a Non Sequitur area of space. </div>

mental_avenger · Jun 28, 2005

Come on, Mental Avenger--don't you think you were just a little unfair? The original context is completely lost. Although “semantically” inaccurate, I was still correct in concept. Unfair? Yevaud and I butt heads occasionally, but I still think he is pretty smart and usually knows what he is talking about. No hard feelings here. <div class="Discussion_UserSignature"> Our Solar System must be passing through a Non Sequitur area of space. </div>

JonClarke · Jun 28, 2005

Sinova Mass extinctions are bad news in the short term but they do open up a lot of niches into which new taxa can evolved. For example, at the end of the Permian the complete extinction of trilobites, tabulate and rugose corals, most of the mammal-like reptiles, and severe reductions in brachiopod diversity led to diversification of crustaceans, scleractinian corals, dinosaurs and bivalves into the vacated niches. In the same way the extinction of the dinosaurs, pterosaurs, and various marine reptiles at the end of the Mesozoic allowed to large scale radiation of mammals and birds. The lag time is about 10-20 My. Mass extinction events more frequent than this would lead to lower species diversity dominated by small, cosmopolitan generalists, which are the taxa than seem best suited to survive such events. Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

sinova · Jun 28, 2005

Jon, Yeah, I know all of what you said. I guess I'm hung up on what you mean by "diversity." I don't quite follow the apparent logic to its ultimate when you say: Mass extinctions may be good for evolutionary diversity in the long run. . . . Mass extinctions are bad news in the short term but they do open up a lot of niches into which new taxa can evolved. Extinctions per se do not create or destroy an environmental niche. Disappearance of frogs from the pond do not destroy the pond (for now let's keep this simple and not get into the interactive web of life ecosystem stuff). All extinction means is that some species perished. WHY the species became extinct is what's definitive. If damsel flies died so the frogs couldn't eat and they starved into extinction, that's one thing; the pond is still there for salamanders to exploit. But if the pond was drained and that was the cause of the frogs' extinction, salamanders and all other pond dwellers are out of luck. In sum: Some causes of extinction can be across the board, while some are selective to a narrow band of species. What I'm getting at is the opening of environmental niches by extinction does not necessarily mean less diversity. Only extinction of the species AND its niche would, in the sense that there was nothing left for future organisms to exploit. So extinctions don't necessarily have to decrease "diversity"-- all it means is that there is a changing of the guard as to WHICH organisms exploit the niche. "Diversity" means diversity (variety, assortment, etc.). "Diversity" does not mean "change." One can argue that it is more likely for an environmental niche to be maximally exploited and have more "diversity" with a greater variety of interactivity and symbiosis if it has had more time to develop. Common sense says that could be true. But it is also true that a mature niche can

JonClarke · Jun 28, 2005

Palaeontologically diversity at a species level increases with time from a mass extinction. Diversity at higher taxonic levels is more complex. Relatively soon after your extinction you can have large numbers of new high level taxa, with only a few species in each. Take whales for example. the diverseified in the Eocene to fill the avaliable niches vacated by the extinction of the marine reptiles. By the Late Eocene there were three major groups (archaeocetes, mysticetes, ondontocetes) compared to the two we have now (mysticetes, ondontocetes). In the Oligocene there was a much greater diversity of cetacean families than now. Since the Miocene family level diversity has decreased, however probably at present there are more species of cetacean than there have every been before. Most, however, belong to a single family, the dolphins. Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

sinova · Jun 28, 2005

I was tweaked by your first comment that mass extinctions may be GOOD for evolutionary diversityand that was compounded when you later told me mass extinctions are BAD news. . . . It sounded like you thought mass extinctions were inherently a "bad thing" and "diversity" something to covet. That parallels a common political ideology prominent today. I engaged the discussion to try to shake out what scientific basis you had for that apparent perspective. Everything you articulately said I already knew, but I don't think you really gave me an answer to that question I had. I guess I was looking for something that wasn't there. Hopefully, readers of your posts will find them of value, so I didn't totally waste your time. Thanks, I'll be more selective with my questions in the future.

yevaud · Jun 28, 2005

Well, MA, I wasn't using a semantical trick to "get out of it." I'm a stand-up guy, and don't try to weasel my way out of things. "Orbit" is the generic term we used. Unless you wish to inform me that a department full of professional astronomers know nothing...? As I pointed out, we still don’t have measurements accurate enough to tell the difference between a very long elliptical orbit and a parabolic or hyperbolic trajectory. At this point, it would probably be nearly impossible to make a definitive determination on long-period vs hyper/parabolic trajectories. Exactly right. We don't know. That is to say, we don't know enough to say anything definitive, one way or another. Here's one mechanism for the perturbation of asteroidal material. The Nasa link I posted was merely to show that the mechanism does exist. http://www.meteor.co.nz/may96_1.html Parabolic and hyperbolic trajectories are neither unknown nor impossible. Hell, we understand the mechanisms well. And not every Earth-crosser by any means has even ever even been *seen* before. So we don't know if it's been in an elliptical orbit or not. So all things being equal, few in the Astronomy world state what kind of orbit it *is* is until (if, when) it's dynamics are known. And so far, we known all of the details on damned few. I don't know about you, but my training states I don't preclude things arbitrarily. And so I wasn't. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

najab · Jun 28, 2005

>It sounded like you thought mass extinctions were inherently a "bad thing" and "diversity" something to covet.That all depends on your view point. Diversity is good for the planet as a whole, I don't really think there's any way you could argue against that point - to more combinations of DNA there are walking around, the more likely it is that DNA will survive. In the same vein, mass-extinctions are a "bad thing" because they reduce the number of combinations.From the perspective of individual species or perhaps whole phyla diversity is a bad thing because it means that there are that many more things competing for your resources and that many more looking to kill you. I'm sure that herbivores aren't overjoyed when another species of carnivore appears on the scene who isn't fooled by the camoflauge their mothers gave them. <img src="/images/icons/smile.gif" />By the same token, mass extinctions are a good things (provided you aren't one of the species that gets wiped out, of course) because it may mean that there are whole ecological niches which aren't being exploited any more - "Ahh, room to breed...er...breathe."

mental_avenger · Jun 28, 2005

When I’m wrong I say I’m wrong. You were correct, “orbit” is apparently used for parabolic and hyperbolic trajectories. I still think they are using the term rather carelessly, but if that is what they use, that is their business. You were also correct in the mechanisms for breaking objects out of the asteroid belt by Jupiter etc. I thought we were talking about single events, not hundreds of thousands of cumulative perturbations over a million years. I don’t generally preclude such things either, that is why I said “rarely”. One of the reasons for that conclusion is that anything on a hyperbolic or parabolic course will never come back again. The vast majority of asteroids must remain in elliptical orbits or we would have lost all the asteroids over these many gigayears. <div class="Discussion_UserSignature"> Our Solar System must be passing through a Non Sequitur area of space. </div>

A CIVILIZATION on MARS? 1B/200M Years Ago? (Pt. 5)

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