Dinosaurs and Treetops

[DSYoungEsq]

http://www.straightdope.com/classics/a4_088.html

I recall seeing something recently to the effect that the sauropods couldn't have lifted their necks up to allow treetop feeding. The scientist who postulated this had determined that the bone structure of the neck vertebrae was such that articulation upward was not possible. He then postulated that it would be difficult, if not impossible, to pump blood up the neck to the head. I can't find the reference now: anyone know who's idea this is and what the buzz is about it?

[speakeasy]

Cecil, baby! You missed a crucial detail.

Dinosaurs probably grew big because it's easier to stomp the begeezus out of a predator when you weigh 6 or 8 tons.

Mammals don't grow that big because we are a higher energy density form of life. Your average mammal can increase it's heat and work output by a factor of 10 from resting to full boogie. The problem for us types is getting rid of the heat. On land, elephants are about the limit. People do it better than most types of animals, even other mammals.

One way for people who are in really stellar shape to hunt is to just start jogging after their chosen prey on a really hot day. Four or five hours later, you can walk up and stab whatever it is for dinner. Zulu hunters do this for a living.

Big animals don't get rid of heat so easy. Apparently swarms of hyperkinetic little animals is a more effective way of exploiting an ecological niche than a few great big slow ones.

Remember, from nature's point of view, it's not the survival of the individual that matters, it's the survival of the species.

Which brings up a scary point; evolution isn't done just yet. There is nothing saying that animals our size and shape are always going to be the most effective. Generally, anything capable of higher energy density will win in a brawl. On the street, that means quicker, faster, stronger, meaner, & smarter.

Quick, what is one type of moving object you can think of that has much higher energy density than people? That is incredibly quicker than us? And that coincidentally happens to be doubling it's intelligence every 18 months? We better stay on top of this particular tiger, kids, there won't be a second chance.

[Momotaro]

First, about the sauropod's neck. Yes, the reference is in a Discover magazine from about a year ago but I can't find it because I'm stranded in a foreign country. It shouldn't be hard to find, there's a big sauropod's (four-legged, long-necked dinosaur's) skeleton on the cover.

What the article said was that their neck had little vertical mobility: they couldn't raise their neck much higher than their shoulders and not much lower than the plane of their legs. This was just enough so that they could get a drink of water, I guess.

They had much more horizontal mobility, but many couldn't even touch their own body with their snout by curling their neck sideways. The incorrect assumption was that since sauropods had long necks they were like giraffes, the basic modern-day equivalent. Not so, it seems.

So why the long neck? One interesting theory is that the long neck counter-balanced the long tail, not the other way around. Sauropods were huge, a natural defence in itself, but they couldn't run; they could only walk fast. A large tyrannosaurus could have walked to this big stomach on legs and have lunch without too much trouble, except if he got smacked on the head by a tail as long as he was.

The tail was a huge limb. It had good horizontal mobility and a small nudge from the big muscles at the base of the tail would have made the tail into a (possibly sound-barrier breaking) whip. So the tail was probably used for defence.

The one exception is the brachiosaurids, whose fore-limbs were longer than their hind-limbs and whose neck structure seems to have supported a near vertical stance. Now, how could the blood have been pumped up to that height? No one knows, but there are theories, such as multiple heart-like muscles distributed through the length of the neck and pumping the blood up there. That seems strange, but with dinosaurs, you never know.

As for the size issue, I would like to point out that there are no inherent problems with large-sized mammals (or any warm-blooded animals). Elephants are not the limit of mammalian gigantism. Following the extinction of the dinosaurs mammals overtook all the niches that had previously been dinosaur territory and in so doing grew to astounding sizes very quickly. One stunning example is the baluchitherium, a rhinoceros-related animal that grew to be 5m (16 feet) tall and weighted roughly 16 metric tons.

Okay, so dinosaurs still win the gold on land for sheer mass, but mammals are the biggest animals in the sea. No animal at the time of dinosaurs approached the size of the blue whale.

Size can be quite an advantage for animals in general. Naturally, larger plant-eaters deter predators, and larger predators can take on a whole new range of prey. Secondly, being bigger makes you less vulnerable to sudden temperature changes.

Here is a little math: volume increases in a given shape by the cube of its length (or any other linear dimension). If you want to visualise this, imagine a cube that has a one-unit long side. Its surface area is therefore six square units. Its volume is one square unit. If you make a cube that has twice the side length, its surface area becomes 24 square units and its volume, 8 cube units.

That means that while its length doubles, its surface becomes four times bigger and its volume, eight times bigger! That's very significant and means that bigger animals have less surface area per volume through which they lose and gain their heat. Therefore they have a stabler body temperature.

One would figure that in the case of a very warm environment, smaller animals are better off. After all, when it gets really hot they can hide in shadows or burrow under the cool earth while big animals are just stuck out there while the heat keeps coming on. For example, just imagine a herd of elephants jostling to get under a tree in the African savanna.

Not so. Using elephants as an example again, big animals receive less heat per volume than smaller ones. As well, the excess heat is safely stored away inside their body, away from organs that wouldn't function as well with so much heat. An elephant can do this long enough to get through the day. A small animal doesn't have enough body volume to do this, and therefore run the risk of overheating and dying. As well, when night comes little mammals must keep moving or hide in a well-insulated place to keep their body temperature at a reasonable level. The African savanna can get rather cool at night. Elephants, on the other hand, don't lose their heat so quickly in the first place and can just release the excess heat they had stored during the day to keep warm and cozy throughout the night.

This only works for mammals and warm-blooded animals, though. Small cold-blooded animals can let their body temperature drop without feeling ill effects, except that naturally they can't be bothered to move then, or only very slowly. This can be a disadvantage when something hairy and warm comes to chew on them in the middle of the night. However, the argument that bigger size makes for stabler body temperature holds true for cold-blooded animals too.


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Only humans do inhuman things.

[Northern Piper]

i believe it was in Discover magazine a few months ago - don't have a cite for it.

[NanoByte]

Speakeasy:

"On the street, that means. . .". . .assault weapons. Pretty good energy density there.

And I'd say nature has more than a one-track mind. She worries about not only about a species and an individual and a part of an individual's surviving, but also of others of each not surviving, that the first might do so, etc., etc. IOW, Darwinian stuff doesn't add up linearly; it's however you want to look at it (preferably without bringing in religious notions).

Ray (With no value, why did I survive?)

[C K Dexter Haven]

The issue of Discover magazine that jti and Momotaro reference is November 1997, about computer-simulations to try to understand dinosaur neck and tail movement. Momo does a good job of summarizing, I'd like to add one minor amendment to his comment that the dinosaurs could not touch their own bodies with their heads. The article found essentially two different types of long necks:
- contortionists (like apatosaurus) with very flexible necks, who could look directly behind itself or twist its neck into a forward-looking S-shape; some of these could almost touch the side of their rib cage with their nose; and
- Strait-jackets (like diplodocus) with very very limited neck mobility.

One conclusion is that in many sauropods the the head was probably held DOWN, lowered, not up, so that "diplodocus with its rigid downward-sloping neck and its head close to the ground, might have spent most of its time feeding like a grazing cow on ground-hugging vegetation."

The giraffe-like pose with head held high was (according to this study) not possible. "The 80-foot long brachiosaurus ... normally held its 30-foot neck at about 20 degrees above the horizontal, it's head only 18 feet above the ground. It could move only some 9 feet to either side. ... The lowest that brachiosaurus could get its head was about five feet off the ground."

[Artboy]

just like to toss my 1/2 cent in here. maybe the reason the dinos were able to reach such enormous proportions stems from the fact that they were able to exploit an abundant resource (land based plant life) without severe predation from others. by the time the plant resource became a contested commodity, herbivores were at most impressive sizes. the evolving predators would then have to be large enough to take them down.

i don't know if the predators evolved from the herbivores, but maybe it at least took some time, evolutionarily speaking, for the predators to follow them onto land.

[DSYoungEsq]

Thank-you for the references to the magazine article I half-remembered. Age does stupid things to memory...wait, that's another thread...

As for the size issue, let's not forget certain facts during the debate:

1) There were dinosaurs of all sizes, large and small, both apparently herbivorous and definitely carnivorous.

2) Mammals came after and started smaller.

3) The climate may have been different, based on the available data on plant life at the time.

And yes, all you creationists, it is bones that exist, and we may all be wrong about evolution, but for one thing, that is another thread in General Questions, and besides, kinda pointless to debate dinosaur development if all you can say about it is: they are big cause God made the bones that way. ;)

[John W. Kennedy]

Actually, mammals have been around for about as long as Dinosaurs, and there was an early age of mammals before the age of Dinsaurs.

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John W. Kennedy
"Compact is becoming contract; man only earns and pays."
-- Charles Williams

[DSYoungEsq]

Actually, mammals have been around for about as long as Dinosaurs, and there was an early age of mammals before the age of Dinsaurs.
Don't suppose you would care to supply some authority for that statement?

The material I read said that mammals are descended from Synapsid reptiles. While it is true Synapsids were present prior to the Mesozoic, it would appear that mammal-like animals didn't start appearing until sometime in the Triassic and there is considerable debate as to when exactly these animals stopped being reptiles and became actual mammals.

As for Dinosaurs, technically, they were diapsid reptiles, specifically the orders saurischia and ornithiscia. Exactly when the diapsids emerged is unclear to me, but clearly they were present early in the Triassic, along with a number of other reptiles often lumped together 'commercially' as "dinosaurs" (e.g. Icthyosaurs).

I stand by my statement: Mammals, TRUE mammals, developed after the dinosaurs and were smaller, in general, than the dinosaurs.

Now if someone can provide reliable source material to refute this, I have been known to listen. ;)

[tomndebb]

DSYoungEsq:I stand by my statement: Mammals, TRUE mammals, developed after the dinosaurs and were smaller, in general, than the dinosaurs.

Now if someone can provide reliable source material to refute this, I have been known to listen.

I will not place mammals prior to dinosaurs, but the Encyclopædia Britannica places the origins of dinosaurs between 230 and 235 million years ago. Mammal Evolution (Savage and Long) places the earliest mammals at exactly the same time. Both sources say that the earliest numbers are fuzzy in either event.

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Tom~

[C K Dexter Haven]

<< but the Encyclopædia Britannica places the origins of dinosaurs between 230 and 235 million years ago. >>

Before or after lunch?

[Momotaro]

Here's what paleobotany, an often unacknowledged field of science, tells us about evolution: all the major (r)evolutions in the animal kingdom were preceded by new adaptations in the plant kingdom. For example, animals moved onto land only after plants had colonized the milieu, and animals could not become bigger until they had a reliable supply of plant matter to feed upon.

Plants, the ultimate non-predators, are the basis of the food chain. They photosynthesize, take raw energy and resources, and store them. They are then predated upon (vegetarians are technically plant-life predators) and so on up the food chain. This is confirmed by the fossil record.

Since plant life has nothing holding it back except the resources it exploits, it naturally covered most of the exposed land mass. Vegetarians followed suit, and predators naturally became bigger to take on new prey. It's really no wonder dinosaurs got as big as they did as long as they were supported by abundant flora. A more interesting question is, why did dinosaurs get so big and become the top of the terrestrial food chain while mammals
were forced to scrounge on the leftovers until they became prey themselves?

The most recent evidence seems to show that both dinosaurs and true mammals appeared at the same time sometime before the Triassic period of the Mesozoic era. At that time advanced representatives of both orders competed for the same resources. Even the mammals attained impressive sizes. From memory, since I don't have my references with me, there were vegetarians of about 3 meters long. In the Triassic period the dinosaurs began getting really big and big species of mammals didn't survive the transition.

Let me define true mammals, though. We are talking about animals that had already developed a vertical stance, differentiated teeth (incisors, canines, molars), viviparous (live birth), characteristic nimbleness, sweat glands, and fur. I'm not pulling your leg there, since there are several skin impressions that show those details clearly.

As for 'true' dinosaurs, they had the vertical stance associated with warm-blooded animals, but they hadn't really improved significantly on the reptilian design. For example, they still had undifferentiated teeth. Only later would feathers and the bipedal stance appear, once dinosaurs had established themselves at the top of the food chain and as size record breakers.

So why did mammals lose out so decisively to dinosaurs?

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Only humans do inhuman things.

[Ray14dot4]

Cecil summarily ignored the questioners conjecture about the possibilty of lesser gravity in the days of the dinosaurs. Granted the questioners centrifugal force hypothesis was a bit absurd but the notion of lesser gravity is not far fetched. The "expanding earth theory" lends direct support to the idea that gravity during the age of dinosaurs was perhaps 80% of todays force due to the earth's mass being proportionately less. This would explain how the extremely large creatures could have lifted their massive necks and indeed even fly. Rather than my going into a lengthy discorse about this very plausible theory, I suggest those interested visit this site for starters: http://www.geocities.com/CapeCanaveral/Launchpad/8098/HomePage.htm

[Momotaro]

Mmmh, I've just read the explanation of the Expanding Earth Theory. I don't buy it. It doesn't make sense to completely discredit the Continental Drift Theory because it contains some inconsistencies. The Expanding Earth Theory is even more far-fetched, especially the cosmological theory that's necessary to justify it.

In spite of this, it's still a fascinating theory and I suggest a thread be posted about it. That is, if anyone can get through the obstuse text and the author's shrill tone.

Gravity has changed through time as a function of the rotational speed of the Earth. As continents drifted (or did they?) the montains obstructed the natural air currents and caused transfers of momentum. Unfortunately, I don't have any data with me on this and I don't know if there is a correlation with that phenomenon and the gigantism of the dinosaurs.

On the other hand, many people now believe that oxygen levels were slightly higher at the time of the dinosaurs. However, paleontologists will agree that, structurally, the dinosaurs were well suited to large sizes. Their relative 'stiffness' of body was possibly a boon to gigantism.

Most likely they didn't really need vastly different gravity or oxygen levels to attain the size they did.

If anyone wants to read a good vulgarisation of advanced paleontological findings as well as an interesting theoretical account of how dinosaurs lived, get your hands on "Predatory Dinosaurs of the World" by Gregory S. Paul.

[Ray14dot4]

Momotaro, you wrote:
"even more far-fetched, especially the cosmological theory that's necessary to justify it."
Galileo was told the same thing about his theory of the solar system.
The "expanding earth theory" (EET) goes back further than the "continental drift theory"
and really what is needed to prove it is
not cosmological but quantum theoretical evidence for the spontaneous creation (or recreation) of matter through fission, fusion or a process yet to be discovered. For example, what happens to all the matter that is sucked in to a black hole? It amazes me that intelligent people can accept the something from nothing Big Bang theory and yet discount the EET in favor of an "always the same size earth theory." Expansion is the paradigm of our universe.

If you prefer a less "shrill", scholarly geological dissertation on the expanding earth theory I recommend you read the material by Professor S. Warren Carey which is contained on the web site I last posted.

There are physics, cosmological and geological newsgroups that have been discussing EET for many years and I'm not sure this board is a good place to start
the thread from scratch again.

[tomndebb]

Ray14dot4:Galileo was told the same thing about his theory of the solar system.

Umm, no. Galileo's first lectures and published texts met with raised eyebrows regarding his claims for moons around Jupiter. Once his original critics got hold of telescopes equalling Galileo's in power, they observed the moons and accepted his claims. The next issue for which Galileo was taken to task was his claim that the planetary orbits were perfect circles--for which his critics quite rightly roasted him.

Going by the same logic, Bill Swiggle was laughed out of the room when he proposed that the sun was extinguished each evening and reignited the next morning as it arose over the flat earth's eastern horizon. So? Pointing out errors in older scientific notions does not justify newer scientific notions.

I do not immediately dismiss the expanding earth theory, but matter leaping into existence (only in the center of a planet?) is not going to go very far to persuade me.

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Tom~

[John W. Kennedy]

Galileo's notion of circular orbits was taken direct from Copernicus, who got it from the existing geocentric system of Aristotle and Ptolemy. On that point, it was he who was the hidebound conservative who had to be corrected by the younger Kepler.

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John W. Kennedy
"Compact is becoming contract; man only earns and pays."
-- Charles Williams

[AuraSeer]

A star does not "implode" due to an increase in mass it collapses because it runs out of fuel.

A star is basically a big, hot cloud of gas. Though it radiates a lot of heat outward, the fusion reactions in its core are constantly generating more energy, and keeping the temperature high.

If you'll recall from basic physics, a hot gas exerts more pressure than a cold gas. Higher pressure causes the size of the gas cloud to be greater. When a star begins to run out of fuel, it also begins to cool down, thus lowering its internal pressure and allowing it to shrink in on itself slightly.

After it has "burned" all the fusable elements it contains, the star will continue cooling and collapsing, until it reaches equilibrium as a big frozen rock.

(Here I'm assuming a small star, so we don't have to talk about neutronium or supernovae. If you want the rest of the gory details, just ask.)

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Of course I don't fit in; I'm part of a better puzzle.

[tomndebb]

Ray14dot4:I can see I landed in a nest of nitpickers. Next time I'll make my historical analogy anal retentively exact.

Tom, no one said "matter leaping into existence (only in the center of a planet?)"
It is a universal process. Stars are near the end of the process (guess what happens to the mass of a star that makes it implode). The Earth near the beginning.

Jupiter could be said to be near the middle since it has characteristics of a brown dwarf.

I'll not waste your time anymore. Check out the newsgroups if your still intrested. I usually don't participate in these pissing contests and now I remember why.

Gee, what did we say? (Good thing he didn't stumble into any of our really good nit-pickers, huh?)

Ray, you posted a link to a site that presents a fairly unfamiliar theory. Your defense appealed first to "they laughed at. . . ." and then appeared to call for matter simply popping into existence with no further explanation.

As noted, I do not dismiss the "exapnding earth" idea out of hand, but it would help your position if you did more than throw out little tidbits and then pout when they weren't accepted or admired.

Since the site that you did linked contains several historical errors regarding the time-line and the currently accepted mechanisms for plate tectonics, (which I am willing to ascribe to the author of the web site, rather than to S. Warren Carey), I see no reason to simply fall down and worship at your postings. If you have an actual argument that you can lay out in a coherent fashion, feel free to do so. I'd enjoy seeing it. If you are going to wander off in a huff because you got tweaked for bad analogies and incomplete information, I doubt that we'll miss you.

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Tom~

[Ray14dot4]

I can see I landed in a nest of nitpickers. Next time I'll make my historical analogy
anal retentively exact.

Tom, no one said "matter leaping into existence (only in the center of a planet?)"
It is a universal process. Stars are near the end of the process (guess what happens to the mass of a star that makes it implode). The Earth near the beginning.
Jupiter could be said to be near the middle since it has characteristics of a brown dwarf.

I'll not waste your time anymore. Check out the newsgroups if your still intrested. I usually don't participate in these pissing contests and now I remember why.

[Momotaro]

Ray14dot4, I'll certainly check the site out. Sounds interesting, even if it flies in the face of what I've taken for granted all these years. We'll see if I can be convinced.

[John W. Kennedy]

Not to mention that the site is the work of an obvious loony. It has all the classic signs -- paranoia, insistence that the orthodox side is going to collapse any day....

Now, of course, the fact that the theory is supported by a loony doesn't necessarily make it wrong.

But it sure as hell doesn't improve the chances of it being right.

------------------
John W. Kennedy
"Compact is becoming contract; man only earns and pays."
-- Charles Williams

[Ray14dot4]

I couldn't resist returning here for a peek. Yes Tom I was in a huff mainly due to having skipped lunch and breakfast and partly because of JWKjr's totally ignoring the topic.

Momotosa I admire your openmindedness.

Auraseer you're stating ONE theory. But you helped make my point. You said (stars are) "constantly generating more energy". I think Albert proved E=M (we don't need the C^2 here). Hmm, just where is all of this energy (matter) materializing from? Has it existed since the beginning of time and if so where was it before then? Don't tell me about the dust cloud theory because then I'll ask where the dust came from
and why dust should be mysteriously congealing to form stars. And a heck of a lot of dust must be balled together to form a supernova.

Also, it seems to me that in order for a massive star to become a black hole it would have to be ADDING more mass until the point of implosion. Otherwise it would ALWAYS have been a black hole. The original theory was that no energy could escape from a black hole. But now we know that they emit enormous amounts of radiation. And so on.
One look at a volcano or earthquake (especially in the Pacific Ocean) tells me our Earth is a producing massive amounts of energy/matter. If our planet's core was just an inert mass of molten rock and iron one would expect it to be cooling not erupting. (Maybe we would be experiencing global cooling not warming?)

Tom, if I seem impatient talking about the subject it's because I've been following it for years, I'm not a very good teacher, and I hate repeating theories when that can be easily accessed elsewhere. As you can see we have diverged from the original expanding earth/ dinosaur subject on to cosmology, philosophy and physics. This what makes the subject so exhausting and a facinating.
Again, I strongly urge anyone whose interested to read the work of Professor S. Warren Carey a preeminent geologist who brilliantly addresses many of these ideas. Amazingly, (I guess they cleared the copyright with him) his latest book is on the web in toto at: http://www.geocities.com/CapeCanaveral/Launchpad/8098/HomePage.htm#Earth Universe

The geological stuff is a bit heavy but the latter half of the book dealing with universal theories is lucid.
BTW, there are many other books related to this subject in one way or another. P.A.M. Dirac for example wrote about the multiplicative creation of matter in his book "Directions in Physics".

JWKjr. go away. You haven't added anything here except your recital of high school science history and calling a webmaster a loony. Read S. Warren Carey's book. Be careful you don't fall off the edge beyond your horizon. And please lose that pseudointellectual signature quote.

[AuraSeer]

Ray14dot4 wrote:
Auraseer you're stating ONE theory. But you helped make my point.

If you think that, you're sadly mistaken.

You said (stars are) "constantly generating more energy". I think Albert proved E=M (we don't need the C^2 here). Hmm, just where is all of this energy (matter) materializing from?

You're misinterpreting my statement, as well as the concept of energy/mass equivalence.

The sun is not "creating" energy out of nowhere. A helium nucleus contains less energy than a pair of independent protons (helium nuclei). When hydrogen fuses to form helium, it falls to that lower energy state; the extra energy has to go somewhere, and is thus emitted as protons.

Has it existed since the beginning of time and if so where was it before then?

Yes, the mass has been around since the beginning of time. Asking where it was "before that" is meaningless, because we're talking about the beginning!

I'm sure you have heard of the Big Bang theory, and it's apparent that you don't accept it. I don't even want to attempt an explanation of Hawking's theories on imaginary time, so we'll just agree to disagree, and leave it at that.

Don't tell me about the dust cloud theory because then I'll ask where the dust came from and why dust should be mysteriously congealing to form stars. And a heck of a lot of dust must be balled together to form a supernova.

I tried to explain this in my post above, but apparently you didn't get it, so I'll be a bit more explicit this time.

In a big cloud of hydrogen, every atom exerts a gravitational force on every other atom. This pull causes the cloud to slowly collapse. Since its mass stays the same as its size decreases, it increases in density and pressure. Also, the distance between particles shrinks, so the gravitational force grows, making the collapse accelerate.

Over a long period of time, the pressure at the center of the cloud continually rises, which also increases temperature (pv=kt). Eventually, if the cloud was big enough to begin with, the temperature and pressure become high enough for hydrogen to begin fusing. At this ignition point, the cloud is now called a star.

Understand yet?

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Of course I don't fit in; I'm part of a better puzzle.

[Momotaro]

Eh, why were dinosaurs so big?


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Only humans do inhuman things.

[Ray14dot4]

See what I mean Tom and Momotosa? The topic has been lost and some people are going wild with their narrow tangential "expertise".
BTW, I have to confess I never read the whole Expanding Earth site I posted. I scanned it and noticed that S. Warren Carey's excellent stuff was contained there so I assumed the entire site was well written. Apparently I was wrong and I apologize to all if the webmaster is somewhat of a shrill loony.
Speaking of which, Auraseer you're starting to sound a bit shrill:
I tried to explain this (the dust cloud theory) in my post above, but apparently you didn't get it, so I'll be a bit more explicit this time.

You never mentioned "dust" you mentioned hydrogen clouds. Does dust = hydrogen in your vocabluary? Good God, there was a special about stars on the Discovery channel last night which made the differences quite clear. Read you own words before you bite someone's head off:
Understand yet?

OK, I'm through nitpicking.
Let's bury the hatchet and acknowledge that we all roughly know the current, conventional explanations for most of the popular physical phenomena. We're here to explore alternativetheories.
Part of what I set down here is my opinion
and part is the opinion of others I've read.

To explore the possibility of whether the earth could have been smaller in the time of the dinosaurs (hence less gravity), let's start with the dust cloud theory:

Dust clouds gravitationally coalesce to form
stars.

My question to you Auraseer is:
If sufficient dust (mass) collects to form a star large enough to become a supernova why does the supernova have to undergo an explosion before it can implode and become a black hole? If it is burning up it's "fuel" it should losing mass and never become a black hole. If it had sufficient mass from
beginning it should have become a black hole instantly.
I submit that the nuclear creation of matter in the core of the star causes it's mass to increase to the point where it explodes and then collapses. A similar nuclear reaction is taking place in our earths core.
Your reply?

[DSYoungEsq]

If sufficient dust (mass) collects to form a star large enough to become a supernova why does the supernova have to undergo an explosion before it can implode and become a black hole? If it is burning up it's "fuel" it should losing mass and never become a black hole. If it had sufficient mass from
beginning it should have become a black hole instantly.
I submit that the nuclear creation of matter in the core of the star causes it's mass to increase to the point where it explodes and then collapses. A similar nuclear reaction is taking place in our earths core.
Quite obviously, Ray, you do NOT understand "the current, conventional explanations" for star formation or star evolution. Let's try one more time.

DUST DOESN'T FORM STARS!

Stars form from coalescing gas. Dust and rocks and such are thought to form planets of rocky nature (such as Earth).

As for the bit about black holes and supernovae, you are not reading what people are writing, nor, apparently, have you taken the time to read a simple astronomy text. Now perhaps someone here has the patience to tutor you in basic astrophysics, but, frankly, I don't feel like it when I know you don't want to listen. But if you are going to question accepted theories (a practice I encourage - it forces the mainstream to actually support theories with logic and evidence), then you MUST start by understanding the processes involved. There are some reasonable ways to attack mainstream astrophysics. Starting the attack by talking about dust forming into stars doesn't help.

[Ray14dot4]

DSYoungEsq:

Glad you're not my lawyer. You interpret theories as fact and you're condecending which makes this trait even more amusing.
http://oposite.stsci.edu/pubinfo/pr/95/44.html

Dust and gas are clearly mentioned here. Even
the scientists writing these press releases call star formation theory "speculation". If it were simply hydrogen (per Auraseer) we're talking about we'd have a photo of nothing (since H is colorless except under spectrography).
That's why the scientists use the term EGG's.
I was using the term "dust" generically, you use "gas".

All pure theory and once again we're not getting anywhere on the original topic due to parrot-like recitations and obsessive semantics.

Thank you Mr."Tutor"

LOL

[DSYoungEsq]

Ray, do you even READ what you link? <lol>

Inside the gaseous towers, which
are light-years long, the interstellar gas is dense enough to collapse
under its own weight, forming young stars that continue to grow as they
accumulate more and more mass from their surroundings.

That is from your link. Note that, while there is dust in the nebula, there is no dust in the EGG's. I recommend actually READING what the site says about star formation. ;)

As for not seeing hydrogen (sigh), you really should learn a thing or two about what happens when light from inside or behind a cloud of interstellar molecular hydrogen (or any other gas) excites the gas. One of those things is that it GLOWS. Hence, the fact it can be seen. ;)

Of course, if you had read the site, you would know that too, since it talks explicitly about this in discussing 'photoevaporation.'

Every post like this you make makes you more clear, I'm thinking... <giggle>

[JillGat]

[[All pure theory and once again we're not getting anywhere on the
original topic due to parrot-like recitations and obsessive semantics. ]]

Hey Ray, chill babyman. I appreciate your contributions on this thread muchly, but people are free to take the topic (almost) anywhere they like.
Jill

[AuraSeer]

Ray14dot4 has exactly six posts on the MB, all of which are in this thread. His profile is blank, including his email address.

I don't want to accuse him of being a troll, but I'm not going to waste any more time trying to educate him.

[Giantrobo]

The reason why Dionsaurs are so big is more simple than everyone thinks. Dinosaurs were on Earth for millions of years, they have all that time to evolve. Just the same way Humans are getting bigger so did Dinosaurs they just had alot more time to do it. All Dinosaurs probably started out small and over the eons evolved to get bigger so they could survive. Many animals go through Gigantism, its a sign that they are nearing the end of thier species.

[John W. Kennedy]

Oh my God! We've got a believer in orthogenesis!

------------------
John W. Kennedy
"Compact is becoming contract; man only earns and pays."
-- Charles Williams

[DrFidelius]

Hey! Who let that Irish Elk in here?

[Jois]

Except we are getting smaller.

Cro-Magnon was 6 feet tall. We are averaging 5'11" for males and 5'5" for women. We did get taller to make up for poor nutrition in the middle ages but we haven't grown a bit in decades.

Our bones aren't as thick as Cro-Magnons, either. We were called "gracile" but we are boardering on dainty.

We can't even fit our allotted number of teeth in our gums anymore.

See, you'll never grow up to be a dino. Find another dream.



------------------
Are you driving with your eyes open or are you using The Force? - A. Foley

[JillGat]

[[We can't even fit our allotted number of teeth in our gums anymore.]]

Speak for yourself. I never had wisdom teeth.
Jill
more highly evolved.

[Jois]

Jill says, "Speak for yourself. I never had wisdom teeth."

That's right! That's right!

Jill is more highly evolved. Woo!

And it is purely natural selection (unless you come from a place that gets you jaw X-ray before marriage) for teens often died of serious infection before antibiotis and dental surgery arrived. Got to breed more often...

15% of Europeans have 2 wisdom teeth missing.
In Asia it goes up to 30% in some regions.

From Stringer, of course, "African Exodus" pp. 228

Jill, you need to add this to your sig line.

------------------
Are you driving with your eyes open or are you using The Force? - A. Foley

[Giantrobo]

Cro-Magnon?! Cro-Magnon are vastly different then modern man. Once modern man moved into Cro-Magnon territory the Cros disappeared. Therefore useing Cro-Magnon to compare modern man against is a flawed argument. We are not decendents of Cro-Magnons. Also, there is a column of this site that Cecil answered, titled Are humans still evolveing? And guess what Cecil said....Yes humans are getting bigger, stronger and faster. Thus it stands to reason in a few more thousand years if the human species is "challenged" enough people on the whole will get even bigger and stronger.

[Jois]

I'm not going to be the one to send them a post card and tell them.

Maybe you shouldn't either. Early Europeans, anatomically modern humans, called Cro Magnons from the site in SW France where first discovered, are Homo sapiens sapiens.

The real McCoys--



------------------
Are you driving with your eyes open or are you using The Force? - A. Foley

[jab1]

"Scientists Discover Fossil Bones of What May Be the Biggest Dinosaur that Ever Lived" (http://www.abcnews.go.com/sections/science/DailyNews/dinosaur_000120.html)

They did not find all the bones (They seldom find them all), so they can only estimate its length: 157 to 167 feet, more than half the length of a football field, halfway from home plate to the outfield fence in most ballparks.

The Discover article referred to earlier MAY be this one: www.britannica.com/bcom/magazine/article/0,5744,48320,00.html (http://www.britannica.com/bcom/magazine/article/0,5744,48320,00.html) It discusses recent findings in Argentina and reveals that no one is certain why dinosaurs that lived in the Southern Hemisphere seemed to have been larger than the ones from up north. Remember too, that the continents were different then. with Laurasia in the north and Gondwanaland in the south.

(When you search the Britannica website, it finds its own entries, PLUS relevant magazine articles and other websites, AND it recommends books which can be purchased from Amazon. It found several Discover articles about dinosaurs and this seemed like the one everyone else was talking about earlier. But withou the title of the article, I could not be sure.)

------------------
&gt;&lt;DARWIN&gt;
___L___L__

[jab1]

Originally posted by Momotaro:
First, about the sauropod's neck. Yes, the reference is in a Discover magazine from about a year ago but I can't find it because I'm stranded in a foreign country. It shouldn't be hard to find, there's a big sauropod's (four-legged, long-necked dinosaur's) skeleton on the cover.

Here's the article you mentioned: www.britannica.com/bcom/magazine/article/0,5744,28765,00.html (http://www.britannica.com/bcom/magazine/article/0,5744,28765,00.html) It describes how paleontologists are using computers to create virtual dinosaurs to see how they moved. (Ignore the thumbnail cover in the upper right corner depicting a radio telescope. They use that same cover on all Discover articles. The articles are also lacking the illustrations, but, curiously, they include the captions that went with them.)

No animal at the time of dinosaurs approached the size of the blue whale. See my post above.

------------------
&gt;&lt;DARWIN&gt;
___L___L__

I was going to suggest this thread (or at least the divergent argument on "growing earth") should head to GD so we don't get a repeat of the 360 deg in a Circle/Velikosky debate thread, but Jill said it's okay... ;)

speakeasy said:
Mammals don't grow that big because we are a higher energy density form of life. Your average mammal can increase it's heat and work output by a factor of 10 from resting to full boogie. The problem for us types is getting rid of the heat. On land, elephants are about the limit. People do it better than most types of animals, even other mammals.

Speakeasy, Cecil did address that point. That's the details of the warm-blooded vs. cold-blooded argument. Along those lines, I saw a Discover article some time before the previously mentioned one that discussed whether dinosaurs were warm or cold blooded, and whether that mattered. Some research indicates that they may have been cold blooded, but had certain features that duplicated the warm-blooded animals, so they were better at energy output than modern reptiles. Not that I recall the details.

I think Artboy answered the main question from the original article. They were big because of an abundant food supply.

That does beg the question of why dinos beat out mammals until the K-T extinction.

CKDextHavn commented:
&lt;&lt; but the Encyclopædia Britannica places the origins of dinosaurs between 230 and 235 million years ago. &gt;&gt;

Before or after lunch?

I didn't follow. What?

Ray14dot4 said:
I can see I landed in a nest of nitpickers. Next time I'll make my historical analogy anal retentively exact.

Ray, this thread is your first entrance to this site. You apparently haven't lurked here, or you would be aware that (a) this site is full of nitpickers; (b) the mating call of the looney is to invoke Galileo (or Einstein, or Einstein and Galileo in a tag team match).

Tom, no one said "matter leaping into existence (only in the center of a planet?)" It is a universal process. Stars are near the end of the process (guess what happens to the mass of a star that makes it implode). The Earth near the beginning.
Jupiter could be said to be near the middle since it has characteristics of a brown dwarf.

Ugh. Auraseer has addressed the star comment. I just like the way you are implying that the Earth will evolve into a Jupiter, then a brown dwarf, and finally a star. Plus, Jupiter is &lt;b&gt;not&lt;/b&gt; a brown dwarf - it is much too small.

more from Ray14dot4:
Also, it seems to me that in order for a massive star to become a black hole it would have to be ADDING more mass until the point of implosion. Otherwise it would ALWAYS have been a black hole. The original theory was that no energy could escape from a black hole. But now we know that they emit enormous amounts of radiation. And so on.

And
If sufficient dust (mass) collects to form a star large enough to become a supernova why does the supernova have to undergo an explosion before it can implode and become a black hole? If it is burning up it's "fuel" it should losing mass and never become a black hole. If it had sufficient mass from beginning it should have become a black hole instantly.
I submit that the nuclear creation of matter in the core of the star causes it's mass to increase to the point where it explodes and then collapses. A similar nuclear reaction is taking place in our earths core.

No, you are greatly mistaken. The reason the star must go supernova after burning off a lot of mass and throwing off more mass in the supernova, but then has enough mass to form a black hole, is because &lt;i&gt;it contracts&lt;/i&gt;. If you squeeze the mass of the earth into the size of a pinhead, you will get a black hole. (I'm not saying that is a possibility - that's an exaggerated visual.) We're talking &lt;b&gt;density&lt;/b&gt;, not just &lt;b&gt;total mass&lt;/b&gt;. Think of it this way - in the Earth's sky there are lots of clouds of water and dust. One cloud weighs more than a 747. How does it stay aloft? Because it is spread over a much greater volume, so the density is low. Same thing with star mass. The matter is held apart by the internal heat and nuclear forces while the gravity holds it together, in a balancing act. When the star goes supernova, the heat is dissapated, and the mass collapses under the pull of gravity without the energy to hold it apart. Then it collapses into a much smaller volume, and thus forms the black hole.

One look at a volcano or earthquake (especially in the Pacific Ocean) tells me our Earth is a producing massive amounts of energy/matter. If our planet's core was just an inert mass of molten rock and iron one would expect it to be cooling not erupting. (Maybe we would be experiencing global cooling not warming?)

1) The Earth is cooling. It is just a slow process, because the molten core generates heat that slows the process.
2) The heat is generated through radioactive decay and by friction (turbulence) caused by internal mixing. Also perhaps there is a dynamo effect.
3) Lava flowing up from the core is not spewing out because there is an increase in matter. Yes, it is under pressure - gravity and thermal pressure.
4) "Global warming" is not related.

Giantrobo said:
Cro-Magnon?! Cro-Magnon are vastly different then modern man. Once modern man moved into Cro-Magnon territory the Cros disappeared. Therefore useing Cro-Magnon to compare modern man against is a flawed argument. We are not decendents of Cro-Magnons.

I believe you are confusing Cro-magnons with Neanderthals. From http://www.talkorigins.org/faqs/homs/specimen.html

"Cro-Magnon Site", Homo sapiens sapiens (modern) Discovered by workmen in 1868 at Cro-Magnon in France. Estimated age is 28,000 years. The site yielded skeletons of about half a dozen individuals, along with stone tools, carved reindeer antlers, ivory pendants, and shells. The Cro-Magnons lived in Europe between 35,000 and 10,000 years ago. They are virtually identical to modern man, being tall and muscular and slightly more robust than most modern humans. They were skilled hunters, toolmakers and artists famous for the cave art at places such as Lascaux, Chauvet, and Altamira.

And http://www.talkorigins.org/faqs/homs/species.html

[quote]&lt;b&gt;Homo sapiens neanderthalensis (was Homo neanderthalensis)&lt;/b&gt;

Neandertal man existed between 230,000 and 30,000 years ago. The average brain size is slightly larger than that of modern
humans, about 1450 cc, but this is probably correlated with their greater bulk. The brain case however is longer and lower
than that of modern humans, with a marked bulge at the back of the skull.

[snip]

&lt;b&gt;Homo sapiens sapiens (modern)&lt;/b&gt;

Modern forms of Homo sapiens first appear about 120,000 years ago. Modern humans have an average brain size of about 1350 cc. The forehead rises sharply, eyebrow ridges are very small or more usually absent, the chin is prominent, and the skeleton is very gracile. About 40,000 years ago, wi

[Irishman]

Great. I run that sig line and screw up my formatting.

[Loren Pechtel]

Ray14dot4: It appears that my clock has more brains than you. When I followed that link to see what you were talking about, it spoke up "coo-koo". I didn't waste my time reading the whole thing, but I did see enough to see it doesn't work.
First, it's attacking the lack of plate tectonics on any body we can see the surface to be able to tell if there are plate tectonics. Of course we see no plate tectonics--all such bodies are far smaller than Earth, their radioactivity won't be enough to maintain a molten core.
Second, the pictures supposedly showing expansion: Consider an airless body like the moon. There's very little to wear down the features. Therefore, there should be numerous great rifts as deep as the structual strength of the rocks permits. When we look at the moon, we see craters, not rifts.
Third, without subduction, how do you explain metamorphic rock? What takes surface rock down many miles to the point it's deformed by heat?
Fourth, plate tectonics tells oil men where to drill. If the theory is no good, why do they find oil?

To address some of your other points on here:
The reason stars don't simply start out as black holes is that they start out a diffuse mass of gas. As it collapses, it gets hot enough to support fusion. That heat keeps it from collapsing further, until it runs out of fuel.
As for the mass loss due to fusion--it's about 1% of the material actually fused (not the entire star except in the case of tiny stars). It's not going to have a big effect on whether it can reach a black hole state or not.

[jab1]

Originally posted by JillGat:
I never had wisdom teeth.
Jill
more highly evolved.


Ah, but are you lactose tolerant or INtolerant? According to www.talkorigins.org/faqs/mutations.html#Q2 (http://www.talkorigins.org/faqs/mutations.html#Q2) , lactose tolerance is a recent mutation. Our distant ancestors were originally lactose intolerant; this encouraged the weaning process. But our more recent ancestors got the bright idea to raise certain animals for milk when they realized they produced more milk than any woman ever could. If you are lactose tolerant, it's a good chance you're descended from dairy farmers or goat-herders and shepherds.It should be understood that it was a matter of chance that the lactose tolerance mutation appeared in a group where it was advantageous. It might have been established first by genetic drift within a group which then discovered that they could use milk. In other words, some daring person who already had the mutated gene tried cow's milk and found it could sustain him or her and got the idea to capture and raise these animals for their milk.

My mother is one-quarter Cherokee. American Indians, with some exceptions, did not drink animal milk. They used their hides, meat and bones, but rarely did they keep them for milk. (Perhaps they would in emergencies, such as the death of a mother, in order to save her baby.) I'm betting they were lactose intolerant, which would explain why my mother is and why I and my two brothers are as well.

Correct me if I'm wrong, please.

As for why dinosaurs got so big, I'd go with the theory of abundant plant life leading to big herbivores (and higher oxygen levels) which in turn led to big carnivores. The Earth's climate seems to have undergone a radical change (caused by continental drift, perhaps) some time in the Cretaceous which led to the proliferation of flowering plants which can endure more radical changes in temperature than non-flowering types. Then there would have been less food for the herbivores, which meant less food for the carnivores, which meant the dinosaurs were already on the decline when that asteroid or comet hit the Yucatan.

I think that's what Robert Bakker says, anyway.

------------------
When all else fails, ask Cecil.

[Jois]

Cheese, man, cheese. If you are lactose unevolved you are supposed to be able to tolerate cheese. Much better to have cheese than just use milk for bathing.

I can't remember about butter, it may also have been a use for butter for the lactose unevolved.


Jois

[{:-Df]

Giantrobo said: "The reason why Dionsaurs are so big is more simple than everyone thinks." Your reasoning aside, this does raise a critical point: namely, beware the terrible Celine Dionsaur! Uggh!

The Discover article...discusses recent findings in Argentina and reveals that no one is certain why dinosaurs that lived in the Southern Hemisphere seemed to have been larger than the ones from up north.
I would think it obvious - tidal forces. Centrifugal force may have weakened the effective force of gravity, but it was not the only force acting. Remember that the earth is tilted on its axis, and it turns out that the south pole is farther from the sun at aphelion and closer at perihelion. And that's clearly the same thing as saying that the path it follows is more elliptical than the path the north pole follows. And that then equals greater tidal forces: stronger attraction by the sun during southern summer, and stronger centrifugal forces trying to fling the dinosaurs into the outer solar system during southern winter. Et viola! Bigger biggies.


But I do have one lingering doubt. Doesn't the fact that I had three wisdom teeth, while making me less [evolved than Jill, still make me wiser? (I had one wisdom tooth removed, and believe me, the difference was immediatley noticeable!)

[Fillet]

{:-Df said:

{QUOTE]I would think it obvious - tidal forces. Centrifugal force may have weakened the effective force of gravity, but it was not the only force acting. Remember that the earth is tilted on its axis, and it turns out that the south pole is farther from the sun at aphelion and closer at perihelion. And that's clearly the same thing as saying that the path it follows is more elliptical than the path the north pole follows. And that then equals greater tidal forces: stronger attraction by the sun during southern summer, and stronger centrifugal forces trying to fling the dinosaurs into the outer solar system during southern winter. Et viola! Bigger biggies.[/QUOTE]

Please tell me you've been overcome by the need to spread a bit o' blarney on this day...

[jab1]

Someone correct me if I'm wrong, but i once heard that the Earth would have to rotate REALLY fast in order for centrifugal force to cancel out some of the force of gravity.

I think we'd have to have five-hour days. And that's assuming that such a high rate of rotation wouldn't rip the Earth to pieces or prevent it from forming in the first place.

------------------
When all else fails, ask Cecil.

[Loren Pechtel]

Originally posted by jab1:
Someone correct me if I'm wrong, but i once heard that the Earth would have to rotate REALLY fast in order for centrifugal force to cancel out some of the force of gravity.

I think we'd have to have five-hour days. And that's assuming that such a high rate of rotation wouldn't rip the Earth to pieces or prevent it from forming in the first place.


It would have to be a lot less than 5 hours. Consider, synchronous orbit is where going around once a day keeps something in orbit. And what is orbit other than the point where the centrifugal force is equal to gravity?
Therefore, to find the day length to cancel surface gravity (at the equator), look at low-Earth orbital periods--something like 80 minutes. The actual value would be slightly less, as it's a few miles closer in.

As for it's ripping Earth apart--it wouldn't be *QUITE* powerful enough to do that. However, loose objects at the equator would not be held down--they would be prone to departing. The worst casualty would be the atmosphere--it would be flung off *VERY* quickly. The oceans would go with it. On the lifeless ball that remained, things like volcanoes would toss rock into space.

[Boris B]

Well, I'll go out on a limb and say that the centrifugal force idea Murphy came up with in the column isn't ridiculous. Centrifugal force from Earth's rotation does offset gravity somewhat, everywhere except at the poles. Sure, it may not be significant; it might be one percent or one ten thousandth of one percent. Significance is in the eye of the beholder. If you want to say it would only be significant if days lasted eight hours, that's a perfectly acceptable definition.

I guess I don't know why Adams or anyone else thinks this is such a stupid idea. Earth spins slower now than it used to; sure, it hasn't been a significant speed decrease (eye of the beholder). Days have been getting (insignificantly) longer and non-polar weights (insignificantly) greater. Until you calculate the amount the Earth has slowed, you wouldn't know this. My point is, Murphy had the principle correct, and can be forgiven for guessing the degree incorrectly.

------------------
What part of "I don't know" don't you understand?

[Boris B]

As to the argument about Cro-Magnon ... here's a link I hope will clear things up:
http://www.emi.net/~bs-soft/Cro-Magnon.html

The name Cro-Magnon is now generally employed in referring to all such anatomically modern humans found in Europe and the Middle East, from their rather sudden appearance about 40,000-30,000 years ago.... the Cro-Magnons ... are classified as Homo sapiens sapiens.

Cro-Magnons are a temporally distinct group of people, not a genetically distinct group of people.

[OliverTwistofLime]

I have nothing to add except that this was a fascinating thread to read and I compliment those who spent the time and energy to produce the responsible material.

------------------
Don't ever say *288* in polite company. Its just two gross!

[jab1]

Originally posted by Boris B:
I guess I don't know why Adams or anyone else thinks this is such a stupid idea. Earth spins slower now than it used to; sure, it hasn't been a significant speed decrease (eye of the beholder). Days have been getting (insignificantly) longer and non-polar weights (insignificantly) greater. Until you calculate the amount the Earth has slowed, you wouldn't know this. My point is, Murphy had the principle correct, and can be forgiven for guessing the degree incorrectly.


I'm not so sure. That would be like saying, "We can fly to the moon!"

"All right!"

"And the trip will take only ten minutes!"

"Uh, wait a minute..."

We know the days were shorter in the past by counting the rings of fossil corals. The days get progressively longer the younger the coral fossil is:

Days per year - Years in the past
435 Days - 850 Million Years Ago
401 Days - 395 MYA
387 Days - 300 MYA
382 Days - 190 MYA
381 Days - 180 MYA

I got this from a Creationist website: www.creation-answers.com/time4.htm (http://www.creation-answers.com/time4.htm) While they accept the evidence that days were shorter in the past, they are skeptical the coral samples really are as old as the carbon-dating indicates. :rolleyes: So take their OTHER findings with a grain of salt.

------------------
When all else fails, ask Cecil.

[jab1]

In my haste, I neglected to finish my post! :o

As you can see, the year was only 16 days longer 180 million years ago when the dinosaurs were really enormous. Sure, it means the Earth was rotating faster then, but not enough to counteract the force of gravity enough to make them weigh less.

I just did a rough calculation. Assuming the Earth took the same number of hours (8760) to orbit the Sun back then (And there is no good reason to assume that it did NOT), then a day was a bit less than 23 hours long, no more than an hour shorter than today. So a ten-ton dinosaur would've weighed 9.99995 tons? :)

Oh, and the main reason the Earth's rotation is slowing is because it's dragging the moon around with it. If the moon were less massive or it did not exist at all, the Earth's days would be much shorter.

(I wonder how you'd design a 23-hour clock...? "High Noon" at 11:30?)

------------------
When all else fails, ask Cecil.

[jab1]

Originally posted by jab1:
skeptical the coral samples really are as old as the carbon-dating indicates.

I made a mistake. You can't use radio-carbon dating to determine the age of fossils that are 850,000,000 years old. Other methods must be used.

------------------
When all else fails, ask Cecil.

[Fillet]

We know the days were shorter in the past by counting the rings of fossil corals. The days get progressively longer the younger the coral fossil is:

{snip}

I got this from a Creationist website: www.creation-answers.com/time4.htm (http://www.creation-answers.com/time4.htm) While they accept the evidence that days were shorter in the past, they are skeptical the coral samples really are as old as the carbon-dating indicates. So take their OTHER findings with a grain of salt.

Actually, the estimates for length of day and year back in the Precambrian were not originally derived from corals at all, because corals don't make their first appearance until the Paleozoic - this is a misunderstanding on the part of the person who compiled that information. The biogenic structures actually used are called stromatolites: these are layered buildups created by the binding and trapping of sediment by thin layers of cyanobacteria ("blue-green algae"). Geoscientists used to think that these layers accumulated on a daily basis. Nowadays, the growth patterns of stromatolites is considered somewhat speculative, and length-of-day estimates are made instead from tidal rhythmites, which are (as their name suggests) deposits that reflect the comings and goings of tidal currents in estuaries. (They are considered more reliable indicators of time because they form via completely inorganic processes, so one doesn't have to worry about the vagaries of biological organisms.) Tidal rhythmites are much rarer than stromatolites in the Precambrian, but enough of them exist to confirm that the length-of-day around 800 million years ago was on the order of 18 hours.

The creationist web site is correct in pointing out that the rate of angular momentum transfer from the Earth to the moon (= rate of lunar retreat = slowing of Earth's rotation rate) has not been constant over geologic time. To my knowledge, no one's come up with any real workable solutions to this particular puzzle.

P.S. on dating methods - radiocarbon dating works reliably on organic materials to 30,000 years ago, less reliably to 45-60,000 years ago. Dating of older sequences (&gt; 500,000 years) generally relies upon U/Pb, Pb/Pb, K/Ar, or Ar/Ar, depending on the type of material to be dated.

[jab1]

Originally posted by Fillet:
Actually, the estimates for length of day and year back in the Precambrian were not originally derived from corals at all, because corals don't make their first appearance until the Paleozoic - this is a misunderstanding on the part of the person who compiled that information.

Well, to be fair, I made that same mistake, though I DID think 800,000,000 years ago was too far back for something as complex as corals. Should've said so, though.

The creationist web site is correct in pointing out that the rate of angular momentum transfer from the Earth to the moon has not been constant over geologic time. To my knowledge, no one's come up with any real workable solutions to this particular puzzle. But any unsolved problem is evidence for the invisible hand of God, remember? ;)

U/Pb, Pb/Pb, K/Ar, or Ar/Ar

Lessee...

U/Pb = Uranium/Lead
K/Ar = Krypton/Argon

Right? (It's been a while since I looked at the Periodic Table.)

------------------
When all else fails, ask Cecil.

[Fillet]

Whoops, sorry, I should've written these out in the interests of full disclosure. :) (note to self: got to get out of the office more)

U/Pb = uranium-238/lead-206
Pb/Pb = lead-207/lead-206
K/Ar = potassium-40/argon-40
Ar/Ar = argon-40/argon-39

There are a bunch of other decay series that can be used for dating, but these are the most common. Rb/Sr (rubidium-87/strontium-87) was also used a lot in the past, but because it tends to give fairly large error limits it's not used much anymore.

[Kyberneticist]

Concerning the variable rate of the angular momentum transferred between the earth and moon.

I remember reading an article recently (on talkorigins.org?) which provided the theory that the shape of the land masses alter the rate at which the moon drags on the earth.

This sort of makes sense. The big bulge of water the moon is making that we call the tides is going to drag a lot less against one super continent called pangaea, then against a series of spread out continents which go almost from the north end to the south end of the earth.

Anybody heard about this/understand it/have links?

[Myron Van Horowitzski]

Why were dinosaurs so big? The answer &lt;snerk&gt; can be found here: http://www.christiananswers.net/dinosaurs/questions.html

------------------
Imbibo, ergo sum.

[JonF]

Perhaps i should let sleeping dogs lie, but I can't resist.

Raydot14:

If sufficient dust (mass) collects to form a star large enough to become a supernova why does the supernova have to undergo an explosion before it can implode and become a black hole? If it is burning up it's "fuel" it should losing mass and never become a black hole. If it had sufficient mass from beginning it should have become a black hole instantly.

1. Gravitational attraction is a nonlinear function of distance. It is proportional to the square of the radius from one center of mass to another.

2. An elementary result from first-year college physics is the proof that a uniform spherical shell of matter exerts no gravitaional force on anything inside.

From these facts, it's relatively easy to calculate the relationship of a non-black-hole star to some piece of matter (which might be part of the star):

A. Either the matter is outside the star and is far enough away that it can (but not necessarily will) escape the gravitational pull of the star, or

B. The matter is inside the star and is not affected (graitationally) by the portion of the star's matter that is farther away from the center, and can (but not necessarily will) escape.

A black hole forms only when the star contracts enough that the mass inside a relatively small radius from the center is high enough to prevent escape.

As for the energy questions, a star radiates energy by "converting" mass to energy. (It's more correct to say that it converts one form of mass-energy to another form). A star can lose a lot of photons without a measurable effect on the mass, but eventually the star's mass is reduced noticably.

The process of collapse and/or explosion is complicated, because of radiation pressure and thermal effects and the size of a star (it takes a long time for something to propagagate from the center of a star to the outside).

------------------
jrf

[Loren Pechtel]

Originally posted by JonF:
2. An elementary result from first-year college physics is the proof that a uniform spherical shell of matter exerts no gravitaional force on anything inside.


I'm afriad I must object to the term "elementary" here. While I have the stated education, I certainly don't regard the calculation as elementary, nor was it something that was discussed. (Gravity was barely touched upon, never applied.)