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Airbagged(was Dive!Dive!Dive!)

Hello all.

Jeffrey Martz, martz@holly.ColoState.EDU selectively wrote in rubbttal to
my posting "Dive!Dive!Dive!"

> In what way is T.rex being "streamlined" going to reduce its mass
> or the damage caused when it hits the ground? 

Streamlining does not reduce mass, but should a frictional force such as
falling at speed be encountered the shape of the object has a great deal to
do with it. A blunt ended object, such as a 2X4 (or elephant), will lose
its speed faster than a streamlined (Tyrannosaurs rex) object upon
impacting the ground regardless of poundage. Unless you're pretty slow this
should be obvious (pardon the pun). Round-nosed bullets deliver more energy
than sharp-nosed versions in the same weight and velocity because they give
up their speed faster and deform easier. If you "drop" anything straight
down its impact force will increase with mass, but no land-bound creature
hits the ground at right angles as the result of natural mishap, besides
cliff falls. The faster an impacting object is traveling the longer the
duration of friction, and the total impact force is divided across that
lenght of time. So, streamlining will allow an object to extend the time
frictional forces are allowed to act upon it, and decrease the peak energy
exterted at the cost of a longer event.

Jeffery continues;

>   Regulating speed so as not to have a potentially fatal accident
> would be a good self-preservation behavior.
>     In summary:
>     1. You haven't noted exactly why Dr. Farlow's caluculations
> regarding mass and the forces of impact at a given speed might be in
> error.
>      2.  You haven't said exactly why you think T.rex's prey animals
> would be so incredibly speedy.
>      3.  You haven't proposed any sort of "safety device" that could
> counteract the force of impact: what sort of things are we
> talking about?  A huge airbag?  An anti-gravity device?

Jeffrey failed to address the mount at the Black Hills Institute, and the
greatly reduced hieght of an apparently running, and attacking,
Tyrannosaurs rex (an exact copy of the specimen used to base the origional
study upon), from the 20' he cited. Whyw? Is it not only possible, but
likely, that Tyrannosaurs rex positioned itself much lower to the ground
than 20' during a chase? Isn't it at least possible that Tyrannosaurs rex
didn't have that far to fall, and the skid distance and impact forces
miscalculated because of it. Points 1 & 3 addressed!(see also paragraph 1)

I don't think we have to "assume" Tyrannosaurs rex was predatory, with the
evidence at the Denver MHN. Oppotunistic scavanger as well? Very likely. In
predatory situations isn't faster always better? Speed to close on a
constantly migrating herd, single out a victim, and make a quick kill with
as little chance of self injury during the kill as possible would seem a
requirement. Trying to avoid being eaten, before growing up, might also be
a good reason to be speedy. I don't think Tyrannosaurs rex was self aware
enough to hold itself in check so as not to run too fast, unless they were
several orders of magnitude more intellectually endowed than we now
believe. If Tyrannosaurs rex could not overtake a prey animal, quickly, the
cost of the chase bankrupts the energy reserves. Intraspecific rivalries
could also contribute to the need for speed. Point 2 addressed!

> Assuming that T.rex is indeed a predator, why assume that the big
> potential prey animals of its time were so speedy?  T.rex had legs
> significantly longer than the ceratopsians and duckbills of its time,
> which were also massive enough for falling to have been a danger.

If this is fact then everything bigger than a cow walked slowly and
cautiously to avoid fatal falls. I'll have to ask for a source of
information on this statement. Is there any fossil evidence of any species
that remotely suggests a fall as cause of death?

> How fast are the speeds derived from these trackways?  How fast does
> sustained herd speed travel have to be?  How much faster is "much faster"?

As to the trackway evidence, I suggested one write Paleoworld or a
learned list subscriber sound off. I only know what I've been
subjected to via the tube on this matter. Hopefully what I've quoted
wasn't a load of "stuff", 'cause the tube never lies about such
things.;-) I do know that any creature on the verge of being eaten
will exert maximum effort to avoid that unpleasantry, and the sight of
a charging Tyrannosaurs rex would surely frighten ANY creature into
headlong, straining-every-locomotion-muscle, flight. Suggesting
otherwise returns us to a time when we thought dinosaurs were slow,
and stupid. This brings us to the other unadressed point of reaction
time, to which Dr. Farlow nor Jeffery nor anyone else can speak. An
unknown factor, that without knowing is the crux of the matter. What
if Tyrannosaurs rex was just too damned agile to suffer a fatal fall,
except rarely?

> As far as the lack "physical evidence" in the form
> of broken necked tyrannosaurs is concerned, why are you so certain this
> is due to the impossibility of a falling T.rex being killed rather than
> T.rexs generally not running so fast that falling was a major cause of
> death?  T.rex being careful to moderate its speed could explain the
> lack of broken necked T.rexs as well as T.rex somehow altering the laws of
> physics, and is probably more plausible..

I've never heard of any predator moderating it's speed. Speed is the most
effective weapon in a predatory animals arsenal. Why would a lion have to
be "that much faster" than a zebra? Without the speed to overtake its prey
Tyrannosaurs rex's aweful bite would be useless. Did I suggest that
Tyrannosaurs rex could alter anything other than the life status of
intended prey, or its running position relative to the surface?
And now a short editorial, if Mickey will allow it.

I don't think it's just me being a little too sensitive about all of this.
I grow weary of responding to and reading messages that show no respect
whatsoever. I'm not exclusively reffering to postings which I'm personally
involved. Things have gotten quite edgey here, and I wonder what is going
on. It seems as though personality has become more important than the
science. I've learned more form this list and its subscribers than I can
measure, but it's becoming more and more a forum of contestants rather than
comrades. If we're losing subscribers because of it let us change our
attitudes. When we challenge someones statements can we not just ask for
explainations and not whip out our poison pen, or keyboard? Calling names
and being a list bully won't advance the science or win admiration. Maybe
waiting a day to respond to a posting would help, or completely ignoring a
message that inspires an angery response. Maybe I'm as much to blame as
anyone, but I herby swear to try to remember I'm writing to real people and
not impersonal entities generated by the WWW. Is it too much to ask?

[ Although I've received a few statements from people who also think
 we're getting edgy around here, there's been no noticeable falloff in
 the number of people subscribed.  Perhaps whatever's eating people
 will end after the elections in the U.S.  I know I'm sick of the
 harsh ads I've been seeing hereabouts in Indiana... -- MR ]