Re: Did the increase of earth's gravity, assist the death of the dinosaurs?


chazwin a écrit dans le message
<1177674367.174091.23350@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>...
On Apr 26, 9:44 pm, rick_so...@xxxxxxxxxxx wrote:
Triassic Period
- Plateosaurus; reasonably long neck, but muscular

Jurrasic
- Brachiosaurus; long necked.

Cretaceous
- Tyrannosaurus; Back to reasonably long muscular neck

Tertiary
- Indricotherium; Normal muscular neck

Quaternary
- Wooly Mamoth; Short muscular neck, trunk hangs down.

The Mamenchisaurus had a neck as long as 49 feet.

http://en.wikipedia.org/wiki/Mamenchisaurus

Since today, if you were to try and hold your arm out for 20 minutes,
you would soon see that gravity must be different today than it was
140 million years ago, when the Mamenchisaurus walked the earth in the
Late Jurrasic period.

And perhaps, it has fluctuated quite a bit of over the last 250
million years which has led to the change in neck size and shape until
we get to the present day.

Although the giraffe has a long neck, it has an over-sized heart, 2
feet long and weighing 25 pounds, which is needed to pump blood to its
head.

By contrast,

"We have determined that the left ventricle in a warm-blooded
Barosaurus, for instance, would have needed to weigh about 2000kg to
pump the blood its brain needed," he says. "This is impossible for at
least three reasons. First, it would be difficult to fit such a heart
in the available space; second, the heart would use more energy than
the entire remainder of the body, and third; the thick walls would be
mechanically so inefficient that they would expend more energy
deforming themselves than in actually pumping the blood."

And so then, if we consider that the argument for natural selection,
and evolution being that they grew long necks to reach leaves high up
in trees, yet if they raised their head, they would have passed out.

So the only logical solution is that gravity has changed. And perhaps
more than once, fluctuating, for who knows what reason, be that
collapse of the earth's crust as it cooled, or the gaining or losing
of moons, or asteroid impact, or what?

There must be some evidence in the ground that gravity has changed,
because presently things do not add up, and the current explanation of
the horizontal neck, does not work for all species of dinosaur who
clearly were not horizontally oriented as perhaps the Mamenchisaurus
was.

http://www.prehistory.com/brachios.htm
52 feet high.

There must be some evidence in sedimentary rock formations, that are
more compacted during those times when gravity was stronger, and less
when not, and it should be apparent in stream beds which can be
compared by the same sediment settling with some compacting more than
at other times, or something.

Gravity is not a thing that can fluctuate. There is no force in nature
that is gravity. The principle upon which we attribute "gravity" is
based upon the fact that particles of matter tend to gather together.
The nuclear bonds of atoms attract other atoms. The net result of this
fact is that proximity to very large bodies casues things to have
weight. This is what we call gravity and its survival as a constant is
wholly dependant on the nature of matter.
The earth cannot remain the same mass and have a different gravity
(rotational centripetal forces not withstanding). This is as certain
as a one inch Jello pudding not being able to support the weight of a
bus and hold its shape.
For the earth's gravity to change significantly, the mass of the earth
would have to change significantly. Thus if the earth were the size of
the moon its gravity would approximate that of the moon. Mars, a
planet of similar size, has a similar gravity to earth.
What "fluctuation" in gravity are you proposing happened in the past?
What the hell is "quite a bit"?
And what was the cause of this fluctuation?



Variation in the effect of gravity are caused by the following:
a) changes in latitude
b) changes in elevation
c) local topography
f) earth tides
g) variation in subsurface density
These changes would not be noticed by animals and can be only detected by
sensitive instruments.

If the rotation of the Earth has slowed this would mean an increase in the
effect of gravity. What effect
this would have had on organisms I do not know. Someone with nothing to do
and the back ground in physics
and geophysics needed could look up the estimates of the slowing of the
Earths rotations and calculate
the change in the acceletation due to gravity. I think it is unlikely that
the magnitude would be enough to have effected evolution.

JL


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