I have often looked at the huge carnivore dinosaurs and wondered how
they could have been mobile when so big. There is some evidence to
suggest that they were not such quick movers (something to do with the
ratio of the femur/tibia length) but still, they are far larger than
elephants who themselves are very slow, labored movers.

I wondered if the lateral strike by the meteor that allegedly blacked
out the sky, could have also had an effect on the earth’s
gravitation. Could a lateral strike against the rotational direction
of the earth have slowed down the rotation speed, reduced the
centrifugal force, therefore increased gravity and as a consequence
lead to the disappearance (or non-evolution following the mass
extinction of the dinosaurs) of land creatures of massive prehistoric
dimensions?

I am not sure of the relationship between gravity and centrifugal
force (I suspect it is minimal), but I assume there is a formula to
work out the rotational speed of a sphere required to exactly
counteract its gravitational force along its equator (assuming a
constant mass density). How fast would the earth need to rotate to
counteract exactly gravity at the equator? What speed to quasars
rotate?

Would be interested to know your thoughts.

Guy

Guy Lux wrote:
I have often looked at the huge carnivore dinosaurs and wondered how
they could have been mobile when so big. There is some evidence to
suggest that they were not such quick movers (something to do with the
ratio of the femur/tibia length) but still, they are far larger than
elephants who themselves are very slow, labored movers.

I wondered if the lateral strike by the meteor that allegedly blacked
out the sky, could have also had an effect on the earth’s
gravitation. Could a lateral strike against the rotational direction
of the earth have slowed down the rotation speed, reduced the
centrifugal force, therefore increased gravity and as a consequence
lead to the disappearance (or non-evolution following the mass
extinction of the dinosaurs) of land creatures of massive prehistoric
dimensions?

I am not sure of the relationship between gravity and centrifugal
force (I suspect it is minimal),

No. I think it is basically the same, even at the
most small level.

I have reasons to believe that gravitation is
caused by the objects occupying less space in a
gravitational field than outside of it. (I usually
call it an inertial field, as they are exactly the
same). Now if you look at an object in a
gravitational field, it is smaller at the bottom
than at the top.

Now do the same reasoning for centrifugal motion :
the object side on the outside is smaller, since
its speed is higher, by length contraction. So the
force comes from the object occupying less space
at the outside of the rotation. Both forces are
exactly caused by the same thing !
An asymmetry in the inertia they undergo.


Would be interested to know your thoughts.


Hope you like it.


Hayek.

Guy Lux wrote:
: I wondered if the lateral strike by the meteor that allegedly blacked
: out the sky, could have also had an effect on the earth’s
: gravitation. Could a lateral strike against the rotational direction
: of the earth have slowed down the rotation speed, reduced the
: centrifugal force, therefore increased gravity and as a consequence
: lead to the disappearance (or non-evolution following the mass
: extinction of the dinosaurs) of land creatures of massive prehistoric
: dimensions?

Probably not, and there is a layer of material
all around the world from one impact, suggesting that
the dust cloud was truly global, and probably killed
all vegetation.

: I am not sure of the relationship between gravity and centrifugal
: force (I suspect it is minimal), but I assume there is a formula to
: work out the rotational speed of a sphere required to exactly
: counteract its gravitational force along its equator (assuming a
: constant mass density). How fast would the earth need to rotate to
: counteract exactly gravity at the equator?

Hope the rotation speed doesn't change much.
The acceleration of gravity is about 9.82 meters per
second per second at the poles and only about 9.79 meters
per second per second at the equator.

The rotation of the Earth does reduce the
measured acceleration by that much.

Joe Fischer

--
3

On 8/18/2003 10:21 AM, Guy Lux wrote:
I have often looked at the huge carnivore dinosaurs and wondered how
they could have been mobile when so big. There is some evidence to
suggest that they were not such quick movers (something to do with the
ratio of the femur/tibia length) but still, they are far larger than
elephants who themselves are very slow, labored movers.

You have obviously never observed an enraged or stampeding elephant. An
elephant can outrun most if not all humans.


Could a lateral strike against the rotational direction
of the earth have slowed down the rotation speed, reduced the
centrifugal force, therefore increased gravity and as a consequence
lead to the disappearance (or non-evolution following the mass
extinction of the dinosaurs) of land creatures of massive prehistoric
dimensions?

No. First, I'm pretty sure there are measurements of the earth's daily
period both before and after, and IIRC they are not wildly different
(with errors of ~10% on the length of a day so long ago, IIRC). Second,
even for a daily rotation of only 1 hour the centrifugal effect at the
equator would only be a few percent of 1 g; it would of course be 0 at
the poles.



I am not sure of the relationship between gravity and centrifugal
force (I suspect it is minimal), but I assume there is a formula to
work out the rotational speed of a sphere required to exactly
counteract its gravitational force along its equator (assuming a
constant mass density). How fast would the earth need to rotate to
counteract exactly gravity at the equator?

I have not done the computation, but I suspect it would be more than one
rotation per second.

What speed to quasars
rotate?

I'm not sure they do. But pulsars are observed to rotate up to several
thousand rotations per second.


Tom Roberts

Tom Roberts wrote in message ...
On 8/18/2003 10:21 AM, Guy Lux wrote:
I have often looked at the huge carnivore dinosaurs and wondered how
they could have been mobile when so big. There is some evidence to
suggest that they were not such quick movers (something to do with the
ratio of the femur/tibia length) but still, they are far larger than
elephants who themselves are very slow, labored movers.

You have obviously never observed an enraged or stampeding elephant. An
elephant can outrun most if not all humans.


True, but for elephants, running is generally reserved for urgent situtations.
The likelyhood that stumbling would be fatal is greater, the larger the animal.

Paul Cardinale

Tom Roberts wrote:
:Guy;
: What speed to quasars
: rotate?
:
: I'm not sure they do. But pulsars are observed to rotate up to several
: thousand rotations per second.

That is not what is observed, they are observed
to pulsate, and the present accepted thought is that
the pulses are due to rotation and magnetic fields.

Joe Fischer

--
3

Russell Blackadar wrote:
: Tom Roberts wrote:
: On 8/18/2003 10:21 AM, Guy Lux wrote:
: How fast would the earth need to rotate to
: counteract exactly gravity at the equator?
:
: I have not done the computation, but I suspect it would be more than one
: rotation per second.
:
: Actually, less than one per hour, unless I've made a mistake:
: f = omega/(2pi) = (1/(2pi)sqrt(g/r) = sqrt(9.8/6000000)
: = 0.0002 sec^-1 = .7 hr^-1
:
: It's the same as the orbital frequency that a satellite would
: have if it orbited at sea level. You get about the same number
: for actual satellites in low-earth orbit, since their height
: above ground is small compared to the diameter of the earth.

[Smile] It is pretty simple without
the math, it is almost 90 minutes. :-)

Joe Fischer

--
3

Thanks, you lot,

Now Hayek, I'm a bit lost on your inertia field. I don't quite
understand how an object occupies less space in a gravitational field
than outside of it, nor how a gravitational field is smaller at the
bottom than at the top. (I undertand how a gravitational field could
be smaller at the inside of the earth....?)

I will keep thinking about it though, thanks for your theory :-)


I like Russell's calculations and agree that geostationary orbit of a
low earth satellite has to be a pretty good pointer to the speed of
rotation required to counteract gravity, as the distance from the
earth's surface is negligable when considering the size of the earth.

I also agree that elephants are pretty quick, but I think the T Rex
(and I believe another even bigger type was recently found and was
given a suitably impressive name) was far bigger than the and also
predatorial thus prey-chasing (not intelligent or subtle enough to
stalk). I imagine if a T Rex stumbled it would have a pretty tough
time. Its little arms would not help. Kangaroos dont fall (but then
T Rexs didn't bounce......

Guy

Guy Lux wrote:
Thanks, you lot,

Now Hayek, I'm a bit lost on your inertia
field. I don't quite understand how an object
occupies less space in a gravitational field
than outside of it,

Inertial field is exactly equal to gravitational
field. General relativity uses this feature.
Eotvosch experiments indicate this is so.

If you have trouble with gravitational
contraction, think of relativistic length
contraction, but since there is no motion in one
direction, the contraction is in all directions.

nor how a gravitational field is smaller at the
bottom than at the top. (I undertand how a
gravitational field could
be smaller at the inside of the earth....?)

That is why I hammer that you consider it an
inertial field. The field *IS* stronger at the
inside of the Earth. There is no gradient, you do
not feel gravity, and you conclude the field is
not so strong. WRONG.

Look at what a clock does : a clock is an
inertiameter. Where it runs slowest, (inertia
slows things down) inertia is greatest. Time runs
slowest at the center of the Earth.


And I said objects where smaller at the bottom
than at the top, in a gravitational field, that is
an inertial field with a gradient. No gradient
(=difference) in the inertial field between
adjacent points, no gravitation.

If you have further questions, I will be glad to
answer them.

Hayek.

"Hayek" skrev i melding ...


Guy Lux wrote:
nor how a gravitational field is smaller at the
bottom than at the top. (I undertand how a
gravitational field could
be smaller at the inside of the earth....?)

That is why I hammer that you consider it an
inertial field. The field *IS* stronger at the
inside of the Earth. There is no gradient, you do
not feel gravity, and you conclude the field is
not so strong. WRONG.

Confusing field and potential?

Paul