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Dinosaurs and gravitational pull

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BOGWarrior89

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Dinosaurs and gravitational pull
« Reply #30 on: January 15, 2007, 10:18:48 PM »
Quote from: "weevil"
Erasmus....okay so that goes back to my question....I realize that dinosaurs weren't the first life on earth but were they the first animal life? If so why were they so big? The only animals alive today that come near their size live under the water as you said. Even the woolly mammoth died out leaving the smaller elephant species. Thanks to 'scientist' I have been informed that mass controls gravity. Could anything have changed the Earth's mass around that time to alter the pull allowing natural selection of smaller species?


The Earth is supermassive compared to even a herd of dinosaurs.  It would have as little effect as adding one to 1,000,000,000,000,000.
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weevil

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Dinosaurs and gravitational pull
« Reply #31 on: January 15, 2007, 10:33:49 PM »
I don't think you understood my question. I'm not conjecturing that the dinosaur's collective mass had anything to do with it. If back in the dinosaur's time the gravitational pull was less than it was when they died out, and that was part of the reason they died out, then what could have caused a change in the earth's gravitational pull? What could possibly change it? Is there a way that scientists could establish a change in the earth's gravitational force?
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Erasmus

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Dinosaurs and gravitational pull
« Reply #32 on: January 15, 2007, 10:41:51 PM »
Quote from: "weevil"
were they the first animal life?


They were not.  For a rather intriguing look at revolutionary developments in animal life, I strongly recommend the PBS miniseries The Shape of Life.

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Could anything have changed the Earth's mass around that time to alter the pull allowing natural selection of smaller species?


The Earth's mass would have to have increased, the stronger gravity favouring smaller animals over the larger ones that couldn't support their weight anymore.

Alternatively, the Earth's rate of spin could have decreased dramatically; a spinning Earth imposes a centrifugal force to objects on its surface proportional to the rate of spin.
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BOGWarrior89

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Dinosaurs and gravitational pull
« Reply #33 on: January 15, 2007, 10:43:50 PM »
Quote from: "Erasmus"
a centrifugal force


WHAT'D YOU SAY?
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cmdshft

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Dinosaurs and gravitational pull
« Reply #34 on: January 15, 2007, 10:44:45 PM »
Wouldn't that centripetal force be offset by gravity then? (Not centrifugal)

And last I checked.. a flat earth does not have centripetal force perpendicular to it's surface, only possible in certain areas on an RE, whether it spins or doesn't.
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weevil

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Dinosaurs and gravitational pull
« Reply #35 on: January 15, 2007, 10:45:50 PM »
So could the Earth's spin have been altered by the meteor that hit the Earth just before the dinosaurs were wiped out? Plus you didn't answer my question as to whether or not scientists have a way of determining the gravitational pull from that time.
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BOGWarrior89

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Dinosaurs and gravitational pull
« Reply #36 on: January 15, 2007, 10:48:21 PM »
Quote from: "weevil"
Plus you didn't answer my question as to whether or not scientists have a way of determining the gravitational pull from that time.


No one knows how to do this, so, no, they wouldn't.
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weevil

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Dinosaurs and gravitational pull
« Reply #37 on: January 15, 2007, 10:50:14 PM »
Hmmmm very interesting....why can't they? Maybe if they examined fossils of the size of animals living back then and the size of animals now!!!!
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Erasmus

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Dinosaurs and gravitational pull
« Reply #38 on: January 15, 2007, 10:54:19 PM »
Quote from: "Hara Taiki"
Wouldn't that centripetal force be offset by gravity then? (Not centrifugal)


Centrifugal force is applied to every object in a rotating reference frame.  It's proportional to angular speed; gravity is not.  If you spin up a merry-go-round and hop on, you will feel a force pressing you to the outside of the merry-go-round.  This force is present regardless of any centripetal force that might be holding you in.

"Centripetal" is a descriptor that can apply to any force; "centrifugal force" is a force in and of itself, like "gravity".
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BOGWarrior89

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Dinosaurs and gravitational pull
« Reply #39 on: January 15, 2007, 11:03:44 PM »
Quote from: "Erasmus"
Quote from: "Hara Taiki"
Wouldn't that centripetal force be offset by gravity then? (Not centrifugal)


Centrifugal force is applied to every object in a rotating reference frame.  It's proportional to angular speed; gravity is not.  If you spin up a merry-go-round and hop on, you will feel a force pressing you to the outside of the merry-go-round.  This force is present regardless of any centripetal force that might be holding you in.

"Centripetal" is a descriptor that can apply to any force; "centrifugal force" is a force in and of itself, like "gravity".

Quote from: "http://en.wikipedia.org/wiki/Centrifugal_force#Fictitious_forces"
A pseudo or "fictitious" centrifugal force appears when a rotating reference frame is used for analysis. The (true) frame acceleration is substituted by a (fictitious) centrifugal force that is exerted on all objects, and directed away from the axis of rotation.


The "force" you feel is your own inertia (unwillingness to turn), which is a property of matter.  The true force is the centripetal force.
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Erasmus

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Dinosaurs and gravitational pull
« Reply #40 on: January 15, 2007, 11:12:53 PM »
Quote from: "BOGWarrior89"
The "force" you feel is your own inertia (unwillingness to turn), which is a property of matter.  The true force is the centripetal force.


So, you admit that I feel a force?  Excellent, you're on the first step towards recovery.

Now, you might want to try and reconcile the fact that "inertia" and "force" are at the very least measured in differing and incompatible units.  They can't be the same thing.

Once you've done that, you can return to the bit about the merry-go-round, that you've so far ignored.  If the merry-go-round's floor is frictionless (or if I am a rolling ball), and I am not tied down, what centripetal force is there?  If I find myself being pulled towards the outside of a spinning merry-go-round, there must be a force pointing outwards.
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BOGWarrior89

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Dinosaurs and gravitational pull
« Reply #41 on: January 15, 2007, 11:17:10 PM »
Quote from: "Erasmus"
Quote from: "BOGWarrior89"
The "force" you feel is your own inertia (unwillingness to turn), which is a property of matter.  The true force is the centripetal force.


So, you admit that I feel a force?  Excellent, you're on the first step towards recovery.

Now, you might want to try and reconcile the fact that "inertia" and "force" are at the very least measured in differing and incompatible units.  They can't be the same thing.

Once you've done that, you can return to the bit about the merry-go-round, that you've so far ignored.  If the merry-go-round's floor is frictionless (or if I am a rolling ball), and I am not tied down, what centripetal force is there?  If I find myself being pulled towards the outside of a spinning merry-go-round, there must be a force pointing outwards.


Last I checked, forces can only be in the same direction of the acceleration (change in velocity, which is a vector) or antiparallel to the acceleration; because of action-reaction pairs, we need a "normal" force to counteract the centripetal force.

Or is my normal force equal to your centrifugal force?

[edit]
Ignore the content of this post, as it is wrong; see my post below for answers.  I'll admit it, Erasmus, you confused me, if only for a few minutes.
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Erasmus

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Dinosaurs and gravitational pull
« Reply #42 on: January 15, 2007, 11:27:56 PM »
Quote from: "BOGWarrior89"
Last I checked, forces can only be in the same direction of the acceleration (change in velocity, which is a vector) or antiparallel to the acceleration; because of action-reaction pairs, we need a "normal" force to counteract the centripetal force.


Don't tell me what I need.

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Or is my normal force equal to your centrifugal force?


Your force is abnormal.  Normality, like centripetality, is a quality that some forces may or may not have; they are not forces themselves.  The centrifugal force is a force itself.

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Given your physics background, you mean the centrifugal force to be equivalent to the normal force, and not the fake force.  My apologies.


No, I don't.  I mean nothing of the sort.  I mean the centrifugal force to be the force that pushes object away from the axis of rotation in a rotating reference frame.
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BOGWarrior89

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Dinosaurs and gravitational pull
« Reply #43 on: January 16, 2007, 12:45:03 AM »
Quote from: "Erasmus"
Quote from: "BOGWarrior89"
The "force" you feel is your own inertia (unwillingness to turn), which is a property of matter.  The true force is the centripetal force.


So, you admit that I feel a force?  Excellent, you're on the first step towards recovery.

I admit to feeling a ficticious force, yes.

Quote from: "Erasmus"
Now, you might want to try and reconcile the fact that "inertia" and "force" are at the very least measured in differing and incompatible units.  They can't be the same thing.

So, when you fly off the merry-go-round, you accelerate off of it?  No, you don't; you fly off at a constant velocity because the centripetal force couldn't keep you going in a circle; this is due to reliance on static friction to keep you rotating.

Quote from: "Erasmus"
Once you've done that, you can return to the bit about the merry-go-round, that you've so far ignored.  If the merry-go-round's floor is frictionless (or if I am a rolling ball), and I am not tied down, what centripetal force is there?  If I find myself being pulled towards the outside of a spinning merry-go-round, there must be a force pointing outwards.

If the floor were frictionless, you'd fly off at a constant velocity.  There is merely an illusion of a force pulling you outward.

Consider this diagram:



Now, velocity changes because the object is moving in a circle (hence the "circular motion" part), which is depicted in this diagram:



Now, if the centripetal force were to no longer force you into circular motion, you'd fly off in a straight line and at a constant velocity, as is shown here:



So, centrifugal force is not a real force.
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Masterchef

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Dinosaurs and gravitational pull
« Reply #44 on: January 16, 2007, 06:55:01 AM »
Quote from: "weevil"
Hmmmm very interesting....why can't they? Maybe if they examined fossils of the size of animals living back then and the size of animals now!!!!

Do you honestly think that gravity is the only possible factor that would effect the size of animals?
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James

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Dinosaurs and gravitational pull
« Reply #45 on: January 16, 2007, 12:25:43 PM »
Quote from: "Tom Bishop"
Gravity doesn't exist, so no that wouldn't happen.


Quoted for truth.
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Sanirius

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Dinosaurs and gravitational pull
« Reply #46 on: January 16, 2007, 12:26:32 PM »
Quote from: "Dogplatter"


Quoted for truth.


Quoted for being stupid.
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Big Giant Head

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Dinosaurs and gravitational pull
« Reply #47 on: January 16, 2007, 04:40:51 PM »
Back to the OPs initial topic, dinosaurs, a possible explanation is the amount of oxygen in the air back then.  Some scientists think that the air at the time of the dinosaurs contained a lot more oxygen gas than it does today. Since the oxygen animals breathe is used in chemical reactions that power their muscles, more oxygen in the air might have made it possible for dinosaurs to get more oxygen into their muscles. That could have made them much stronger than animals today—strong enough to carry around huge bodies.  

So the question still remains, what is it that changed the levels of oxygen?  Certainly a meteor impacting the earth could throw enough dust into the atmosphere for this to happen but wouldn't it stand to reason then, that eventually the dust would dissipate and the oxygen levels would return?  Perhaps the meteor that struck earth was of sufficient magnitude to slightly alter the earth's axis.  Was the earth on a complete vertical axis at some point?  A change of the axis could be enough to radically change the earth's atmosphere and temperature making it an inhospitable place for such large creatures to become prolific again - except in the water.... or my sister.

As an aside, how do they (they being the sciencey type people) know the speed at which the earth rotates?  Bring centrifugal force into it and wouldn't we all just be flung off into outer space?
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weevil

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Dinosaurs and gravitational pull
« Reply #48 on: January 16, 2007, 04:49:25 PM »
Quote from: "Big Giant Head"
Since the oxygen animals breathe is used in chemical reactions that power their muscles, more oxygen in the air might have made it possible for dinosaurs to get more oxygen into their muscles. That could have made them much stronger than animals today—strong enough to carry around huge bodies.  



 


Thank you Big Giant Head. At last someone has thrown another theory into the arena. You must have a big giant brain in that big giant head!
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Big Giant Head

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Dinosaurs and gravitational pull
« Reply #49 on: January 16, 2007, 04:55:14 PM »
[/quote] Thank you Big Giant Head. At last someone has thrown another theory into the arena. You must have a big giant brain in that big giant head![/quote]

You're welcome Weevil! The topic seemed like it was getting lost and I for one feel this is a very interesting topic.  

Further to what I said before, there is also this to consider...

The evidence for more oxygen in the air at the time of the dinosaurs comes from bubbles in 100-million-year-old amber, tree sap that hardened during the time of the dinosaurs. By crushing the amber and analyzing the gases that come out, scientists at the U. S. Geological Survey think they can tell what the air was like back then.

Gotta love that tree sap, it could very well hold many secrets to the earth's past.

EDIT: Ah crap, I stuffed up the quoting thing - so much for my big giant brain!
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me

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Dinosaurs and gravitational pull
« Reply #50 on: January 16, 2007, 05:02:17 PM »
I was told there were multiple things, there was the meteorite which impacted.
The meteorite hit some rocks which sent stuff into the air which reacted with the water in the air to make very acidic rain which=very dangerous.
At the time there was also atleast 1 supervolcano eruption which would cause a lot of havoc. i dont claim to know it all but thats what i know, these 2 things would cause a big environmental change.. i think
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cmdshft

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Dinosaurs and gravitational pull
« Reply #51 on: January 16, 2007, 05:05:45 PM »
It's possible it was a volcano, the eruption at Vesuvius which covered Pompeii supposedly was large enough of a eruption to affect global climate conditions, even if it was by the smallest bit.
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sodapop112

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Dinosaurs and gravitational pull
« Reply #52 on: January 16, 2007, 05:55:39 PM »
what about an underwater volcano.


are all mountins volcanos or all all vocanos mountins?
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he kinds of equations that they have now are the kinds of equations you would get in an approximation scheme to some underlying theory, but nobody knows what the underlying theory is.

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BOGWarrior89

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Dinosaurs and gravitational pull
« Reply #53 on: January 16, 2007, 06:06:18 PM »
Quote from: "Big Giant Head"
centrifugal force


WHAT'D YOU SAY!?
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Big Giant Head

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Dinosaurs and gravitational pull
« Reply #54 on: January 16, 2007, 06:10:03 PM »
Quote from: "BOGWarrior89"
WHAT'D YOU SAY!?


I said, centrifugal force.  Pardon my French.
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BOGWarrior89

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Dinosaurs and gravitational pull
« Reply #55 on: January 16, 2007, 06:11:11 PM »
Quote from: "Big Giant Head"
Quote from: "BOGWarrior89"
WHAT'D YOU SAY!?


I said, centrifugal force.  Pardon my French.


No such thing exists, I hope you know that.  It's centripetal force.  Read the posts to which I linked you.
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weevil

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Dinosaurs and gravitational pull
« Reply #56 on: January 16, 2007, 06:22:36 PM »
BogWarrior89  we just got off that BORING argument and now you are starting up again! Big Square Head was trying to establish another discussion.
Dont pontificate!
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sodapop112

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Dinosaurs and gravitational pull
« Reply #57 on: January 16, 2007, 06:23:13 PM »
Dumbledore's Army blows!
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he kinds of equations that they have now are the kinds of equations you would get in an approximation scheme to some underlying theory, but nobody knows what the underlying theory is.

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Big Giant Head

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Dinosaurs and gravitational pull
« Reply #58 on: January 16, 2007, 06:31:26 PM »
Quote from: "weevil"
BogWarrior89  we just got off that BORING argument and now you are starting up again! Big Square Head was trying to establish another discussion.
Dont pontificate!


Thank you Weevil.  

Just to clarify Boggy...

Centrifugal force (from Latin centrum "center" and fugere "to flee") is a term which may refer to two different forces which are related to rotation. Both of them are oriented away from the axis of rotation, but the object on which they are exerted differs.

A real or "reactive" centrifugal force occurs in reaction to a centripetal acceleration acting on a mass. This centrifugal force is equal in magnitude to the centripetal force, directed away from the center of rotation, and is exerted by the rotating object upon the object which imposes the centripetal acceleration. Although this sense was used by Isaac Newton, it is only occasionally used in modern discussions.
A pseudo or "fictitious" centrifugal force appears when a rotating reference frame is used for analysis. The (true) frame acceleration is substituted by a (fictitious) centrifugal force that is exerted on all objects, and directed away from the axis of rotation.
Both of the above can be easily observed in action for a passenger riding in a car. If a car swerves around a corner, a passenger's body seems to move towards the outer edge of the car and then pushes against the door.

In the reference frame that is rotating together with the car (a model which those inside the car will often find natural), it looks as if a force is pushing the passenger away from the center of the bend. This is a fictitious force, not an actual force exerted by some other object. The illusion occurs when the reference frame is the car, because that ignores the car's acceleration. A number of physicists treat it much as if it were a real force, as they find that it makes calculations simpler and gives correct results.

Considered fictitious or phantom does not quantify its non-existence.  

You goose.

Back on topic now if we please...
Nyah.
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sodapop112

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Dinosaurs and gravitational pull
« Reply #59 on: January 16, 2007, 06:33:17 PM »
is that like when you take a glass of water and put it upsidedown then up again really fast and it doesnt spill
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he kinds of equations that they have now are the kinds of equations you would get in an approximation scheme to some underlying theory, but nobody knows what the underlying theory is.

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