Gravitational pull of stars

The FE faq says that gravity, which is actually the acceleration of all the universe's matter in one direction, decreases with altitiude because of the gravitiational pull of the stars and moon. How is it that the Earth cannot have a gravitiational pull, but stars and the moon do?

!!

Knowledge is power 8-)

I think you will find it highly unlikely that you will get a coherent response to this querie from the FE'ers.

Good Luck though!!!

Thanks!

Still no FE responses...

Unimportant.... Dogplatter.... I'm waiting

Still no FE responses...

Honestly, this has got to be one of the most irritating forum behaviors ever.  If you don't get a response to your post, suck it up.  Maybe nobody is interested in responding.  Don't think that this implies that you have accomplished something.

Your question is an old and tired one, that I will now attend to inserting in the FAQ.

The answer is that object X having property P in no way entails object Y having property P.  Your argument is a non sequitur.  It's like asking "How is it that snakes do not have legs, but dogs and cats do?"  Snakes are not dogs and cats.  The Earth is not a star or the moon.  It doesn't follow that each must have all the properties of the others, and no more.

Erasmus, mass is mass... what youre saying is true in a specific sense, with your carrot and snake arguments... but the only problem being once you take into account the four forces of the universe, specifically gravity.

All masses exhibit these four forces, with gravity, everything pulls tward the mass that is the most dense and has the most mass, which is what causes the spherical nature of matter, and why i personally believe the earth can only be round.

All masses exhibit these four forces, with gravity,

First of all, not all matter with mass interacts via all four forces.  Neutrons, for example, do not interact electromagnetically.  Leptons do not interact strongly.

The notion that all matter must interact gravitationally is a fairly useful assumption if you begin with the assumption that all other modern physics is correct.  However, it is only fairly useful, and the degree to which it is flawed is clear in that physicist nowadays postulate the existence of all sorts of "dark matter" that creates essentially a negative gravitational field instead of a positive one.

If there can be "antigravitationally" interacting matter, why is it so unreasonable to suppse that there might be gravitationally inert matter?

Well lets see, you were talking about dark matter... i have heard of it, but I am confused, what happens when dark matter and normal matter interact.  As electrically inert matter only forms in combonation of the positive and negativly charged pieces of matter, nuetrons are combonations of protons and electrons.

when i said with gravity, i meant with gravity being one of the four forces.

nuetrons are combonations of protons and electrons.

Neutrons are a combination of 3 quarks, namely 2 down and 1 up.  It has nothing to do with a combination of protons and electrons.

oh im sorry, i wasnt aware of that, i guess my chemistry teacher is retarded

First of all, not all matter with mass interacts via all four forces.

Correct.

If there can be "antigravitationally" interacting matter, why is it so unreasonable to suppse that there might be gravitationally inert matter?

also correct.

However we are speaking of the earth. The earth isn't a unknown only detected by radio telescopes, Nor is it minutely small sub-atomic particle.

The earth is a very large, very tangible mass. This mass has gravity and follows Newtonian physics.  Same as all the other planets in our Solar system. and same as the stars in the Original Posters question.

oh im sorry, i wasnt aware of that, i guess my chemistry teacher is retarded

High school or undergrad?  

with gravity, everything pulls tward the mass that is the most dense and has the most mass, which is what causes the spherical nature of matter

The reason things form spheres is not due to gravity, but to the fact that a sphere has the lowest surface area for a given volume (lowest energy).

High School

well Engineer, wouldnt the lowest mass per the volume correspond to density, simmilar to what i was saying earlier?

when i said with gravity, i meant with matter being one of the four forces.

.... matter is a force?

wow... that was a collosal brainfart,let me go back and change that

The earth is a very large, very tangible mass. This mass has gravity and follows Newtonian physics.  Same as all the other planets in our Solar system. and same as the stars in the Original Posters question.

Now you're just going in circles.  FEers are claiming that what we're told about astronomy is wrong, so this is begging the question.  The notion that all mass generates a gravitational field is an assumption of Newton because it seemed to work nicely in the model he thought was correct.  There's no a priori reason to believe this assumption, and in light of the fact that most scientists now believe the assumption to be false anyway, are FEers really doing anything qualitatively different?

Isn't that assumption proved to be correct by the plumb line brought up by someone else, and the mountain.  Qualitativly, it would de different, as the engineer brought up

Isn't that assumption proved to be correct by the plumb line brought up by someone else, and the mountain.

Even if some parts of the Earth's crust generated a gravitational field -- and considering how difficult this is to measure, we need to see some pretty convincing experimental evidence -- it doesn't mean that as a whole, the Earth generates a gravitational field of the strength required to accelerate objects at the rate of 1g.

It's like holding a plumb line with a magnet on the end near an MRI machine and concluding from that that the whole world generates a massive electromagnetic field.  Except that in the case of gravity, it's unimaginably harder (like, 10^36 times harder) to measure.

excuse my circular logic. I hope EVERYONE questions science. RE and FE alike. Answering unanswered questions and correcting flawed logic is fundimental in science.

Newtons model could easily be wrong, @ least wrong on a universal level. Not ALL matter will react the way he predicted. Science is advanceing and learning more and more about things we KNOW to be true, and some of those things we KNOW are we now finding to be wrong.

Newton was CORRECT however on how the Earth works. He even invented Calculus to predict the exact speed of a falling object @ any point in time. His assumption in this case turns out to be fact, and mathmatically proven. It might not be true in "dark matter" it might not be true on a sub-atmoic level, but it is true on Earth and true on any other visible planet.

actually erasmus, its 10^-11 times harder. the gravitational constant is 6.67x10^-11.

Both cats and dogs posses a gravitational field, and both are affected by gravitational fields. The universe doesn't check how similar they are before appliying fundamental forces on them.

This is the dumbest answer in the FAQ with the exception of the elephants and turtles thing.

The earth is not the moon, but they both have mass, which is all you need for gravity to affect you (and it would affect you even if you didn't) We already know that the earth has mass, so giving exemples of things unaffected by certain forces is completely useless.

Even if some parts of the Earth's crust generated a gravitational field -- and considering how difficult this is to measure, we need to see some pretty convincing experimental evidence -- it doesn't mean that as a whole, the Earth generates a gravitational field of the strength required to accelerate objects at the rate of 1g.

The pendulum experiment will work no matter where you are on earth. And how could a planet have only some parts of it having a gravitational field and others not, how does that work? Some part of earth are massless?

This is the dumbest answer in the FAQ with the exception of the elephants and turtles thing.

What have you got against Discworld?

Over a year later and the first question I asked remains unanswered.

The FE faq says that gravity, which is actually the acceleration of all the universe's matter in one direction, decreases with altitiude because of the gravitiational pull of the stars and moon. How is it that the Earth cannot have a gravitiational pull, but stars and the moon do?

The earth is propelled upwards at a rate of 9.8m/s², causing most of the gravitational effect we feel.  It is powered by dark energy.  Similarly everything else also possesses gravitation, powered by its own dark energy field.  The earth itself has a monster dark energy field, which is the reason why the sun and stars and everything in the known universe is propelled upwards along with it.  But the smaller dark energy fields of the celestial bodies do have an effect on objects on earth as well (though not nearly as pronounced).  Therefore your question is based on an invalid assumption.  Everything in the universe possesses gravitation.

Therefore your question is based on an invalid assumption.  Everything in the universe possesses gravitation.

Then why does the FAQ say otherwise?

Quote from: Thus Spake Roundy on November 21, 2007, 12:51:13 PM

Therefore your question is based on an invalid assumption.  Everything in the universe possesses gravitation.

Then why does the FAQ say otherwise?

It doesn't.  (Show me where it does)

Quote from: Althalus on November 21, 2007, 12:54:31 PM

Quote from: Thus Spake Roundy on November 21, 2007, 12:51:13 PM

Therefore your question is based on an invalid assumption.  Everything in the universe possesses gravitation.

Then why does the FAQ say otherwise?

It doesn't.  (Show me where it does)

Q: "What about gravity?"

A: The Earth is accelerating upwards at 1g (9.8m/s^2) along with every star, sun and moon in the universe. This produces the same effect as gravity.

Q: "Why does gravity vary with altitude?"

A: The moon and stars have a slight gravitational pull

Roughly halfway down the page. For stars to have a gravitational pull, there must be gravity.