Question about gravity.

reply to post by moebius


Yes I do.

The gravity train theory is simply scientific ignorance and incompetence passed down from generation to generation.

Sure they make you calculate the force of the train as a freshman in physics. But they only have you calculate the mass of the Earth that is below the train. They lie to you and say the mass of the part of the Earth that is above the train has no influence, so they don't even include that factor in their calculations. Thus the ignorance ensues.

Originally posted by spy66
It is not earth's mass that is pulling us down. It is the atmosphere. It is the weight that is above us.

Are you joking, or are you serious?

So according to you, if there is no atmosphere, there is no gravity?

Originally posted by illuminated0ne

Originally posted by spy66
It is not earth's mass that is pulling us down. It is the atmosphere. It is the weight that is above us.

Are you joking, or are you serious?

So according to you, if there is no atmosphere, there is no gravity?

Correct.

But, you will never have a solid without some kind of atmosphere. Do you know why?

Originally posted by illuminated0ne
reply to post by moebius

 

Yes I do.

The gravity train theory is simply scientific ignorance and incompetence passed down from generation to generation.

Sure they make you calculate the force of the train as a freshman in physics. But they only have you calculate the mass of the Earth that is below the train. They lie to you and say the mass of the part of the Earth that is above the train has no influence, so they don't even include that factor in their calculations. Thus the ignorance ensues.

I actually made a post about that... it's back a couple of pages. ...

Originally posted by spy66

But, you will never have a solid without some kind of atmosphere. Do you know why?

There are some serious misconceptions of gravity/mass going on here

Asteroids appear to fly in the face of that statement, unless you're proposing that they have no mass or that they all have atmospheres?
Air pressure acts all around objects so you can cancel out any mass increase due to atmospheric pressure (vector sum is zero).

The proposed tunnel, if enclosed in a vacuum would have no mass within it apart from the 10kg projectile so the tunnel itself would impart no gravitational force on the weight.
But:
The tunnel is surrounded over its entire length by the total mass of the planet which would exert a gravitational acceleration virtually the same as that which would be experienced with no tunnel. The weight would fall at an initial acceleration of 9.82m/sec^2 and accelerate all the way to the centre of mass with no terminal velocity because of the vacuum (no drag). Once past the centre of mass the gravitational acceleration becomes -ve, therefore slowing the weight down and it would reach standstill at the same distance from the centre of mass as it was released from, only on the opposite end of the tunnel.
Without friction it would oscillate up and down indefinitely.

reply to post by illuminated0ne

No you obviously don't.

Show me your derivation for the force on the mass and how it deviates from the solution presented here: www.math.purdue.edu...

ROFL

Reading through this thread, and it seems to me as though you have absolutely no grasp on physics and science, spy66. Why are you in a physics class if you cant grasp basic classical physics? Gravity is not a push, it is a pull. Gravity always pulls inwards to the center of the object where g=0. Vacuum does not affect gravity, and it certainly does not stop motion from occuring. Classical Electromagnetism tells us that matter travels at its fastest possible speed in vacuum.

Please, spy66, stop assuming everything you are saying is correct when it flies in the face of already tested and proven theories.

I'm pretty sure that the galactic federation of physics misconceptions would obliterate earth if someone drilled a whole through the whole planet, isolated that whole in a vacuum, and then attempted to perform an experiment dropping something down that hole.

Originally posted by WhatAreThey
I'm pretty sure that the galactic federation of physics misconceptions would obliterate earth if someone drilled a whole through the whole planet, isolated that whole in a vacuum, and then attempted to perform an experiment dropping something down that hole.

But think of the children! They need to know what would happen!

reply to post by WhatAreThey

But... one could actually do it with an asteroid

Edit:
I mean drill a hole into one. Not let one pass through earth, hehe.

A isolated vacuume tunnel that runs fron N to S. Have a even vacuume atmosphere from N to S. That means the vacuume dosent change even if it runs through earth senter. Only a change in the vacuume atmosphere from the N to the senter of earth would make the 10kg mass accelerate/travel. Wouldnt you agree?

reply to post by spy66


"vacuum atmosphere"

Anyway, a vacuum does not stop gravity (remember, space is a vacuum) and it would go to the south pole, back and forth until it came to rest in the center because it is in a vacuum.
An object that is at rest will stay at rest unless an unbalanced force acts upon it.
An object that is in motion will not change its velocity unless an unbalanced force acts upon it.

Now if you started in the center of the tube, then it would not move, however gravity is the acting force that will move the object from north to south and so on.

Originally posted by moebius
reply to post by ImaFungi

 

Mass creates gravity. At center of mass of a body the gravity is zero because it is "canceled" by the surrounding mass. You are literally pulled in all directions with the same force magnitude. All physical forces have this property called superposition, means the resulting force is a sum of all forces.

Couldnt gravity possibly have something to do with the movement of a body through space? earth is rotating, revolving,, and traveling with the galaxy through space-time.... at the center of the earth,, wouldnt this have some significance to take into account, these movements? or because the center is shielded from the "outside" space-time,,, then center would not know it is "traveling" through space-time at all,, there for this effect im thinking of, which would be like a piece of paper stuck on a moving cars windshield,, will not be felt in the center?

reply to post by ImaFungi


In classical "newtonian" physics no. It only depends on mass and distance. There is no velocity involved.

When you get really fast relativistic effects will become noticeable. This is where it gets a bit more complicated. Einstein Field Equations: 10 coupled non-linear second order partial differential equations.

Originally posted by moebius
reply to post by ImaFungi

 

In classical "newtonian" physics no. It only depends on mass and distance. There is no velocity involved.

When you get really fast relativistic effects will become noticeable. This is where it gets a bit more complicated. Einstein Field Equations: 10 coupled non-linear second order partial differential equations.

ok,, but with motion of planet included,, wouldnt there be gravity at the center,,, from all mass surrounding the center,, moving towards the center from the planets momentum through space-time?

isnt that why the conditions of the center of the earth are as they are,, i guess that has to do with pressure but also gravity? similar to what occurs at the center of a spiral galaxy, gravitationally wise?

also how can you omit aspects of reality in favor of your model of reality ? I dont want to know about in classical newtonian physics if that is not accurate to reality...

I think the object wouldn't go to the south pole. It would gain speed, travel through Earth's center, make it toward the south pole, but before it can reach it, the object would spring back up toward the north pole, losing some of its kinetic energy due to Earth's gravity. After some of this up and down movement the objet would have spent the totality of its kinetic energy and will come to a rest, and its position will be Earth's gravitational neutral point - its center.

Originally posted by WhatAreThey
I'm pretty sure that the galactic federation of physics misconceptions would obliterate earth if someone drilled a whole through the whole planet, isolated that whole in a vacuum, and then attempted to perform an experiment dropping something down that hole.

Not if they didn't catch us!!!

reply to post by swan001


with no force acting on it besides gravity (drag, friction, etc.), it would continue the oscillation indefinitely. PE would convert to KE and continue back and forth unless there was something else to cause a loss in one of them.

reply to post by spy66


I was reading most of the posts here and couldn't stop laughing. I am assuming spy66 is a K-12 student? then just go to the NASA website and read here (link provided below), and understand that forces do act in a vacuum.
NASA link to explain falling objects

In our solar system, our star is so heavy that there are about 12 planets that are in free fall towards the sun regardless of vacuum. Of course the question is why don't the planets eventually crash into the sun.

And to be honest, gravity is a theory. there is no direct evidence of a particle called a graviton. However, we do know that forces do act in a vacuum. For example, our moon's gravity affects our oceans tides.

The word "tides" is a generic term used to define the alternating rise and fall in sea level with respect to the land, produced by the gravitational attraction of the moon and the sun.

NOAA link

spy66 i think you misunderstand what a vacuum is. I think what you had in mind was to create a void of energy? which is really impossible since there is evidence that energy suddenly explodes in a void.

There is no gravity, the earth sucks.

reply to post by ImaFungi

You are asking a quite fundamental question. Does a mass (or charge) interact with itself (its own field)? This also goes beyond classic physics. But for low velocities this effects can be neglected.

In general you have to work with so called "effective" fields to take self interaction into account. This is above my skill level I fear (would have to look up stuff myself). I recommend to talk to a physicist.

For math inclined a few links:
www.itp.uni-hannover.de...
arxiv.org...