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trendal
J♠


Registered: 04/17/01
Posts: 20,815
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Re: Vacuum. [Re: Diploid]
#5962299 - 08/14/06 10:39 AM (17 years, 5 months ago) |
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Quote:
Diploid said: I know a free-falling object is unaffected by "gravitation".
Then why is it falling?
Because nothing is supporting it while inside a gravitational well 
He's right, in a sense - during free fall you are "at rest" with respect to the gravitational field you are in.
Think of it this way: when I sit here, in my computer chair, I can feel gravity pulling me downwards. There must be an imbalance of forces if I can actually feel a net force. Hence I would say gravity is "acting upon" me while I sit in my chair.
During free fall, however, I can not feel any net force acting upon me (and if I were to bring some much more sensitive instruments along for the fall, they would agree that there is no net force acting upon me). If there is no net force acting upon me...then how can gravity be acting upon me? I am, in essence, at rest with respect to the Earth's gravitational field.
Or maybe I'm just stoned 
I am positive I read this once in a book. It may have been "The Fabric of the Cosmos" by Brian Green, I think.
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Once, men turned their thinking over to machines in the hope that this would set them free. But that only permitted other men with machines to enslave them.
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ClammyJoe
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Re: Vacuum. [Re: trendal]
#5962351 - 08/14/06 11:00 AM (17 years, 5 months ago) |
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Even if, He can't run around saying that someone in free fall is unaffected by gravity, thats just total horse shit.
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trendal
J♠


Registered: 04/17/01
Posts: 20,815
Loc: Ontario, Canada
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Quote:
TheMadConductor said: Even if, He can't run around saying that someone in free fall is unaffected by gravity, thats just total horse shit.
Why is it horse shit?
To be affected by a force, there must be a net force in a given direction. If there is a net force, that force can be measured.
Follow?
So if a net force can always be measured, but no net force is detected during free fall (excluding air resistance...) then it follows that no net force is acting upon an object in free fall.
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Once, men turned their thinking over to machines in the hope that this would set them free. But that only permitted other men with machines to enslave them.
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Diploid
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Re: Vacuum. [Re: trendal]
#5962453 - 08/14/06 11:39 AM (17 years, 5 months ago) |
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Calling gravity a force is a bit of a misnomer. It's an 'interaction' of matter.
If something is in freefall and the thing it's falling toward is moved, then the trajectory of the freefall will change. This is due to the effect of gravity.
So, even in freefall, you are under the influence of, and affected by, gravity.
-------------------- Republican Values: 1) You can't get married to your spouse who is the same sex as you. 2) You can't have an abortion no matter how much you don't want a child. 3) You can't have a certain plant in your possession or you'll get locked up with a rapist and a murderer. 4) We need a smaller, less-intrusive government.
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trendal
J♠


Registered: 04/17/01
Posts: 20,815
Loc: Ontario, Canada
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Re: Vacuum. [Re: Diploid]
#5962471 - 08/14/06 11:46 AM (17 years, 5 months ago) |
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Stoned, then 
But if you move the object whatever is falling will experience a net force again, during its change in trajectory.
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Once, men turned their thinking over to machines in the hope that this would set them free. But that only permitted other men with machines to enslave them.
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Diploid
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Re: Vacuum. [Re: trendal]
#5962492 - 08/14/06 11:53 AM (17 years, 5 months ago) |
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But if you move the object whatever is falling will experience a net force again, during its change in trajectory.
Actually, no. If you're floating in space and a massive object instantly appears nearby, you will start falling toward it and experience no forces.
If the massive thing is moved, it can be considered as vanishing from one point in space, then instantly reappearing at an adjacent point in space along it's tack. You'd still feel no forces.
-------------------- Republican Values: 1) You can't get married to your spouse who is the same sex as you. 2) You can't have an abortion no matter how much you don't want a child. 3) You can't have a certain plant in your possession or you'll get locked up with a rapist and a murderer. 4) We need a smaller, less-intrusive government.
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DocPsilocybin
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Re: Vacuum. [Re: TODAY]
#5962745 - 08/14/06 01:24 PM (17 years, 5 months ago) |
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Quote:
TODAY said: Well...that's what they say about space. But there are these things called neutrinos that are totally inert (won't react with anything...oh wait, they will react with something but that something doesn't exist in space) that are being emitted by the sun and other stars that may actually make up the vacuum of space.
If I understand the purpose of your question, I too don't understand how any space empty of particles can exist. Neutrinos and possibly other particles that don't react with anything are possibly the makeup of this 'empty' space.
First off lets get some things straight.
Neutrinos are not totally neutral. They are a neutral lepton so they can only interact with other matter by way of gravity or the weak nuclear force. Meaning they won't interact by way of strong nuclear force or eletromagnetism. An electromangetic interaction is what we commonly experience during our everyday life. If you push your hands together this is an example of an electromagnetic interaction between the electrons surrounding the atoms of both hands repelling each other.
But arguing about neutrinos, their interactions with matter, and whether or not they actually have mass and can actually be defined as matter is silly.
He asked about a vacuum. A vacuum is defined by a space relatively free of matter therefore having a lesser pressure than the surrounding atmosphere. Going on about if you can achieve a perfect vacuum is sort of....pointless and not answering the question.
-------------------- You can't hold a man down without staying down with him. -- Booker T. Washington
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DocPsilocybin
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Quote:
iateshaggy said: if u were unaffected by gravity then u wouldn't need a parachute. u could just fly back up when u got close to the ground.
now, to the vacuum stuff. i'd have to agree that u can't make a perfect vacuum. nasa has a giant vacuum chamber in their houston facility and it even has a little air in it, but it is so little that an air molecule can travel from the floor to the ceiling w/o bumping another molecule.
it's kinda interesting how celestial bodies break the rules of osmosis.
Sorry, just a little point here. Osmosis is diffusion in application to water (since in biology it plays a huge role). The proper word would be diffusion. Butttt... I would have gone with entropy myself. They're all related. Diffusion arises due to entropy.
I'm a stickler. I know.
-------------------- You can't hold a man down without staying down with him. -- Booker T. Washington
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DocPsilocybin
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Re: Vacuum. [Re: Gomp]
#5962787 - 08/14/06 01:39 PM (17 years, 5 months ago) |
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Quote:
Gomp said:
Quote:
Diploid said: I know a free-falling object is unaffected by "gravitation".
Then why is it falling?
Cause it is not resting on anything thick enough to sustain its mass.
Key word - Density..
But, I wont argue on your/that way of seeing gravity. 
Lets make this simple. If you have a book on a table and suddenly the table is not there where does the book go?
It falls to the floor, right? Because of gravity, right?
Where does density fit into this picture.
-------------------- You can't hold a man down without staying down with him. -- Booker T. Washington
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DocPsilocybin
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Re: Vacuum. [Re: Gomp]
#5962796 - 08/14/06 01:43 PM (17 years, 5 months ago) |
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Quote:
Gomp said:
Quote:
Diploid said: Cause it is not resting on anything thick enough to sustain its mass.
But if you take the same object out into interstellar space where essentially there is no gravity at all, and then if you don't rest it on anything, it won't fall. Only when it's near a source of gravity, will it fall.
Why would that be?
Vacuum..
Again, sorry I'm not trying to pick on you gomp but maybe there's just something that I'm not seeing in your way of thinking.
How is vacuum an answer? You're not explaining anything.
-------------------- You can't hold a man down without staying down with him. -- Booker T. Washington
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DocPsilocybin
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Re: Vacuum. [Re: Gomp]
#5962809 - 08/14/06 01:46 PM (17 years, 5 months ago) |
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Quote:
Gomp said:
Quote:
iateshaggy said: so by your way of thinking, how are we "not affected" by the moon gravity since we're not resting on it?
Again, not "your way of thinking", but "a way of thinking", but that is semantics I guess.
Anyways; Good question.
But we are.  
What I am look at here is the effect of electromagnetism, and magnetoelectrism.. 

Electromagnetism? Sure, gravity pulls your body toward the center of the earth and the eletromagetism between your molecules on your shoes and those of the sidewalk keep you from crashing into it's center. I don't see where you're coming from though, or what you mean.
What does electromagnetism have anything to do with this topic or your previous posts?
-------------------- You can't hold a man down without staying down with him. -- Booker T. Washington
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DocPsilocybin
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Re: Vacuum. [Re: trendal]
#5962838 - 08/14/06 01:53 PM (17 years, 5 months ago) |
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Quote:
trendal said:
Quote:
TheMadConductor said: Even if, He can't run around saying that someone in free fall is unaffected by gravity, thats just total horse shit.
Why is it horse shit?
To be affected by a force, there must be a net force in a given direction. If there is a net force, that force can be measured.
Follow?
So if a net force can always be measured, but no net force is detected during free fall (excluding air resistance...) then it follows that no net force is acting upon an object in free fall.
If you're falling you're accelerating. Force equals mass X acceleration. F=MA. That whole arguement is wrong.
You'd have a net force of a whole crap load of Newtons in the direction that the ground is coming at you from and you tell me there's no force there when you hit.
-------------------- You can't hold a man down without staying down with him. -- Booker T. Washington
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DocPsilocybin
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Re: Vacuum. [Re: Diploid]
#5962853 - 08/14/06 01:57 PM (17 years, 5 months ago) |
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Quote:
Diploid said: But if you move the object whatever is falling will experience a net force again, during its change in trajectory.
Actually, no. If you're floating in space and a massive object instantly appears nearby, you will start falling toward it and experience no forces.
If the massive thing is moved, it can be considered as vanishing from one point in space, then instantly reappearing at an adjacent point in space along it's tack. You'd still feel no forces.
You mean to tell me that if you start moving (accelerate) there has been no force applied to you?
I want some of this magic stuff that makes things move without forces being applied.
-------------------- You can't hold a man down without staying down with him. -- Booker T. Washington
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Diploid
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You mean to tell me that if you start moving (accelerate) there has been no force applied to you?
An object in freefall experiences no force. This is why astronauts orbiting the Earth feel no weight. An orbit is a constant freefall.
-------------------- Republican Values: 1) You can't get married to your spouse who is the same sex as you. 2) You can't have an abortion no matter how much you don't want a child. 3) You can't have a certain plant in your possession or you'll get locked up with a rapist and a murderer. 4) We need a smaller, less-intrusive government.
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DocPsilocybin
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Re: Vacuum. [Re: Diploid]
#5963066 - 08/14/06 03:16 PM (17 years, 5 months ago) |
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An object in free fall is constantly accelerating and therefore MUST be acted upon by a force through the fundamental law that F=MA.
Astronauts in orbit experience VERY little weight. But a force MUST be acting on them to keep them from just shooting off into space in a straight line. Otherwise they would not be in orbit. They would be flying through space in a straight line at a constant velocity until some force acted upon them to change that condition.
-------------------- You can't hold a man down without staying down with him. -- Booker T. Washington
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trendal
J♠


Registered: 04/17/01
Posts: 20,815
Loc: Ontario, Canada
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If you can't measure a force...there probably isn't one there 
Take an accelerometer with you on a sky diving trip and you'll see what I mean.
No net force is acting upon you during free fall.
--------------------
Once, men turned their thinking over to machines in the hope that this would set them free. But that only permitted other men with machines to enslave them.
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DocPsilocybin
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You can measure it through the change in velocity.
And yes, a NET force is acting upon you during free fall otherwise you wouldn't be accelerating downward.
An objects motion does not change when the net forces are zero. If you're moving at a CONSTANT velocity then the net force is zero. But if you're falling you're accelerating, and the NET force is a NON ZERO number.
-------------------- You can't hold a man down without staying down with him. -- Booker T. Washington
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RedNucleus
Causal Observer


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Re: Vacuum. [Re: Gomp]
#5963368 - 08/14/06 04:54 PM (17 years, 5 months ago) |
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Thought experiment:
I jump out of a helicopter that is hovering still. Under the helicopter hangs a rope that is 100 feet long. I fall 100 feet and grab the bottom of the rope. Am I affected by gravity now? I am still far from Earth's surface. I climb up the rope a ways, and then let go for split moments. One second: I fall 5 meters and grab the rope again. A tenth of a second: I fall 0.05 meters and grab the rope again. A millionth of a second: I fall 1E-12 meters and grab the rope again. Did gravity stop affecting me whenever my fingers left the rope? Did gravity somehow stop affecting me entirely for a millionth of a second, and then slam right back? I would imagine that if this was true, it would be extremely destructive to my body.
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Namaste
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ChuangTzu
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Re: Vacuum. [Re: Diploid]
#5963657 - 08/14/06 06:26 PM (17 years, 5 months ago) |
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When you're freefalling, you don't feel a force but you're still subjected to one. F = ma, man. = ) If you're accelerating, a force is being applied.
Granted, "forces" are a kind of kludged way of dealing with physics. Hamiltonian mechanics is in some ways more "fundamental" than Newtonian mechanics and don't involve the use of forces at all.
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Asante
Mage


Registered: 02/06/02
Posts: 86,795
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Here's one 
If you put a supermassive black hole to the left and one to the right, is the space in between more so a vacuum than in the same space without the supermassive black holes? The fabric of space sure stretches thin between the two.
-------------------- Omnicyclion.org higher knowledge starts here
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