Super Genius
Posts: 1,135 
Location: Montreal
Location: Montreal
August 27th, 2007, 11:19 AM
From a practical point of view, we pretty much all understand what gravity is... When we drop something, it falls to the ground... It's pretty simple...
But when you really think about it, gravity is not that easy to comprehend, if it can be comprehended at all...
In classical Newtonian physics, gravity is seen as a force... But in Einstein's theory of relativity, gravity seems to result from curvatures in the spacetime continuum...
So what IS gravity? Anyone here able to vulgarize a bit? Has the scientific community come to any official conclusions?
From a practical point of view, we pretty much all understand what gravity is... When we drop something, it falls to the ground... It's pretty simple...
But when you really think about it, gravity is not that easy to comprehend, if it can be comprehended at all...
In classical Newtonian physics, gravity is seen as a force... But in Einstein's theory of relativity, gravity seems to result from curvatures in the spacetime continuum...
So what IS gravity? Anyone here able to vulgarize a bit? Has the scientific community come to any official conclusions?
^^^^^^^^^^^^^^^^^^^
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Location: Newfoundland!
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August 27th, 2007, 11:22 AM
gravity is almost certainly the einsteinian version of gravity... a curvature of space-time. However, Newton's approximation is still in heavy use today because it's SO close to the truth, mathematically, it'd be silly to make the equations so much more complex for a trillionth of a percent more accuracy. In most cases, that is.
gravity is almost certainly the einsteinian version of gravity... a curvature of space-time. However, Newton's approximation is still in heavy use today because it's SO close to the truth, mathematically, it'd be silly to make the equations so much more complex for a trillionth of a percent more accuracy. In most cases, that is.
Chief Mogrifier
Posts: 8,885
August 27th, 2007, 11:40 AM
Without getting into relativity, and with a respectful wave to Mr. Newton, Gravity is that which causes any two bodies to attract each other with a force directly proportional to the mass of those bodies, and inversely proportional to the square of the distance between them.
Without getting into relativity, and with a respectful wave to Mr. Newton, Gravity is that which causes any two bodies to attract each other with a force directly proportional to the mass of those bodies, and inversely proportional to the square of the distance between them.
Time Out
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August 27th, 2007, 11:48 AM
Well i would love to to have that in plain english...can it be explained to me in plain english..i can grasp cocepts but you go and add the square of the distance into it and i'm flopping on the floor in fetal position....
would really like an idea of the einstien's timespace deal put into it....
i thought it was like you have this fabric of the universe and a large object puts a sort of dint into it and smaller objects go to it....
Well i would love to to have that in plain english...can it be explained to me in plain english..i can grasp cocepts but you go and add the square of the distance into it and i'm flopping on the floor in fetal position....
would really like an idea of the einstien's timespace deal put into it....
i thought it was like you have this fabric of the universe and a large object puts a sort of dint into it and smaller objects go to it....
Steven Hawking's Tutor
Posts: 5,930
August 27th, 2007, 11:49 AM
Sir Isaac Newton famously discovered gravity when he sat under a tree in Cambridge in the 1660s and an apple fell on his head (the tree's descendant is still in that city and is marked by a plaque).
In scientific terminology gravitation and gravity are distinct. "Gravitation" is the attractive influence that all objects exert on each other, while "gravity" specifically refers to a force which all massive objects (objects with mass) are theorized to exert on each other to cause gravitation. Although these terms are interchangeable in everyday use, in theories other than Newton's, gravitation is caused by factors other than gravity. For example in general relativity, gravitation is due to spacetime curvatures which causes inertially moving objects to tend to accelerate towards each other.
In his "Principia", published in 1687, Newton wrote: “I deduced that the forces which keep the planets in their orbs must be reciprocally as the squares of their distances from the centers about which they revolve; and thereby compared the force requisite to keep the Moon in her orb with the force of gravity at the surface of the Earth; and found them answer pretty nearly.”
<B>
wikipedia.org
--------------
Today, a unit to measure gravity is named after the scientist - the Newton (N).
A newton is the amount of force required to accelerate a body with a mass of one kilogram at a rate of one meter per second squared. Algebraically, N = kg·m/s².
Examples
Sir Isaac Newton famously discovered gravity when he sat under a tree in Cambridge in the 1660s and an apple fell on his head (the tree's descendant is still in that city and is marked by a plaque).
In scientific terminology gravitation and gravity are distinct. "Gravitation" is the attractive influence that all objects exert on each other, while "gravity" specifically refers to a force which all massive objects (objects with mass) are theorized to exert on each other to cause gravitation. Although these terms are interchangeable in everyday use, in theories other than Newton's, gravitation is caused by factors other than gravity. For example in general relativity, gravitation is due to spacetime curvatures which causes inertially moving objects to tend to accelerate towards each other.
In his "Principia", published in 1687, Newton wrote: “I deduced that the forces which keep the planets in their orbs must be reciprocally as the squares of their distances from the centers about which they revolve; and thereby compared the force requisite to keep the Moon in her orb with the force of gravity at the surface of the Earth; and found them answer pretty nearly.”
<B>
Quote:
</B> Isaac Newton's theory of universal gravitation (part of classical mechanics) states the following:
where:
Newton's law of gravitation resembles Coulomb's law of electrical forces. Newton's law is used to calculate the Gravitational force between two masses; similarly Coulomb's Law is used to calculate the magnitude of electrical force between two charged bodies. Coulomb's Law's equation has the product of two charges in place of the product of the masses which is in Newton's Law of Gravitation. Hence, according to Coulomb's Law, the electrical force is proportional to the product of the charged bodies divided by the distance between them.
Every single
point mass attracts every other point mass by a force pointing along the line combining the two. The force is proportional to the product of the two masses and inversely proportional to the square of the distance between the point masses:
where:
- F is the magnitude of the gravitational force between the two point masses,
- G is the
- gravitational constant,
- m1 is the mass of the first point mass,
- m2 is the mass of the second point mass,
- r is the distance between the two point masses.
Newton's law of gravitation resembles Coulomb's law of electrical forces. Newton's law is used to calculate the Gravitational force between two masses; similarly Coulomb's Law is used to calculate the magnitude of electrical force between two charged bodies. Coulomb's Law's equation has the product of two charges in place of the product of the masses which is in Newton's Law of Gravitation. Hence, according to Coulomb's Law, the electrical force is proportional to the product of the charged bodies divided by the distance between them.
wikipedia.org
--------------
Today, a unit to measure gravity is named after the scientist - the Newton (N).
A newton is the amount of force required to accelerate a body with a mass of one kilogram at a rate of one meter per second squared. Algebraically, N = kg·m/s².
Examples
- 1 N is the force of Earth's gravity on an apple with a mass of about 102 g (1⁄9.8 kg).
- On Earth's surface, a mass of 1 kg exerts a force of approximately 9.8 N on its support. The approximation of 1 kg corresponding to 10 N is sometimes used as a rule of thumb in everyday life and in engineering (except where strict accuracy is required).
- The force of Earth's gravity on a human being with a mass of 70 kg is approximately 686 N.
- The scalar product of force and distance (N×m)— a force of 1 N carried out over a distance of 1 m— is one joule, the basic unit of energy in the SI.
August 27th, 2007, 11:51 AM
Quoting DocDred
The demo I saw on it used a large sheet of stretchy plastic. Set two balls on the plastic, and the larger one creates a larger dip, and the smaller one rolls into it. Overly simplistic I'm sure, but, it was a kids demo. lol.
Well i would love to to have that in plain english...can it be explained to me in plain english..i can grasp cocepts but you go and add the square of the distance into it and i'm flopping on the floor in fetal position....
would really like an idea of the einstien's timespace deal put into it....
i thought it was like you have this fabric of the universe and a large object puts a sort of dint into it and smaller objects go to it....
would really like an idea of the einstien's timespace deal put into it....
i thought it was like you have this fabric of the universe and a large object puts a sort of dint into it and smaller objects go to it....
Time Out
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August 27th, 2007, 11:54 AM
and pulled out a plumb and said what good boy am I
Quoting karrie
LOL !!!did not view that yet...but my fabric deal was done from some ole cranky science kids show where they used a blanket.....took 45 years for me to talk about it and use the word fabric of the universe...LOL!!!
The demo I saw on it used a large sheet of stretchy plastic. Set two balls on the plastic, and the larger one creates a larger dip, and the smaller one rolls into it. Overly simplistic I'm sure, but, it was a kids demo. lol.
and pulled out a plumb and said what good boy am I
Time Out
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August 27th, 2007, 11:56 AM
zzzzzzzzz dude remind me not to hire you as a party clown ....LOL!!!
Quoting hermanntrude
that was fun Here's a fun little flash game
zzzzzzzzz dude remind me not to hire you as a party clown ....LOL!!!
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Location: Newfoundland!
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August 27th, 2007, 11:57 AM
the old stretchy sheet demonstration is an excellent metaphor. It shows a 2-D fabric being stretched in a 3D way, giving rise to an effect you couldn't possibly understand if you were a 2D creature living on the 2D surface
the old stretchy sheet demonstration is an excellent metaphor. It shows a 2-D fabric being stretched in a 3D way, giving rise to an effect you couldn't possibly understand if you were a 2D creature living on the 2D surface
A modern nomad
Posts: 1,118
Location: Berlin, Germany
Location: Berlin, Germany
August 27th, 2007, 12:26 PM
What is the shortest path from a to b? Easy to answer if the terrain is flat, but drop a big hill in the middle of the path and the shortest path then has to go around it. That then is the relativistic version of gravity, grossly simplified.
General relativity is necessitated by the simple observations that no information can travel instantaneously (This requires that the gravitational field radiate in a specific fashion and must have a radiative evolution equation.) and that the inertial mass and the gravitational mass of any object is the same (there are preferred paths through space which requires the geometric interpretation of General relativity).
Hope that helps.
What is the shortest path from a to b? Easy to answer if the terrain is flat, but drop a big hill in the middle of the path and the shortest path then has to go around it. That then is the relativistic version of gravity, grossly simplified.
General relativity is necessitated by the simple observations that no information can travel instantaneously (This requires that the gravitational field radiate in a specific fashion and must have a radiative evolution equation.) and that the inertial mass and the gravitational mass of any object is the same (there are preferred paths through space which requires the geometric interpretation of General relativity).
Hope that helps.
Time Out
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August 27th, 2007, 12:53 PM
dear
Niflmir now that i know yer a woman i know i know certain aspects of our online exchanges together has changed...I actually like you as a poster very much...in fact yer one of my favs in certain kinda a way...but add the fact your a woman and i'm completly ga ga now......hopefully you will only take this in utmost of nicest intents.....
do you do hugs?
do you do online smackers like MMWWUUUUUAAAAAAAAAHHHHH?
I know i'm compensating with banal male antics to make up for my moroness....
Quoting Niflmir
I could only dream of dating someone like you....it doesn't help me at all what ya just said, i'm a moron....but man sitting in a little cafe sipping that cat bean coffee you adore ..i would be transfixed listening to you go on about this....
What is the shortest path from a to b? Easy to answer if the terrain is flat, but drop a big hill in the middle of the path and the shortest path then has to go around it. That then is the relativistic version of gravity, grossly simplified.
General relativity is necessitated by the simple observations that no information can travel instantaneously (This requires that the gravitational field radiate in a specific fashion and must have a radiative evolution equation.) and that the inertial mass and the gravitational mass of any object is the same (there are preferred paths through space which requires the geometric interpretation of General relativity).
Hope that helps.
General relativity is necessitated by the simple observations that no information can travel instantaneously (This requires that the gravitational field radiate in a specific fashion and must have a radiative evolution equation.) and that the inertial mass and the gravitational mass of any object is the same (there are preferred paths through space which requires the geometric interpretation of General relativity).
Hope that helps.
dear
Niflmir now that i know yer a woman i know i know certain aspects of our online exchanges together has changed...I actually like you as a poster very much...in fact yer one of my favs in certain kinda a way...but add the fact your a woman and i'm completly ga ga now......hopefully you will only take this in utmost of nicest intents.....
do you do hugs?
do you do online smackers like MMWWUUUUUAAAAAAAAAHHHHH?
I know i'm compensating with banal male antics to make up for my moroness....
Time Out
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Location: Honour our Fallen
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August 27th, 2007, 01:19 PM
i really do...now ya got all the wrong parts down there...i think their ugly .....
*the crying game song starts to play in background*
Doc screams in pain*****"the humanity" ****
*Takes full javex bleach bath....scrubs out mouth from licking the monitor...**** I loved her words ..they were beautiful...i licked them to be close to her.....* sniffles*
Grabs Glenlivet....drowns sorrows...
Quoting Niflmir
awe man....i thought in the cat crappin coffee bean thread you refered to yourself as a woman...man...i was gonna wooo you....i love your intellect...
Where in the name of the abyss named Ginnungagap are you getting that from? I am a man, man.
i really do...now ya got all the wrong parts down there...i think their ugly .....
*the crying game song starts to play in background*
Doc screams in pain*****"the humanity" ****
*Takes full javex bleach bath....scrubs out mouth from licking the monitor...**** I loved her words ..they were beautiful...i licked them to be close to her.....* sniffles*
Grabs Glenlivet....drowns sorrows...
