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NewTime
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14 May 2020, 9:31 am

Gravity is not a force according to general relativity, but at the same time is one of the four fundamental forces. Seems like a contradiction.



Fnord
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14 May 2020, 9:49 am

NewTime wrote:
Gravity is not a force according to general relativity, but at the same time is one of the four fundamental forces. Seems like a contradiction.
Gravity is well-approximated by Newton's law of universal gravitation, which describes gravity as a "force" that causes any two bodies to be attracted to each other, with the force proportional to the product of their masses and inversely proportional to the square of the distance between them.

Gravity is most accurately described by the General Theory of Relativity, not as a force, but as a consequence of the curvature of spacetime caused by the uneven distribution of mass.

Nowadays, scientists refer to the four fundamental forces as the Four Fundamental Interactions of Physics.


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14 May 2020, 9:51 am

The term of "force" in physics is not something fundamental, its meaning can depend on context.

In broader sense, a force is something that affects movements of bodies. In this sense, gravity is one of four (known) fundamental forces.
In narrower sense, "force" is a value you put into Newton equations to calculate movements of bodies. GR does not use Newton equations for gravity, so it is not "force" in this sense.


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quite an extreme
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15 May 2020, 4:51 pm

NewTime wrote:
Gravity is not a force according to general relativity, but at the same time is one of the four fundamental forces. Seems like a contradiction.

At least it causes a force that is strong enough to keep you on the ground. :mrgreen:
Gravity seems to be a direct result of the additional room that is related to mass and energy.


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15 May 2020, 4:59 pm

Gravity is an interesting subject. If you ask someone "What is gravity?" their reply will not usually be the answer, as nearly every time they will describe what it does, but not what it is.


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naturalplastic
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15 May 2020, 5:24 pm

quite an extreme wrote:
NewTime wrote:
Gravity is not a force according to general relativity, but at the same time is one of the four fundamental forces. Seems like a contradiction.

At least it causes a force that is strong enough to keep you on the ground. :mrgreen:
Gravity seems to be a direct result of the additional room that is related to mass and energy.


Actually there is no gravity. Earth sucks.



naturalplastic
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15 May 2020, 5:26 pm

Actually there is no gravity. The entire earth, which is actually flat, is constantly accerlating UPward at ten meters a second per second. So it just LOOKS like stuff falls TO earth at ten meters per second per second. And that's why we are pined to the Earth's surface.



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15 May 2020, 5:27 pm

Earth sucking is gravity.


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Mountain Goat
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15 May 2020, 5:44 pm

We measure gravity by metres per second if a "Body" falls. 9.8 metres per second is said to be the terminal velocity. But can gravity be regarded as a force? I mean.. Well. If we drop something it falls to tje ground but the force is the items speed.. But there again, gravity is doing that... BUT, what if we look at things from a different perspective. I am NOT a flat earther. However I don't buy into the concept that the earth is spinning, as from what I personally see, that the earth is more likely to be still and everything else moves around it. I do agree that something moves as we see it. None of us can deny this...
But just supposing I am right and the earth is either still or relatively still, and everything outside the earth pushes onto the earth, and this push is what we call gravity. This does make sense as a theory because when the moon passes overhead it will interupt this "Push" and cause a high tide (And the second lower high tide is caused as a type of after effect as the moon is causing the same interuption of the force at the opposite side of the earth. It is why one high tide is higher then the next high tide).
Now in certain seasons, the Moon comes much closer to the earth and so the interuption of this force is in a greater area, and the sea is not pushed so much in this area and hence why we get very high tides at these times. When the tide is out the furthest the force from everything in space upon the earth has no interuption whatsoever, so it gives its full force upon the water which causes the tide to be at its lowest point.

Now ok, it is just a theory I have by my mind linking things together that other people have said, and thinking about what I see for real (I don't live that far from the sea).
I realize some of you will not agree and that is fine. It is just a theory.


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15 May 2020, 6:03 pm

Gravity? Not sure. But levity — now that's a force.


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naturalplastic
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15 May 2020, 6:09 pm

Darmok wrote:
Gravity? Not sure. But levity — now that's a force.


Levity would be a "farce". Not a "force". :D



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15 May 2020, 6:36 pm

Mountain Goat wrote:
We measure gravity by metres per second
Wrong.  The effect of gravity -- its acceleration -- is measured on Earth as 9.8 meters per second per second, or 9.8 m/sec^2. It is also measured as 9.8 gravs, or 9.8 x 1.0 m/sec/sec.
Mountain Goat wrote:
if a "Body" falls. 9.8 meters per second is said to be the terminal velocity.
Wrong. Terminal velocity is the speed when an object falling through a fluid (usually air) is no longer getting faster. For example, the terminal velocity of a skydiver in a belly-to-earth (i.e., face down) free-fall position through the atmosphere is about 195 km/h.
Mountain Goat wrote:
But can gravity be regarded as a force? I mean.. Well. If we drop something it falls to tje ground but the force is the items speed.. But there again, gravity is doing that... BUT, what if we look at things from a different perspective.
Wrong. Force in Newtons is mass in kilograms multiplied by the acceleration in meters per second per second.
Mountain Goat wrote:
I am NOT a flat earther. However I don't buy into the concept that the earth is spinning...
Wrong. The Earth makes one complete rotation every 86,400 seconds, which is 24 hours.
Mountain Goat wrote:
But just supposing I am right and the earth is either still or relatively still, and everything outside the earth pushes onto the earth, and this push is what we call gravity.
Wrong. It is the curvature of space-time that forces object together. Just as a skydiver falls toward the Earth, the Earth is also falling toward the skydiver.
Mountain Goat wrote:
This does make sense as a theory because when the moon passes overhead it will interupt this "Push" and cause a high tide (And the second lower high tide is caused as a type of after effect as the moon is causing the same interuption of the force at the opposite side of the earth. It is why one high tide is higher then the next high tide).
Wrong. Gravity cannot be interrupted -- there is no interruption of gravity. Water on the Moon side of the Earth is attracted to the Moon, while water on the opposite side is driven out by the inherent centrifugal "force" of the Earth and Moon orbiting around each other.
Mountain Goat wrote:
Now in certain seasons, the Moon comes much closer to the earth...
Wrong. This is not seasonal, but it is cyclical (and therefore predictable) due to the elliptical nature of the Earth-Moon co-orbit.
Mountain Goat wrote:
Now ok, it is just a theory I have by my mind linking things together that other people have said, and thinking about what I see for real (I don't live that far from the sea). I realize some of you will not agree and that is fine. It is just a theory.
Wrong. It is not a theory. Theories are hypotheses that have been tested and proven valid or invalid. It is not even an hypothesis. It is only an opinion, and an incorrect one at that. This is not a matter of me disagreeing with you, it is a matter of me agreeing with hundreds of years of scientific observations and measurements, and of you disagreeing with established scientific facts.


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Mountain Goat
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15 May 2020, 7:53 pm

Fnord wrote:
Mountain Goat wrote:
We measure gravity by metres per second
Wrong.  The effect of gravity -- its acceleration -- is measured on Earth as 9.8 meters per second per second, or 9.8 m/sec^2. It is also measured as 9.8 gravs, or 9.8 x 1.0 m/sec/sec.
Mountain Goat wrote:
if a "Body" falls. 9.8 meters per second is said to be the terminal velocity.
Wrong. Terminal velocity is the speed when an object falling through a fluid (usually air) is no longer getting faster. For example, the terminal velocity of a skydiver in a belly-to-earth (i.e., face down) free-fall position through the atmosphere is about 195 km/h.
Mountain Goat wrote:
But can gravity be regarded as a force? I mean.. Well. If we drop something it falls to tje ground but the force is the items speed.. But there again, gravity is doing that... BUT, what if we look at things from a different perspective.
Wrong. Force in Newtons is mass in kilograms multiplied by the acceleration in meters per second per second.
Mountain Goat wrote:
I am NOT a flat earther. However I don't buy into the concept that the earth is spinning...
Wrong. The Earth makes one complete rotation every 86,400 seconds, which is 24 hours.
Mountain Goat wrote:
But just supposing I am right and the earth is either still or relatively still, and everything outside the earth pushes onto the earth, and this push is what we call gravity.
Wrong. It is the curvature of space-time that forces object together. Just as a skydiver falls toward the Earth, the Earth is also falling toward the skydiver.
Mountain Goat wrote:
This does make sense as a theory because when the moon passes overhead it will interupt this "Push" and cause a high tide (And the second lower high tide is caused as a type of after effect as the moon is causing the same interuption of the force at the opposite side of the earth. It is why one high tide is higher then the next high tide).
Wrong. Gravity cannot be interrupted -- there is no interruption of gravity. Water on the Moon side of the Earth is attracted to the Moon, while water on the opposite side is driven out by the inherent centrifugal "force" of the Earth and Moon orbiting around each other.
Mountain Goat wrote:
Now in certain seasons, the Moon comes much closer to the earth...
Wrong. This is not seasonal, but it is cyclical (and therefore predictable) due to the elliptical nature of the Earth-Moon co-orbit.
Mountain Goat wrote:
Now ok, it is just a theory I have by my mind linking things together that other people have said, and thinking about what I see for real (I don't live that far from the sea). I realize some of you will not agree and that is fine. It is just a theory.
Wrong. It is not a theory. Theories are hypotheses that have been tested and proven valid or invalid. It is not even an hypothesis. It is only an opinion, and an incorrect one at that. This is not a matter of me disagreeing with you, it is a matter of me agreeing with hundreds of years of scientific observations and measurements, and of you disagreeing with established scientific facts.


I still think my theory is more plausable... :P It is to me anyway.


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16 May 2020, 9:43 am

Mountain Goat wrote:
Gravity is an interesting subject. If you ask someone "What is gravity?" their reply will not usually be the answer, as nearly every time they will describe what it does, but not what it is.


To me, gravity is an intrinsic property of certain particles of matter/anti-matter. Using Albert Einstein’s Special Theory of Relativity, all matter/anti-matter is made of energy (electromagnetic radiation, ie. light). In the process to form particles of matter/anti-matter, electromagnetic vectors get bent upon themselves until they link up with themselves. Once that happens, the now enclosed momentum vector gains an attraction (gravity) to other electromagnetic vectors, closed or otherwise. I like to think that the energy used to form the particle gives rise to the intrinsic properties of said particle. Gravity is not the only property that a particle gains upon formation. Magnetism, strong force and weak force are all gained in various degrees depending upon the amount of energy used and type of partial formed.

If one takes an individual particle of matter, this attractive pull (gravity) is very small. However, this property is additive as one puts more and more particles together. Once a certain amount of matter has gathered together, the attractive force becomes so great that it transforms the particles into neutrons, starting the birth of a neutron star. Gaining much more particles of matter will increase the gravity to the point that a black hole forms around the surface of the neutron star. How far out the black hole extends from the neutron star is dependent upon how much matter has been transferred into the center (neutron star). This pull is extremely strong, as it can bend the path of electromagnetic energy towards the center if the energy crosses the event horizon.



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16 May 2020, 2:00 pm

Mountain Goat wrote:
We measure gravity by metres per second if a "Body" falls. 9.8 metres per second is said to be the terminal velocity. But can gravity be regarded as a force? I mean.. Well. If we drop something it falls to tje ground but the force is the items speed.. But there again, gravity is doing that... BUT, what if we look at things from a different perspective. I am NOT a flat earther. However I don't buy into the concept that the earth is spinning, as from what I personally see, that the earth is more likely to be still and everything else moves around it. I do agree that something moves as we see it. None of us can deny this...
But just supposing I am right and the earth is either still or relatively still, and everything outside the earth pushes onto the earth, and this push is what we call gravity. This does make sense as a theory because when the moon passes overhead it will interupt this "Push" and cause a high tide (And the second lower high tide is caused as a type of after effect as the moon is causing the same interuption of the force at the opposite side of the earth. It is why one high tide is higher then the next high tide).
Now in certain seasons, the Moon comes much closer to the earth and so the interuption of this force is in a greater area, and the sea is not pushed so much in this area and hence why we get very high tides at these times. When the tide is out the furthest the force from everything in space upon the earth has no interuption whatsoever, so it gives its full force upon the water which causes the tide to be at its lowest point.

Now ok, it is just a theory I have by my mind linking things together that other people have said, and thinking about what I see for real (I don't live that far from the sea).
I realize some of you will not agree and that is fine. It is just a theory.


If it were five hundred years ago...and if Galileo, Copernicus, and Isaac Newton, were all still in the future, then your theory would actually kinda make sense. I mean that your theory would be compatible with the lesser amount of data they had back then. In fact you seemed to have reinvented the geocentric cosmology of Ptolemy - how they all thought that the universe was constructed- when they thought about it back in Greco-Roman, and in Medieval times. The earth is NOT flat (they knew THAT much), but they thought that the earth is the center of the universe, and the stars are pin pricks of light in the firmament- a larger sphere outside of the earth that contains the earth. The firmament spins around while the smaller sphere of the earth is stationary (which is why the stars appear to go around us-they actually do go around us). And the "planets" (sun, moon, mercury, Venus, Mars, Jupiter, and Saturn) wander around the sky above the earth's surface, but lower than the firmament.

So assuming that the Universe really IS set up that way then... you're saying that the firmament (the thing the stars are embedded in) puts out a force of repulsion. The big sphere somehow pushes down onto the surface, and onto the center of the smaller sphere of the earth, and that this force pins our feet to the earth's surface, and causes stuff to fall to the earth's surface. But that the wandering planets can actually block this force when they are overhead. Not completely block it, but partially block it- and that they block it by an amount proportional to their size and mass or something. So if Mars passes overhead the effect is negligible (because Mars and Venus are just of point of light), but if a big disk like either the sun or the moon passes over the effect is big enough for water to pile up as a high tide. The Moon being more effective even then the sun in blocking the force. And when the Sun and moon line up you get a super high tide.

That notion would have made sense back then. But sorry. It just doesn't fit into the cosmology we have today. We now know that the sun is the center of the Solar system , and that the earth goes around the sun, and that the stars are other suns far away, and that there is no firmament. No single dome out there that contains all of the stars. So there isn't any way for the whole cosmos to "push down on us". And we know that the earth does spin.



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19 May 2020, 1:57 pm

yes of course it is, man!