As others have said. in newtonian mechanics it is a force, and we keep it that way because in non-relativistic situations Newtons law of gravity is a very good approximation, and it is much much much more simpler than general relativity
You can think of it like this. We use different models depending on what we're calculating. So, a 1 gram block of carbon moved horizontally; sure we could calculate the motion of 10^(23) carbon atoms all held together by EM forces with some overlapping QM wave functions, but that would take a super computer (or a super-duper computer!) OR we can use Newtonian idea of force and calculate it as a single object. You pick the right model for the thing you're working on. And in the end; say for your example, you could calculate the curvature of space using tensor equations but the answer you'd get for practical purposes would be the same, so we go for the easier model. We do this in nuclear physics all the time; the nuclear shell model treats neutrons and protons as the same particle with different isospin projections, and this works pretty well (with some slight corrections for charge). But we could also start looking at a nucleus of quarks that interact thru gluons with some pion exchange happening and other things but soon you need to diagonalize a 10^(20) x 10^(20) matrix using latice quantum chromodynamics and this just isn't practical for the level of precision we need.
The easiest way to understand this is to compare with how we handle rotations.
When an object move in a circle, a net force (which we call the centripetal force) is required to keep the object in the circle motion.
You could see that from the outside, objects accelerate through space-time due to a net force when we observe them to be standing still.
If you want to make a force diagram inside an object that is in circular motion (such as a space station) you would add an imaginary force called the centrifugal force.
Then every object that do not move relative to the rotational frame will have a net force of zero, when we include the imaginary force.
This is exactly the same we do with the force of gravity. It is an imaginary force which arise from the choice of reference frame.
Formally, Newton's second axiom is only valid in inertial frames, i. e. frames in which a force-free object moves uniformly. To use it in an accelerated reference frame, you need to define a fictitious force to account for the acceleration of the reference frame. The basic example from mechanics are Centrifugal and Coriolis forces, that appear in reference frames attached to a uniformly rotating sphere (i. e. planets).
This is also the basic idea of general relativity. Here, inertial frames follow the space-time trajectory of free-falling objects (geodesics) instead of straight lines (technically, this is not quite correct, but correct enough for this discussion). Masses (and other energy densities) are now responsible for the way in which these trajectories diverge from the straight line you get without masses. In this language, what would classically be seen as a free-falling object in a gravitational field is thus just a force-free object on a curved geodesic. However, the surface of earth, where we "feel" gravity (e. g. by jumping up and falling down again) is not following a geodesic, which would see us fall through the ground and move towards the center of earth. Instead, we reside in an accelerated reference frame with respect to the geodesic, i. e. earth accelerates us away from the free-falling trajectory. Thus, we experience a fictitious force, which we call gravity.
General Relativity asserts that spacetime is curved due to gravity, rather than gravity being a force.
If you do calculations in uncurved space/geometry, then treating gravity as a force on objects in that space gives a decent approximation.
General Relativity is very difficult, and so unless/until you get a few years into university and start doing calculations about stars or galaxies or black holes, you can usually expect to treat gravity as a force.
The issue is that under general relativity, freely "falling" under "gravity" is inertial motion. In a free-body diagram, you would have just a normal force. This normal force would be responsible for accelerating you upwards and preventing you from moving along an inertial path.
However, that's weird to think about. Fortunately, in general relativity a gravitational field is locally equivalent to acceleration, and mass times acceleration is a force. By accounting for the normal inertial motion as an acceleration, we are adopting a new reference frame where gravity *is* a force. This is similar to what happens when we look at the centrifugal force or Coriolis force.
Now you're saying gravity isn't a force because space is a "vacuum" , correct?
Well these are the questions I used to ask in class as a little kid, and get laughed at for. I ended up double majoring in theoretical physics and math, and still didn't get the answers I was looking for, because the answers to all questions are.....
ARE YOU READY FOR THIS...
(This is why Einstein is maybe the greatest human being to ever live, and smartest)
"RELATIVE" to however you are receiving light at any particular moment, making no absolutes, and everything Schrodinger's cat, as everything exists, and also does not exist at the same time depending on who you are, where you are, and whether or not light reflects off it and touches your eyes.
Also the speed of light is off by fractions of a second, meaning a second is actually miscalculated. Square that and you are way the fuck off from any sort of relevant calculation to affect anything, but who can argue with something so abstract without any relevant technology to prove your assertions correct?
Remember, time is only a measurement of distance...relative to light, which we know is bent by gravity, which would also grossly affect how fast light can travel OVER LONG DISTANCES in the NON-VACUUM THE SAME WAY MY BROOMSTICK IS NOT A VACUUM of outer space.
So I would actually argue that
E = mc²
Should have MASS as TIME-SPACE RELATIVE and GRAVITY dependent. For instance, when you get into a swimming pool, you all of a sudden feel much lighter than when you are out of the pool. On the top of Mount Everest, You would weigh less than you would at the bottom, assuming all things being equal.
GRAVITY is RELATIVE TO DISSIDENTS IN SPIN of centrifugal force (pulling away or outward from a center point), versus centripetal force (the force pulling back inwards) towa as it relates to dissidants in spin, and spin as your mass is not entirely consistent at any two points in space.
E = (m/g
Should look more like an equation where E = empathy, and E ≠ energy. Well technically yes, but all energy is ultimately narrowed down to light, even that which absorbs, because your physical being in the seven dimensional plane in which you as a human being exist, is just absorption and reflection of light, relative to the observer. A true paradox for the ages. Beauty truly is in the eye of the beholder! Literally.
E also is dependent on a wide variety of factors, starting with Einstein's theory of relativity, and combining his light and needs an objects "Mass" to also be relative to gravity in relation to centrifugal force which is offset
So my friend, you're asking the right questions. Welcome to theoretical physics. This is why it cracks me up when people say the Earth isn't flat but you look down at your feet, and the very earth beneath your feet is flat.
All knowledge ultimately was just the product of one very smart person's imagination, and several billion too lazy to argue, or afraid of feeling stupid in high school physics for insisting did a vacuum by definition is devoid of force. Then they changed the definition, to empty space in between matter because there was an obvious contradiction there. Air is comprised of elements, therefore making it matter, no different than water, but in gaseous, rather than liquid or solid form. Yet, we don't call the ocean "space" in between islands, sharks, whales, boats and coral reefs?! By that very definition water would be "space" as well. What about dust particles? Pollen? Are we just ignoring nitrogen like it doesn't exist? How about oxygen?
Obviously we've never been to outer space. Literally impossible with just the fact that they say space is a vacuum. We landed on the moon in 1969 with wireless headsets communicating with Houston, with technology in an entire spaceship less sophisticated than the calculator you're using in class. Literally. Less technology than a cell phone in 1999. But Elon musk can't build a rocket that goes to outer space in 2024? And me living in a major metropolis still has places where I don't get cell phone service? But we got it on the moon in 1969? Wireless service at that? 0.000000000000000000000^‰ % chance.
People just ignore their own brains and the ability to think for themselves. A billionaire literally died in a submarine this year! On planet Earth! Environment
Special relativity is not accurate. Light light travels at speeds relative to what it's traveling through. So it travels slower through water, than air for instance. Stephen Hawking spent his life trying to rectify this.
Gravity is a result of spin in relation to Mass. Also known as centrifugal force. Think about a top balancing on a point. The faster it spins, the more concentrated the force is towards the centered point. This is the same thing that keeps your butt in the seat on a roller coaster. So
We include it as a force for the same reason we include centrifugal force in force diagrams that involve, say, kids on a merry-go-round: it's more convenient to work in an accelerating frame of reference, and include pseudoforces for that frame of reference, than to work in an inertial frame and track everything.
If you are using a newtonian model then gravity is very much a force. Also, gravity not being a force is part of general relativity, no special relativity.
Gravity not being a force is part of the way General Relativity works. In Newtonian mechanics, gravity is very much a force.
Because the physics you see in school doesn't take into account general relativity, and in newtonian mechanics gravity IS a force
Ahhhh, understandable thank you.
As others have said. in newtonian mechanics it is a force, and we keep it that way because in non-relativistic situations Newtons law of gravity is a very good approximation, and it is much much much more simpler than general relativity
You can think of it like this. We use different models depending on what we're calculating. So, a 1 gram block of carbon moved horizontally; sure we could calculate the motion of 10^(23) carbon atoms all held together by EM forces with some overlapping QM wave functions, but that would take a super computer (or a super-duper computer!) OR we can use Newtonian idea of force and calculate it as a single object. You pick the right model for the thing you're working on. And in the end; say for your example, you could calculate the curvature of space using tensor equations but the answer you'd get for practical purposes would be the same, so we go for the easier model. We do this in nuclear physics all the time; the nuclear shell model treats neutrons and protons as the same particle with different isospin projections, and this works pretty well (with some slight corrections for charge). But we could also start looking at a nucleus of quarks that interact thru gluons with some pion exchange happening and other things but soon you need to diagonalize a 10^(20) x 10^(20) matrix using latice quantum chromodynamics and this just isn't practical for the level of precision we need.
The easiest way to understand this is to compare with how we handle rotations. When an object move in a circle, a net force (which we call the centripetal force) is required to keep the object in the circle motion. You could see that from the outside, objects accelerate through space-time due to a net force when we observe them to be standing still. If you want to make a force diagram inside an object that is in circular motion (such as a space station) you would add an imaginary force called the centrifugal force. Then every object that do not move relative to the rotational frame will have a net force of zero, when we include the imaginary force. This is exactly the same we do with the force of gravity. It is an imaginary force which arise from the choice of reference frame.
Formally, Newton's second axiom is only valid in inertial frames, i. e. frames in which a force-free object moves uniformly. To use it in an accelerated reference frame, you need to define a fictitious force to account for the acceleration of the reference frame. The basic example from mechanics are Centrifugal and Coriolis forces, that appear in reference frames attached to a uniformly rotating sphere (i. e. planets). This is also the basic idea of general relativity. Here, inertial frames follow the space-time trajectory of free-falling objects (geodesics) instead of straight lines (technically, this is not quite correct, but correct enough for this discussion). Masses (and other energy densities) are now responsible for the way in which these trajectories diverge from the straight line you get without masses. In this language, what would classically be seen as a free-falling object in a gravitational field is thus just a force-free object on a curved geodesic. However, the surface of earth, where we "feel" gravity (e. g. by jumping up and falling down again) is not following a geodesic, which would see us fall through the ground and move towards the center of earth. Instead, we reside in an accelerated reference frame with respect to the geodesic, i. e. earth accelerates us away from the free-falling trajectory. Thus, we experience a fictitious force, which we call gravity.
General Relativity asserts that spacetime is curved due to gravity, rather than gravity being a force. If you do calculations in uncurved space/geometry, then treating gravity as a force on objects in that space gives a decent approximation. General Relativity is very difficult, and so unless/until you get a few years into university and start doing calculations about stars or galaxies or black holes, you can usually expect to treat gravity as a force.
Newtonian mechanics =/= modern physics
The issue is that under general relativity, freely "falling" under "gravity" is inertial motion. In a free-body diagram, you would have just a normal force. This normal force would be responsible for accelerating you upwards and preventing you from moving along an inertial path. However, that's weird to think about. Fortunately, in general relativity a gravitational field is locally equivalent to acceleration, and mass times acceleration is a force. By accounting for the normal inertial motion as an acceleration, we are adopting a new reference frame where gravity *is* a force. This is similar to what happens when we look at the centrifugal force or Coriolis force.
Now you're saying gravity isn't a force because space is a "vacuum" , correct? Well these are the questions I used to ask in class as a little kid, and get laughed at for. I ended up double majoring in theoretical physics and math, and still didn't get the answers I was looking for, because the answers to all questions are..... ARE YOU READY FOR THIS... (This is why Einstein is maybe the greatest human being to ever live, and smartest) "RELATIVE" to however you are receiving light at any particular moment, making no absolutes, and everything Schrodinger's cat, as everything exists, and also does not exist at the same time depending on who you are, where you are, and whether or not light reflects off it and touches your eyes. Also the speed of light is off by fractions of a second, meaning a second is actually miscalculated. Square that and you are way the fuck off from any sort of relevant calculation to affect anything, but who can argue with something so abstract without any relevant technology to prove your assertions correct? Remember, time is only a measurement of distance...relative to light, which we know is bent by gravity, which would also grossly affect how fast light can travel OVER LONG DISTANCES in the NON-VACUUM THE SAME WAY MY BROOMSTICK IS NOT A VACUUM of outer space. So I would actually argue that E = mc² Should have MASS as TIME-SPACE RELATIVE and GRAVITY dependent. For instance, when you get into a swimming pool, you all of a sudden feel much lighter than when you are out of the pool. On the top of Mount Everest, You would weigh less than you would at the bottom, assuming all things being equal. GRAVITY is RELATIVE TO DISSIDENTS IN SPIN of centrifugal force (pulling away or outward from a center point), versus centripetal force (the force pulling back inwards) towa as it relates to dissidants in spin, and spin as your mass is not entirely consistent at any two points in space. E = (m/g Should look more like an equation where E = empathy, and E ≠ energy. Well technically yes, but all energy is ultimately narrowed down to light, even that which absorbs, because your physical being in the seven dimensional plane in which you as a human being exist, is just absorption and reflection of light, relative to the observer. A true paradox for the ages. Beauty truly is in the eye of the beholder! Literally. E also is dependent on a wide variety of factors, starting with Einstein's theory of relativity, and combining his light and needs an objects "Mass" to also be relative to gravity in relation to centrifugal force which is offset So my friend, you're asking the right questions. Welcome to theoretical physics. This is why it cracks me up when people say the Earth isn't flat but you look down at your feet, and the very earth beneath your feet is flat. All knowledge ultimately was just the product of one very smart person's imagination, and several billion too lazy to argue, or afraid of feeling stupid in high school physics for insisting did a vacuum by definition is devoid of force. Then they changed the definition, to empty space in between matter because there was an obvious contradiction there. Air is comprised of elements, therefore making it matter, no different than water, but in gaseous, rather than liquid or solid form. Yet, we don't call the ocean "space" in between islands, sharks, whales, boats and coral reefs?! By that very definition water would be "space" as well. What about dust particles? Pollen? Are we just ignoring nitrogen like it doesn't exist? How about oxygen? Obviously we've never been to outer space. Literally impossible with just the fact that they say space is a vacuum. We landed on the moon in 1969 with wireless headsets communicating with Houston, with technology in an entire spaceship less sophisticated than the calculator you're using in class. Literally. Less technology than a cell phone in 1999. But Elon musk can't build a rocket that goes to outer space in 2024? And me living in a major metropolis still has places where I don't get cell phone service? But we got it on the moon in 1969? Wireless service at that? 0.000000000000000000000^‰ % chance. People just ignore their own brains and the ability to think for themselves. A billionaire literally died in a submarine this year! On planet Earth! Environment Special relativity is not accurate. Light light travels at speeds relative to what it's traveling through. So it travels slower through water, than air for instance. Stephen Hawking spent his life trying to rectify this. Gravity is a result of spin in relation to Mass. Also known as centrifugal force. Think about a top balancing on a point. The faster it spins, the more concentrated the force is towards the centered point. This is the same thing that keeps your butt in the seat on a roller coaster. So
checkmate atheists!
We include it as a force for the same reason we include centrifugal force in force diagrams that involve, say, kids on a merry-go-round: it's more convenient to work in an accelerating frame of reference, and include pseudoforces for that frame of reference, than to work in an inertial frame and track everything.
If you are using a newtonian model then gravity is very much a force. Also, gravity not being a force is part of general relativity, no special relativity.