Saw this a while back. Kind of mind bending after a lifetime of thinking that gravity was a force. I can follow most of what the vid talks about but, if gravity isn't a force, how does it bend space through time? In other words, matter tells spacetime how to curve, and spacetime tells matter how to move (6:45). That doesn't "just happen." Something is forcing this to occur. It seems to me that what this vid is focusing on is describing what is observed from the point of view of an inertial observer rather than explaining what gravity actually consists of. That is, it doesn't explain why mass curves spacetime. It only explains how objects behave in spacetime.
Saw this a while back. Kind of mind bending after a lifetime of thinking that gravity was a force. I can follow most of what the vid talks about but, if gravity isn't a force, how does it bend space through time?
Gravity does not bend space through time. Mass curves spacetime. Your next sentence shows that you know this but I am responding to this one because it seems out of place.
In other words, matter tells spacetime how to curve, and spacetime tells matter how to move (6:45).
Matter does not 'tell' spacetime, it simply curves (warps) spacetime. Much like a magnet does not tell metal to com hither. Again, just being precise on the language.
That doesn't "just happen." Something is forcing this to occur.
In other words, "how, exactly, does matter curve spacetime?". Great question! Waiting for that theory of everything that reconciles quantum gravity with the curvature of spacetime. This video focused on getting across the point that what we perceive as gravity is really just the effects of us accelerating through curved spacetime and that left alone, mass would simply travel at a constant velocity in a straight line (from the perspective of the mass) but from an inertial observer the mass is following a curvy path. The reason is that the mass is indeed following a straight line in spacetime but spacetime is not a flat surface but is contoured and we see the mass following the contours.
It seems to me that what this vid is focusing on is describing what is observed from the point of view of an inertial observer rather than explaining what gravity actually consists of. That is, it doesn't explain why mass curves spacetime. It only explains how objects behave in spacetime.
Agreed. Similar to why quantum physics does not (cannot) explain why the Higgs Boson gives mass to particles but notes (in incredibly accurate precision) how the behavior manifests.
I didn't mean gravity bends space by means of, or through, time. I meant space moving through time.
Matter does not 'tell' spacetime, it simply curves (warps) spacetime.
I think you're being a bit too literal here. The quote is from the vid, hence the timestamp. The mass of an object is what "tells" spacetime how much to curve. In other words, knowing the mass of an object tells you how much spacetime curves around it. I think that is all they meant.
This video focused on getting across the point that what we perceive as gravity is really just the effects of us accelerating through curved spacetime and that left alone, mass would simply travel at a constant velocity in a straight line (from the perspective of the mass) but from an inertial observer the mass is following a curvy path. The reason is that the mass is indeed following a straight line in spacetime but spacetime is not a flat surface but is contoured and we see the mass following the contours.
Yes. That was easy enough to follow. My objection to the vid is that it says gravity is not a force, which I don't think they did a very good job of explaining why it isn't. Everything in the vid seemed about what we are seeing observationally and I agree with it. What I have serious doubts about is that they say gravity isn't a force. Explaining how things actually move on, around or near a gravity well doesn't do much to explain why gravity isn't a force. To my mind, gravity is whatever mechanism that causes mass to curve space. As I said elsewhere, that certainly sounds like a force to me. One of the reasons I posted this was that I thought it was an interesting take on the issue, but the other was that I wanted input from others as to whether they thought the title of the vid was misleading or unjustified.
I am trying to be precise. When trying to understand a complex subject, language like that is misleading. It is like when Professor Krauss uses language like "something from nothing". That language is very misleading.
My objection to the vid is that it says gravity is not a force, which I don't think they did a very good job of explaining why it isn't.
I agree that it is a arguably misleading to categorically claim there is no force of any kind in the curving of spacetime. It is misleading because we simply do not yet know why mass curves spacetime. We just know how to predict the effects of same (much like we can predict quantum dynamics but do not know what actually causes all the behavior we observe).
To my mind, gravity is whatever mechanism that causes mass to curve space.
Logical.
As I said elsewhere, that certainly sounds like a force to me. One of the reasons I posted this was that I thought it was an interesting take on the issue, but the other was that I wanted input from others as to whether they thought the title of the vid was misleading or unjustified.
The video title is of course designed to grab attention. Same reason Krauss does what he does. This video author is very prolific and clearly is out to monetize. There is no escaping the marketing aspect of this stuff.
Gravity is a force of attraction that exists between any two masses, any two bodies, any two particles. Gravity is not just the attraction between objects and the Earth. It is an attraction that exists between all objects, everywhere in the universe. Sir Isaac Newton (1642 -- 1727) discovered that a force is required to change the speed or direction of movement of an object. He also realized that the force called "gravity" must make an apple fall from a tree, or humans and animals live on the surface of our spinning planet without being flung off. Furthermore, he deduced that gravity forces exist between all objects.
Newton's "law" of gravity is a mathematical description of the way bodies are observed to attract one another, based on many scientific experiments and observations. The gravitational equation says that the force of gravity is proportional to the product of the two masses (m1 and m2), and inversely proportional to the square of the distance (r) between their centers of mass. Mathematically speaking,
where G is called the Gravitational Constant. It has a value of 6.6726 x 10-11 m3 kg-1 s-2.
The effect of gravity extends from each object out into space in all directions, and for an infinite distance. However, the strength of the gravitational force reduces quickly with distance. Humans are never aware of the Sun's gravity pulling them, because the pull is so small at the distance between the Earth and Sun. Yet, it is the Sun's gravity that keeps the Earth in its orbit! Neither are we aware of the pull of lunar gravity on our bodies, but the Moon's gravity is responsible for the ocean tides on Earth.
Yes, that's what I grew up believing. The vid, however, denies that gravity is a force, which I find to be a dubious claim, because something is causing space to curve. The vid seems to be more about what is observed and how we should think about what we are observing rather than speaking specifically about what gravity is.
For instance, while the experience of standing on the Earth and accelerating at 1G on a spaceship may be experientially indistinguishable, they are caused by two entirely different things. The first is the attraction of masses and the second is caused by the acceleration of a spaceship due to chemical processes. I found the vid unconvincing that gravity is not a force, since there must be some attribute of mass that bends spacetime. The closest I've come to an explanation is theories about gravitons.
According to the video and Einstein's theory, gravitons don't exist. Matter curves space-time and the more massive the more curve. The only explanation for this space time curvature I can think of is mass moving near the speed of light, electrons.
The vid, however, denies that gravity is a force, which I find to be a dubious claim, because something is causing space to curve. The vid seems to be more about what is observed and how we should think about what we are observing rather than speaking specifically about what gravity is.
We do not know what gravity fundamentally is. We know (can observe) the effects it has, the most extreme example being a black hole. Gravitons has been hypothesized. But it's the observed influence of gravity that can be called a gravitational force, based on Newton's Law of universal gravitation. But this a simplistic explanation.
That seems to be the case, hence my... reluctance, let's say, to take this vid's claim that gravity isn't a force as fact. How can one say it doesn't exist when they don't fundamentally know what it is in the first place? Whatever gravity is, it's bending spacetime and that sounds like a force to me.
For instance, while the experience of standing on the Earth and accelerating at 1G on a spaceship may be experientially indistinguishable, they are caused by two entirely different things. The first is the attraction of masses and the second is caused by the acceleration of a spaceship due to chemical processes. I found the vid unconvincing that gravity is not a force, since there must be some attribute of mass that bends spacetime. The closest I've come to an explanation is theories about gravitons.
What is presented in the video could be tested. According to the video, two bodies of equal mass should not be attracted to each other since the curvature of spacetime would be the same for both. Neither of the bodies could fall into the gravity well of the other.
Pay close attention to the space ship example. The reason the bottom of the space presses against the astronaut is because a force has been applied to the spaceship. The astronaut is not falling into a gravity well caused by the rockets.
According to the video, two bodies of equal mass should not be attracted to each other since the curvature of spacetime would be the same for both. Neither of the bodies could fall into the gravity well of the other.
Not sure where you got that. That is, I didn't see it in the vid. Not sure how equal masses would cancel out gravitational attraction.
Not sure where you got that. That is, I didn't see it in the vid. Not sure how equal masses would cancel out gravitational attraction.
The video used the spaceship model to explain that the spaceship followed the curvature of space caused by the planet instead of being attracted by a force of gravity. The mass of the spaceship would also curve space. A spaceship the same mass as the planet would cause the same curvature of space as the planet. Would a spaceship of the same mass as the planet follow the curvature caused by the planet? Or would the spaceship's own curvature of space prevent it from following the planet's curvature of space?
Would a spaceship of the same mass as the planet follow the curvature caused by the planet? Or would the spaceship's own curvature of space prevent it from following the planet's curvature of space?
As I understand it, the answer is the same as why a bowling ball and a softball will land at the same time when dropped from a height. A normal mass spaceship would fall into a planet's gravity well along a certain path. If I'm thinking of this correctly, so would a spaceship of the same mass as the gravity well.
To explain, let's look at two balls of different masses dropped from a height. I have long forgotten the equation but basically, the mass of the planet and the mass of the softball attract each other at a given value. The mass of the bowling ball is attracted at the same value. People naturally think the heavier ball should land first because it's heavier, but its inertia is harder to overcome than the softball. So much so that it ends up falling at the same rate as the softball. In other words, if the bowling ball is ten times more attracted to the earth than the softball is, it's also ten times harder to move because of its intertia.
It would be the same for a planet and a spaceship with the mass of that planet. While each is attracting the other with the same gravitational force, the inertia of each is much greater than a normal massed spaceship so it ends up being the same. Sort of. This doesn't take into account that, considering the planet sized mass of the spaceship would be great enough to actually move the planet, whereas the normal massed spaceship wouldn't even be noticed by the planet so the paths wouldn't be exactly the same, but I think you get what I'm saying.
If the spaceship is in motion relative to the planet, then velocity and momentum could pull it towards or away from the gravity well of the planet, depending on the trajectory.
Both objects are curving spacetime. Given they are the same mass I would expect the behavior to be similar to the dance (gravitational waves) of two equivalent stars on their way to a destructive collision.
Speaking of spaceships with the mass of a planet, that's pretty much what you'd have to have in order to have the sort of gravity you see in SiFy such as Star Trek. That has obvious problems associated with it.
Both objects are curving spacetime. Given they are the same mass I would expect the behavior to be similar to the dance (gravitational waves) of two equivalent stars on their way to a destructive collision.
LOL. It's actually kind of hard to think about, really. It would depend on the velocity of the spacecraft but, holy cow! Can you imagine the engines the thing would have to have to be anything other than a space station? Anyway, if the spacecraft could move at, say, 0.1c, I don't think it would be much of a slow dance and really bad news for whatever was on the planet.
To explain, let's look at two balls of different masses dropped from a height. I have long forgotten the equation but basically, the mass of the planet and the mass of the softball attract each other at a given value. The mass of the bowling ball is attracted at the same value. People naturally think the heavier ball should land first because it's heavier, but its inertia is harder to overcome than the softball. So much so that it ends up falling at the same rate as the softball. In other words, if the bowling ball is ten times more attracted to the earth than the softball is, it's also ten times harder to move because of its intertia.
Yep, that's the classic experiment. But, as you point out, there are three objects involved; two balls and the planet. And the mass of the either ball is miniscule compared to the mass of the planet. The Newtonian physics is that the balls and the planet are attracted to each other through gravitation attraction according to their respective masses.
It would be the same for a planet and a spaceship with the mass of that planet. While each is attracting the other with the same gravitational force, the inertia of each is much greater than a normal massed spaceship so it ends up being the same. Sort of. This doesn't take into account that, considering the planet sized mass of the spaceship would be great enough to actually move the planet, whereas the normal massed spaceship wouldn't even be noticed by the planet so the paths wouldn't be exactly the same, but I think you get what I'm saying.
Yes, I get what you are saying. However, the video is saying gravity is not a force, so, according to the video there would not be gravitational attraction between the spaceship (of any mass) and the planet.
The video is saying there isn't gravity. The spaceship follows the curvature of spacetime. That's my question, without gravity would two equal masses be attracted to each other? Two equal masses would curve space the same, so, it should be like two equal masses on a flat plane. Like two planet sized billiard balls on an extremely large billiard table.
If the spaceship is in motion relative to the planet, then velocity and momentum could pull it towards or away from the gravity well of the planet, depending on the trajectory.
The video is saying that gravity is not a force which means there isn't gravitational attraction. If the spaceship and planet are of equal masses then their relative motions should be comparable to motion on a flat plane.
Fortunately, starships in ST have gravity generators (a classic sci fi trope) to produce artifical gravity. Some sci-fi shows are a little more realistic, simulating gravity via centrifugal force.
The video is saying there isn't gravity. The spaceship follows the curvature of spacetime. That's my question, without gravity would two equal masses be attracted to each other? Two equal masses would curve space the same, so, it should be like two equal masses on a flat plane. Like two planet sized billiard balls on an extremely large billiard table.
That's kind of why I posted this. I think the vid is wrong by saying there is no force such as gravity. They also don't explain why there isn't. They just state it. Instead, they just state that objects just follow the curve created by the mass without explaining how the curve is generated in the first place. I mean, we all know mass is involved but what mechanism creates the curved spacetime?
I think that what the vid must mean is that people tend to think gravity is a force that reaches out and sort of "grabs" masses and pulls them toward each other. That isn't the case. It's more like that thing you see where you have the rubber sheet with a heavy weight in the middle. You accelerate a ball along the rim of it, pushing it straight but it immediately starts to circle and descend toward the heavy weight. It isn't that the heavy weight is reaching out to the ball in any way at all. It's just warping the space around it into something the ball has to follow.
In that sense, it's still wrong, in my opinion, to say there's no force such as gravity, but it does explain what may be a common misconception. That mass "reaches out" with some sort of force to attract other masses. Still, something is curving space and that, I think, is gravity. It just doesn't work the way many think it does.
I think that what the vid must mean is that people tend to think gravity is a force that reaches out and sort of "grabs" masses and pulls them toward each other. That isn't the case. It's more like that thing you see where you have the rubber sheet with a heavy weight in the middle. You accelerate a ball along the rim of it, pushing it straight but it immediately starts to circle and descend toward the heavy weight. It isn't that the heavy weight is reaching out to the ball in any way at all. It's just warping the space around it into something the ball has to follow.
Well, NASA's proposal to park an object near an asteroid to deflect the asteroid kinda depends upon gravity being an attractive force. NASA's concept depends upon the gravitational attraction of the space craft.
I'd have to watch the video again to pull out the specific segment but the guy showed a field equation (of some sort) and simply set the force to zero in the equation with a hand waving explanation. That isn't the same as gravity not being a force; that's a special condition where the force of gravity would be zero.
Which circles back to my question of a spaceship that is the same mass as the planet. What the guy is presenting is a bar trick like counting fingers to show you have 11. You know - 1,2, skip 3, 4, 5, 6, 7, 8, 9, 10, 11.
Which circles back to my question of a spaceship that is the same mass as the planet. What the guy is presenting is a bar trick like counting fingers to show you have 11. You know - 1,2, skip 3, 4, 5, 6, 7, 8, 9, 10, 11.
Well, if you like that, you'd love the one I just watched, saying time creates gravity. Never heard that before. You can see it here , if you're interested. In my opinion, though, is the squirrel analogy ends up being more confusing than an explanation. Maybe because I end up thinking about all the conditions that have to be met in order for the analogy to work in any sort of way. I get what the guy is saying but he does a poor job, or none at all, at explaining why the gradient pulls one mass toward another. I suspect he's oversimplified the whole thing into uselessness.
Well, if you like that, you'd love the one I just watched, saying time creates gravity. Never heard that before. You can see it here , if you're interested. In my opinion, though, is the squirrel analogy ends up being more confusing than an explanation. Maybe because I end up thinking about all the conditions that have to be met in order for the analogy to work in any sort of way. I get what the guy is saying but he does a poor job, or none at all, at explaining why the gradient pulls one mass toward another. I suspect he's oversimplified the whole thing into uselessness.
Well, the squirrel model can be tested under conditions of zero gravity. If I recall correctly, the time dilation the guy talks about has only been observed in a gravitational field. The observations (that I am aware of) suggest that time dilation is caused by the gravity field; not that time dilation creates a gravity field. In zero gravity the head of the squirrel would not be higher than its feet; there isn't up/down in zero gravity.
BTW, if I understand how gravity waves are measured, gravity waves are detected by observing distortions in spacetime. I haven't wrapped my head around how a gravity spike is created though. Based on the mass/gravity relationship, a spike in gravity would require a sudden increase in mass (like merging black holes) followed by a sudden decrease in mass (which I don't understand).
In zero gravity the head of the squirrel would not be higher than its feet; there isn't up/down in zero gravity.
Yeah. That's why I think it was a bad example. In trying to simply things he just created more issues.
BTW, if I understand how gravity waves are measured, gravity waves are detected by observing distortions in spacetime. I haven't wrapped my head around how a gravity spike is created though.
I haven't even looked at gravity waves, yet.
Having had a day to think about all this, though, I think the point of the vid was supposed to be that gravity isn't a force of attraction, as Gordy's quote of NASA's description describes it. If gravity just warps space around the mass, then I think that's correct, but it still doesn't change gravity as a force but, rather, what that force acts on.
If gravity just warps space around the mass, then I think that's correct, but it still doesn't change gravity as a force but, rather, what that force acts on.
I think we should just hold off on calling gravity anything right now. It was originally viewed as one of the four fundamental forces. Einstein has shown that this likely is not the case and quantum physics can handle all of the fundamentals except for gravity.
Until we understand how mass distorts space-time it is premature for us to affix properties onto the phenomenon by labeling it a force or claiming it is not a force. We simply do not yet know.
Yeah. That's why I think it was a bad example. In trying to simply things he just created more issues.
IMO what videos are doing is flipping the causal relationship by manipulating the mathematics. And the examples are mathematically consistent. To me what is overlooked is that the mathematics is used to describe reality. The videos seem to be trying to use reality to describe the mathematics.
Until we understand how mass distorts space-time it is premature for us to affix properties onto the phenomenon by labeling it a force or claiming it is not a force. We simply do not yet know.
What we do know with a high degree of certainty is that gravity and distortion of spacetime are associated with mass. As I understand it, all of the four fundamental forces are associated with mass in some way.
Considering the impact gravity has on the universe, it seems odd that gravity is the weakest of the fundamental forces.
The 'strength' of gravity depends upon the amount of concentrated mass. At this point we can only conjecture about black holes but it does appear that sufficient concentrated mass can result in a gravitation field that will overcome the other fundamental forces.
Increasing mass increases gravity. I'm not aware of anything suggesting that increasing mass increases the other fundamental forces.
I think we should just hold off on calling gravity anything right now.
To my mind, "gravity" now has the status of Dark Matter (not the Netflix series). It's a place holder, in other words. I'm perfectly okay with calling gravity "the force that curves space" since I suspect even quantum physics won't change that.
Ah science. Not only is it intellectually stimulating and a useful process for discovery and knowledge, but also useful for recreational activities and entertainment.
S E E D E D C O N T E N T
Saw this a while back. Kind of mind bending after a lifetime of thinking that gravity was a force. I can follow most of what the vid talks about but, if gravity isn't a force, how does it bend space through time? In other words, matter tells spacetime how to curve, and spacetime tells matter how to move (6:45). That doesn't "just happen." Something is forcing this to occur. It seems to me that what this vid is focusing on is describing what is observed from the point of view of an inertial observer rather than explaining what gravity actually consists of. That is, it doesn't explain why mass curves spacetime. It only explains how objects behave in spacetime.
Gravity does not bend space through time. Mass curves spacetime. Your next sentence shows that you know this but I am responding to this one because it seems out of place.
Matter does not 'tell' spacetime, it simply curves (warps) spacetime. Much like a magnet does not tell metal to com hither. Again, just being precise on the language.
In other words, "how, exactly, does matter curve spacetime?". Great question! Waiting for that theory of everything that reconciles quantum gravity with the curvature of spacetime. This video focused on getting across the point that what we perceive as gravity is really just the effects of us accelerating through curved spacetime and that left alone, mass would simply travel at a constant velocity in a straight line (from the perspective of the mass) but from an inertial observer the mass is following a curvy path. The reason is that the mass is indeed following a straight line in spacetime but spacetime is not a flat surface but is contoured and we see the mass following the contours.
Agreed. Similar to why quantum physics does not (cannot) explain why the Higgs Boson gives mass to particles but notes (in incredibly accurate precision) how the behavior manifests.
I didn't mean gravity bends space by means of, or through, time. I meant space moving through time.
I think you're being a bit too literal here. The quote is from the vid, hence the timestamp. The mass of an object is what "tells" spacetime how much to curve. In other words, knowing the mass of an object tells you how much spacetime curves around it. I think that is all they meant.
Yes. That was easy enough to follow. My objection to the vid is that it says gravity is not a force, which I don't think they did a very good job of explaining why it isn't. Everything in the vid seemed about what we are seeing observationally and I agree with it. What I have serious doubts about is that they say gravity isn't a force. Explaining how things actually move on, around or near a gravity well doesn't do much to explain why gravity isn't a force. To my mind, gravity is whatever mechanism that causes mass to curve space. As I said elsewhere, that certainly sounds like a force to me. One of the reasons I posted this was that I thought it was an interesting take on the issue, but the other was that I wanted input from others as to whether they thought the title of the vid was misleading or unjustified.
I am trying to be precise. When trying to understand a complex subject, language like that is misleading. It is like when Professor Krauss uses language like "something from nothing". That language is very misleading.
I agree that it is a arguably misleading to categorically claim there is no force of any kind in the curving of spacetime. It is misleading because we simply do not yet know why mass curves spacetime. We just know how to predict the effects of same (much like we can predict quantum dynamics but do not know what actually causes all the behavior we observe).
Logical.
The video title is of course designed to grab attention. Same reason Krauss does what he does. This video author is very prolific and clearly is out to monetize. There is no escaping the marketing aspect of this stuff.
According to NASA:
Gravity is a force of attraction that exists between any two masses, any two bodies, any two particles. Gravity is not just the attraction between objects and the Earth. It is an attraction that exists between all objects, everywhere in the universe. Sir Isaac Newton (1642 -- 1727) discovered that a force is required to change the speed or direction of movement of an object. He also realized that the force called "gravity" must make an apple fall from a tree, or humans and animals live on the surface of our spinning planet without being flung off. Furthermore, he deduced that gravity forces exist between all objects.
Newton's "law" of gravity is a mathematical description of the way bodies are observed to attract one another, based on many scientific experiments and observations. The gravitational equation says that the force of gravity is proportional to the product of the two masses (m1 and m2), and inversely proportional to the square of the distance (r) between their centers of mass. Mathematically speaking,
where G is called the Gravitational Constant. It has a value of 6.6726 x 10-11 m3 kg-1 s-2.
The effect of gravity extends from each object out into space in all directions, and for an infinite distance. However, the strength of the gravitational force reduces quickly with distance. Humans are never aware of the Sun's gravity pulling them, because the pull is so small at the distance between the Earth and Sun. Yet, it is the Sun's gravity that keeps the Earth in its orbit! Neither are we aware of the pull of lunar gravity on our bodies, but the Moon's gravity is responsible for the ocean tides on Earth.
Yes, that's what I grew up believing. The vid, however, denies that gravity is a force, which I find to be a dubious claim, because something is causing space to curve. The vid seems to be more about what is observed and how we should think about what we are observing rather than speaking specifically about what gravity is.
For instance, while the experience of standing on the Earth and accelerating at 1G on a spaceship may be experientially indistinguishable, they are caused by two entirely different things. The first is the attraction of masses and the second is caused by the acceleration of a spaceship due to chemical processes. I found the vid unconvincing that gravity is not a force, since there must be some attribute of mass that bends spacetime. The closest I've come to an explanation is theories about gravitons.
According to the video and Einstein's theory, gravitons don't exist. Matter curves space-time and the more massive the more curve. The only explanation for this space time curvature I can think of is mass moving near the speed of light, electrons.
We do not know what gravity fundamentally is. We know (can observe) the effects it has, the most extreme example being a black hole. Gravitons has been hypothesized. But it's the observed influence of gravity that can be called a gravitational force, based on Newton's Law of universal gravitation. But this a simplistic explanation.
That seems to be the case, hence my... reluctance, let's say, to take this vid's claim that gravity isn't a force as fact. How can one say it doesn't exist when they don't fundamentally know what it is in the first place? Whatever gravity is, it's bending spacetime and that sounds like a force to me.
What is presented in the video could be tested. According to the video, two bodies of equal mass should not be attracted to each other since the curvature of spacetime would be the same for both. Neither of the bodies could fall into the gravity well of the other.
Pay close attention to the space ship example. The reason the bottom of the space presses against the astronaut is because a force has been applied to the spaceship. The astronaut is not falling into a gravity well caused by the rockets.
That's the one thing about gravity that is certain.
Not sure where you got that. That is, I didn't see it in the vid. Not sure how equal masses would cancel out gravitational attraction.
The video used the spaceship model to explain that the spaceship followed the curvature of space caused by the planet instead of being attracted by a force of gravity. The mass of the spaceship would also curve space. A spaceship the same mass as the planet would cause the same curvature of space as the planet. Would a spaceship of the same mass as the planet follow the curvature caused by the planet? Or would the spaceship's own curvature of space prevent it from following the planet's curvature of space?
How about a combination much like wave interference?
As I understand it, the answer is the same as why a bowling ball and a softball will land at the same time when dropped from a height. A normal mass spaceship would fall into a planet's gravity well along a certain path. If I'm thinking of this correctly, so would a spaceship of the same mass as the gravity well.
To explain, let's look at two balls of different masses dropped from a height. I have long forgotten the equation but basically, the mass of the planet and the mass of the softball attract each other at a given value. The mass of the bowling ball is attracted at the same value. People naturally think the heavier ball should land first because it's heavier, but its inertia is harder to overcome than the softball. So much so that it ends up falling at the same rate as the softball. In other words, if the bowling ball is ten times more attracted to the earth than the softball is, it's also ten times harder to move because of its intertia.
It would be the same for a planet and a spaceship with the mass of that planet. While each is attracting the other with the same gravitational force, the inertia of each is much greater than a normal massed spaceship so it ends up being the same. Sort of. This doesn't take into account that, considering the planet sized mass of the spaceship would be great enough to actually move the planet, whereas the normal massed spaceship wouldn't even be noticed by the planet so the paths wouldn't be exactly the same, but I think you get what I'm saying.
If the spaceship is in motion relative to the planet, then velocity and momentum could pull it towards or away from the gravity well of the planet, depending on the trajectory.
Both objects are curving spacetime. Given they are the same mass I would expect the behavior to be similar to the dance (gravitational waves) of two equivalent stars on their way to a destructive collision.
Speaking of spaceships with the mass of a planet, that's pretty much what you'd have to have in order to have the sort of gravity you see in SiFy such as Star Trek. That has obvious problems associated with it.
LOL. It's actually kind of hard to think about, really. It would depend on the velocity of the spacecraft but, holy cow! Can you imagine the engines the thing would have to have to be anything other than a space station? Anyway, if the spacecraft could move at, say, 0.1c, I don't think it would be much of a slow dance and really bad news for whatever was on the planet.
Yep, that's the classic experiment. But, as you point out, there are three objects involved; two balls and the planet. And the mass of the either ball is miniscule compared to the mass of the planet. The Newtonian physics is that the balls and the planet are attracted to each other through gravitation attraction according to their respective masses.
Yes, I get what you are saying. However, the video is saying gravity is not a force, so, according to the video there would not be gravitational attraction between the spaceship (of any mass) and the planet.
The video is saying there isn't gravity. The spaceship follows the curvature of spacetime. That's my question, without gravity would two equal masses be attracted to each other? Two equal masses would curve space the same, so, it should be like two equal masses on a flat plane. Like two planet sized billiard balls on an extremely large billiard table.
The video is saying that gravity is not a force which means there isn't gravitational attraction. If the spaceship and planet are of equal masses then their relative motions should be comparable to motion on a flat plane.
Fortunately, starships in ST have gravity generators (a classic sci fi trope) to produce artifical gravity. Some sci-fi shows are a little more realistic, simulating gravity via centrifugal force.
That's kind of why I posted this. I think the vid is wrong by saying there is no force such as gravity. They also don't explain why there isn't. They just state it. Instead, they just state that objects just follow the curve created by the mass without explaining how the curve is generated in the first place. I mean, we all know mass is involved but what mechanism creates the curved spacetime?
I think that what the vid must mean is that people tend to think gravity is a force that reaches out and sort of "grabs" masses and pulls them toward each other. That isn't the case. It's more like that thing you see where you have the rubber sheet with a heavy weight in the middle. You accelerate a ball along the rim of it, pushing it straight but it immediately starts to circle and descend toward the heavy weight. It isn't that the heavy weight is reaching out to the ball in any way at all. It's just warping the space around it into something the ball has to follow.
In that sense, it's still wrong, in my opinion, to say there's no force such as gravity, but it does explain what may be a common misconception. That mass "reaches out" with some sort of force to attract other masses. Still, something is curving space and that, I think, is gravity. It just doesn't work the way many think it does.
Obviously, there is a gravitational effect, which is why I am not giving the video much credence.
By any other name ...
Well, NASA's proposal to park an object near an asteroid to deflect the asteroid kinda depends upon gravity being an attractive force. NASA's concept depends upon the gravitational attraction of the space craft.
I'd have to watch the video again to pull out the specific segment but the guy showed a field equation (of some sort) and simply set the force to zero in the equation with a hand waving explanation. That isn't the same as gravity not being a force; that's a special condition where the force of gravity would be zero.
Which circles back to my question of a spaceship that is the same mass as the planet. What the guy is presenting is a bar trick like counting fingers to show you have 11. You know - 1,2, skip 3, 4, 5, 6, 7, 8, 9, 10, 11.
Well, if you like that, you'd love the one I just watched, saying time creates gravity. Never heard that before. You can see it here , if you're interested. In my opinion, though, is the squirrel analogy ends up being more confusing than an explanation. Maybe because I end up thinking about all the conditions that have to be met in order for the analogy to work in any sort of way. I get what the guy is saying but he does a poor job, or none at all, at explaining why the gradient pulls one mass toward another. I suspect he's oversimplified the whole thing into uselessness.
Well, the squirrel model can be tested under conditions of zero gravity. If I recall correctly, the time dilation the guy talks about has only been observed in a gravitational field. The observations (that I am aware of) suggest that time dilation is caused by the gravity field; not that time dilation creates a gravity field. In zero gravity the head of the squirrel would not be higher than its feet; there isn't up/down in zero gravity.
BTW, if I understand how gravity waves are measured, gravity waves are detected by observing distortions in spacetime. I haven't wrapped my head around how a gravity spike is created though. Based on the mass/gravity relationship, a spike in gravity would require a sudden increase in mass (like merging black holes) followed by a sudden decrease in mass (which I don't understand).
Yeah. That's why I think it was a bad example. In trying to simply things he just created more issues.
I haven't even looked at gravity waves, yet.
Having had a day to think about all this, though, I think the point of the vid was supposed to be that gravity isn't a force of attraction, as Gordy's quote of NASA's description describes it. If gravity just warps space around the mass, then I think that's correct, but it still doesn't change gravity as a force but, rather, what that force acts on.
I think we should just hold off on calling gravity anything right now. It was originally viewed as one of the four fundamental forces. Einstein has shown that this likely is not the case and quantum physics can handle all of the fundamentals except for gravity.
Until we understand how mass distorts space-time it is premature for us to affix properties onto the phenomenon by labeling it a force or claiming it is not a force. We simply do not yet know.
IMO what videos are doing is flipping the causal relationship by manipulating the mathematics. And the examples are mathematically consistent. To me what is overlooked is that the mathematics is used to describe reality. The videos seem to be trying to use reality to describe the mathematics.
What we do know with a high degree of certainty is that gravity and distortion of spacetime are associated with mass. As I understand it, all of the four fundamental forces are associated with mass in some way.
Yes the phenomenon I described is mass distorting space-time. And all four fundamental forces deal with the interaction of matter.
Not sure what point you are trying to make.
Considering the impact gravity has on the universe, it seems odd that gravity is the weakest of the fundamental forces.
Weak but far reaching and grows stronger with mass.
The 'strength' of gravity depends upon the amount of concentrated mass. At this point we can only conjecture about black holes but it does appear that sufficient concentrated mass can result in a gravitation field that will overcome the other fundamental forces.
Increasing mass increases gravity. I'm not aware of anything suggesting that increasing mass increases the other fundamental forces.
Not much "strength," but infinite range.
To my mind, "gravity" now has the status of Dark Matter (not the Netflix series). It's a place holder, in other words. I'm perfectly okay with calling gravity "the force that curves space" since I suspect even quantum physics won't change that.
That is how I see it too.
If you violate Newton's "law" of gravity, you will float off into space.
Maybe I should give up on my anti-gravity research.
Whenever I drink Helium, I sound silly.
What science majors invent in their off time.
Ah science. Not only is it intellectually stimulating and a useful process for discovery and knowledge, but also useful for recreational activities and entertainment.