It’s an phrasing of how gravity works with equations that have the same form as Maxwell’s equations. And frankly, it’s pretty neat: writing the laws for gravity this way gets you mechanics while approximately accounting for general relativity (how approximate and what it leaves off, I’m not sure of).
When I first found out about this, it blew my mind to know that gravity acts just like electromagnetism, but for different properties. We all know about the parallel between Coulomb’s law and Newton’s law of gravitation, but the gravitoelectromagnetism (GEM) equations show that it goes a lot deeper.
Besides being a good way to ease into an intuitive understanding of the Einstein field equations, to me, it’s basically saying that gravity and EM are both obeying some more general law. Anyone know if work has been done in unifying gravity and EM this way? All I hear about is that it’s easy to unify strong, weak, and EM forces, but gravity is the stumbling block, so this should be something they’d want to explore more.
Yet when you go investigate “gravitational induction” to find out how the gravitic parallel to magnetic fields works, you find that this gravitomagnetic field is called the torsion field, and its existence is (at least approximately) implied by general relativity, but then the Wikipedia page says that the torsion field is a pseudoscientific concept. Hm...
So, anyone have an understanding of the GEM analogy and can make sense of this? Does it suggest a way to unify gravity and EM? Or how to create a coil of mass flow that can “gravitize” a region (as a coil of current magnitizes a metal bar)?
it’s basically saying that gravity and EM are both obeying some more general law
No, what’s happening is that under certain approximations the two are described by similar math. The trick is to know when the approximations break down and what the math actually translates to physically.
Does it suggest a way to unify gravity and EM?
No.
Keep in mind that for EM there are 2 charges while gravity has only 1. Also, like electric charges repel while like gravitic charges attract. This messes with your expectations about the sign of an interaction when you go from one to the other. That means your intuitive understanding of EM doesn’t map well to understanding gravity.
True, but what got me the most interested is the gravitic analog of magnetic fields. It shows that masses can produce something analogous to magnetism by their rotation. Rotate one way, you drag the object closer; rotate the other way, you push it away. This allows both attraction and repulsion in the equations for gravity, and suggests something similar is going on that generates magnetism.
Your link to “torsion field” talks about a completely different concept than the one in GEM. That concept is indeed a notorious example of pseudoscience here in Russia.
I’d mostly like to echo what mindviews said—similar math is not unification—and point out that there was an actual attempt at unification in Kaluza-Klein theory. But I don’t actually know anything about that, I should note...
I’m intrigued by the notion and would like to hear more from someone who can tell me whether I can take this seriously. That ‘approximately accounting for’ part scares me. Is that just word chioce that makes it sound scary? Or perhaps an approximation in the way that Newtonian physics is an approximation? Or maybe it is only an approximation is as much as it suffers the same problem all our theories do of being unable to unify all of our physics at once… I’d need someone several levels ahead of me to figure that out.
It’s definitely better of an approximation than Newtonian physics. This paper might help, as it derives the GEM equations from GR and specifically states what simplifying assumptions it uses, which look to be basically “for greater-than-subatomic distances”. And that’s exactly where you care about gravity anyway. (At subatomic distances, the other three forces dominate.)
Gravitomagnetism—what’s up with that?
It’s an phrasing of how gravity works with equations that have the same form as Maxwell’s equations. And frankly, it’s pretty neat: writing the laws for gravity this way gets you mechanics while approximately accounting for general relativity (how approximate and what it leaves off, I’m not sure of).
When I first found out about this, it blew my mind to know that gravity acts just like electromagnetism, but for different properties. We all know about the parallel between Coulomb’s law and Newton’s law of gravitation, but the gravitoelectromagnetism (GEM) equations show that it goes a lot deeper.
Besides being a good way to ease into an intuitive understanding of the Einstein field equations, to me, it’s basically saying that gravity and EM are both obeying some more general law. Anyone know if work has been done in unifying gravity and EM this way? All I hear about is that it’s easy to unify strong, weak, and EM forces, but gravity is the stumbling block, so this should be something they’d want to explore more.
Yet when you go investigate “gravitational induction” to find out how the gravitic parallel to magnetic fields works, you find that this gravitomagnetic field is called the torsion field, and its existence is (at least approximately) implied by general relativity, but then the Wikipedia page says that the torsion field is a pseudoscientific concept. Hm...
So, anyone have an understanding of the GEM analogy and can make sense of this? Does it suggest a way to unify gravity and EM? Or how to create a coil of mass flow that can “gravitize” a region (as a coil of current magnitizes a metal bar)?
No, what’s happening is that under certain approximations the two are described by similar math. The trick is to know when the approximations break down and what the math actually translates to physically.
No.
Keep in mind that for EM there are 2 charges while gravity has only 1. Also, like electric charges repel while like gravitic charges attract. This messes with your expectations about the sign of an interaction when you go from one to the other. That means your intuitive understanding of EM doesn’t map well to understanding gravity.
True, but what got me the most interested is the gravitic analog of magnetic fields. It shows that masses can produce something analogous to magnetism by their rotation. Rotate one way, you drag the object closer; rotate the other way, you push it away. This allows both attraction and repulsion in the equations for gravity, and suggests something similar is going on that generates magnetism.
Your link to “torsion field” talks about a completely different concept than the one in GEM. That concept is indeed a notorious example of pseudoscience here in Russia.
I’d mostly like to echo what mindviews said—similar math is not unification—and point out that there was an actual attempt at unification in Kaluza-Klein theory. But I don’t actually know anything about that, I should note...
I’m intrigued by the notion and would like to hear more from someone who can tell me whether I can take this seriously. That ‘approximately accounting for’ part scares me. Is that just word chioce that makes it sound scary? Or perhaps an approximation in the way that Newtonian physics is an approximation? Or maybe it is only an approximation is as much as it suffers the same problem all our theories do of being unable to unify all of our physics at once… I’d need someone several levels ahead of me to figure that out.
It’s definitely better of an approximation than Newtonian physics. This paper might help, as it derives the GEM equations from GR and specifically states what simplifying assumptions it uses, which look to be basically “for greater-than-subatomic distances”. And that’s exactly where you care about gravity anyway. (At subatomic distances, the other three forces dominate.)
(At least, they do when the other forces are configured to counter each other.)
Be careful, you are near fringe science domain.