Does gravity sometimes get transmitted faster than the speed of light?












2












$begingroup$


Consider Earth moving around the Sun. Is the force of gravity exerted by Earth onto the Sun directed towards the point where Earth is "right now", or towards the point where Earth was 8 minutes ago (to account for the speed of light)?
If it's the former, how does the Sun "know" the current orbital position of Earth? Wouldn't this information have to travel at the speed of light first?



If it's the latter, it would force a significant slowdown of Earth's orbital motion, because the force of gravity would no longer be directed perpendicular to Earth's motion, but would lag behind. Obviously, this isn't happening.



So it appears that the force of gravity is indeed directed towards the current orbital position of Earth, without accounting for the delay caused by the speed of light. How is this possible? Isn't this a violation of the principle that no information can travel above the speed of light?










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$endgroup$








  • 1




    $begingroup$
    This is not limited to gravity. The same applies to electromagnetism.
    $endgroup$
    – safesphere
    3 hours ago










  • $begingroup$
    Related: physics.stackexchange.com/questions/101919/…
    $endgroup$
    – Kyle Oman
    2 hours ago










  • $begingroup$
    Related: physics.stackexchange.com/q/5456
    $endgroup$
    – Dan Yand
    1 hour ago
















2












$begingroup$


Consider Earth moving around the Sun. Is the force of gravity exerted by Earth onto the Sun directed towards the point where Earth is "right now", or towards the point where Earth was 8 minutes ago (to account for the speed of light)?
If it's the former, how does the Sun "know" the current orbital position of Earth? Wouldn't this information have to travel at the speed of light first?



If it's the latter, it would force a significant slowdown of Earth's orbital motion, because the force of gravity would no longer be directed perpendicular to Earth's motion, but would lag behind. Obviously, this isn't happening.



So it appears that the force of gravity is indeed directed towards the current orbital position of Earth, without accounting for the delay caused by the speed of light. How is this possible? Isn't this a violation of the principle that no information can travel above the speed of light?










share|cite|improve this question









$endgroup$








  • 1




    $begingroup$
    This is not limited to gravity. The same applies to electromagnetism.
    $endgroup$
    – safesphere
    3 hours ago










  • $begingroup$
    Related: physics.stackexchange.com/questions/101919/…
    $endgroup$
    – Kyle Oman
    2 hours ago










  • $begingroup$
    Related: physics.stackexchange.com/q/5456
    $endgroup$
    – Dan Yand
    1 hour ago














2












2








2





$begingroup$


Consider Earth moving around the Sun. Is the force of gravity exerted by Earth onto the Sun directed towards the point where Earth is "right now", or towards the point where Earth was 8 minutes ago (to account for the speed of light)?
If it's the former, how does the Sun "know" the current orbital position of Earth? Wouldn't this information have to travel at the speed of light first?



If it's the latter, it would force a significant slowdown of Earth's orbital motion, because the force of gravity would no longer be directed perpendicular to Earth's motion, but would lag behind. Obviously, this isn't happening.



So it appears that the force of gravity is indeed directed towards the current orbital position of Earth, without accounting for the delay caused by the speed of light. How is this possible? Isn't this a violation of the principle that no information can travel above the speed of light?










share|cite|improve this question









$endgroup$




Consider Earth moving around the Sun. Is the force of gravity exerted by Earth onto the Sun directed towards the point where Earth is "right now", or towards the point where Earth was 8 minutes ago (to account for the speed of light)?
If it's the former, how does the Sun "know" the current orbital position of Earth? Wouldn't this information have to travel at the speed of light first?



If it's the latter, it would force a significant slowdown of Earth's orbital motion, because the force of gravity would no longer be directed perpendicular to Earth's motion, but would lag behind. Obviously, this isn't happening.



So it appears that the force of gravity is indeed directed towards the current orbital position of Earth, without accounting for the delay caused by the speed of light. How is this possible? Isn't this a violation of the principle that no information can travel above the speed of light?







orbital-motion relativity






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share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked 4 hours ago









cuckoocuckoo

43416




43416








  • 1




    $begingroup$
    This is not limited to gravity. The same applies to electromagnetism.
    $endgroup$
    – safesphere
    3 hours ago










  • $begingroup$
    Related: physics.stackexchange.com/questions/101919/…
    $endgroup$
    – Kyle Oman
    2 hours ago










  • $begingroup$
    Related: physics.stackexchange.com/q/5456
    $endgroup$
    – Dan Yand
    1 hour ago














  • 1




    $begingroup$
    This is not limited to gravity. The same applies to electromagnetism.
    $endgroup$
    – safesphere
    3 hours ago










  • $begingroup$
    Related: physics.stackexchange.com/questions/101919/…
    $endgroup$
    – Kyle Oman
    2 hours ago










  • $begingroup$
    Related: physics.stackexchange.com/q/5456
    $endgroup$
    – Dan Yand
    1 hour ago








1




1




$begingroup$
This is not limited to gravity. The same applies to electromagnetism.
$endgroup$
– safesphere
3 hours ago




$begingroup$
This is not limited to gravity. The same applies to electromagnetism.
$endgroup$
– safesphere
3 hours ago












$begingroup$
Related: physics.stackexchange.com/questions/101919/…
$endgroup$
– Kyle Oman
2 hours ago




$begingroup$
Related: physics.stackexchange.com/questions/101919/…
$endgroup$
– Kyle Oman
2 hours ago












$begingroup$
Related: physics.stackexchange.com/q/5456
$endgroup$
– Dan Yand
1 hour ago




$begingroup$
Related: physics.stackexchange.com/q/5456
$endgroup$
– Dan Yand
1 hour ago










4 Answers
4






active

oldest

votes


















3












$begingroup$


Cuckoo asked: So it appears that the force of gravity is indeed
directed towards the current orbital position of Earth, without
accounting for the delay caused by the speed of light. How is this
possible?




If the motion is straight or circular the aberration cancels out, see Steve Carlip: Aberration and the Speed of Gravity:




Steven Carlip wrote: The observed absence of gravitational
aberration requires that "Newtonian'' gravity propagates at a speed
ς>2×10¹⁰c. By evaluating the gravitational effect of an accelerating
mass, I show that aberration in general relativity is almost exactly
canceled by velocity-dependent interactions, permitting ς=c. This
cancellation is dictated by conservation laws and the quadrupole
nature of gravitational radiation.




or to quote the Wikipedia article on the subject:




Wikipedia wrote: Two gravitoelectrically interacting particle
ensembles, e.g., two planets or stars moving at constant velocity with
respect to each other, each feel a force toward the instantaneous
position of the other body without a speed-of-light delay because
Lorentz invariance demands that what a moving body in a static field
sees and what a moving body that emits that field sees be symmetrical.
In other words, since the gravitoelectric field is, by definition,
static and continuous, it does not propagate.







share|cite|improve this answer









$endgroup$













  • $begingroup$
    I would be thankful for any comments on my answer below. I kind of made an interpretation of your answer, but I'm not sure I said everything correctly.
    $endgroup$
    – Elias Riedel Gårding
    2 hours ago



















1












$begingroup$

No, gravitational influences never travel faster than the speed of light. However, a naive incorporation of a speed-of-gravity delay would actually lead to the Earth's orbital motion speeding up, not slowing down. (Think about the geometry carefully.) I explained here why that doesn't actually happen in general relativity.






share|cite|improve this answer









$endgroup$





















    0












    $begingroup$

    Think of the gravitational field as curved space. Like a bump in space time. This bump will stay constant over time more or less. The planet then just looks at the bump and moves accordingly. However if the sun were to explode it might cause a small ripple in spacetime that would reach the earth in 8 minutes






    share|cite|improve this answer









    $endgroup$





















      0












      $begingroup$

      I was going to write an incorrect answer at first, but having researched a bit
      what Yukterez wrote, I think I may be able to offer some intuition.



      First, let's look at the solar system in the centre-of-mass frame, where the
      Sun is essentially stationary in the middle. Here, the force on the Earth is
      directed towards the Sun's position 8 minutes ago, which conveniently is the
      same as its current position. So this doesn't affect the Earth's position in
      the way you say.



      If the Sun and Earth were moving at a constant velocity to each other, they
      would, like Yukterez wrote, still be attracted to the instantaneous position of
      the other body. This is not because of a faster-than-light influence, but
      because gravity is more than a simple attractive force between objects
      (analogous to the electric field in electromagnetism). For moving sources,
      there are other components of the gravitational field (roughly analogous to the
      magnetic field). You can view this as the force travelling at the speed of
      light, but being directed towards the position of the source "predicted" based
      on its past linear motion.



      However, if the source is accelerating, like the Earth around the Sun, the
      effects are less obvious. Then, you really can't view it only as an attractive
      force towards any position (I think, correct me if I'm wrong), but you get
      more complex things like gravitational waves. But still, nothing ever travels faster than
      light.





      As I am more familiar with electromagnetism, let's take an example from there.
      If two oppositely charged bodies ($A$ and $B$) are moving with constant
      velocity towards each other, we can view the system in the rest frame of $A$.
      Here, it emits only a static electric field, given by the Coulomb formula, and
      $B$ therefore feels an attraction directly towards it. In the rest frame of $B$,
      this means that the attraction is towards the instantaneous position. But how
      can this be since the electric field is propagating at a finite speed? The
      answer is that since now $A$ is moving, it also emits a magnetic field. While
      this doesn't affect $B$ directly (since $B$ is stationary here), it does affect
      the electric field and makes it point in a different direction (towards the
      instantaneous position).






      share|cite|improve this answer









      $endgroup$













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        4 Answers
        4






        active

        oldest

        votes








        4 Answers
        4






        active

        oldest

        votes









        active

        oldest

        votes






        active

        oldest

        votes









        3












        $begingroup$


        Cuckoo asked: So it appears that the force of gravity is indeed
        directed towards the current orbital position of Earth, without
        accounting for the delay caused by the speed of light. How is this
        possible?




        If the motion is straight or circular the aberration cancels out, see Steve Carlip: Aberration and the Speed of Gravity:




        Steven Carlip wrote: The observed absence of gravitational
        aberration requires that "Newtonian'' gravity propagates at a speed
        ς>2×10¹⁰c. By evaluating the gravitational effect of an accelerating
        mass, I show that aberration in general relativity is almost exactly
        canceled by velocity-dependent interactions, permitting ς=c. This
        cancellation is dictated by conservation laws and the quadrupole
        nature of gravitational radiation.




        or to quote the Wikipedia article on the subject:




        Wikipedia wrote: Two gravitoelectrically interacting particle
        ensembles, e.g., two planets or stars moving at constant velocity with
        respect to each other, each feel a force toward the instantaneous
        position of the other body without a speed-of-light delay because
        Lorentz invariance demands that what a moving body in a static field
        sees and what a moving body that emits that field sees be symmetrical.
        In other words, since the gravitoelectric field is, by definition,
        static and continuous, it does not propagate.







        share|cite|improve this answer









        $endgroup$













        • $begingroup$
          I would be thankful for any comments on my answer below. I kind of made an interpretation of your answer, but I'm not sure I said everything correctly.
          $endgroup$
          – Elias Riedel Gårding
          2 hours ago
















        3












        $begingroup$


        Cuckoo asked: So it appears that the force of gravity is indeed
        directed towards the current orbital position of Earth, without
        accounting for the delay caused by the speed of light. How is this
        possible?




        If the motion is straight or circular the aberration cancels out, see Steve Carlip: Aberration and the Speed of Gravity:




        Steven Carlip wrote: The observed absence of gravitational
        aberration requires that "Newtonian'' gravity propagates at a speed
        ς>2×10¹⁰c. By evaluating the gravitational effect of an accelerating
        mass, I show that aberration in general relativity is almost exactly
        canceled by velocity-dependent interactions, permitting ς=c. This
        cancellation is dictated by conservation laws and the quadrupole
        nature of gravitational radiation.




        or to quote the Wikipedia article on the subject:




        Wikipedia wrote: Two gravitoelectrically interacting particle
        ensembles, e.g., two planets or stars moving at constant velocity with
        respect to each other, each feel a force toward the instantaneous
        position of the other body without a speed-of-light delay because
        Lorentz invariance demands that what a moving body in a static field
        sees and what a moving body that emits that field sees be symmetrical.
        In other words, since the gravitoelectric field is, by definition,
        static and continuous, it does not propagate.







        share|cite|improve this answer









        $endgroup$













        • $begingroup$
          I would be thankful for any comments on my answer below. I kind of made an interpretation of your answer, but I'm not sure I said everything correctly.
          $endgroup$
          – Elias Riedel Gårding
          2 hours ago














        3












        3








        3





        $begingroup$


        Cuckoo asked: So it appears that the force of gravity is indeed
        directed towards the current orbital position of Earth, without
        accounting for the delay caused by the speed of light. How is this
        possible?




        If the motion is straight or circular the aberration cancels out, see Steve Carlip: Aberration and the Speed of Gravity:




        Steven Carlip wrote: The observed absence of gravitational
        aberration requires that "Newtonian'' gravity propagates at a speed
        ς>2×10¹⁰c. By evaluating the gravitational effect of an accelerating
        mass, I show that aberration in general relativity is almost exactly
        canceled by velocity-dependent interactions, permitting ς=c. This
        cancellation is dictated by conservation laws and the quadrupole
        nature of gravitational radiation.




        or to quote the Wikipedia article on the subject:




        Wikipedia wrote: Two gravitoelectrically interacting particle
        ensembles, e.g., two planets or stars moving at constant velocity with
        respect to each other, each feel a force toward the instantaneous
        position of the other body without a speed-of-light delay because
        Lorentz invariance demands that what a moving body in a static field
        sees and what a moving body that emits that field sees be symmetrical.
        In other words, since the gravitoelectric field is, by definition,
        static and continuous, it does not propagate.







        share|cite|improve this answer









        $endgroup$




        Cuckoo asked: So it appears that the force of gravity is indeed
        directed towards the current orbital position of Earth, without
        accounting for the delay caused by the speed of light. How is this
        possible?




        If the motion is straight or circular the aberration cancels out, see Steve Carlip: Aberration and the Speed of Gravity:




        Steven Carlip wrote: The observed absence of gravitational
        aberration requires that "Newtonian'' gravity propagates at a speed
        ς>2×10¹⁰c. By evaluating the gravitational effect of an accelerating
        mass, I show that aberration in general relativity is almost exactly
        canceled by velocity-dependent interactions, permitting ς=c. This
        cancellation is dictated by conservation laws and the quadrupole
        nature of gravitational radiation.




        or to quote the Wikipedia article on the subject:




        Wikipedia wrote: Two gravitoelectrically interacting particle
        ensembles, e.g., two planets or stars moving at constant velocity with
        respect to each other, each feel a force toward the instantaneous
        position of the other body without a speed-of-light delay because
        Lorentz invariance demands that what a moving body in a static field
        sees and what a moving body that emits that field sees be symmetrical.
        In other words, since the gravitoelectric field is, by definition,
        static and continuous, it does not propagate.








        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered 3 hours ago









        YukterezYukterez

        4,47911135




        4,47911135












        • $begingroup$
          I would be thankful for any comments on my answer below. I kind of made an interpretation of your answer, but I'm not sure I said everything correctly.
          $endgroup$
          – Elias Riedel Gårding
          2 hours ago


















        • $begingroup$
          I would be thankful for any comments on my answer below. I kind of made an interpretation of your answer, but I'm not sure I said everything correctly.
          $endgroup$
          – Elias Riedel Gårding
          2 hours ago
















        $begingroup$
        I would be thankful for any comments on my answer below. I kind of made an interpretation of your answer, but I'm not sure I said everything correctly.
        $endgroup$
        – Elias Riedel Gårding
        2 hours ago




        $begingroup$
        I would be thankful for any comments on my answer below. I kind of made an interpretation of your answer, but I'm not sure I said everything correctly.
        $endgroup$
        – Elias Riedel Gårding
        2 hours ago











        1












        $begingroup$

        No, gravitational influences never travel faster than the speed of light. However, a naive incorporation of a speed-of-gravity delay would actually lead to the Earth's orbital motion speeding up, not slowing down. (Think about the geometry carefully.) I explained here why that doesn't actually happen in general relativity.






        share|cite|improve this answer









        $endgroup$


















          1












          $begingroup$

          No, gravitational influences never travel faster than the speed of light. However, a naive incorporation of a speed-of-gravity delay would actually lead to the Earth's orbital motion speeding up, not slowing down. (Think about the geometry carefully.) I explained here why that doesn't actually happen in general relativity.






          share|cite|improve this answer









          $endgroup$
















            1












            1








            1





            $begingroup$

            No, gravitational influences never travel faster than the speed of light. However, a naive incorporation of a speed-of-gravity delay would actually lead to the Earth's orbital motion speeding up, not slowing down. (Think about the geometry carefully.) I explained here why that doesn't actually happen in general relativity.






            share|cite|improve this answer









            $endgroup$



            No, gravitational influences never travel faster than the speed of light. However, a naive incorporation of a speed-of-gravity delay would actually lead to the Earth's orbital motion speeding up, not slowing down. (Think about the geometry carefully.) I explained here why that doesn't actually happen in general relativity.







            share|cite|improve this answer












            share|cite|improve this answer



            share|cite|improve this answer










            answered 1 hour ago









            tparkertparker

            22.9k147122




            22.9k147122























                0












                $begingroup$

                Think of the gravitational field as curved space. Like a bump in space time. This bump will stay constant over time more or less. The planet then just looks at the bump and moves accordingly. However if the sun were to explode it might cause a small ripple in spacetime that would reach the earth in 8 minutes






                share|cite|improve this answer









                $endgroup$


















                  0












                  $begingroup$

                  Think of the gravitational field as curved space. Like a bump in space time. This bump will stay constant over time more or less. The planet then just looks at the bump and moves accordingly. However if the sun were to explode it might cause a small ripple in spacetime that would reach the earth in 8 minutes






                  share|cite|improve this answer









                  $endgroup$
















                    0












                    0








                    0





                    $begingroup$

                    Think of the gravitational field as curved space. Like a bump in space time. This bump will stay constant over time more or less. The planet then just looks at the bump and moves accordingly. However if the sun were to explode it might cause a small ripple in spacetime that would reach the earth in 8 minutes






                    share|cite|improve this answer









                    $endgroup$



                    Think of the gravitational field as curved space. Like a bump in space time. This bump will stay constant over time more or less. The planet then just looks at the bump and moves accordingly. However if the sun were to explode it might cause a small ripple in spacetime that would reach the earth in 8 minutes







                    share|cite|improve this answer












                    share|cite|improve this answer



                    share|cite|improve this answer










                    answered 3 hours ago









                    zoobyzooby

                    1,319514




                    1,319514























                        0












                        $begingroup$

                        I was going to write an incorrect answer at first, but having researched a bit
                        what Yukterez wrote, I think I may be able to offer some intuition.



                        First, let's look at the solar system in the centre-of-mass frame, where the
                        Sun is essentially stationary in the middle. Here, the force on the Earth is
                        directed towards the Sun's position 8 minutes ago, which conveniently is the
                        same as its current position. So this doesn't affect the Earth's position in
                        the way you say.



                        If the Sun and Earth were moving at a constant velocity to each other, they
                        would, like Yukterez wrote, still be attracted to the instantaneous position of
                        the other body. This is not because of a faster-than-light influence, but
                        because gravity is more than a simple attractive force between objects
                        (analogous to the electric field in electromagnetism). For moving sources,
                        there are other components of the gravitational field (roughly analogous to the
                        magnetic field). You can view this as the force travelling at the speed of
                        light, but being directed towards the position of the source "predicted" based
                        on its past linear motion.



                        However, if the source is accelerating, like the Earth around the Sun, the
                        effects are less obvious. Then, you really can't view it only as an attractive
                        force towards any position (I think, correct me if I'm wrong), but you get
                        more complex things like gravitational waves. But still, nothing ever travels faster than
                        light.





                        As I am more familiar with electromagnetism, let's take an example from there.
                        If two oppositely charged bodies ($A$ and $B$) are moving with constant
                        velocity towards each other, we can view the system in the rest frame of $A$.
                        Here, it emits only a static electric field, given by the Coulomb formula, and
                        $B$ therefore feels an attraction directly towards it. In the rest frame of $B$,
                        this means that the attraction is towards the instantaneous position. But how
                        can this be since the electric field is propagating at a finite speed? The
                        answer is that since now $A$ is moving, it also emits a magnetic field. While
                        this doesn't affect $B$ directly (since $B$ is stationary here), it does affect
                        the electric field and makes it point in a different direction (towards the
                        instantaneous position).






                        share|cite|improve this answer









                        $endgroup$


















                          0












                          $begingroup$

                          I was going to write an incorrect answer at first, but having researched a bit
                          what Yukterez wrote, I think I may be able to offer some intuition.



                          First, let's look at the solar system in the centre-of-mass frame, where the
                          Sun is essentially stationary in the middle. Here, the force on the Earth is
                          directed towards the Sun's position 8 minutes ago, which conveniently is the
                          same as its current position. So this doesn't affect the Earth's position in
                          the way you say.



                          If the Sun and Earth were moving at a constant velocity to each other, they
                          would, like Yukterez wrote, still be attracted to the instantaneous position of
                          the other body. This is not because of a faster-than-light influence, but
                          because gravity is more than a simple attractive force between objects
                          (analogous to the electric field in electromagnetism). For moving sources,
                          there are other components of the gravitational field (roughly analogous to the
                          magnetic field). You can view this as the force travelling at the speed of
                          light, but being directed towards the position of the source "predicted" based
                          on its past linear motion.



                          However, if the source is accelerating, like the Earth around the Sun, the
                          effects are less obvious. Then, you really can't view it only as an attractive
                          force towards any position (I think, correct me if I'm wrong), but you get
                          more complex things like gravitational waves. But still, nothing ever travels faster than
                          light.





                          As I am more familiar with electromagnetism, let's take an example from there.
                          If two oppositely charged bodies ($A$ and $B$) are moving with constant
                          velocity towards each other, we can view the system in the rest frame of $A$.
                          Here, it emits only a static electric field, given by the Coulomb formula, and
                          $B$ therefore feels an attraction directly towards it. In the rest frame of $B$,
                          this means that the attraction is towards the instantaneous position. But how
                          can this be since the electric field is propagating at a finite speed? The
                          answer is that since now $A$ is moving, it also emits a magnetic field. While
                          this doesn't affect $B$ directly (since $B$ is stationary here), it does affect
                          the electric field and makes it point in a different direction (towards the
                          instantaneous position).






                          share|cite|improve this answer









                          $endgroup$
















                            0












                            0








                            0





                            $begingroup$

                            I was going to write an incorrect answer at first, but having researched a bit
                            what Yukterez wrote, I think I may be able to offer some intuition.



                            First, let's look at the solar system in the centre-of-mass frame, where the
                            Sun is essentially stationary in the middle. Here, the force on the Earth is
                            directed towards the Sun's position 8 minutes ago, which conveniently is the
                            same as its current position. So this doesn't affect the Earth's position in
                            the way you say.



                            If the Sun and Earth were moving at a constant velocity to each other, they
                            would, like Yukterez wrote, still be attracted to the instantaneous position of
                            the other body. This is not because of a faster-than-light influence, but
                            because gravity is more than a simple attractive force between objects
                            (analogous to the electric field in electromagnetism). For moving sources,
                            there are other components of the gravitational field (roughly analogous to the
                            magnetic field). You can view this as the force travelling at the speed of
                            light, but being directed towards the position of the source "predicted" based
                            on its past linear motion.



                            However, if the source is accelerating, like the Earth around the Sun, the
                            effects are less obvious. Then, you really can't view it only as an attractive
                            force towards any position (I think, correct me if I'm wrong), but you get
                            more complex things like gravitational waves. But still, nothing ever travels faster than
                            light.





                            As I am more familiar with electromagnetism, let's take an example from there.
                            If two oppositely charged bodies ($A$ and $B$) are moving with constant
                            velocity towards each other, we can view the system in the rest frame of $A$.
                            Here, it emits only a static electric field, given by the Coulomb formula, and
                            $B$ therefore feels an attraction directly towards it. In the rest frame of $B$,
                            this means that the attraction is towards the instantaneous position. But how
                            can this be since the electric field is propagating at a finite speed? The
                            answer is that since now $A$ is moving, it also emits a magnetic field. While
                            this doesn't affect $B$ directly (since $B$ is stationary here), it does affect
                            the electric field and makes it point in a different direction (towards the
                            instantaneous position).






                            share|cite|improve this answer









                            $endgroup$



                            I was going to write an incorrect answer at first, but having researched a bit
                            what Yukterez wrote, I think I may be able to offer some intuition.



                            First, let's look at the solar system in the centre-of-mass frame, where the
                            Sun is essentially stationary in the middle. Here, the force on the Earth is
                            directed towards the Sun's position 8 minutes ago, which conveniently is the
                            same as its current position. So this doesn't affect the Earth's position in
                            the way you say.



                            If the Sun and Earth were moving at a constant velocity to each other, they
                            would, like Yukterez wrote, still be attracted to the instantaneous position of
                            the other body. This is not because of a faster-than-light influence, but
                            because gravity is more than a simple attractive force between objects
                            (analogous to the electric field in electromagnetism). For moving sources,
                            there are other components of the gravitational field (roughly analogous to the
                            magnetic field). You can view this as the force travelling at the speed of
                            light, but being directed towards the position of the source "predicted" based
                            on its past linear motion.



                            However, if the source is accelerating, like the Earth around the Sun, the
                            effects are less obvious. Then, you really can't view it only as an attractive
                            force towards any position (I think, correct me if I'm wrong), but you get
                            more complex things like gravitational waves. But still, nothing ever travels faster than
                            light.





                            As I am more familiar with electromagnetism, let's take an example from there.
                            If two oppositely charged bodies ($A$ and $B$) are moving with constant
                            velocity towards each other, we can view the system in the rest frame of $A$.
                            Here, it emits only a static electric field, given by the Coulomb formula, and
                            $B$ therefore feels an attraction directly towards it. In the rest frame of $B$,
                            this means that the attraction is towards the instantaneous position. But how
                            can this be since the electric field is propagating at a finite speed? The
                            answer is that since now $A$ is moving, it also emits a magnetic field. While
                            this doesn't affect $B$ directly (since $B$ is stationary here), it does affect
                            the electric field and makes it point in a different direction (towards the
                            instantaneous position).







                            share|cite|improve this answer












                            share|cite|improve this answer



                            share|cite|improve this answer










                            answered 2 hours ago









                            Elias Riedel GårdingElias Riedel Gårding

                            35318




                            35318






























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