11–20 of 125 posts
> If it is spinning extremely rapidly, the gyroscope remains rigidly locked in the direction it has been set, its sights fixed on...Kiev—hence the term inertial guidance systems. This is clearly false... right? If you translate the gyroscope, it won't be pointing at Kiev anymore, it will be pointing to the side of Kiev. The gyroscope doesn't magically point at a target, it provides a stable reference direction that t…
Anyone know of (or want to give) a clear explanation of how gyros behave? I found the article to be unclear on a number of points. I was also unclear on this: "The first triumph of general relativity was its exact prediction of the orbital precession of Mercury’s perihelion" —does a perihelion precess? I thought it was the planet which was precessing and the perihelion shifted (changing the shape of the planet's orbi…
The faster the gyro spins, the less important the imparted velocity will be relative to the particle's speed, which is why a gyro is more stable the faster it spins.
Anyone know of (or want to give) a clear explanation of how gyros behave? I found the article to be unclear on a number of points. I was also unclear on this: "The first triumph of general relativity was its exact prediction of the orbital precession of Mercury’s perihelion" —does a perihelion precess? I thought it was the planet which was precessing and the perihelion shifted (changing the shape of the planet's orbi…
Classically, you would expect the shape and position/rotation of the orbit to be constant. In reality, its rotation in the orbital plane changes due to GR.
Maybe I'm wrong but it's wrong to say we don't know how a gyro works. We can accurately and precisely predict the behavior of a gyro, derive the mathematical equations necessary and the model we use is general for all moving objects. This is the greatest level of knowing you can have. Maybe the author meant that a gyro's motion is not intuitive to most humans. That I can agree with. For me, even the fact that my smar…
In this case it sounds like we've derived an algorithm that relates to the inputs and outputs, but the inputs that cause the formula itself are unknown.
My understanding is that if you go far enough back a lot of physics is like this, but it sounds like we can't even go very far back here.
Maybe I'm wrong but it's wrong to say we don't know how a gyro works. We can accurately and precisely predict the behavior of a gyro, derive the mathematical equations necessary and the model we use is general for all moving objects. This is the greatest level of knowing you can have. Maybe the author meant that a gyro's motion is not intuitive to most humans. That I can agree with. For me, even the fact that my smar…
We can predict the behavior of a gyro but there is still a fundamental question of what a gyro is relative to since GR tells us there is no universal reference frame. Are gyroscopes entirely local or does the gravity of distant galaxies present a sort of universal reference frame? Or is it something else entirely?
Anyone know of (or want to give) a clear explanation of how gyros behave? I found the article to be unclear on a number of points. I was also unclear on this: "The first triumph of general relativity was its exact prediction of the orbital precession of Mercury’s perihelion" —does a perihelion precess? I thought it was the planet which was precessing and the perihelion shifted (changing the shape of the planet's orbi…
My (undergraduate) understanding of the precession of the orbit of Mercury is that the longitude of the periapsis in Sun coordinates changes over time. The shape of the orbit stays the same, unless maybe it's changed a bit by perturbations from the outer planets. Classically, you would expect the shape and position/rotation of the orbit to be constant. In reality, its rotation in the orbital plane changes due to GR.
My understanding of precession is that there are two levels of rotation: an object rotating on some axis A, with axis A rotating around another axis B. So in the case of the perihelion precessing, what would be the corresponding parts? I was assuming the only precession taking place was of Mercury itself because the axis it rotates on (axis A) rotates about some other B axis.
Edit: to clarify, if the above is a correct description of precession, then in order for the perihelion itself to precess it would need to be rotating, and the axis it's rotating about would need to be rotating about another axis. My understanding is that neither the perihelion nor the orbit are rotating, so they can't be precessing.
Maybe I'm wrong but it's wrong to say we don't know how a gyro works. We can accurately and precisely predict the behavior of a gyro, derive the mathematical equations necessary and the model we use is general for all moving objects. This is the greatest level of knowing you can have. Maybe the author meant that a gyro's motion is not intuitive to most humans. That I can agree with. For me, even the fact that my smar…
In physics (and in many other areas) it is unsatisfying to wave your hands and say "it is so because our measurements prove it". A theoretical model that explains why the measurements come out the way they do is far more valuable because it leads to other insights. We can predict the behavior of a gyro but there is still a fundamental question of what a gyro is relative to since GR tells us there is no universal refe…
Something else entirely. You don't need other galaxies or a universal reference frame. Even if the gyroscope were the only thing in the universe, it would be easy to tell if it were spinning: a very tiny person standing on the inside rim would be held down if it were spinning, or free floating if it were not.
https://www.youtube.com/watch?v=e7LcmWiclOs
It just reinforces the (incorrect?) intuition that spacetime is "something" rather than nothingness between things. Why can't motion be relative to spacetime rather than other objects?
Earlier quoted context omitted.
In physics (and in many other areas) it is unsatisfying to wave your hands and say "it is so because our measurements prove it". A theoretical model that explains why the measurements come out the way they do is far more valuable because it leads to other insights. We can predict the behavior of a gyro but there is still a fundamental question of what a gyro is relative to since GR tells us there is no universal refe…
> Are gyroscopes entirely local or does the gravity of distant galaxies present a sort of universal reference frame? Or is it something else entirely? Something else entirely. You don't need other galaxies or a universal reference frame. Even if the gyroscope were the only thing in the universe, it would be easy to tell if it were spinning: a very tiny person standing on the inside rim would be held down if it were s…
So there was the animation that Caltech put out today or yesterday of the neutron star collision that was just detected, and it visualized gravitational waves moving outward from the stars: https://www.youtube.com/watch?v=e7LcmWiclOs It just reinforces the (incorrect?) intuition that spacetime is "something" rather than nothingness between things. Why can't motion be relative to spacetime rather than other objects?