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The Forgotten Mystery of Inertia

americanscientist.org

1–10 of 125 posts

Re: The Forgotten Mystery of Inertia

#5
Is Mach's principle related to equivalence principle? It's so strange that inertia mass just so happens to be exactly the same as gravitational mass.

Can Mach's principle and equivalence principle be derived from some more fundamental laws or are they accepted as axioms?

Re: The Forgotten Mystery of Inertia

#6
> 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 the rest of the IGS can compute its deviation from, to adjust its course.

Re: The Forgotten Mystery of Inertia

#7
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 orbit?)

Also, I came across this (seemingly) related gem the other day: ("Why is Linear Motion Relative but Rotation Absolute?") https://www.quora.com/Why-is-linear-motion-relative-but-rota...

Re: The Forgotten Mystery of Inertia

#9
post #6

> 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…

He elides the inner workings of an inertial guidance system because it's not really necessary. The point is that the gyroscope provides an absolute reference point, which seems weird in the face of relativity.

Re: The Forgotten Mystery of Inertia

#10
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 smartphone is performing billions of calculations every second is non-intuitive. Doesn't mean I don't know how it works.

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