One of those ever accessible curiosities: objects in motion tend to stay in motion, objects at rest tend to stay at rest. We've heard it countless times, yet, while it explains the force pulling our bodies in a swerving car or how the sweeping curves of the planets counteract the Sun's gravity, it's a profound mystery why such a rule exists at all. What would we see sitting in a windowless box that, from outside, is being obviously accelerated in some direction, perhaps by rockets? From the outside, any untethered objects within the box would, following the law of inertia, remain at a constant speed as the box accelerated "up" to them. Inside, the objects appear to fall down, and though more massive objects are harder to restrain (f=ma), the objects all move "down" with the same acceleration. The situation is exactly the same as being "at rest" in a gravitational field. This is, as many of you know, the equivalence principle formulated by Einstein. The question then arises, if inertial forces can be considered gravitational in origin, and gravitational forces originate in clumps of matter, from what clumps of matter do inertial forces originate? Ernst Mach imagined the fixed stars. You look out on a clear night, the stars standing in the sky, your arms at rest against your sides. . . but, suddenly, the stars begin to whirl around you, making impossible circles at tremendous speeds, your arms are pulled out from your sides. The law of inertia, as stated in the familiar formulation I mentioned at the start, would produce the above situation if you were to go out under the stars and spin, your body accelerating and pulling your arms out. Mach claims that instead of spinning your body, setting the stars in motion about your body results in the same effect. "Fixed stars," of course, refers simply to all the distant matter of the Milky Way and galaxies beyond. In fact, the further "shells" of space you imagine around you, the more matter they contain as well as having greater circles to make around you. What do you guys think? I think its a very appealing idea, not only for the beautiful symmetry involved, but also, as the last paragraph explains, the more distant and intangible parts of the universe have the biggest effect on our local inertia. It makes me wonder how many other properties and laws for our microcosm depend so sensitively on the megacosm.
Gravity is inherent in the fabric of the quantum field. It isn't made by matter, matter responds to it. If you put a man in a swimming pool he gets wet, he hasn't made wetness by his presence in the pool. MelT
Maybe I should better explain: the rules governing the electromagnetic force include electrostatic forces as well as an extra force produced by charges that are accelerating. This force is magnetism. What Mach essentially proposes is that gravitational "charges"(a.k.a masses) also produce an additional force besides their static gravitational force, a sort of gravitomagnetic force. This force is what we experience as inertia. The force is miniscule considering individual objects, which is why the relative motion of the walls of a spinning bucket seem to have no effect on the surface of the water therein contained; the water can inertially climb the walls as the bucket spins, spinning the water with it, but here there is no relative motion between the bucket and water, but later the bucket has stopped spinning while the water goes on and yet even with this change in their relative motions the inertia is not effected. Even later, the water has stopped spinning and there is again no motion between the walls and water, but this time there are no inertial effects! Mach's idea resolves this puzzling situation. For when the water spins in our bucket, from its perspective the entire universe appears to accelerate around it, producing a noticeable gravitomagnetic, or inertial, force. While it seems this force may be infinite, if the universe is so, but there can be a sort of gravitational Doppler effect when taking the recession of the universe into account that can ensure a finite force.
In this case, can accelerating matter be supposed to produce an additional response in the quantum field?
I know what you're saying. I'm saying that I don't agree with Mach's conclusion. Inertia and gravity are not the result of matter, but an effect that matter induces. Just as theoretical as Mach, obviously.. MelT
Oh, alright, I don't think this idea is truth if that's what it sounds like lol, its pretty interesting though. My first objection would be: does this inertial force have to travel at the speed of light to effect an object? If so, then I think that would put an end to the speculation, but then I think, well, it's not an inertial frame in the first place, so does that even apply?
I wonder if the gaps between those fibrous structures, made of galaxies and galaxy clusters, would be wide and empty enough to have an effect on an area's local inertia. If we could travel in their vicinity or within them, maybe Mach's assertion would be testable.
Acceleration always affects matter and the space/quantum field it moves through, it can't not. You get wet at all speeds in a swimming pool. What do you personally mean by inertial force? MelT
Its not that I was doubting lol; only Mach's conjecture that the effect comes from a sort of gravitomagnetic force from distant gravitational fields, thats what I have no certainty of. I imagine that from inertial frames objects obey the usual law of inertia, bur from the accelerated frame this appears as a force, akin to gravity as Einstein noted. I'd love for that to be elaborated on though, since you seem to have serious objections to Mach's speculation. I want this thread to really develop the idea of inertia though, it's one of the most interesting phenomenon I know of.