another newbie question - what is the current understanding of what inertia is? ie, what is it that provides resistance to acceleration?
Lorentz said:Why is there even a need for the law of inertia? I thought of it and within classical Physics I don't see the need of the concept inertia at all.
I like your idea here. I have a similar problem with the inertia definition. It does not seem usable and that makes me think it is incomplete. I think that the problem starts with the classical thinking that all force applied to a body goes into kinetic energy. (Of course, some converts to a mass equivalent according to relativity, but this is a small amount.). How do we know that some of the energy is not going into some other type of energy, let's say just its "inertial content". Like balancing thermodynamic energies of various types this may be a reservoir of "formation energy" that has to do with the energy of the mass that holds the object together as one mass. So we should think of it as the force of acceleration is being split between the two energy reservoirs: Kinetic and formation, and so wonder what the rule of this conservation is.
I say this because we look at Galileo's conclusion from the ramp experiment as the inductive leap that started the inertia idea. His conclusion was that the ball rolling down a ramp onto a flat surface must continue on forever at the same velocity if all opposing forces were removed. Classical energy theorem analysis agrees. But why should we believe the ball will go forever. Only a finite amount of energy was tranferred to the ball. Why would that transfer a constant mass (due to relativity - the small amount) and also a kinetic energy over all time without ever being spent. How do we know the ball won't start slowing down eventually? We believe it will only receive a finite velocity with a given force, why then should it have that finite velocity for infinite time? Wouldn't the energy that provided the impulse radiate away slightly over time?
Scientists are looking at the Pioneer 10 mission and saying that the probe started slowing when it went past jupiter (Discover, Oct 2003). It was getting further from any gravitational pull, especially from the sun. It should have been at a final constant speed and there was no gravitational source to slow it. So scientists are looking at dark energy that is being used to explain the same problem with expanding galaxies. However some are looking to modified newtonian dynamics (MOND) and saying the Newton's standard law is not valid at extremes of "low acceleration". But I think it may be that we have to rethink the inertia idea.