How Does Energy Influence Our Understanding of Inertia?

[Andrew Mason]

LOL. At least I got a response to this very mundane question.
Okay. Here's my take on it followed by another related question. If I'm off by a lot, then someone please stop and correct me.


If I were to take an educated guess at the reason for Inertia, I suppose it has to do with conservation of Energy (never mind the underlying reason for that for a second). When force is applied to an object (mass) causing it to gain velocity, this Inertia is retained as long as the object doesn't encounter some other external force. I suppose in this sense, it makes perfect sense that an object in motion should stay in motion while at rest, it should stay at rest (speaking relative to any given frame of reference).

You are asking one of the most fundamantal questions in physics. You will not find a completely satisfactory answer but it is certainly a question worth asking.

The law of conservation of energy exists because there is inertia. So it may be backward to say that inertia is needed to preserve the law of conservation of energy.

Try asking the question this way? What would our universe look like if matter had no inertial?

Any amount of energy would make any amount of matter move at any speed (relativity sets a limit at the speed of light). Location would have no meaning. So our concept of distance and time is intimately associated with inertia. Energy is defined in terms of mass (inertia), distance and time so our concept of energy depends upon inertia. Ultimately, it is only because there is inertia that we can have any measure of the concepts of location or distance, speed, time and energy.

AM

 

[Yor_on]

So if gravity is the objects 'straight paths' through SpaceTime and momentum is that objects invariant mass times the velocity.
Then inertia is a measure of what 'resists/brake' it when the object changes its motion.

Inertia relates to the object 'traveling' and will be situated at the same place relative the object at all times.
Following that same 'easiest path' as our traveling object does.
We won't be able to measure it though, except when changing its motion.

And momentum relates to the object too, and will have a magnitude of 'force' even though we only will be able to measure it as a comparison between reference frames.

The only difference I see is that momentums 'force arrow' in spacetime will be decided/defined by the interaction between reference frames.
That is, it will be not existent until the interaction between reference frame comes into being.
But Inertias 'force arrow' will be defined by the geometric properties of spacetime even without any other reference frame.
And will be correlated as being at the same place, relative the objects velocity.
Is that correct?

 

[Landru]

When dealing with the concept of Inertia (Newton's First Law of motion), is there an explanation of why this is so or do we accept it for what it is based on observations and experiments? While realizing that asking for more and more underlying reasons can be recursive and has to stop somewhere, I was just wondering if Inertia was to be taken as a given.

You have to put energy into an object to give it inertia and when you take inertia away it will release energy so I think fundementaly it reduces to an expression of energy.

Since there is a limit to the amount of inertia something can have as it can't move faster than speed of light, you can't claim that inertia is purely referencial or relative. You can't claim a moving object has no energy up until it crashes into something, because it is always moving at some speed between a dead stop and the speed of light and in all cases it will give off energy once it bumps into something. An equation using Newtonian physics would regard inertia as referencial to a frame, like a car hitting a tree on a moving planet in a moving solar system, but in reality inertia can't be purely referencial.

 

[WaveJumper]

When dealing with the concept of Inertia (Newton's First Law of motion), is there an explanation of why this is so or do we accept it for what it is based on observations and experiments? While realizing that asking for more and more underlying reasons can be recursive and has to stop somewhere, I was just wondering if Inertia was to be taken as a given.

If you want to see the whole picture, you'll have to wait for the TOE. Hopefully, during our lifetime, we will be able to see what the most brilliant physicists of our time dub -- "read the mind of God".

 

[ThomasT]

When dealing with the concept of Inertia (Newton's First Law of motion), is there an explanation of why this is so or do we accept it for what it is based on observations and experiments? While realizing that asking for more and more underlying reasons can be recursive and has to stop somewhere, I was just wondering if Inertia was to be taken as a given.

I think of the underlying cause of inertia (a material object's resistance to changes in velocity) as the isotropic expansion of the universe.

If I were to take an educated guess at the reason for Inertia, I suppose it has to do with conservation of Energy (never mind the underlying reason for that for a second). When force is applied to an object (mass) causing it to gain velocity, this Inertia is retained as long as the object doesn't encounter some other external force. I suppose in this sense, it makes perfect sense that an object in motion should stay in motion while at rest, it should stay at rest (speaking relative to any given frame of reference).

The conservation of energy might not hold on the universal scale. There's no way to know of course, but if a finite (though incalculable and incomprehensible) amount of energy was imparted via some sort of 'big bang' event, and if the dominant form of this imparted energy is the kinetic energy of the isotropic expansion (the mother of all forms of energy), then it might be that this energy is dissipating and decreasing as the universe evolves toward equilibrium with whatever 'medium' it was created, and is expanding, in.

I would tend to go with some form of isotropic dark energy as the underlying cause, but this is pure speculation (and we know how dangerous that can be on these boards).

Any good natural philosopher is going to wonder, and speculate, about the cause(s) of intertia. I think your idea that it's directly linked to some form of isotropic dark energy makes sense. And, maybe this isotropic dark energy is the energy of the isotropic expansion.

I agree with you that it would seem that inertia is a necessary byproduct of an isotropically expanding universe. To take our general speculations a step further, maybe the universe is a humongous disturbance in some fundamental medium of unknowable structure. A universal wavefront isotropically expands toward equilibrium with this fundamental (perhaps nonparticulate) medium, and forms the boundary between this fundamental medium and the contents of the universe (a vast hierarchy of interacting particulate media) -- and our material world (our sensory perceptions) are interfaces between (superpositions of?)various interacting wave complexes (particulate media).

An interesting and perplexing thing about what's observed is the apparent existence of scale-specific organizing principles.

But maybe one day gravity, etc., will be understood in terms of wave mechanics, and as a necessary byproduct of the universal isotropic expansion.

Such a wave model, conceptually unifying and accounting for everything (including biological phenomena), would be, conceptually, quite simple -- but quite complex in its execution. It seems that actually constructing such a working model is beyond the capabilities of current physics.

Anyway, I think it's good to keep using our imaginations and speculating about things like the deep nature of inertia. It's an important step (as well as learning the mainstream scientific treatments of stuff) in developing new models and theories.

 

[jimgram]

There is a TOE that suggests that all "things" in the universe have a position. They (or it) simply exist, and there it is. There can't be a thing called 'motion' because that simply is a human invention to describe the relative position of two or more things. There obviously is no 'frame of reference' (another human invention), no 'absolute rest', and so forth. But for a thing to exist and be real, it resists any change in its position. Thus, we have the term 'inertia' that gives a quantity to that resistance. Then, we invented 'mass', because, on earth, things are more or less heavy. Mass = Inertia. When we begin describing two or more things in terms of their relationship to each other (I.E. 'motion'), then we invent the terms velocity, distance, and acceleration), and we re-define the term 'inertia' to make it a composite of 'mass' and velocity'.

If a 'thing' did not resist a change in its position then it would not be detectable nor could it influence any other thing. That would be the definition of 'non-existent'.

 

[Dogov]

An inertial property is "mechanical". In order to define an inertial property of matter further understanding of energy-mass relationships is needed. For example: When Einstein proposed that energy and matter were related by E=mc^2, he was defining energy related to the "momentum" of matter. The total "energy" associated with matter must be defined as "infinite". A mechanical property of inertia results from a "work" function of matter. In nature, there are no freeloaders. Anything that exists, works. Much discussion is needed to support this and can be found at www.geocities.com/dogov/inertia.htm .
Good Luck with your studies!
Gregg