Matter and Inertia

[timetraveldude]

Consider this thought experiment. If only one object existed in all the universe and it was moving would it have inertia?

[JohnDubYa]

It has inertia regardless of whether or not it was moving. Inertia is not a function of speed.

[krab]

Consider this thought experiment. If only one object existed in all the universe and it was moving would it have inertia?
If it was just one object, you would not be able to define movement. So the question is improper. A more interesting question is If there was one object plus yourself as observer, would both of you have inertia?

[timetraveldude]

It has inertia regardless of whether or not it was moving. Inertia is not a function of speed.
The question is more about what is the cause of inertia.

[timetraveldude]

If it was just one object, you would not be able to define movement. So the question is improper. A more interesting question is If there was one object plus yourself as observer, would both of you have inertia?That is true but given the fact that you can't define motion does an object completely isolated have inertia?

[Pergatory]

Inertia requires a frame of reference. If your frame of reference includes this object at rest, then the object will have no inertia in that frame. If your frame of reference has the object in motion, then the object has inertia in that frame.

[TALewis]

Inertia requires a frame of reference. If your frame of reference includes this object at rest, then the object will have no inertia in that frame. If your frame of reference has the object in motion, then the object has inertia in that frame.

Isn't that describing momentum? I thought inertia and momentum were different things.

Inertia is an object's resistance to a change in its state of motion. To my understanding, mass is a measure of inertia. If your object has mass, then it has inertia, whether it is at rest or not. Zero momentum is not equivalent to zero inertia.

[Pergatory]

I'm sorry, you're right, for some reason I always have those two switched in my mind. The object will always have inertia regardless of whether it is in motion or not. Of course, without an understanding of our own universe, we would never know it has inertia because no external forces would act upon it. However, we know it would still have inertia because if some force WERE to suddenly act upon it, it would exert equal and opposite forces to oppose its acceleration.

[timetraveldude]

I'm sorry, you're right, for some reason I always have those two switched in my mind. The object will always have inertia regardless of whether it is in motion or not. Of course, without an understanding of our own universe, we would never know it has inertia because no external forces would act upon it. However, we know it would still have inertia because if some force WERE to suddenly act upon it, it would exert equal and opposite forces to oppose its acceleration.The question remains does the object I described have inertia?

[Pergatory]

The question remains does the object I described have inertia?
If your object has mass, then it has inertia, whether it is at rest or not.

You have answered your own question. By isolating the object, you only ensure that no forces will act upon it. You are nullifying the effect of inertia because how can an object resist zero change? However, nullifying inertia does not eliminate inertia. If some force in the future should act upon that object, inertia will again spring into action. As long as the object has mass and is governed by physics as we know, it will always have inertia.

Allow me to draw an analogy: If you slack all tension in a rubber-band and set it on a table, is the rubber-band still elastic?

[Gokul43201]

If it has mass, it has inertia.

[timetraveldude]

If it has mass, it has inertia.If motion is not defined [for the object] how can inertia be defined?

[Gokul43201]

If some internal reaction within the object causes it to divide into two or more parts, then the velocities of these parts (in the frame of the mother object - the bomb) is inversely related to their inertias. These parts could recombine (because they are oppositely charged ?) and re-form into the mother object, which then has velocity in the frame of one of the sub-parts.

[Integral]

It is not clear to me that Physics, which was created to model our multi-particle universe, has anything meaningful to say about such a non physical universe. Non Physical assumptions lead to no meaningful results.

[timetraveldude]

If some internal reaction within the object causes it to divide into two or more parts, then the velocities of these parts (in the frame of the mother object - the bomb) is inversely related to their inertias. These parts could recombine (because they are oppositely charged ?) and re-form into the mother object, which then has velocity in the frame of one of the sub-parts.Stick to the topic there is nothing mentioned about dividing. Just answer the question.

[timetraveldude]

It is not clear to me that Physics, which was created to model our multi-particle universe, has anything meaningful to say about such a non physical universe. Non Physical assumptions lead to no meaningful results.I understand and agree with your point. What I am trying to do is build up an idea based on this hypothetical situation that will eventually have some physical meaning.

[Pergatory]

If motion is not defined [for the object] how can inertia be defined?

Why is motion a requisite for inertia? You said yourself that if the object has mass, it has inertia. This is the only requisite. Motion is merely a matter of the frame of reference. Inertia exists independant of a frame of reference. To say that an isolated object would not have inertia is to say that an isolated object would not have mass.

I can tell you are trying to lead us somewhere with this and not having much luck. Why don't you just come out and say what you're trying to say?

[timetraveldude]

Why is motion a requisite for inertia? You said yourself that if the object has mass, it has inertia. This is the only requisite. Motion is merely a matter of the frame of reference. Inertia exists independant of a frame of reference. To say that an isolated object would not have inertia is to say that an isolated object would not have mass.

I can tell you are trying to lead us somewhere with this and not having much luck. Why don't you just come out and say what you're trying to say?I'm not trying to lead you somewhere. I am trying to get a discussion going.

Inertia is resistance to change in motion. If motion is not defined how can resistance to change in motion be defined?

[Pergatory]

If no current is going through a wire, does it still have resistance?

If a tree falls in the woods, and on one is around to hear it...

[timetraveldude]

If no current is going through a wire, does it still have resistance?

If a tree falls in the woods, and on one is around to hear it...You examples do not apply. You have confused current not being present in a particular place with the non-existence of current anywhere. Resistance still exists in the wire because you could apply a current to it. As far as the second example goes that is just a stupid question. If you are not going to ask adult questions then leave.

[Gokul43201]

If your object is going to be sitting about in space doing nothing (it's not allowed to blow up and give rise to anything useful) why bother talking about it. There's nothing happening there. What's to talk about ? Chuck momentum, time, energy, temperature, color, etc. out the window. They are all meaningless. Why just 'inertia' ?

And 'inertia' is not a physical quantity. It is an archaic term that is now loosely used by people who are afraid of using real physical terms.

If you're not there in this universe with your lonely object, how do you know it's there? And if this is some hypothetical universe, why stick with our existing framwork of physics. But if you do, then what caused this abject to be in its current state - did it result from a uniform distribution of particles that gravitationally condensed onto your object ? There are so many more pertinent questions to ask that "does it have inertia?"

And finally, is this object rotating ? If not, I've got more things to chuck out the window...

[Pergatory]

You examples do not apply. You have confused current not being present in a particular place with the non-existence of current anywhere. Resistance still exists in the wire because you could apply a current to it. As far as the second example goes that is just a stupid question. If you are not going to ask adult questions then leave.

Don't get condescending on me. Your question is philosophical, not scientific. It's trivial. It's no different from the questions I have asked. You are asking whether something exists when it cannot be measured, and its effects are non-existant. No one will ever be able to answer your question with certainty because your scenario is, as Integral pointed out, non-physical. If your understanding is lacking such that you cannot see the connection between your question and mine, that gives you no right to insult my responses.

[NateTG]

If you are not going to ask adult questions then leave.
His question makes as much sense as yours.

The object's inertia is equal to \frac{0}{0}

[pallidin]

I find the question interesting, and somewhat of a paradox.
In a universe devoid of all matter except for a single mass object, the object cannot be "moving" because it is moving relative to nothing, unless one defines "boundaries" of the universe; thus establishing a frame of referance.
Also, does that object have a "changing position" at any given time, with respect to that devoid universe? If the "universe" is considered "eternally" extensive, the answer is no, as position is meaningless in an eternal environment.
If you have an infinite yardstick, such that both ends continue to infinity, can one mark two segments separate from each another? One might think yes, but infinity cannot be divided, thus discreet separation is not possible.
Movement, per say, requires separation of identity locality and this is not possible in an infinite universe.
Thus, your object cannot move, and so cannot ever experience the attributes of inertia.

[Gokul43201]

...If you have an infinite yardstick, such that both ends continue to infinity, can one mark two segments separate from each another? One might think yes, but infinity cannot be divided, thus discreet separation is not possible.

What is the set of integers if not such a yardstick. So do you not have distict integers in this set ? Is this infinite yardstick not divided into finite segments ?

[pallidin]

What is the set of integers if not such a yardstick. So do you not have distict integers in this set ? Is this infinite yardstick not divided into finite segments ?

Infinity cannot be segmented, else the concept of infinity is of no effect.

[pallidin]

An infinite yardstick will curve upon itself, thus having no "ends". Being an infinite extension, this "curving upon itself" will continue again and again without end.
Thus, what happens is that if you mark 2 separate points on that infinite yardstick, the multiple curvings will "blur" any distinction between the two, so much so that the "blurring" encompasses the entire infinite yardstick, and the "2 separate marks" become one with infinity!

[Gokul43201]

You state this as if it counters my objection. How do you resolve the conflict between your statement and my example ?

What do you mean by "infinity", "segmented", and "of no effect" ? Could you clarify using mathematical terms instead of vagaries.

EDIT : I retract above questions (though my first is still unanswered), and would like to replace them with others, but some other time...don't have the energy for this banter.

[pallidin]

Given the nature of the concept of "infinity", mathematical expression is hard pressed with valid extensions.
Thus I can offer none but the most foundational and, argurably, useless, as the concept of infinity is as different as quantum mechanics is to classical.

[krab]

Look up Mach's Principle. According to which an object's inertia depends upon all the other mass in the universe. It is not falsifiable, so strictly not in the domain of physics. But this line of thinking did led Einstein to the General Theory of Relativity.

[Michael F. Dmitriyev]

Consider this thought experiment. If only one object existed in all the universe and it was moving would it have inertia?
If you speak a word "universe" then it means existence of all attributes inherent in it.
This is the space, time, gravitation, light and … at least one black hole in the center of this universe. Without each of this “component” existence of universe and object (mass) itself is impossible. Then, what is your question ?

[HallsofIvy]

Stick to the topic there is nothing mentioned about dividing. Just answer the question.

He did answer the question. You're just saying that you don't like the answer!

[Dina-Moe Hum]

I think Timetraveldude question is not well set. The only "unique object" possible is an elementar particle. In this case the question has no sense because there could never be inertial effects. To have it, we should demonstrate that it is not adimensional and it can rotate (not the quantistic spin, of course).

All other objects are formed by more than one particle, so there can be inertial effects.

I think I would probably used the following question instead: "Given a universe with just one elementar particle, the total energy of this universe is greater than zero?" and I think the anwer is "no"

[timetraveldude]

I think Timetraveldude question is not well set. The only "unique object" possible is an elementar particle. In this case the question has no sense because there could never be inertial effects. To have it, we should demonstrate that it is not adimensional and it can rotate (not the quantistic spin, of course).

All other objects are formed by more than one particle, so there can be inertial effects.

I think I would probably used the following question instead: "Given a universe with just one elementar particle, the total energy of this universe is greater than zero?" and I think the anwer is "no"Does this elementary particle you talk about have size?