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simond
05-06-02, 04:03 PM
I know what it is, but how does it come about?

ta
Simon

James R
05-07-02, 12:13 AM
It seems to be associated with mass.

We're not sure what causes mass yet. There was a theory concerning Higgs bosons, but they haven't been found yet, so it's still an open question.

05-07-02, 12:15 AM
Welcome to here.

simond
05-07-02, 02:52 AM
Originally posted by James R
It seems to be associated with mass.

We're not sure what causes mass yet. There was a theory concerning Higgs bosons, but they haven't been found yet, so it's still an open question.

Glad to have found this place :)

Yeah, I've heard of the higgs Boson - what energy levels is it expected to be found at?

But can inertia be explained without knowing what causes mass?

Inertia has bugged me for a while - looks like it's going to continue to ;)

cheers
Simon

Merlijn
05-07-02, 05:35 AM
Hi and welcome simond,
I have been thinking about that too. I fear I have too little knowledge of fundamental physics to come up with something constructive. The only thing I can think of is that inertia may be a property of space rather than of mass (in which case one may be able to explain inertia without knowing the cause of mass).

simond
05-07-02, 01:53 PM
Hi Merlijn

I'm realising that I probalby don't know what inertia is at all, appart from the standard newtonian definition.

looks like it pretty meaningless to ask the question if we don't know what mass is caused by.

hay ho.

regards
Simon

Merlijn
05-08-02, 09:57 AM
"I'm realising that I probalby don't know what inertia is at all, appart from the standard newtonian definition. "
same here. but it is very interesting thing.
so I appeal to all of those who have some more insight in fundaments of physics to contribute.

(Q)
05-08-02, 11:59 AM
Inertia is that quantity which is dependent upon mass, the more mass, the more inertia.

But as James R puts it, we don't know what causes mass. Therefore it would be highly speculative for anyone to suggest they might know what causes inertia.

But if one were to be speculative, we could say we might know these answers in our lifetime. Of course, I'm going out on a limb here. ;)

Saith
09-09-05, 11:02 AM
How I understood it, mass is the result of the curvature of space (basically warped space). Isn't that how it is describe in general relativity?

If I was to speculate where inertia came from then I would guess that it was the result of warped space trying to move thru unwarped space or the result of, as one website put it, the "interaction of an object with the background of all matter in the universe".

I would imagine something like a magnet would probably have its own kind of inertia if a magnetic field had a huge range like gravity and was always an attractive force. The universe is really uniform so the force would be pulling all objects in all directions, making them hard to move in any direction.

btw: incase anyone doesn't notice, this thread is a 3 years old

Nisus
09-09-05, 11:13 AM
Inertia is the tendency of any state of affairs to persist in the absence of external influences. Specifically, in physics, it is the tendency of a body to maintain its state of uniform motion unless acted on by an external force. (This is called Newton's first law of motion, taken from Galileo's principle.)

wikipedia omg...

gnasher
09-09-05, 09:39 PM
Sir Issac Newton is mostly to blame.

Things don't want to change. They are, like myself, and are pleased to keep themselves to themselves.

Mass always has to be present. What will the energy interact with / effect otherwise? Obviously, with itself, but what measurable effect would it have? Forces have to be applied on something, or they can't be called a force. Similarly, when a particle take a chance and decides to become matter, it can sometimes expect its mates who are still energy to act on it, unless they are really exotic and don't interact with anything.

'We're not sure what causes mass yet'? Many people are quite sure that it it is a specific state of order of quarks. A few ups, and a down or two. OK, make that a total of three.

cato
09-09-05, 10:48 PM
some have suggested that it is an electromagnetic interaction.

gnasher
09-23-05, 09:00 PM
Who suggested that Cato? What has EM got to do with inertia?

dzerzhinsky
09-24-05, 02:01 AM

It's an electromagnetic interaction.

By creating an 'electromagnetic vacuum' around yourself, all objects passing close to you completely lose their inertia. This would make a really good bulletproof shield if you think about it.

Light
09-24-05, 02:19 AM

It's an electromagnetic interaction.

By creating an 'electromagnetic vacuum' around yourself, all objects passing close to you completely lose their inertia. This would make a really good bulletproof shield if you think about it.

?????? And just how do you intend for that article to explain your last statement??

hybrid
02-13-08, 10:00 AM
inertia is the internal motion of an object to stabilize its present state.

the process of inertia as a motion is the appearance of mass in space in an instant in successive intervals.

Spud Emperor
02-13-08, 10:06 AM
You fucking scientific trippers.
It's so easy. It's the reluctance of a moving body to change direction.
That's all.

err,.. off the top of my head.

neelakash
02-13-08, 11:11 AM
Inertia is one of the fundamental properties of matter/particle which is,by some strange token, is identical with the body's/particle's gravitational mass.

Pandaemoni
02-13-08, 11:30 AM
There are two kinds of "mass" in a sense. Gravitational mass and inertial mass. So far as we know the two are equivalent, but without knowing more about where these masses come from, it's impossible to say that they might not someday be uncoupled in some way.

Still I would not suggest that inertia is necessarily a property of mass as much of the time when we use the term "mass" we use it as a proxy to describe its inertia. I think inertial may be what we mean by "mass" in those contexts.

Montec
02-13-08, 01:37 PM
Hello all
Here is an "off the wall" (as in bouncing) simple model for inertia. Take two parallel reflective surfaces and reflect a beam of light off of one onto the other. The path of the beam (as it bounces/reflects) is inertia. The angle of the beam is speed. The intensity of the beam is mass. If you deform the mirrors then the path is changed.

Hehe, just a wild idea.

:)

blobrana
02-13-08, 02:33 PM
>>What is inertia?

Apart form the simple explanations given; I don't know,
though i have an idea that the higgs boson, virtual photons, quantum entanglement, all could have some role in conveying inertia (and particle mass).

Reiku
02-17-08, 03:20 PM
Inertia has no exception in relativity, when it comes to explanations. However, there is a leading idea that inertia has something to do with the innate properties of matter, when one considers a thing moving through the Zero Point Energy Field... The idea is really appeasing to me.

paulfr
02-20-08, 08:00 AM
I know what it is, but how does it come about?

It comes about by the existence of mass and gravitation.

How ?

Isn't that the same as asking why ?
No one knows as that is a question for religion IMO.

Vkothii
02-20-08, 08:48 PM
Inertia is an explanation. It explains why you can't tell the difference between being on the Earth's surface and accelerating in a spacecraft (at 1g).
I guess you can explain an explanation.

Chatha
02-21-08, 11:49 PM
Newton's first law in one word

Vkothii
08-15-08, 06:56 AM
The magnetic and electric fields have all kinds of "particles" in them, as well as massless bosons (which are not allowed to contribute to the curvature of spacetime).
Lots of reasons to think that photons don't interact with inertia, or gravity; they travel along geodesics.

BenTheMan
08-15-08, 08:42 AM
First of all:

Vern---stop presenting your own theories as fact.

Secondly, Vkothii---

The magnetic and electric fields have all kinds of "particles" in them, as well as massless bosons (which are not allowed to contribute to the curvature of spacetime).
Lots of reasons to think that photons don't interact with inertia, or gravity; they travel along geodesics.

This is not right. Photons have an energy, and it is energy density that contributes to the curvature of spacetime. This is what Einstein's equations say.

Vern
08-15-08, 08:47 AM
Vern---stop presenting your own theories as fact.
Oops; sorry BenTheMan. I should have said "I suspect that" before the facts I presented.

Vkothii
08-15-08, 09:14 AM
Yes, I should have said they don't contribute to Einstein's curvature term, but to the other one whatever it's called.
Has to do with the tension of the field, I think.

Light doesn't have inertia though.

Vern
08-15-08, 09:20 AM
Light doesn't have inertia though.
I suspect that the inertia in light is represented by the frequency. It does not spontaneously change. It behaves just like inertia.

Vkothii
08-15-08, 09:23 AM
No, frequency is equivalent to momentum.
That's Max Planck for ya, huh?

Vern
08-15-08, 09:32 AM
No, frequency is equivalent to momentum.

From Wiki: Search term inertia.

In common usage, however, people may also use the term "inertia" to refer to an object's "amount of resistance to change in velocity" (which is quantified by its mass), and sometimes its momentum,

Vkothii
08-15-08, 09:47 AM
Time for some math, I'd say.
Inertia is also only ever used in mechanics and dynamic theories of matter - stuff that can be weighed with a mass spectrometer, characterised a lot of other ways, I know, I've done it in a chem analytics course at a university, photons interact with matter in a lot of ways, but you can't get an inertial reaction in a MS graph.

BrJLa
08-15-08, 12:02 PM
I would say inertia is a function of relativity. Based on my layman's understanding, relativity says that for any two objects in motion relative to each other, you can't say which one is moving relative to the other. Or which one is moving and which one is standing still.

When an object gets acted on by either acceleration or deceleration, that changes things. You can then be said to be moving or slowing. But once in motion or in stillness, relativity resets and you can no longer say, between two objects, which one is moving and which one is still.

Inertia is that state of not being able to name where the motion really is.

Vern
08-15-08, 12:17 PM
Hi BrJLa; from what I know of relativity you have it right. But I can't see how inertia can be a function of it.
My own reasoning of it is: take the question, What Is Inertia? It is something about mass that makes it remain in its state of motion. Then What Is Mass? Well we know that the measure of the amount of mass can be obtained by applying the equation Mass = Planck's constant times frequency divided by the speed of light squared. The only thing in the equation that is not a constant is frequency. Frequency is electromagnetic change. By choosing units of measure we can arrive at Mass = electromagnetic change.
From that you can deduce that Mass is electromagnetic change.
From that you can say that inertia is a property of electromagnetic change. And as Maxwell described electromagnetic change it tends to remain the same frequency unless acted upon by some outside force.

So that's how I get to suspecting that inertia comes form the stability of the frequency of the constituents of mass.

I don't know if it is right but it works for me :)

BrJLa
08-15-08, 12:22 PM
I'm just making this up off the top of my head, but I'd ask what motion even means once you act on an object. You push it to a point. You stop acting on it. Then what?

If it's just me and a ball in the middle of empty space, and I exert a certain amount of force on the ball, who is to say whether it is pushing away from me and I am still, or it is still and I'm pushing away from it?

So I'd say the object doesn't have inertia. The motion between us has inertia.

BrJLa
08-15-08, 12:25 PM
So I'd say inertia is "In the relative motion between two objects, one of the objects needs to be acted on for the relative motion to change."

Vern
08-15-08, 12:28 PM
So I'd say the object doesn't have inertia. The motion between us has inertia.
I can see how you could conclude that. I myself like the Lorentz version to explain relativity phenomena. His keeps a fixed frame of reference. So we pick the frame of the CMB as the fixed frame and describe the motion of everything relative to that.

Vkothii
08-15-08, 07:14 PM
What you're talking about, at this juncture, is the equivalence principle (http://en.wikipedia.org/wiki/Equivalence_principle):

Which is so last century. C'mon guys.

Vern
08-15-08, 07:26 PM
What you're talking about, at this juncture, is the equivalence principle:
You lost me there; I don't see the connection.

Vkothii
08-15-08, 09:05 PM
Go back 100 years, give or take, and check out what a certain patent clerk was doing with the mathematical ideas of a James Clerk; see if that makes a connection.

Montec
08-15-08, 11:23 PM
Inertia is a particles resistance to a changing rate of time.

:)

Vkothii
08-16-08, 05:43 AM
You mean: "to a changing rate of acceleration"

Vern
08-16-08, 06:43 AM
Go back 100 years, give or take, and check out what a certain patent clerk was doing with the mathematical ideas of a James Clerk; see if that makes a connection.
I like your way of referencing it; but I don't see a connection with Einstein either.

Vkothii
08-16-08, 06:51 AM
So now, you're saying SR and GR don't explain inertia?

Vern
08-16-08, 08:12 AM
So now, you're saying SR and GR don't explain inertia?
Einstein's theories may describe inertia; but they do not find its cause.

Vkothii
08-16-08, 08:14 AM
Ok, so you have a field theory that looks like the one Peter Higgs describes?
Does it fit current theories at all?

Vern
08-16-08, 10:51 AM
I don't have a theory. I just suspect that the final irreducible constituent of all physical reality may be the electromagnetic field.

Montec
08-16-08, 04:24 PM
You mean: "to a changing rate of acceleration"

Hmm, I believe that acceleration is the result of a force acting on a particle while a particle's inertia is a resistance to an accelerating force.

So I will stick with

Inertia is a particles resistance to a changing rate of time.

This idea works with both changing speed (straight line acceleration) and relative tangential (angular acceleration) motion.

:)

Vkothii
08-16-08, 05:52 PM
OK, they should give you a 1/2 mark for trying, I guess.

BrJLa
08-16-08, 07:36 PM
Hmm, I believe that acceleration is the result of a force acting on a particle while a particle's inertia is a resistance to an accelerating force.

So I will stick with

This idea works with both changing speed (straight line acceleration) and relative tangential (angular acceleration) motion.

:)

But I think this is pretty close to what I said. Inertia is a state of neither accelerating nor decelerating, each of which require force. I'm probably not expressing it exactly right, but your explanation sounds to me like a variation of what I'm saying.

BrJLa
08-16-08, 07:39 PM
You mean: "to a changing rate of acceleration"

I don't get this. I would think that it was resistance to acceleration, rather than resistance to a changing rate of acceleration. Any acceleration - even a constant state of acceleration - seems to me would require overcoming inertia.

Vkothii
08-16-08, 07:49 PM
You haven't done any Newtonian mechanics, have you?
(Hint: a body's inertia or resistance to change in motion, is rate of change - of velocity, and acceleration too, but not "rate of change of time", that is constant in Newtonian rest frames. "Time rate" is meaningless in kinematics; but not in relativistic reference frames.)

paulfr
08-16-08, 11:27 PM
You haven't done any Newtonian mechanics, have you? (Hint:

Gosh Vkothii, you are quite an arrogant individual.
My guess is you are a youngster full of yourself.
That is going to catch up with you one of these days.
Wish I could be around to see it.

Cheers

BrJLa
08-16-08, 11:57 PM
You haven't done any Newtonian mechanics, have you?
(Hint: a body's inertia or resistance to change in motion, is rate of change - of velocity, and acceleration too, but not "rate of change of time", that is constant in Newtonian rest frames. "Time rate" is meaningless in kinematics; but not in relativistic reference frames.)

Uh, no. I haven't come any where close. I'm a normal person trying to relate to these concepts. I don't know about rate of change of time. I didn't say anything about time rate. I'm only talking about the difference between velocity and acceleration. It seems to me that inertia is resistance to acceleration, rather than resistance to a change in the rate of acceleration. Inertia is the tendency to maintain velocity. To the extent you try to increase or decrease velocity, you have to overcome inertia. That's why I said that even maintaining steady acceleration requires overcoming inertia.

But I don't know anything other than a normal person's experience of trying of trying to understand this stuff.

BrJLa
08-17-08, 12:03 AM
Go back 100 years, give or take, and check out what a certain patent clerk was doing with the mathematical ideas of a James Clerk; see if that makes a connection.

The other thing I don't get is, based on James Clerk's ideas, the notion that inertia should require explaination seems to pre-suppose that the background electromagnetic waves formed an effective ether. It's precisely because they have no friction that inertia exists.

Vkothii
08-17-08, 01:41 AM
A is for being arrogant - you don't need to learn about [measuring] inertia in a school lab or at uni.

You can get kid's books, start young with the magnets, wires, solenoids; it isn't all that much effort to set up a lab of sorts at home.
You know? I certainly knew that when I was younger. But the math eluded me until later at high school. Fortunately the tertiary institute I attended had a Physics prof who had thought about experiments for first year; thinking over what we looked at after we had, how long most of it has stayed with me, I'd say he was a fairly intelligent man.

Just be prepared, here at t' forum to have someone get arrogant on your case - deal with it.

BrJLa: fixed magnets can have inertia, and bits of metal in a magnetic field can too; why, and what metals?

D H
08-17-08, 02:50 AM
You mean: "to a changing rate of acceleration"
You didn't really mean that did you? There is no need to invoke high order derivatives of position to describe "inertia". (The rate of acceleration is jerk, and changing that rate means some even higher order derivative of position: snap, crackle, pop, ...)

Resistance to change in velocity (not change in rate of velocity) is all that is needed to describe inertia.

The concept of inertia is a bit outmoded. Inertia as described by Galileo and Newton is synonymous with mass (specifically, inertial mass). Why use two terms for the same thing? Science in general doesn't like synonyms as they are confusing. As such, the term inertia is not used by itself in physics nowadays. It is used as a qualifier -- for example, inertial frame and inertial mass. Inertial frame: The tendency to stay at rest or to continue moving in a straight line (Newton's first law) is true only in an inertial frame. Inertial mass: The "m" in F=ma is inertial mass.

Explaining inertia as mass is begging the question: What is mass? First off, there are two kinds of mass: Inertial mass and gravitational mass. In Newtonian mechanics, inertial mass is the "m" in F=ma and gravitational mass is F=Gm1m[/sub]2/r2. As far as we can tell, inertial and gravitational mass are equal. We don't know why; all we have at hand are experiments that indicate they are equal and axioms that assert that they are equal (the Galilean equivalence principle in Newtonian mechanics and the Einstein equivalence principle in relativistic mechanics).

So, what is inertial mass? We don't know. All we have at hand is an axiom describing how things with mass behave: F=ma, and generalizations of this axiom to general relativity. We do have an idea: The Higgs boson. Nobody has seen a Higgs boson -- yet. This "we don't know" answer is not very satisfactory, and it is one of the driving reasons for developing the Large Hadron Collider.

Vkothii
08-17-08, 02:55 AM
If someone said "rate of time change", I think I would say "you mean: rate of acceleration", which is why I did.

If there's a resistance to the change in velocity or acceleration, it's because either exist; inertia measures the change, in terms of the body in motion.

D H
08-17-08, 03:23 AM
If someone said "rate of time change" and I answered "you mean: rate of acceleration", I would welcome all corrections because sometimes I too am guilty of posting incredibly stupid comments.

Challenger78
08-17-08, 03:27 AM
You fucking scientific trippers.
It's so easy. It's the reluctance of a moving body to change direction.
That's all.

err,.. off the top of my head.

I feel the same way..

Montec
08-18-08, 11:25 AM
Hehe, it all boils down to cause and effect. It can be shown that "gravity" and "centrifugal force" are effects caused by "time gradients". Inertia (ie the resistance to a change in a particle's speed) must be linked to these "time gradients" for a particle to be affected by the pseudo forces generated by "time gradients".

Special Relativity (SR) and General Relativity (GR) both can use time rates to establish "time gradients" to explain "gravity" and "centrifugal force". SR may be used to explain inertia if we let the relationship "inertia = resistance to change in a time rate" be a postulate.

How "time rates" and "time gradients" are established is still a question that needs to be answered.

:)

Vkothii
08-18-08, 03:28 PM
How large are these gradients? Why doesn't the earth's rotation rate speed up and slow down as we travel through space? Because of being in the solar system's gravity well?

Montec
08-18-08, 07:22 PM
Hello Vkothii

I used two facts as a basis for my ideas regarding "time gradients".
1) Atomic clocks located at sea level tick at the same rate everywhere on the Earth.
2) The Earth's polar radii is approximately 22km shorter than the equatorial radii.

This means that water flows to a "slower time rate" instead of the common idea of "water flowing downhill" (the 22km hill). This also means that centrifugal force establishes a "time gradient" between a particle and the focus/center of the particle's curved path. Since the particle is in motion then (by SR) a time gradient is formed from a faster time rate at the focus to a slower time rate at the particle. This opposes the time rates, from gravitational time gradients, caused by mass which are slower at the focus/center.

So an orbit can be thought of as a path through space where the two pseudo forces (gravity and centrifugal force) cancel each other out or if you prefer where the particle's "time rate" is equal to the "time rate" at the focus/center of the particle's curved path.

So we have gravitational "time rates/gradients" that exist, as fields, outside of mass and "time rates/gradients" that exist relative to the center of a particle's curved path which leaves us with inertia related to changing (time rates) speeds.

:)

BenTheMan
08-19-08, 09:03 AM
I think DH has answered the question in post #58 quite elegantly.