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MPMin

Does a magnetic field have mass?

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44 minutes ago, Mordred said:

Different locations on Earth can have different gravitational potentials even at sea level. Same problem. 

 

If standardised weights (on earth) are not satisfactory then what is the best way to quantify mass? 

22 hours ago, Mordred said:

Can energy exist on it own ? The answer is no it can't.

Are you suggesting that energy cannot exist without matter? 

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Are you being intentionally and willfully obtuse?

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without mass not matter. Mass and energy always go together 

Matter only accounts for fermionic particles. There are bosons that have an invariant mass.

One way to measure is with an accelerometer 

Recall mi=mg

Edited by Mordred

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16 hours ago, swansont said:

I specified a DC field. I didn't say any field, and I had commented earlier that I was discussing DC/static fields, as this is what the OP implied. Bringing up EMPs (again) is taking my discussion out of context. 

I don’t believe I was taking this discussion or your comments out of context. To bring a certain issue back to light (pun intended)  consider the filament wire of an incandescent bulb conducting a direct current to emit light, under a steady current the light appears static but we know the light is emanating out from the wire and so is the magnetic field even though it appears static as well. 

18 minutes ago, Mordred said:

without mass not matter. Mass and energy always go together 

 

So massless partials have no energy as without mass there’s no energy either? 

 

28 minutes ago, MPMin said:

Can energy exist on it own ? The answer is no it can't.

Or are matter and energy basically the same thing? If so then energy exists  on its own in any case. 

Edited by MPMin

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Think of mass and energy as flips of the same term but account for total mass not just rest mass.

Matter particles are just the fermionic family of SM particles. Bosons with no rest mass can have inertial mass.

Edited by Mordred

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5 hours ago, MPMin said:

Does this apply to chemical reactions that balance? The mass of one side of the equation always equals the other side thus no loss of mass occurs according to chemical equations.

The mass would only be equal on both sides if energy were included, which it isn’t usually. 

If energy is not included then the mass on both sides will not necessarily be equal. 

5 hours ago, MPMin said:

Are you suggesting that energy cannot exist without matter? 

Photons have energy but are not matter. That can be considered to be mass (but I would never do that).

You seem to mix up "matter" and "mass". They are not the same thing. Mass is a property of matter. As is energy. But non-material things can also have energy.

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6 hours ago, MPMin said:

But practically speaking what’s wrong with quantifying mass by weighing it on earth?

How would you weigh it?

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2 hours ago, studiot said:

How would you weigh it?

I would use scales, what would you use seeing as it’s worth asking? 

3 hours ago, Strange said:

The mass would only be equal on both sides if energy were included, which it isn’t usually. 

Does this mean that, as an example, 2H2 + O2 weighs more than 2H2O? (at the same place on earth) 

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13 minutes ago, MPMin said:

Does this mean that, as an example, 2H2 + O2 weighs more than 2H2O? (at the same place on earth) 

It certainly has more mass. (I am not going to get into the mass vs weight sidetrack. That might be better in a separate thread.)

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7 hours ago, MPMin said:

I don’t believe I was taking this discussion or your comments out of context. To bring a certain issue back to light (pun intended)  consider the filament wire of an incandescent bulb conducting a direct current to emit light, under a steady current the light appears static but we know the light is emanating out from the wire and so is the magnetic field even though it appears static as well. 

Light is comprised of real photons. Not the same thing 

7 hours ago, MPMin said:

So massless partials have no energy as without mass there’s no energy either? 

No, they have energy E=pc

7 hours ago, MPMin said:

Or are matter and energy basically the same thing? If so then energy exists  on its own in any case. 

No. Matter is a description of kinds of particles. Energy is a property that all matter has, but things that are not matter have energy, too

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1 hour ago, MPMin said:

I would use scales, what would you use seeing as it’s worth asking? 

Weight is a measure of the force (of attraction) experienced by a body on Earth (or other planet).

Because of the rotational speed of the Earth this force is a combination of the gravitational attraction and the centripetal force due to the rotation.

Since the radius of rotation varies from point  to point on the Earth the net force of attraction varies.

This difference can be measured with suitably sensitive instruments. It is much large than the sort of difference that occurs due to mass changes because of heat energy, chemical reactions and and so on.

Difference types of 'weighing' machines measure either mass or force so a spring balance will disagree with a beam balance.

 

That is why I asked the question.

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On 9/2/2019 at 3:17 AM, swansont said:

No. Mass is a form of energy. All mass is energy. Not all energy is mass (kinetic energy)

Can you elaborate on that statement please?

Does that mean all mass is energy and following on that, that everything is energy?

What "properties"  does energy have? 

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3 minutes ago, beecee said:

Does that mean all mass is energy and following on that, that everything is energy?

Mass and energy are equivalent. They are both properties of "things" (in the most general sense). 

3 minutes ago, beecee said:

What "properties"  does energy have? 

Energy is a property. But I suppose the one property it has is that it is conserved. One definition of energy is simply that it is a bookkeeping device, a conserved property of systems.

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11 hours ago, swansont said:

Light is comprised of real photons. Not the same thing 

 

What do you mean by real photons? 

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2 hours ago, beecee said:

Can you elaborate on that statement please?

E=mc^2

The energy content of an object at rest is proportional to its mass. 

An object can also have KE (or energy associated with its motion) which is not part of the rest energy. 

2 hours ago, beecee said:

Does that mean all mass is energy

Yes

2 hours ago, beecee said:

and following on that, that everything is energy?

No. Mass and energy are properties. Everything has energy. Many things have mass.

2 hours ago, beecee said:

What "properties"  does energy have? 

It is a property, not a substance.

6 minutes ago, MPMin said:
 

What do you mean by real photons? 

Not virtual

2 hours ago, Strange said:

Energy is a property. But I suppose the one property it has is that it is conserved. One definition of energy is simply that it is a bookkeeping device, a conserved property of systems.

I would say that it’s a property of time-translation symmetry, but that is probably too pedantic in this level of discussion.

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10 hours ago, swansont said:

An object can also have KE (or energy associated with its motion) which is not part of the rest energy. 

If two objects are identical atom for atom, does the object with the greater KE have the greater mass than the other?

10 hours ago, swansont said:

No. Mass and energy are properties. Everything has energy. Many things have mass.

To be clear, mass and energy are properties of what exactly? 

 

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3 minutes ago, MPMin said:

If two objects are identical atom for atom, does the object with the greater KE have the greater mass than the other?

Yes. Which is why physics always uses the rest mass which is the "real" mass of the object.

4 minutes ago, MPMin said:

To be clear, mass and energy are properties of what exactly? 

Of "things" in the most general sense. Anything we can measure the properties of (definitions tend to get circular when you reach the fundamental concepts) whether that is matter or photons or complete systems.

(One could go down a wormhole of what is a "thing", what is "real", what "exists", etc.)

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45 minutes ago, MPMin said:

If two objects are identical atom for atom, does the object with the greater KE have the greater mass than the other?

No. KE does not contribute to rest mass. If one has a greater KE than the other then it means it's moving faster in the frame of reference being used.

39 minutes ago, Strange said:

Yes. Which is why physics always uses the rest mass which is the "real" mass of the object.

One must be careful in identifying which mass is being used. IMO relativistic mass should always be identified as such, and using "mass" should mean rest mass. When you don't, as in this case, it looks like our answers contradict each other (I said no and you said yes), when they are pointing out the same thing.

 

The faster-moving object in this example has more energy. It does not have more rest mass.

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19 minutes ago, swansont said:

The faster-moving object in this example has more energy. It does not have more rest mass.

This is interesting and perhaps I’m getting confused here but if my understanding is correct then if the two atomically identical objects were both at rest but one had more thermal energy than the other then the one with more thermal energy would have a greater mass than the other, Interestingly greater thermal energy means the atoms have more KE. It would seem that when atoms have more KE it counts towards the mass of the object.

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31 minutes ago, MPMin said:

This is interesting and perhaps I’m getting confused here but if my understanding is correct then if the two atomically identical objects were both at rest but one had more thermal energy than the other then the one with more thermal energy would have a greater mass than the other, Interestingly greater thermal energy means the atoms have more KE. It would seem that when atoms have more KE it counts towards the mass of the object.

You are correct.

But these are different.In the case of the thermal energy of atoms, there is no rest frame where it becomes zero. So there is an energy contribution to the mass in the rest frame of the object. And so it contributes to the rest mass.

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1 hour ago, MPMin said:

This is interesting and perhaps I’m getting confused here but if my understanding is correct then if the two atomically identical objects were both at rest but one had more thermal energy than the other then the one with more thermal energy would have a greater mass than the other, Interestingly greater thermal energy means the atoms have more KE. It would seem that when atoms have more KE it counts towards the mass of the object.

Thermal energy is not KE of the object, it's vibrational and rotational KE of the constituent particles. The center-of-mass does not move when considering thermal motion. That's what matters in determining the KE.

I have pointed out before (and even before that) that the distinction is with the motion of the center of mass (CoM). 

 

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On 9/6/2019 at 5:56 AM, Strange said:

Mass and energy are equivalent. They are both properties of "things" (in the most general sense). 

Energy is a property. But I suppose the one property it has is that it is conserved. One definition of energy is simply that it is a bookkeeping device, a conserved property of systems.

 

On 9/6/2019 at 8:41 AM, swansont said:

E=mc^2

The energy content of an object at rest is proportional to its mass. 

An object can also have KE (or energy associated with its motion) which is not part of the rest energy. 

Yes

No. Mass and energy are properties. Everything has energy. Many things have mass.

It is a property, not a substance.

Not virtual

I would say that it’s a property of time-translation symmetry, but that is probably too pedantic in this level of discussion.

Thanks fellas...just some mild confusion and a debate I'm having. All clear now!

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Sort of points out the problems that arises when using the rest mass descriptive instead of the invariant mass. Reminds me of the endless debates that occured when rest mass was the standard terminology.

 

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11 hours ago, swansont said:

That's what matters in determining the KE.

That’s only if you want to consider the translational KE in isolation 

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12 hours ago, MPMin said:

That’s only if you want to consider the translational KE in isolation 

If you want to know what the KE is, you are by definition considering it in isolation. It depends on mass and speed. You had already said the items were identical, so the mass is the same. 

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