# How is mass divided by volume to measure density ?

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6 minutes ago, Complexity said:

I mean something like , we lit a candle in a room , the light emitted is not as bright as the flame , what physically divides the light around the room ?

This sounds like you are thinking of the inverse square law: the intensity of the light falls off as the square of the distance: twice as far away, the light will be one fourth as bright.

This can be understood by thinking of the light from the candle being spread out over the surface of a sphere centred on the source. As the distance increases, the radius of the sphere increases and the surface area of the sphere increases with the square of the radius (A = 4 pi r2) so the light per unit area falls by r2.

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5 minutes ago, MigL said:

The light spreads out into the volume of the room, and become more diffuse.

I could give you the mathematical relationship, but I'm getting the impression that would be useless.

Yes the light spreads out (divides) , into the volume of the room . The question is what makes it ''spread out ''?

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6 minutes ago, Complexity said:

Is it not true that the mathematical concept always represents a  physical act of separation although the physical part may be in imagination rather than physical applying it ?

If not , please provide a demonstration of other use .

You can do arithmetic on any numbers without needing to have (or imagining) any physical relationship.

3 minutes ago, Complexity said:

Yes the light spreads out (divides) , into the volume of the room . The question is what makes it ''spread out ''?

Because it is a wavefront that radiates from the source.

Note that it in't the division sign in the inverse square law that causes the light to spread out (divide); the mathematics just describes the result.

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1 minute ago, Strange said:

You can do arithmetic on any numbers without needing to have (or imagining) any physical relationship.

How can that be meaningful ?

Unless you mean 1kg of gold and 1kg of feathers type situation ?

1kg = 1kg so no need for the gold or feathers ?

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7 minutes ago, Complexity said:

How can that be meaningful ?

Unless you mean 1kg of gold and 1kg of feathers type situation ?

1kg = 1kg so no need for the gold or feathers ?

No need for the kg, either.

I just mean that I can divide 27 by 61 (two numbers generated by a random number generator) with no thought as to physical meaning. A lot of mathematics has no physical meaning or application.

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17 minutes ago, Strange said:

No need for the kg, either.

I just mean that I can divide 27 by 61 (two numbers generated by a random number generator) with no thought as to physical meaning. A lot of mathematics has no physical meaning or application.

Ok, I see your point now but I still do not feel I've being given the answer to my original question in the context I mean .

I will redefine my question  :

What force spreads light throughout  a volume ?

Edited by Complexity

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3 minutes ago, Complexity said:

What force spreads light throughout  a volume ?

No force is involved. It is just what light does: it is a form of radiation, so it radiates. At the speed of light. By definition. With no constraints, it will radiate evenly in all directions result in the inverse square relationship.

If you want to ask "why does light behave like it does" then that probably is not a question physics can answer. What science does is observe things happening and attempt to describe them as accurately as possible.

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18 minutes ago, Strange said:

No force is involved. It is just what light does: it is a form of radiation, so it radiates.

I disagree in '' It is just what light does''.

Isn't it imperative that scientists , especially physicists , look for completeness in  an answer rather than ' 'It is just what light does''?

I'm sure you are aware of the term causality and I do consider that lights speed has to have a cause  .

Wouldn't the correct statement on force be : There is no known force involved to this present date ?

Isn't it possible that in the very near future we could establish the cause of electromagnetic radiation distribution throughout a volume ?

Edited by Complexity

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Just now, Complexity said:

I disagree in '' It is just what light does''.

Isn't it imperative that scientists , especially physicists , look for completeness in  an answer rather than ' 'It is just what light does''?

I'm sure you are aware of the term causality and I do consider that lights speed has to have a cause  .

Wouldn't the correct statement on force be : There is no known force involved to this present date ?

Ins't it possible that in the very near future we could establish the cause of electromagnetic distribution throughout a volume ?

Even if you come up with a more fundamental explanation of why light radiates as it does, you would still be able to ask "why" about that explanation too.

For example, in Maxwell's equations, the speed of light depends on the permittivity and permeability of free space (these equations also explain why accelerated charges generate radiation). But then you can ask, why do the permittivity and permeability have those values. But as far as we know, they are just constants of nature. If someone comes up with a theory that gives those values, we can still say "but why that theory".

I am not suggesting that we should not ask questions, just that there is always a limit to how far our answers go.

There is no reason to think a force is required to make light move and we have two perfectly good theories as to why it does move in the ways it does.

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13 minutes ago, Strange said:

There is no reason to think a force is required to make light move and we have two perfectly good theories as to why it does move in the ways it does.

I totally agree with what you are saying but sometimes the why answer is completed .

I have good reason to think and consider there is a force involved .

In observed spectral emissions can you please answer how energy  makes a transition from a high energy state to a lower energy state?

Doesn't this imply a change of position for some of the energy ?

Isn't the higher energy state attracted to the  lower energy state ?

Edited by Complexity

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45 minutes ago, Complexity said:

What force spreads light throughout  a volume ?

No force is involved it is simply geometry.  An explosion spreads out the same way.  So does sound.

5 minutes ago, Complexity said:

I totally agree with what you are saying but sometimes the why answer is completed .

I have good reason to think and consider there is a force involved .

In observed spectral emissions can you please answer how energy  makes a transition from a high energy state to a lower energy state?

Doesn't this imply a change of position for some of the energy ?

You really need to learn some basic physics and science before you start trying to make hypotheses.  Most of your ideas are so wrong it is difficult to try figure out what you are trying to say let alone give you an answer that you can understand.

Edited by Bufofrog

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10 minutes ago, Bufofrog said:

No force is involved it is simply geometry.  An explosion spreads out the same way.  So does sound.

''In physics, the second law of thermodynamics says that heat flows naturally from an object at a higher temperature to an object at a lower temperature, and heat doesn't flow in the opposite direction of its own accord.''

Why if not an attractive force by the lower temperature ?

Would it be incorrect to say that the object at a lower temperature has <E of the higher temperature object ?

Edited by Complexity

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7 minutes ago, Complexity said:

In observed spectral emissions can you please answer how energy  makes a transition from a high energy state to a lower energy state?

Not easily. Unless you have a background in quantum theory. In which case, you wouldn't be answering the question.

7 minutes ago, Complexity said:

Doesn't this imply a change of position for some of the energy ?

There is not really a change in position. The electron (if that is the case we are talking about) goes to a higher energy state, where it has a different range of allowed locations. When it goes to a lower energy state, a photon is emitted. But this is not because the electron "moves" to a new position, it is the state of the system (the whole atom) that changes. Electrons don't move from one place to another in the classical sense.

10 minutes ago, Complexity said:

Isn't the higher energy state attracted to the  lower energy state ?

That makes no sense.

10 minutes ago, Complexity said:

I have good reason to think and consider there is a force involved .

You might think you do. But, based on what you have said so far, this is probably a case where you have made up a story that makes sense to you and so it seems perfect, because it is exactly tailored to your level of understanding. It will almost certainly not make any sense to anyone else, because it is based on almost zero knowledge of physics.

1 minute ago, Complexity said:

''In physics, the second law of thermodynamics says that heat flows naturally from an object at a higher temperature to an object at a lower temperature, and heat doesn't flow in the opposite direction of its own accord.''

Why if not an attractive force by the lower temperature ?

Random motion and statistics. There is definitely no force involved there.

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3 minutes ago, Strange said:

Random motion and statistics. There is definitely no force involved there.

F=ma

How can anything move position without there being an applied force ?

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1 minute ago, Complexity said:

F=ma

How can anything move position without there being an applied force ?

And this perfectly exemplifies how you are attempting to use ideas that you do not understand.

Firstly, things can move without a force being applied. That is Newton's first law. A force is required to change the state of motion.

Secondly, heat is not a "thing" so there is nothing that a force could be applied to (were it necessary).

I don't think you will be able to get answers to your questions until you realise / admit how little you know and realise that, therefore, you need to learn what is known, rather than making up stories that you think make sense.

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42 minutes ago, Complexity said:

I disagree in '' It is just what light does''.

Isn't it imperative that scientists , especially physicists , look for completeness in  an answer rather than ' 'It is just what light does''?

I agree that "it is just what light does" is not very formal.

But

Newton's first law (which is pretty fundamental) could be stated

A material body will continue doing its own thing unless acted on by a force.

In the case of a material body its own thing means (is defined as) "moving in a straight line or state of rest."

Similarly you could say

Light will continue doing its own thing unless acted on by a focusing or deflecting agent or there is something in the way.d be defined as

Where doing its own thing could be defiend as

"Filling the space available to it in all directions"

This would be analogous to "a gas expands to fill its container in all directions"

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17 minutes ago, Strange said:

And this perfectly exemplifies how you are attempting to use ideas that you do not understand.

Firstly, things can move without a force being applied. That is Newton's first law. A force is required to change the state of motion.

Secondly, heat is not a "thing" so there is nothing that a force could be applied to (were it necessary).

I don't think you will be able to get answers to your questions until you realise / admit how little you know and realise that, therefore, you need to learn what is known, rather than making up stories that you think make sense.

An object will remain in motion unless an external force acts on that object . I am aware of the laws of motion and I am additionally aware of thermodynamics . Radiated heat is a thing and can be seen using thermal cameras . If it weren't a thing , thermal cameras wouldn't observe temperature differences of the emission spectrum .

Would you say that it is a fare comment to state  >E  transfers to <E , i.e heat transfer

9 minutes ago, studiot said:

I agree that "it is just what light does" is not very formal.

But

Newton's first law (which is pretty fundamental) could be stated

Newtons first law could be applied if when light exits glass , it didn't speed up again .

Light does speed up when exiting glass so this to me  is suggestive of either a propulsion force or an attractive force  creating the constant momentum .

Edited by Complexity

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2 hours ago, Complexity said:

I agree but nonetheless the equation does represent something physical !

no, 1/2 does not.

2 hours ago, Complexity said:

Perhaps I have not defined my question specifically enough .

What physical reality divides light by an unspecified physical volume ?

That’s still not defined specifically enough. What are you blathering about?

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3 minutes ago, swansont said:

no, 1/2 does not.

That’s still not defined specifically enough. What are you blathering about?

What specifically creates the momentum of EMR ?

I believe there is a force that attracts it .

Edited by Complexity

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1 hour ago, Complexity said:

Yes the light spreads out (divides) , into the volume of the room . The question is what makes it ''spread out ''?

It’s not division, and you are talking about the intensity (a property of the light) which varies as 1/r^2 for a point source.

Basically you are repeatedly confusing the map and the land. They aren’t the same thing.

7 minutes ago, Complexity said:

What specifically creates the momentum of EMR ?

I believe there is a force that attracts it .

I don’t care what you believe. This would be something for speculations, if you had a model so it could be tested, or it’s a WAG, in which case it has no place here.

1 hour ago, Complexity said:

I disagree in '' It is just what light does''.

Isn't it imperative that scientists , especially physicists , look for completeness in  an answer rather than ' 'It is just what light does''?

science discusses how nature behaves, not necessarily why it behaves that way. You reach a point where the latter can’t be tested, so it’s not subject to science.

Quote

I'm sure you are aware of the term causality and I do consider that lights speed has to have a cause  .

Wouldn't the correct statement on force be : There is no known force involved to this present date ?

Isn't it possible that in the very near future we could establish the cause of electromagnetic radiation distribution throughout a volume ?

No, because we understand what a force is and when it’s required

32 minutes ago, Complexity said:

F=ma

How can anything move position without there being an applied force ?

F=ma tells me that anything can move without an applied force. A force is required to change the motion (acceleration)

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6 minutes ago, Complexity said:

What specifically creates the momentum of EMR ?

I believe there is a force that attracts it .

The momentum is inherent because it has energy.

If there is a force attracting it (there isn't) then one would have to ask what is the nature of that force, what creates it, how does it interact with electromagnetic radiation, why doesn't it interact with other things, etc., etc.

One would also have to ask: why do you think that all of established physics is wrong?

However, I think you are in danger of moving from asking questions to promoting your own ideas. If you do that then the thread will be moved to Speculations (and the it will be closed because you are not able to provide any scientific support for your ideas).

I strongly suggest you actually learn some basic physics before making up more fairy stories. Otherwise you will always be in this twilight zone of making up ideas that are then rejected for reasons you don't understand.

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If you want to be stupid about it, you can consider density  in terms of physically splitting things.

If I take an apple and dice it into 1cm cubes then the number of cubes I get is (approximately) the volume of the apple.

And, I have similarly shared out all the mass of the apple among all those cubes.

The density of the apple is the average mass of each cube.

The question "what divides the apple?" is a bit meaningless, but as good an answer as any is "my imagination".

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44 minutes ago, Complexity said:

Newtons first law could be applied if when light exits glass , it didn't speed up again .

Light does speed up when exiting glass so this to me  is suggestive of either a propulsion force or an attractive force  creating the constant momentum .

No it couldn't.

You did ask for some more rigour and I gave it to you.

I said

49 minutes ago, studiot said:

Newton's first law (which is pretty fundamental) could be stated

A material body will continue doing its own thing unless acted on by a force.

Light is not a material body.

So Newton's first law is not applicable to it.

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Trying to catch up.

2 hours ago, Complexity said:

I mean something like , we lit a candle in a room , the light emitted is not as bright as the flame , what physically divides the light around the room ?

And

2 hours ago, Complexity said:

Yes the light spreads out (divides) , into the volume of the room . The question is what makes it ''spread out ''?

Seems to ask two different questions.
First, Why is the light not as bright? You are probably familiar with photons. The list can be modelled as photons radiated away from the light source at the speed of light.The photons, unless they are absorbed (and maybe re-emitted) will continue in a straight line. Each individual photon is unaffected by the distance traveled. So each photon will reach, for instance and observer's eyes, at some distance. An observer closer to the light source will be hit by more photons per second and interpret it as bright light. An observer further away will be hit by fewer photons. This is kind of similar to an explosion, further away there is less risk to be hit by shrapnel. But important, each individual photon is not spread out. It is just that fewer photons will reach the observer that is further away.
Second: What propels a photon on its way to the observer? Nothing. Since photons travel at constant speed there is no change in momentum requiring anything to push the photons. Photons are massless (and also not a material body as @studiot said above) they are not modelled using Newton's physics. Explaining further would require some more rigor than my crude attempts at analogies above. So again:

2 hours ago, Ghideon said:

What concepts of math and physics are you familiar with that could act as a common starting point? Do you have a reference to something you read about light that raised the question?

Edited by Ghideon

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1 hour ago, Complexity said:

F=ma

How can anything move position without there being an applied force ?

That is a perfectly valid Newtonian equation.

Now substitute values in for the variables.
For light, m=mo=0  IOW it has zero rest mass because it can never be at rest.
So your perfectly valid equation, when mis-applied in the case of light or heat, gives you the non-sensical solution 0=0.

Now you're doing Physics  .
( being very sarcastic )

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