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Bill S. Offline OP
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Forgive the pun in the subject line.

I've been reading odd bits recently about the fact that the "m" in E=mc^2 is mass, not matter. The corollary of this seems to be that in a nuclear reaction mass, not matter, is converted to energy.

That seemed to make very good sense, but of course I can never just accept something at face value and leave it at that.

This is a list of points I have gleaned from various sources; followed by a single question.

I have a quantity of matter and I measure its mass as 1kg.
That 1kg could also be said to be the mass/energy of the matter.
This means that the energy associated with the mass must also be associated with the matter.
Some of the matter undergoes nuclear fission.
Where the parent nucleus is more energetic than the daughter nuclei, energy is released.
Some of the mass has been converted to energy.
None of the original matter has been converted to energy.
This must mean that if I could collect all the remaining particles, the quantity of matter would be the same as that with which I started.

If I measured this matter, would its mass still be 1kg?


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E=MC2 is for objects that have mass but aren't moving

Read the section "Applicability of the strict mass–energy equivalence formula" ( Energy Mass Equivalence)

Full version:
E2 = (MC2 )2 + (PC)2

See the new term P which is the sum of the momentum vectors.

So no after your fission event the masses won't add up because you have some particles moving very fast with a lot of momentum AKA a lot of energy.

It is most definitely matter (or specifically atoms) that are changed during a fission event you get equations like

Heavy Atomic atom + neutron ===> fission fragments + 2 to 4 neutrons + approx 200 MeV energy

The heavy atomic atom is usually uranium, plutonium etc
The fission fragments are like barium, strontium, caesium, krypton

So an example using Uranium 235 going to fission fragments of barium and krypton

U235 + neutron => Ba140 + Kr94 + 3 neutrons + 202.5MeV

**I have left out the U236 intermediate step
** The neutrons released fuel the chain reaction providing the free neutron on left side

It is also worth pointing out in a matter/anti-matter annihilation event there is no mass left at all there is 100% conversion of matter to energy of any other form photons, particle pairs and the like. The most likely production is photons (but anything not forbidden by QM can be produced), so your mass disappears to be replaced by massless particles moving at the speed of light. However your energy is conserved by the full version of the equation above with the momentum terms.

If you want all that put into a much better expression nuclear fission converts matter energy into a lot of other forms of energy and if done violently will kill you smile

Last edited by Orac; 12/09/15 08:05 AM.

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Bill S. Offline OP
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Sorry. I posted that in the wrong thread. frown

It has to be said that this thread seems to be rapidly converging with "Open Challenge"

Last edited by Bill S.; 12/09/15 11:28 PM.

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Originally Posted By: Orac
It is also worth pointing out in a matter/anti-matter annihilation event there is no mass left at all there is 100% conversion of matter to energy


Is that always the case? Can't a muon and anti-muon annihilate to leave an electron and positron + energy?


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Originally Posted By: Bill S.
Is that always the case? Can't a muon and anti-muon annihilate to leave an electron and positron + energy?

Arg you are right and yeah there are a couple of others, now I think about it. Okay so tell how did you know about that interaction that isn't exactly layman science magazine.

Ok lets change that to SOMETIMES matter/anti matter interactions can result to in 100% conversion of mass to energy ... fixed smile


Last edited by Orac; 12/13/15 05:10 AM.

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Originally Posted By: Orac
Ok lets change that to SOMETIMES matter/anti matter interactions can result to in 100% conversion of mass to energy .


Would this energy be in the form of photons?

If so, I guess that puts you in the (majority?) group who maintain that photons are not matter.

We amateurs can have problems with the conflicting views of experts.

"The photon is a wave/particle of Matter and has a measure of Energy but the photon is not Energy." (New England Physics Forum)


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Quote:
Okay so tell how did you know about that interaction


Blame Matt Strassler. smile


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Originally Posted By: Bill S.
Would this energy be in the form of photons?

Yes

Originally Posted By: Bill S.
If so, I guess that puts you in the (majority?) group who maintain that photons are not matter.

We amateurs can have problems with the conflicting views of experts.

Yes and I wouldn't call it a conflict, really what we are talking about translating meaning in a general sense. Scientifically in a paper of any technical discussion you always use the more precise descriptions photons, fermions, bosons and the like.

You know the problem matter is a very inexact term like describing something as cold. Most would consider 0 degree cold but to say an Inuit Indian that may not be what they call cold but more mild.

If you want to object and use matter in a wider sense in discussion I am happy to remember that and adapt discussion it really doesn't change the science.

Originally Posted By: Bill S.
"The photon is a wave/particle of Matter and has a measure of Energy but the photon is not Energy." (New England Physics Forum)

You have a problem with that statement? or more of above objecting to me equating matter-antimatter annihilation turning matter to energy?

Both statements are generically right and wrong depending how you define energy and matter the problem you detailed above. You are really getting a handle on stuff now and you realize you can attack anything I tell you under classical descriptions because they are very inexact. I used matter and energy in what would be sort of layman use but it will fail badly if you apply more scientific meaning like that description.

You seriously understand enough now to realize nobody can give you an exact answer to lots of problems in classical terms. I dare say you also get, or could work out why lots of classical physics leads to crazy wrong conclusions.

If you want a more accurate answer we need to get off these layman terms and on a different framework and now you get why the different frameworks exist and why they are careful in definitions.

So in QM for example Energy is an operator acting on the waveform hence it's like any currency not something you can define to something physical (https://en.wikipedia.org/wiki/Energy_operator). The problem is I am not sure how I could communicate with any layman using that definition as there first comment will be I am not a wave smile

If you want to switch to a different framework we can you have enough background to do it now.

Last edited by Orac; 12/17/15 04:06 AM.

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Originally Posted By: Orac
Originally Posted By: Bill S
"The photon is a wave/particle of Matter and has a measure of Energy but the photon is not Energy."
You have a problem with that statement?


No. I think one would have to a good definition of energy to object to that. However, if a photon is not matter, unless you define matter in a particular way; could you also define energy in such a way as to be able to argue that a photon is energy?

Probably only a "hitch-hiker" would ask questions like; Is a photon matter? Is a photon energy? Is matter converted to energy in a nuclear reaction? and expect to get a clear answer.


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Originally Posted By: Bill S.
Probably only a "hitch-hiker" would ask questions like; Is a photon matter? Is a photon energy? Is matter converted to energy in a nuclear reaction? and expect to get a clear answer.

Again there are clear answers just not within the messy framework of classical physics that layman are familiar with.

You need to recognize the problem that average English speech simply is not a suitable framework to try and derive a really technical answer of science.

Try another technical field like computer programming and using only layman speech. Do you think you can answer a technical question which would remotely make sense given the restriction?

Stuff is just stuff it doesn't have to match ambiguous and often historically wrong layman definitions.

Energy is one of those funny concepts in classical physics that it has been treated historically as something "real and physical" yet there is no basis for that belief.

There is a lot of discussion of this in teaching of science at the moment along these lines
http://www.learner.org/workshops/energy/workshop1/real.html

I am definitely one of the ones, urging that they not teach something that is totally misleading.

Last edited by Orac; 12/20/15 03:40 PM.

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Originally Posted By: Orac
Try another technical field like computer programming and using only layman speech. Do you think you can answer a technical question which would remotely make sense given the restriction?


Get real, Orac! I couldn't answer a question about computer programming in any language.

That's not quite true. There is one I could answer: "Do you know anything about computer programming?"
"No".



Thanks for that link. All I need is some time to explore it.


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Ah! Have you seen the new book "Thing Explainer" by Randall Munroe? It is a science book written using the 1000 most common words in the English language. You can find out more about it at Amazon

So maybe you can explain advanced physics in layman' language.

Bill Gill


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C is the universal speed limit.
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Bill S. Offline OP
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Thanks Bill, could be just what I need. The trouble is that at the rate at which I am reading at present, it's going to take me a long time to work through the books waiting to be read.


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If you use electronic books one of the cool things about electronic stores is you can get the audio version of books and listen to them in your car etc.


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Some digital books come with the ability to have them spoken. However, I don't much go for that. I like the ability to go back and recheck what I just read and do quick back checks when I think something doesn't mesh with what I read before.

As far as listening to a book while I am driving, I figure that either I would have to concentrate on my driving and not catch what the book said, or I would get distracted by the book and have an accident. So I will go ahead an keep on reading by eye.

And if the book is something I think I need to study then I really need to read it so I can take time to think it through when it says something I really need to understand.

Bill Gill


C is not the speed of light in a vacuum.
C is the universal speed limit.

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