Can matter be completely converted to energy as suggested by E=mc2?

[atyy]

So its just called rest mass for the heck of it?

Quantum mechanically, I'd say that's a good way to start thinking about it (ie. quantum mechanically it's just something in the dispersion relation of a wave). The name really makes sense only classically. Remember that even "particle" and "movement" don't have the same meaning in quantum mechanics as in classical mechanics. Particles do not move in trajectories with definite momentum and position at all times.

 

[thefifthlord]

Well then I'm sorry for dragging this along. I was too sure of my logic to check my assumptions.

Thanks for the replies.

BTW, this should be stickied so no more like these are made, i was aware of similar topics but none of them addressed all the issues.

 

[jtbell]

So its just called rest mass for the heck of it?

I mean honestly, I've been ranting on here for hours... Why in the world would they call something at rest when its still moving in some way.

This is why many physicists (myself included) prefer to use the term invariant mass, which can be calculated via $mc^2 = \sqrt {E^2 - (pc)^2}$, which gives the same result for any particular particle in any inertial reference frame. This avoids the incongruity of talking about "rest mass" of a particle that is never at rest.

I consider the term "rest mass" to be a historical anachronism which will unfortunately probably never die because of its widespread use in pop-sci books and even many introductory textbooks.

 

[diazona]

You're talking quantum mechanically, right? Because if even an isolated classical particle can't be at rest in some reference frame, something is seriously wrong with my understanding...

BTW, this should be stickied so no more like these are made, i was aware of similar topics but none of them addressed all the issues.

The same could be said of half the threads here. Of course, I'm not the one to make such a decision, but it's awfully presumptuous to assume that your particular misunderstanding needs to be brought to everybody's attention.

 

[Dale]

So its just called rest mass for the heck of it?

The polite term is for "historical reasons". But yes, that is essentially correct.

 

[Frame Dragger]

The polite term is for "historical reasons". But yes, that is essentially correct.

I think these terms of art trip people up more than teachers and professionals realize. I know that terms such as "colour and spin" often are chosen for some vague reason (three primary colours for isntance) in QM. "Rest Mass" really is incredibly misleading, and as another user Zenith said in another thread, "Perception shapes thinking." I know that it's difficult to use language to communicate mathematical concepts, but if we expect people to look at theoretical physics/SR/GR/QM the way they grasp concepts such as "radio" and chain reaction there has to be more effort to universally formalize the language.

For god's sake, this is the hardest (as in hard/soft) science there is and one of the primary subatomic particles is named from Finnegan's Wake! "Three quarks for muster mark...". BIOLOGY has clearer nomenclature, and yes, I mean that as an insult to us all. The language must keep pace with the times... anachronisms that misleading are nothing for the community to be proud of.

 

[atyy]

I think these terms of art trip people up more than teachers and professionals realize. I know that terms such as "colour and spin" often are chosen for some vague reason (three primary colours for isntance) in QM. "Rest Mass" really is incredibly misleading, and as another user Zenith said in another thread, "Perception shapes thinking." I know that it's difficult to use language to communicate mathematical concepts, but if we expect people to look at theoretical physics/SR/GR/QM the way they grasp concepts such as "radio" and chain reaction there has to be more effort to universally formalize the language.

For god's sake, this is the hardest (as in hard/soft) science there is and one of the primary subatomic particles is named from Finnegan's Wake! "Three quarks for muster mark...". BIOLOGY has clearer nomenclature, and yes, I mean that as an insult to us all. The language must keep pace with the times... anachronisms that misleading are nothing for the community to be proud of.

So, why is an action potential a depolarization?

 

[Frame Dragger]

So, why is an action potential a depolarization?

That's incredibly simple. Without depolarization at the axon hillock there would be no voltage and therefore the firing threshold of the neuron would never be met and the neuron wouldn't be able to carry out the electrical portion of its electrochemical communication. Why do you ask?

EDIT: Did you ask me this because you think I'm slandering Biology? I'm sorry if I offended, but in the hierarchy of sciences physics is by its very nature the most fundamental. A complete understanding of physics could allow a complete understanding of all other sciences. No other science is so fundamental. That doesn't make them unworthy pursuits, or "easy", it just is a fact of life that each science is derived in sequence: Physics, Chemistry, Organic Chemistry/Biology. They logically lead to each other, although that is certainly not how they were constructed in real life. Please don't mistake an observation and a bit of rhetorical flair for a real stab at a branch of scientific research.

 

[Naty1]

If so then how do we define rest mass seeing as everything's moving?

Absolute zero doesn't mean "no motion".

An increasingly confined particle will become incredibly active in accordance with the Heisenberg uncertainty principle...as it's wavelength is constrained it's frequency increases...

Zero point energy is the minimum energy of a system...check it out for a start at http://en.wikipedia.org/wiki/Zero-point_energy

 

[Altabeh]

From above:
"

I don't think that is accurate; in any case QED has been experimentally verified to exquisite detail, roughly 1 part in 10¹²...and special relativity is pretty secure so far that photons ARE massless...

Yeah... no one criticized the experimental aspect of QED and if the theory itself gets shaky by assuming a massive photon, then nothing can change the observed results. So your post is pointless. We were just taking about the loss of gauge invariance in QED which would be there if we assumed photons are massive.

AB

 

[atyy]

That's incredibly simple. Without depolarization at the axon hillock there would be no voltage and therefore the firing threshold of the neuron would never be met and the neuron wouldn't be able to carry out the electrical portion of its electrochemical communication. Why do you ask?

But a depolarization does mean zero voltage (potential difference). So if there is a depolarization, then there is zero voltage. An action potential is a voltage - (50 mV potential difference between the inside and outside of the cell), not a depolarization.

EDIT: Did you ask me this because you think I'm slandering Biology? I'm sorry if I offended, but in the hierarchy of sciences physics is by its very nature the most fundamental. A complete understanding of physics could allow a complete understanding of all other sciences. No other science is so fundamental. That doesn't make them unworthy pursuits, or "easy", it just is a fact of life that each science is derived in sequence: Physics, Chemistry, Organic Chemistry/Biology. They logically lead to each other, although that is certainly not how they were constructed in real life. Please don't mistake an observation and a bit of rhetorical flair for a real stab at a branch of scientific research.

Nah, I thought you're "slandering physics"

 

[Naty1]

Why in the world would they call something at rest when its still moving in some way.

It's all relative, pun intended.

Many terms in common use today have historical origins...physics included...their adoped intepretation on is regularly superseded at a later date by new discoveries or theories that make them somewhat obsolete. It's analogous to asking why left and right have the orientation we all recognize.

 

[Frame Dragger]

But a depolarization does mean zero voltage (potential difference). So if there is a depolarization, then there is zero voltage. An action potential is a voltage - (50 mV potential difference between the inside and outside of the cell), not a depolarization.



Nah, I thought you're "slandering physics"

When depolarization occurs there are ion pumps in the cell which allow for the voltage to occur, and then flood the cell to bring it back into equilibrium. I should add that depolarization in biology is almost a completely different term than it is in physics. Frankly, other than amusing yourself I'm unclear on the purpose of this inquiry.

 

[Dale]

I think these terms of art trip people up more than teachers and professionals realize.

I agree, but I don't know a solution. The historical terms and concepts are in all of the historical documents which are still in use today. Unfortunately, we can't edit the past in order to clear things up. In the end I think it is required that each person learn the terminology with all of its many vagaries and flaws and understand that it is essentially what you would expect as the result of such a very poorly organized committee.

I would love to be able to issue an executive decree banning the term "relativistic mass" in favor of "total energy" and replacing the term "rest mass" with the term "invariant mass" and one more decree requiring any unqualified use of the term "mass" to refer to the invariant mass.

 

[Frame Dragger]

I agree, but I don't know a solution. The historical terms and concepts are in all of the historical documents which are still in use today. Unfortunately, we can't edit the past in order to clear things up. In the end I think it is required that each person learn the terminology with all of its many vagaries and flaws and understand that it is essentially what you would expect as the result of such a very poorly organized committee.

I would love to be able to issue an executive decree banning the term "relativistic mass" in favor of "total energy" and replacing the term "rest mass" with the term "invariant mass" and one more decree requiring any unqualified use of the term "mass" to refer to the invariant mass.

Agreed on all fronts, but since we (the USA) couldn't even make the switch to metric as a society, I'm guessing that reconciling this language may take a longer period of time than the theories will remain as they are now. Sort of like recession speed increasing past c :)

 

[DaveC426913]

I think these terms of art trip people up more than teachers and professionals realize.

I agree, but I don't know a solution.

I disagree. The solution is to pay attention. The sciences are not a place to go if you're looking or neat packaged ideas that fit into your preconceptions.

A student needs to know what an ampere is to understand how to use it. Or a litmus test. Or a particle at rest.

A student will run into lots of trouble if he hears a word or phrase and starts demanding that he knows what it means, despite people telling him it is not as he expects.

 

[Frame Dragger]

I disagree. The solution is to pay attention. The sciences are not a place to go if you're looking or neat packaged ideas that fit into your preconceptions.

A student needs to know what an ampere is to understand how to use it. Or a litmus test. Or a particle at rest.

A student will run into lots of trouble if he hears a word or phrase and starts demanding that he knows what it means, despite people telling him it is not as he expects.

This is a somewhat hermetic view of science. Everyone who needs to understand concepts in physics to enrich their lives doesn't need these pointless hurdles in their way. Yes, people should pay attention as that is the only practical solution to the problem, however that isn't ideal and it is a pointless waste of energy.

If we're looking to discard preconceptions than using terms such as colour and spin and rest-state, etc... are not going to help people. The concept of colour and rotation and rest are fundamental for all people before physics can EVER enter the equation. That means all people must learn and keep track of these multiple definitions.

It's possible, it's not overly taxing, but it's a pointless and wasteful exercise that COULD be corrected.

 

[DaveC426913]

Everyone who needs to understand concepts in physics to enrich their lives doesn't need these pointless hurdles in their way.

This is the same rationale that led to one US state petitioning to redefine pi as 3.

Let's get rid of hurdles involved in students actually learning the science. Let's put science on laminated placards in large letters to make it easier for them to pass the year.

 

[Frame Dragger]

This is the same rationale that led to one US state petitioning to redefine pi as 3.

Let's get rid of hurdles involved in students actually learning the science. Let's put science on laminated placards in large letters to make it easier for them to pass the year.

There is a VAST difference between codifying language that is archaic, and simplifying the fundamental science for the sake of people who have no business in that field. You're too smart not to know that... having some rhetorical fun are we?

 

[atyy]

Would anyone go so far as to say with 't Hooft "But there is another pedagogical point. I see no reason to shield students against the phenomenon of changes of convention and notation. Such transitions are necessary whenever one switches from one field of research to another. They better get used to it."?

 

[Frame Dragger]

Does this in any way add to the science, or the process of sharing information across multiple disciplnes? If so, I'm aching to hear the ways it does. It's an admirably Calvinist attitude, but in terms of learning and information sharing it is indefensible... which is probably why when I keep making points about efficiency, the riposte is off that topic entirey. Hence, this is the pride and ignorance of academia you so often find in the best people. Ah well.

 

[atyy]

Well, if you object to "colour" because it existed in plain English first, then recall that "mass" was used in Newtonian theory first.

 

[Frame Dragger]

Well, if you object to "colour" because it existed in plain English first, then recall that "mass" was used in Newtonian theory first.

I object to colour because while it's easy to understand both the reasoning and the results, it is a needless use of a fundamental concept. Let's be honest, science tends to let these things be named by their discoverers, or collective whimsy. Again... "Three quarks for muster mark." Cute, but not really useful. Shouldn't scientific language evolve with the times instead of becoming a linguistic ruin?

EDIT: Also, the fact that it existed in "plain english" isn't the issue. The fact that we as a species are sight-primary when it comes to senses, and colour is not just a preconcieved linguistic notion, but a VERY basic one. That may explain the modern etymology, but it doesn't excuse it.

 

[HallsofIvy]

This is the same rationale that led to one US state petitioning to redefine pi as 3.

I feel I have to jump into rebut this calumny! (The state was Indiana, by the way.) Specifically, what happened was that House Bill No 246, Indiana Legislature, 1897 began "A bill for an act introducing a new mathematical truth and offered as a contribution to education to be used only by the state of Indiana free of cost by paying any royalties whatever on the same, provided it is accepted by the official action of the legislature of 1997". Of course, you can't charge royalties for the use of "a new mathematical truth' or any truth! But a legislator offered this bill on behalf of a constitutent and, since it didn't actually commit the state to doing anything, most legislators didn't bother to look at it very closely. The paper included trisection of an angle, duplicating the cube, and squaring the circle! It also noted that his quadrature of the circle has been "published in the American Mathematical Monthly, where it was, in fact, run as an advertisement. It also claimed that the work had been approved by specificly named people at the National Astronomical Observatory, University of Michigan, and Johns Hopkins- all of whom later denied even knowing the person who wrote it. The paper doesn't give a value for pi, although as many as nine different values can be deduced from his various calculations.

This is from Underwood Dudley's book "Mathematical Cranks" where he also gives references to "The legal values of $\pi$", published in the Mathematical Intelligencer, volume 7 (1985) pages 69- 72, and "Indiana's squared circle" buy Arthur Hallerberg, in the Mathematics Magazine, volume 50 (1977), pages 136 to 140.

Let's get rid of hurdles involved in students actually learning the science. Let's put science on laminated placards in large letters to make it easier for them to pass the year.

 

[DaveC426913]

I feel I have to jump into rebut this calumny! (The state was Indiana, by the way.) Specifically, what happened was that House Bill No 246, Indiana Legislature, 1897 began "A bill for an act introducing a new mathematical truth and offered as a contribution to education to be used only by the state of Indiana free of cost by paying any royalties whatever on the same, provided it is accepted by the official action of the legislature of 1997". Of course, you can't charge royalties for the use of "a new mathematical truth' or any truth! But a legislator offered this bill on behalf of a constitutent and, since it didn't actually commit the state to doing anything, most legislators didn't bother to look at it very closely. The paper included trisection of an angle, duplicating the cube, and squaring the circle! It also noted that his quadrature of the circle has been "published in the American Mathematical Monthly, where it was, in fact, run as an advertisement. It also claimed that the work had been approved by specificly named people at the National Astronomical Observatory, University of Michigan, and Johns Hopkins- all of whom later denied even knowing the person who wrote it. The paper doesn't give a value for pi, although as many as nine different values can be deduced from his various calculations.

This is from Underwood Dudley's book "Mathematical Cranks" where he also gives references to "The legal values of $\pi$", published in the Mathematical Intelligencer, volume 7 (1985) pages 69- 72, and "Indiana's squared circle" buy Arthur Hallerberg, in the Mathematics Magazine, volume 50 (1977), pages 136 to 140.

Um, can you paraphrase? What is the upshot?

 

[DaveC426913]

There is a VAST difference between codifying language that is archaic, and simplifying the fundamental science for the sake of people who have no business in that field.

Is there a vast difference between simplifying the use of hard to calculate values for the sake of people who have no business in that field, and simplifying the use of hard to intuit terms for the sake of people who have no business in that field?


How would changing the name of a quark do anything? The names are arbitrary; they mean nothing. The meat of the issue is in the properties, and properties can not be summed up in one word. To change them to something you think is more intuitive is to fool a student into thinking a thing's name describes it.

 

[Char. Limit]

Color makes no sense, considering that quarks are too small to be colored.

Spin makes no sense,
as the particle is not actually spinning.

My personal issues are documented in another thread happily titled "Particles in the Palette".

 

[Dale]

Color makes no sense, considering that quarks are too small to be colored.

I agree with this.

Spin makes no sense,
as the particle is not actually spinning.

But I think that spin is a good name, it is angular momentum and things that spin have angular momentum.

 

[Frame Dragger]

Is there a vast difference between simplifying the use of hard to calculate values for the sake of people who have no business in that field, and simplifying the use of hard to intuit terms for the sake of people who have no business in that field?


How would changing the name of a quark do anything? The names are arbitrary; they mean nothing. The meat of the issue is in the properties, and properties can not be summed up in one word. To change them to something you think is more intuitive is to fool a student into thinking a thing's name describes it.

Preserving a formal asthetic because you can't see the possible benefits and see some fundamental good in learning meaningless terms with multiple meanings across similar disciplines, is wrong-headed. I didn't say anything needed to be intuititve, and in fact a not insignificant portion of my small number of posts here have argued against the need for intuition in GR/QM.

That said, what do linguistic and historical anachronisms have to do with the smooth operation of a science? You really think replacing, "rest mass" with "invarient" mass is dumbing things down?!The solution is called, "inventing a new term" or using formalized nomenclature. Other fields do it for the sake of efficiency and communication, and it works. Don't be contrary for the sake of being contrary... this field is plenty arcane and mysterious to most already. Do you think, "colour charge" or "tensor" is harder to explain to someone?... and yet TENSOR is a great term, and "colour charge" is a waste of language.

 

[Char. Limit]

Wth is color charge?

Also, on spin, isn't it more to do with magnetism than actual spinning? I think I saw somewhere that the spin of an electron would lead to an angular velocity close to 100c, if spin were actual angular momentum.

 

[Dale]

what do linguistic and historical anachronisms have to do with the smooth operation of a science?

People still refer to the 1905 paper by Einstein on a regular basis, and I answered a question just yesterday with reference to an 1851 experiment by Fizeau. Like it or not, science is a very historical subject. A well-constructed experiment performed more than one and a half centuries ago or a brilliant theory conceived more than one century ago are still relevant today. That entails a lot of baggage. Especially as today's scientists are trained by the previous generation of scientists who coined terms that are still in use today despite dramatic changes in the theory.

I actually like the term "quark" precisely because it is unambiguously new and not likely to ever be mistaken for any other concept.

 

[Dale]

Also, on spin, isn't it more to do with magnetism than actual spinning? I think I saw somewhere that the spin of an electron would lead to an angular velocity close to 100c, if spin were actual angular momentum.

No, it is actual angular momentum. The problem isn't with spin, the problem is with the classical picture of particles as little billiard balls. It is angular momentum, but it is associated with a quantized excitation of a field and not with a little billiard ball.

 

[atyy]

No, it is actual angular momentum. The problem isn't with spin, the problem is with the classical picture of particles as little billiard balls. It is angular momentum, but it is associated with a quantized excitation of a field and not with a little billiard ball.

While we're digressing, could you comment on whether it is "kwork" or "kwark" to rhyme with "Muster Mark"?

 

[Frame Dragger]

Let me try to be simplistic and clear here.

Why spin is a "bad" term.
If I tell you that something is gague invariant, or is time-symmetric then we have no misunderstanding save those that arise from a lack of knowledge.

If I use the term spin, it is only the context which allows you to determine what kind of spin I mean. Is it the real spin of physical quantities or the description of the inexplicable angular momentum of a single particle? That is why the terminology needs to evolve, espcially as information sharing becomes a more critical part of advancing theories.

 

[Char. Limit]

But the electron IS an 8-ball. Why do you think it has a white spot with a black center? And if you knock one into the corner hole (nucleus) you win the game (start a _______ reaction).

And it's pronounced kwork.