
#1
Jan2014, 03:00 AM

P: 6

Hi, I'm new both to this forum and to physics in general. Here's hoping I've posted in the right place....
I'm basically trying to understand the difference between energy and matter and how one can become the other. Please bear with me, I'm a total layman and can't seem to get a definitive answer anywhere online. So I guess I get the basics: Matter is made up of atoms which are made up of subatomic particles. But the added mass of the individual particles doesn't add up to the total mass of the atom. The remaining mass is made up of energy. The energy that was needed to bind the particles into a nucleus is converted into mass when the strong force takes over from the EM force. Which means that matter is partly converted energy.... But what about the particles that make up the atom? Were the protons, electrons and neutrons matter before they became bound together? Or were these particles themselves energy to begin with? The reason I'm confused is because free electrons are supposed to be electrical energy, not matter. And, seeing as photons are free moving and they are energy, I'm assuming that subatomic particles are energy until they are bound into an atom, making them matter.....? So essentially I'm asking, are protons, electrons and neutrons always matter, or can they be energy as well? Sorry if this is a dumb question. I'm certainly no physicist, just curious. 



#2
Jan2014, 03:20 AM

Sci Advisor
PF Gold
P: 2,067

Energy comes in a number of forms  thermal energy, potential energy, kinetic energy and others as well. Mass is a form of energy  but energy is not mass.
Exactly what energy is, is slightly tricky. Its actually what's defined by this theorem called Noether's Theorem: http://math.ucr.edu/home/baez/noether.html http://www.physics.ucla.edu/~cwp/art...g/noether.html What the theorem says is if something very fundamental and important to physics, called the Lagrangian, doesn't change when you do something to it like change your coordinates, then a conserved quantity exists. It turns out kinetic and potential energy are the invariant quantities associated with time invariance. Because of this nifty fact nowadays we define energy this way, and lo and behold it turns out mass is a form of energy. So basically because energy is what this nifty theorem says it is, mass is a form of energy. If you want to pursue this further, the book to get is Lenny Suskinds book: http://www.amazon.com/TheTheoretica.../dp/046502811X It also has associated video lectures: http://theoreticalminimum.com/ Thanks Bill 



#3
Jan2014, 04:05 AM

P: 724

Not a dumb question at all. The way you worded it I believe all answers will be somewhat incorrect as some of the particles you listed are composite but mass is conserved and some of the fundamental particles comprise the electromagnetic fields that span spacetime and are even more difficult to define. Let's hear the better informed posters as I am also not a physicist. 



#4
Jan2014, 06:02 AM

P: 6

Energy is Matter is Energy?  confused layman hereSorry, I must be the least mathematical person on the planet. Is there a way of simplifying the definition of energy in a nontechnical way? 



#5
Jan2014, 06:15 AM

P: 6





#6
Jan2014, 06:22 AM

Mentor
P: 11,255

Energy is a property of something, not a "something" in itself.
For a sort of analogy, consider the color blue. Something can be blue, but you can't have just "blue" all by itself. 



#7
Jan2014, 06:29 AM

Sci Advisor
PF Gold
P: 2,067

You have run into a fundamental problem with physics  at some point the jig is up  you simply can't explain some things without math. Unfortunately this is one of them. Simply accept under the modern definition of energy mass is a form of energy. Energy can be transformed into one form or another  but can't be destroyed ie is conserved. One can convert mass into say kinetic energy (eg when uranium atoms split they fly apart but the mass of what they split into is a bit less  it has been converted to kinetic energy) and the energy in photons into mass (for example you bang two photons together, which have no mass, and you can get an electron and a positron out  which have mass) and things like that. Jtlbell is correct  energy is simply a property things have that is conserved. If mass suddenly appears something else with this property energy disappears and conversely. Thanks Bill 



#8
Jan2014, 12:12 PM

P: 2

bhobba:
Physics use math, to create models which allow to predict behavior of natural phenomena. But math does not carry an explanation itself. There are numerous examples when using a math model we end up in trouble e.g. some solutions to Schroedringer equation lead to infinity etc. If we don't have a good, imaginable process and we base all our understanding on math we are using  this is not good physics. It is like predicting a strange, elongated star when looking through a telescope with a scratch and being sure it is there, becase telescope shows so. Physics describes reality, math is a model  less or more useful, but just a model. But coming back to your question Noname: Answer is difficult, because we still don't know what makes particles massive. We don't have a good explanation to this yet. Esistance of Higgs boson carries some answers, but not all. So, while we may enjoy using our smartphones and electronics, we as civilization still don't know this very basic thing  what is mass? Go for it, you may find an answer. Look at the math, but don't get overwhelmed by it. Math is not reality. More to your question Noname: Were the protons, electrons and neutrons matter before they became bound together? Or were these particles themselves energy to begin with? As said before, energy is just a parameter, so a particle cannot be its own parameter. However, electron and positron can come to life just from a single high energy photon of Xray, right in the middle of vacuum. So in a sense, they come from pure electromagnetic energy of a photon, which vanishes the same moment. You probably could imagine a whole proton or neutron come to life in a similar manner, but we are unable to produce such a ultra high energy photon  the only way to produce e.g. protons (or other hadrons) for us a civilization is to create it through a set of collisions of smaller particles. If we can prove that those smaller particles come to life from a single photon, than not directly, we can prove that a proton could come from a single flash of electromagnetic energy. I hope this lengthy answer sheds some light on what caught your attention. 



#9
Jan2014, 12:22 PM

Sci Advisor
PF Gold
P: 2,226

Energy depends on frame of reference, e.g. in Newtonian physics transaltional kinetic energy is (mv^2)/2, but the value of 'v' and hence kinetic energy depends on the frame of reference. Mass doesn't depend on frame of reference and if you like the mass of a system is precisely the energy of the system that can't be transformed away by a change of frame of reference.




#10
Jan2014, 04:46 PM

P: 2

jcsd:
This is a great mathematical explanation, but no offence  it says nothing about physical world. You just explained what comes from equations. 



#11
Jan2014, 05:09 PM

Mentor
P: 16,485

The equations describe the physical world. That is why we perform experiments, to make sure that we are using equations that do, in fact, describe the world.
If you think that they do not say anything about the physical world then you must not know how to speak the single best language we have for describing the physical world. 



#12
Jan2014, 05:16 PM

Mentor
P: 16,485





#13
Jan2014, 05:53 PM

P: 6

Matter is a concentrated form of energy. Think of what happens when you split an atom causing an atomic explosion or bomb. You are converting matter (atoms) into energy.




#14
Jan2514, 01:52 AM

P: 6

I think I get it a bit better now. I'm gonna watch a documentary on this subject tonight and hopefully it will cement my understanding.
I find physics fascinating but have very little comprehension of maths, so it's interesting to read the almost philosophical mini debate here about the relationship between maths and physics. I'm gonna stay curious. Thanks for your help! 



#15
Jan2514, 02:26 AM

Sci Advisor
PF Gold
P: 2,067

Even good old Euclidean geometry which explains the many properties of points and lines says otherwise. Thanks Bill 


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