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Can mass be created or destroyed?

by physicsnewbie
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mmwave
#2
Aug16-03, 01:41 AM
P: 211
Well, the simple answer is matter cannot be created or destroyed.

The more complicated answer is that in some nuclear reactions particles can be converted into energy ( like in a hydrogen bomb). If that happened to your atoms you would said they were destroyed. If you consider the familiar equation E=mc2 it means there is an equivalence between matter and energy.

I'm sure someone else will give us a more complicated answer.
FZ+
#3
Aug16-03, 09:02 AM
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mmwave: You mean yes, matter can be created or destroyed, right?

Other examples: matter-antimatter annihilation, pair production by energetic photon...

Correction: mass in the conventional sense can be destroyed, but mass/energy is conserved.

LURCH
#4
Aug16-03, 11:23 AM
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Can mass be created or destroyed?

As far as we know, mass cannot be created or destroyed, it can only change form. Matter can become energy, and energy can become matter, but always according to e=m2. So, when a matter-antimatter reaction occurs, the mass of the matter (and antimatter) is converted to energy of equal mass, which propogates outward in verious forms (heat, light, a kinetic shockwave, sound waves, etc), and gets spread out thinner and thinner throughout the cosmos, but never looses anything in quantity. If you ever found a way to capture all the energy that was released in the reaction, and condense it back together into matter, you would have the same amount of mass as the original amount of material used.
jcsd
#5
Aug16-03, 12:09 PM
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Mass means invariant mass and it can be destroyed and created that can be seen in the anihilation of a low energy and high energy electron-poistron pair (equation 1 is an anihilation of a low-energy pair whereas 2 and 3 are high energy pairs).

1) e+e- → γγ

2) e+e- → uû (π°) *

3) e+e- → μ+μ-


*I couldn't find the correct ascii symbols for antiquarks

In these equation the mass on left hand side of the equation totals 1.022 Mev/c2, but on the right hand-side the mass is 1)0 2)1.057 3)2.114, so obviously the mass has changed during these anhilations.

As long as you understand though that invariant mass is essientially 'mass-energy' and can be converted back and forth between other sorts of energy (e.g. K.E.).
mmwave
#6
Aug16-03, 01:14 PM
P: 211
Originally posted by FZ+
mmwave: You mean yes, matter can be created or destroyed, right?

Other examples: matter-antimatter annihilation, pair production by energetic photon...
No. In our everyday lives it is sufficient to say that matter is not destroyed. Your examples are for physics labs and stars and are really the conversion of energy to matter or matter to energy covered in my second paragraph. I believe the better way to look at it from a physics stand point is that matter is just a form of energy.
jcsd
#7
Aug16-03, 04:06 PM
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btw can everyone see the character set I've used for the equations in my last post?

Just in case you can't, here's the equations in written form:

1) electron + positron -> two photons

2) electron + positron -> an up quark and an up antiquark (a neutral pion)

3) electron + positron -> a muon and an anti-muon
mmwave
#8
Aug16-03, 07:25 PM
P: 211
Hi Jcsd,

I could read your first character set so thanks for doing the ascii thing too. EDIT: could NOT read them

Why would they call it invariant mass if it can be converted to energy and disappear? That seems like variation to me.
Hurkyl
#9
Aug16-03, 07:33 PM
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It's invariant under Lorentz transformations; any two (inertial) observers will record the same invariant mass for an object, in contrast with things like speed, kinetic energy, or distance which generally vary between different observers.
Ivan Seeking
#10
Aug17-03, 03:48 PM
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It seems that this issue of "invariant mass" and "mass" is really just a matter of definition.

What term can we use to address the "source" of inertia and gravity?

...if the term "mass" is now treated as meaning rest mass.

Does the concept of mass beyond this notion fail for some reason, or is this this merely a convention?

Perhaps the concept of mass, beyond rest mass, is thought to be simply unnecessary?
Cyberice
#11
Aug20-03, 06:01 PM
P: 50
Can mass be created or destroyed?



If it couldn't the bigbang would have never occured. People fail to realize that. They say that nothing existed before the big bang. Well if that's true then WHAT BLEW UP? :-) So either we deny physics its rules or throw bigbang out the window, the communities choice.
jcsd
#12
Aug20-03, 06:13 PM
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Originally posted by Cyberice
Can mass be created or destroyed?



If it couldn't the bigbang would have never occured. People fail to realize that. They say that nothing existed before the big bang. Well if that's true then WHAT BLEW UP? :-) So either we deny physics its rules or throw bigbang out the window, the communities choice.
No all the matter aound today was there at the time of the bigbang contained within the singularity.
russ_watters
#13
Aug20-03, 10:10 PM
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Originally posted by Cyberice
Can mass be created or destroyed?
So either we deny physics its rules or throw bigbang out the window, the communities choice.
Option A. It is a fundamental part of the Big Bang theory that the rules of science break down at a point just after the Big Bang. So the normal rules don't apply. The truth is we don't know where the matter came from. But it did come from the Big Bang.
Tail
#14
Aug24-03, 01:28 PM
P: 197
Originally posted by FZ+
mmwave: You mean yes, matter can be created or destroyed, right?

Other examples: matter-antimatter annihilation, pair production by energetic photon...
How would you go about creating/destroying mass? What exactly would you do?
jcsd
#15
Aug24-03, 02:25 PM
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Originally posted by Tail
How would you go about creating/destroying mass? What exactly would you do?
see my previous post. In 1) (invariant) mass is destroyed in 3) it is created
Tail
#16
Aug24-03, 02:42 PM
P: 197
But that was not what I was asking, obviously. I'd like to know just how one can create or destroy matter.
jcsd
#17
Aug24-03, 02:50 PM
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Originally posted by Tail
But that was not what I was asking, obviously. I'd like to know just how one can create or destroy matter.
Well, no it's not obvious that that wasn't what you were asking as those are a few of the ways of creating and destroying mass (matter).
Ring
#18
Aug24-03, 10:24 PM
P: 17
Mass and energy are not things they're properties of a system. If you define your system to include all the products of the interacting particles then the mass and energy remain the same.

If a nuclear weapon is detonated in a vault the vault weighs the same before and after the detonation.


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