Are the following observations accurate: 

"E=MC2 shows that Energy converts to Matter or vici versa at the speed
of light squared. Speed, or velocity, to use the correct term, is a
measure of time. Time is a measure of something happening in space, so
we think of space-time as a single dimension.

Throw a log on the fire. Watch as matter is transformed into heat
energy. Note that this is happening in time and space, and we have
arrived the core of Einstein?s equation."

Is E=MC2 really that simple, in its essense?

Hi, thank you for submitting your question to Answers.Google, I
believe I can provide the information you are seeking.

Since 2005 is the International Year of Physics, this is a great question.

Sorry to say, your idea has no relationship to Einstein?s discovery or
the famous equation.

Briefly, remembering that since about 1880 or so it has become
increasingly impossible to really discuss details of anything in
physics in English or other language without benefit of mathematics,
what the equation says is that matter and energy are two forms of the
same thing and that you convert between the two by either multiplying
or dividing by the speed of light squared.

But this conversion is just like converting between inches and
centimeters, it isn?t an explanation, it is just a number.

The equation says nothing in particular about time or the speed of
conversion, in fact, although time is a component of speed, this
equation squares speed and time squared is meaningless, at least in
this context.

See http://www.madsci.org/posts/archives/sep2001/1000903792.Ph.r.html

This irreverent look at the question actually offers a pretty good explanation:
http://www.stresscure.com/hrn/einstein.html

How he came up with the equation is relatively simple, so to speak. He
saw that an easy way to explain some experimental results by others
was to assume that the speed of light was constant.

By using the speed of light as a constant in some earlier equations of
physics, one result that popped out was that e=mc*2 which surprised a
lot of people, including Einstein. The equation says nothing about how
to convert either direction, it just provides an equation for
determining the magnitude of the conversion.

You will find a simple, algebraic derivation at:
http://www.kineticbooks.com/physics/17467/17514/sp.html

Space time is not a single dimension; Relativity says that space and
time are made up of 4 dimensions. This has since been surpassed most
recently by super string theory or M (manifold) theory which, the last
time I checked, required 11 dimensions.

en.wikipedia.org/wiki/M-theory

You can find a calculator and explanation of the equation at
http://www.1728.com/einstein.htm

You?ll find a simplified explanation of Relativity vs Classical Mechanics at:
www.newtonphysics.on.ca/EINSTEIN

There is an FAQ on mass energy conversion at:
http://www.newtonphysics.on.ca/faq/generalization.html

Find a look at the famous equation at:
http://www.eequalsmcsquared.auckland.ac.nz/sites/emc2/

Go to www.discovery.com and search on relativity:

Please don?t feel bad about getting the idea so wrong. It is simply
impossible to discuss modern physics in any meaningful sense using any
language other than mathematics.

This started about the time Einstein began his work and went
completely out of control in the mid-1920s when quantum mechanics was
created.

Think I?m exaggerating? A friend of mine at Harvard won the Nobel
Prize for his work on quantum mechanics. It took almost 50 years for
experts to realize what he had actually contributed and award the
prize.

Also, quantum mechanics was essentially invented twice in two
different mathematical forms and it took years to even demonstrate
that they were equivalent.

Modern physics is complicated and you can make contradictory
statements about it in English which are both true because they aren?t
contradictory in the language of physics which is math.

Another thing to remember when people say one theory has proven
another wrong and such is that Einstein worked mostly with constant
velocities, not acceleration.

Google search term: meaning of mc squared

Thank you again for turning to Answers.Google for help. If a lot of
people add comments saying how wrong I am. They may be correct in part
but I ask you to remember that this was a simplified explanation of
something which takes years of study and an understanding of
mathematics at the level of differential equations at a minimum and
preferably a working familiarity with tensor analysis to really
explain and, unfortunately, also to fully understand the explanation.

One rule we had when I studied physics was, if it makes sense it is
probably wrong. We also used to say about some relatively easy
proboem, "Hey, it's only rocket science, not quantum physics."

I hope I have encouraged you to continue delving into the fascinating
field of modern physics rather than turning you off completely.

---

Request for Answer Clarification by davidetal1234-ga on 21 Feb 2005 18:01 PST

Thanks v. much, siliconsamurai, for your answer. Having read through
your answer and the links I remain confused about some things (well,
many things actually, but we need not go there!) and write to seek
clarification:

1) On some sites I found people talking about M = Mass; others as
M=Matter? So, although this is as basic as it gets, are there terms
equivilent..as in mass is a measure of matter??

2) I wrote: " E=MC2 shows that Energy converts to Matter or vici versa
at the speed of light squared"

You wrote: "what the equation says is that matter and energy are two
forms of the same thing and that you convert between the two by either
multiplying
or dividing by the speed of light squared". 

I understand the distinction - I *think* - between my treating E and M
as two different things (which transform into each other), and your
statement that they are two "forms" of the same thing. This is an
important semantic (if that is the right word).

This means that the rock and the gravity acting on that rock are two
"versions" of the same underlying reality; and that there is no such
thing as 'pure matter" (hence no Absolute Zero) and no 'pure energy'.
Happy with this understanding...Clarication sought: have I understood
you correctly?

3) Then you added: "But this conversion is just like converting
between inches and centimeters, it isn?t an explanation, it is just a
number." This seems terribly important to me. I understood from it
that we cannot (yet) explain exactly *how* one form (eg: E) converts
into another form (M), but all we understand is that it does, and does
so at C2. Have I understood this correctly? This M-theory/string
theory stuff is the search for the explanation...yeah?

4) The references in comments to atomic bombs and nuclear fusion...I
get that M transforms into E in this process, and people get killed.
But I still fail to get why we cannot understand why *any*
tranformation of M=E ...such as the log in the fire ....is not
identical in principle at least to what happens in an atom bomb.

5) Finally!!...if all this clarification amounts really amounts to a
'new question', then please let me know what tip to would be
appropriate..., as I would be most grateful for your response!

Thanks v. much

David

---

Clarification of Answer by siliconsamurai-ga on 22 Feb 2005 06:35 PST

HI, OK, I?ll try but I can?t make it much simpler without introducing
too make misstatements which would lead you even futher astray.

Re: matter vs mass

1)Matter is the state of energy which is what you probably think of as
solid. Mass is the amount of that matter.

The sites which ?confuse? the two are simply trying to reword things
so more people understand. Mass is the actual quantity of Matter.

2)The distinction is that nothing in the equation implies how quickly
anything is being converted. Nothing known except light (actually, the
theory of Relativity says that nothing capable of carrying a signal)
occurs at the speed of light, certainly it doesn?t occur at the square
of the speed of light. When you square light velocity and multiply by
mass, the new unit you get is energy. Just which unit of energy (erg,
joule, hoursepower, etc.) depends on which units you use to measure
mass and which you use to measure velocity.

Gravity ? The Theory of Relativity says that gravity doesn?t and can?t
?act? on anything, gravity is a characteristic of the shape of
4-dimmensional space time. (up/down, right/left, back/forward, and
duration)

?Pure matter? is a nonsense term with no meaning in this context, so
is ?pure energy.? That is, there is no such thing as ?impure energy?
or ?impure matter? in Relativity.

?Absolute zero? can?t be reached because matter has a tiny amount of
atomic motion no matter how much you cool it. This has little or
nothing to do with Relativity.

3) You sort of have it right as long as you remember that c*2 is just
the conversion factor. Cheer up, getting it ?sort of right? is about
all you can expect from looking at this in any language other than
mathematics (and sometimes even then, that?s one reason why there are
lots of engineers but there aren?t very many physicists.)

String theory is the latest attempt at a unified field theory which
Einstein tried to develop for about 45 years with absolutely no
success. The UFT is an attempt to link all physical theories together
? the practical result might be anti-gravity and such.

Here?s the situation from the time of Maxwell, who demonstrated that
electricity and magnetism are closely related and wrote a few very
basic equations demonstrating that.

Einstein produced a theory of gravity which said gravity is
essentially just the shape of space which is distorted by any mass.
The usual demonstration is to place a weight in the center of a sheet
of rubber stretched on a frame, then roll a marble across the surface.
The path is exactly what we would expect if the weight were exerting a
?gravitational? pull on the marble (when you include friction.)

The Grand Unified Field Theory would show how gravity is related to
electromagnetism.

This is all very simplified. If you would like to post a question on
string theory (also known as M or Manifold theory now), I, or someone
else can explain that.

4) GREAT Question! Yes this part you have right, ANY transformation of
M to E is exactly equivalent to a nuclear reactor, an atomic bomb,
what happens inside a star, or when a subatomic partical decays.

The problem is, if you burn something, such as a piece of paper in a
sealed container filled with air or oxygen, no mass is converted to
energy. The weight never changes even a tiny amount.

Fire is a chemical reaction (exothermic ? that is, it released energy)
but it does NOT convert mass into energy, it merely releases chemical
energy stored in the matter. An endothermic (energy absorbing ? sort
of) reaction is required to make explosives or to grow a tree. All
that happens when you burn a log is that a good portion of the
sunlight and chlorophyll reaction which converted basic minerals into
the wood, is release in a very short time.

When you burn something all the original elements (carbon, oxygen,
nitrogen, etc.) remain in exactly their original amounts, they are
just changed in form, for example, a lot of the carbon combines with
oxygen to become carbon dioxide CO2 and a lot of the hydrogen combine
with oxygen to become water H2O.

Nuclear reactions, even very small ones which are occurring in your
body all the time such as isotopes decaying, actually involve a change
in mass and are thus covered by E=MC*2.

When you combine hydrogen in a basic fusion reaction you no longer
have hydrogen, you get energy plus a new element.

When you break up uranium or plutonium, you get several different elements.

In both processes the mass of the latter is less than the mass or the
former, hence they produce energy by destroying mass. To a great
extent you can say that physicists understand exactly how and why this
happens.


Finally, Yes, I feel that most of this clarification does amount to an
entirely new question in my opinion but that?s up to you to decide.

I just hope I have been of assistance ? don?t feel bad, this is NOT a
simple subject, it is just a lot simpler if you understand the math.

As always, please remember that this is a very simplified explanation,
anyone with knowledge of physics could find a dozen ?mistakes? but
that is because it is simplified, not because I don?t understand the
concepts.

If you want an explanation of string theory from me just post the
question to my attention, although you will really need to understand
quantum mechanics first and remember that as you progress from
Newtonian mechanics to Relativistic mechanics to Quantum mechanics and
beyond, it gets progressively more difficult to put into words - most
scientists of the time couldn't understand Relativity and the next
generation which understood Relativity fought tooth and nail against
Quantum mechanics because they didn't understand it.

Since I also restore cars and used to re-engineer heavy equipment I
sometimes tell people I am a factory trained mechanic - car, truck,
Newtonian, Relativitistic, and Quantum.

Let me know if this didn't answer your questions.

Your answer and the subsequent clarification were extensive and
thoughtful. I can't really say that they answered my question BUT ONLY
becuase I have learned from you that I did not really know what I was
asking! So that really is the answer to my question! The result: I
know much more, including knowing what I dont know...and I will
continue musing muchly about the mysteries of E=M^2...Thank you.

David

No.  Those observations are not accurate.  They are not even close.

Just a reminder, xarqi's accurate comment was about the original
question and posted before my answer, although he/she may have
something to say about my answer too (GRIN).

I like you, siliconsamurai-ga.

I did not, and will not, read any of the links you showed above but I believe you. 

I thought E=mc^2 meant the potential energy stored in a matter is
equal to the mass of the matter multiplied by the square of the speed
of light. I thought it is related to the explosive power/energy of
atomic bombs. When I was young, after I learned about E=mc^2 in
Science in Grade school, I wondered at the power that a piece of my
finger nail that I had just clipped if it were made into an atomic
bomb! If they can make that devastating bomb from an atom, how much
more would it be if they use a piece of cut finger nail? (How simple
the mind works when you are young.)

ticbol

Yes, you were almost exactly right as a youngster, the equation is
related to atomic power. Although there are other energies involved,
most of the energy in an atomic explosion is from the destruction of a
tiny amount of matter, or rather it's conversion into energy - it
takes quite a big effort to initiate the conversion which is why
everyone was so excited at the possibility of cold fusion which has
disappeared from the headlines but is still being quietly worked on by
a few people.

To siliconsamurai-ga:

Yes, I have something to say about your answer: it was superb!

By the way David, I didn't want to complicate or confuse things
further and it didn't really matter in this instance, but just for
future reference, the usual way to write an equation like this in
plain text is E=MC^2 where the "^" symbol indicates raising to a power
or you could write E=MC*C. Where I wrote MC*2 was definately not
correct but I felt it would make sense to you while you probably
hadn't seen that use of the "^" symbol.

Siliconsamurai-ga

Please reconsider your assertion that "if you burn something, such as
a piece of paper in a sealed container filled with air or oxygen, no
mass is converted to energy. The weight never changes even a tiny
amount."

I believe the following sources are reputable:

"Even in chemical processes there are tiny changes in mass which
correspond to the energy released or absorbed in a process. When
chemists talk about conservation of mass, they mean that the sum of
the masses of the atoms involved does not change. However, the masses
of molecules are slightly smaller than the sum of the masses of the
atoms they contain (which is why molecules do not just fall apart into
atoms). If we look at the actual molecular masses, we find tiny mass
changes do occur in any chemical reaction."
http://www2.slac.stanford.edu/vvc/theory/relativity.html

"The well-understood heat that was given off in a chemical process was
long supposed to be a product of "energy" somehow stored in the atoms
of the elements involved.  But Einstein became suspicious that the
very mass of the atoms themselves were somehow the source of the
heat--that heat (as energy) was the result of a transformation of a
small amount of mass itself into energy form.  In fact, mass was
itself merely stored energy.
He thus hypothesized that the amount of energy given off in a chemical
reaction was measurable in terms of loss of mass in the elements
involved.  In the end, he came up with the well-known theory that
energy (E) contained in something was equatable to the product of the
mass (M) of that same something and the speed of light times itself
(c2) or E = mc2."
http://www.newgenevacenter.org/biography/einstein2.htm

"Mass and energy are very different properties of matter, and E=mc2
applies just as much to chemical reactions (a burning match) as it
does to reactions in the nucleus (the burning of the stars)."
http://www.ccmr.cornell.edu/education/ask/?quid=590

"Einstein's mechanics applies equally well to any chemical reaction.
In a chemical reaction the amount of energy released in each
interaction represents a very small mass equivalent. So we do not
notice the difference between the mass before and after the reaction.
In chemistry we use the law of conservation of mass but it is not
precisely correct. The need to use relativistic mechanics is more
evident in nuclear reactions. Perhaps that is why we associate
Einstein more with nuclear energy than with chemical energy."
http://www.jnp.hume.ca/cdbook/MCH12.html

Thanks!
Richard-ga

Siliconsamurai (and Richard GA)

Thanks for your efforts guys. Deeply appreciated. Didn't know that
this was the Year of Physics, but maybe this is why the universe has
deposited questions about physics in my brain! What follows is just
some comments on all the comments; feedback if you like from your
'student'!

I must say that I was most relieved to read that chemical reactions
'obey' E=MC^2. Not sure why, but perhaps it has something to do with
me being able to strike a match and watch E=MC^2; no high maths
involved!

I now see that 'hidden' in E=M^2 is a third or underlying variable.
That variable is 'matter'. Hidden, at least, to me! The equation tells
us - I have now learned - that 'matter in its Energy form' may convert
to 'matter in its Mass form' and if this happens, the amount of Energy
that is released is a product of Mass and the number C^2.

In chemical reactions, the amount of "matter in Mass form' that
converts to 'matter in Energy form' is tiny (logs on fires); in
nuclear fusion, the amount is very large (suns and atom bombs).

Given this,  I can source a lot of my confusion about the equation to
'M' and my treating it as Matter, when in fact it stands for Mass.
Yeah yeah: I am sure a slow learner!

Given this, there are several questions which are immediately begged: 

*why "C^2" in the equation? Is this arbitary given given that C^2 is
not real in any sense, as nothing happens faster than C. Referencing
siliconsamurai's earlier observation, if it really is just a
conversion number (like fareignheit to centegrade), could we use
another number if we wanted to? I have now read that Einstien's
breakthrough was around treating the speed of light as a contant -
hence C - but the question I think still stands. Put more clearly
perhaps: 'what **information** do we glean from using C^2 which some
other massive number wouldnt give us?

* if E and M(ass) are forms of matter ...or to quote one of the
websites....a "property" of matter...or 'versions of matter'...are
there any other forms/properties/versions which matter takes? Putting
notions of God to the side, I'm pretty damned sure that I would have
heard if there were any!

* back to this 'pure' business: matter is ***always*** a combination
of E and M as proven by Absolute Zero never having been reached. This
tells us something very important: E=MC^2 is a description of matter.
'matter' is never equivilent to just E or M; it is always and only
equvilent to "E=M" in some combination. Expressed another way: all
Mass contains Energy (sub-atomic particles/('strings'?) which are
moving); all Energy contains Mass (all movement contains some
sub-atomic particles/'strings'). Thus, matter is a combinatin of Mass
and Energy. And that is the nature of reality. Therefore
**'gravitons'** have to exist, even though we have yet to find them!
 
Sheesh. Feel I am streching way past the boundaries of GA etiquette in
raving on like this, so please ignore all of the above if it is rude
to carry on in this way, and, again, thanks v. much for your
illumination of my poor brain!

David

David, I'm sorry to have to point out that you have missed one of the
most important points.

"In chemical reactions, the amount of "matter in Mass form' that
converts to 'matter in Energy form' is tiny (logs on fires); in
nuclear fusion, the amount is very large (suns and atom bombs)."

In a chemical reaction NO MATTER IN ANY FORM CONVERTS TO ENERGY.

Chemical reactions have no connection with the famous equation any
more than the potential energy of a car parked at the top of a hill
has any connection with the mass energy equation despite the fact that
it would be very destructive and a lot of energy would be released if
the brakes failed.

Richard, I respect your comment but I believe it is a disservice to
the client who probably isn't prepared to really participate in what
would be a post graduate-level technical discussion. Remember, this is
a question about basic Relativity as stated about 100 years ago, not
the latest theories.

Understanding Relativity and QM is difficult enough if we just stick
to basics, after all, they are only approximations anyway.

Gasp! 

Seems that either you are right, Siliconsamuria GA, about these
chemical reactions, or Richard GA is right. The weight of website
references is clearly  with Richard, but is that the way to the truth?
You are adamant that Richard and these websites are wrong. Perhaps the
'way forward' would be to find a site that supports the view that
chemical reactions having nothing to do with E=M^C2, perhaps?

'Curiouser and curiouser' cried Alice...:)

David

I'm not sure if this will help or not, but here goes.

What e=mc^2 does tell us is that any energy has a mass equivalent, so
it is true to say that the chemical energy liberated by combustion
also has a mass equivalent.  It does not however mean that that energy
was produced by the conversion of matter into energy.  Matter is not
the sole medium of exchange of energy, and energy stored in chemical
bonds can be liberated as heat without the transformation of matter.

Zeez, I think I am hooked by this E=mc^2 thing again---in its
simpler/simplified meaning. I am not a physicist but I love science,
especially when I was young.

Truly, Physics for physicists/thinkers is mostly about math or
calculations. But Physics for us gawkers is also about
science---meaning about the whys of the natural/physical things in
this the world around us and beyond---about explanations of these
whys.

Back then I already knew that E=mc^2 is about nuclear physics. My
understanding then for energy is about power, for mass is about the
total substance or "matter" in a matter, for c is about some very
large quantity. Hence, the stored power in any matter is a really
very, very big quantity. That is why they worked on atoms only to
produce the atomic bomb---otherwise, if they use larger masses, like 5
kilos of steel, they might blow up the earth with the BOMB.

Of course as I grew older, and as I gathered from leisurely reading
articles about E=mc^2 once in a while as they crossed my path, I
learned not to go further in trying to understand fully that equation.
Like Mathematics, the more  I know about E=mc^2, the more I know less
of it---because you are being sucked into the world of luxons,
tardyons, gluons, protons, pothons, gluballs, gamma, different
meaning/kind of mass, momentum, inertia, quanta, relativity, etc....
It boggles the mind, I always say. Not for my brain, nope.

Anyway, E=mc^2 is about the consequence of very big energy from
releasing the hold of "whatever-on" on the
happy-to-be-separated-but-strapped-to-each-other positive protons in
the nucleus of the atoms of radioactive very heavy metals like
plutoniom isotopes. (Or from "welding"/forcing-to-combine nuclear
particles) Enough force is to be applied, like the initial explosion
of the atomic bomb, to release this mind-boggling energy in the
resulting splitting/forced-separation of the positive particles in
each of the nuclei of some heavy-metal atoms. Can you imagine c^2? It
is 300Million times 300Million = 90,000Million-Million of something.
About 9*10^16 something! So if they split some atoms of, say, a
combined mass of 0.1 kgm, multiplied that by 9*10^16 m^2/sec^2, you'd
get about 9*10^15 joules of energy. Looking that up for its
equivalence in heat alone, you will understand why Japan surrendered
after just two baby atomic bombs...considering that the Japanese
didn't know the meaning of surrender before that.

Burning, explosions (atomic or not), do not create/destroy mass.
Before, during,  or after burning or explosions, the mass involved is
always constant---the Law of Conservation of Mass.

Zeez, who said Physics is easy? 
Let me maintain/retain what little I understand/think-I-understand
about Physics so far. I could be wrong, but its okay. At least I
know/think-I-know something about Physics. I can get by when
encountering questions like the one above once in a while.

I think that the answers above are confusing and partially misleading.
I will try to give a simple explanation. the main idea is:

********************************************************************
The relation between energy and mass is like the relation between a
building's height and its shadow's length. The shadow is a projection
of the building, and the mass is a projection of the energy.
********************************************************************

This means several things: 

A. If the sun is at 45 degrees, the shadow's length is always equal to
the height, and we can write: l=h, where l is the shadow's length, and
h is the building's height. This is equivalent to E=mc^2.

B. We cannot convert shadow's length to height or vice versia. We can
only change the height, and thus the shadow's length will change.
Similarly, WE CANNOT CONVERT ENERGY TO MASS OR VICE VERSIA.

C. What we can do, is to take energy from a system, and thus
indirectly reduce its mass (i.e., its resistance to acceleration or
its gravitation).

D. Even in a TNT explosion, chemical energy is passed to the
environment, so the TNT after the explosion has less energy than
before, and therefore it will have lower mass. THERE IS NO PRINCIPAL
DIFFERENCE BETWEEN THIS "MASS-ENERGY" TRANSFORMATION AND WHAT HAPPENS
IN A NUCLEAR REACTION.

E. In an atomic bomb, the heat energy passed to the world has made the
bomb lighter, but MADE THE WORLD HEAVIER. Therefore mass did not
"dissapear" or have been "converted" to energy. The source of the
energy in this case is the potential of the 'strong force' between the
particles.

F. Even a particle with no apparent potential energy has a "resting
energy", which projects a "resting mass". This resting energy can be
transformed to other energy (e.g. in annihilation of an electron and a
positron), and therefore the particle will "lose mass" along with
losing its resting energy. Again, the energy is passed from place to
place, while the mass only "follows' it.

amirc, that is wrong so many ways I don't even know where to begin but-

D. Even in a TNT explosion, chemical energy is passed to the
environment, so the TNT after the explosion has less energy than
before, and therefore it will have lower mass. THERE IS NO PRINCIPAL
DIFFERENCE BETWEEN THIS "MASS-ENERGY" TRANSFORMATION AND WHAT HAPPENS
IN A NUCLEAR REACTION.

Absolute nonsense. there is no TNT after the explosion, the components
that made up the TNT have not lost any mass,  Here is a common sense
way to look at it without even thinking about real physics - if the
components had lost mass then, over the past few billion years of
chemical reactions the Universe would have completely dissappeared as
each reaction caused a loss of mass.


E. In an atomic bomb, the heat energy passed to the world has made the
bomb lighter, but MADE THE WORLD HEAVIER. Therefore mass did not
"dissapear" or have been "converted" to energy. The source of the
energy in this case is the potential of the 'strong force' between the
particles..

Absolutely, positively, 100% wrong. Energy has no weight or mass so it
can't make anything heavier.

Your other ideas are similarly incorrect.

Your comments show an understanding of science which was prevalent in the 1800's.

You appear to be completely misunderstanding all of Physics since
about 1890, including conservation of energy. If your ideas were
correct then most modern technology wouldn't work.

Sorry, please don't take this as a personal attack but I can't let
this misinformation pass unchallenged.

Just thought I'd say thanks again to Google Answers for referencing my
website: www.1728.com
It's good to know my website is highly regarded.  Being cited by
Google Answers is confirmation of that.

wolf

Dear Siliconsamurai-ga, 

Although I don't like using that style of expression, I would like to
use your first sentence as an opening (only with switching my name
with yours, of course).

D. Of course "The TNT after the explosion" means "the components that
made up the TNT". I thought it was obvious. I hope you didn't
seriously think that my intention was that the TNT compound is
unchanged (If you did, than I am really insulted?).
As for your "common sense" argument: I'm afraid you did not understand
my explanation. It does not imply that the universe's mass decreases
with a chemical reaction (I really don't know how you concluded this,
but maybe I didn't explain myself well). Maybe this will help:
Some of the mass of the TNT before the explosion was the projection of
its potential chemical energy, but most of it was the projection of
the rest energy of its particles. The latter is not changed in the
explosion. The former decreases with the decrease in the potential
energy, but increases the rest of the world's mass by increasing its
energy. Therefore, the total mass of the universe did not change.

E. See response to D. 

I see now that my explanation may not have been as clear as I thought,
so I guess you're right about that.

It's worth mentioning that I've verified the interpretation presented
above with a Physics Dr. . Additionally, In order to minimize future
quarrels, I suggest you look at the lecture of Prof. Michael Fowler
from University of Virginia, at
http://galileo.phys.virginia.edu/classes/252/mass_and_energy.html,
which says similar things (e.g., "Give a ballpark estimate of the
change in mass of a million tons of TNT on exploding. ... So the
change in weight is of order 10-10 x106 tons, about a hundred grams.")

You too, please don't take this personally, and let me once again
quote you, this time for your fine ending sentence.

P.S. Regardless of who's right, a good idea would be to express
yourself more cautiously and less confidently in future debates.

Saying that something is "absolutely wrong", "nonsence", "shows no
understanding" etc. doesn't make you right. It just makes you more
embarrassed when you turn out to be wrong.

Amirc10...thank you for your comments. As a result of them I have
posted a new question about 'pure energy'.

I also agree with the tenor our your comments. An enquiry about E=MC^2
has - after a couple of answers and many comments by several people,
finally decended into something of a slanging match. This leaving me
(someone with a high school certificate) pretty convinced that no one
really understands that formula! There are many possible
understandings/beliefs about it and reality remains mysterious, or so
it seems. Perhaps it will ever be thus.

David

David, I'm sincerely sorry you have been so misled by some comments by
people who haven't studied physics for years and who aren't qualified
researchers.

No, I am not embarrased for actually understanding the past 120 years of physics.

Actually a LOT of people thoroughly understand the equation, they are
called physicists.

Don't be misled by mere comments by people who may have no more
qualifications here than a valid e-mail address and one or two
comments - that doesn't make them correct.

FYI, If anyone is interested, PBS is re-running The Elegant Universe in
most areas this week.

It can explain a lot of basic cosmology - check your schedules to see
if it is airing in your area.

Disclaimer - Although I used to work for the station which produces
Nova (WGBH), I am no longer affiliated with the station and am simply
pointing out that this is an interesting program.

Just stumbled across this and thought I could step in to adjudicate :)
siliconsamurai's answer is pretty much correct, and I recommend that
you use his answer to help you gain your intuitive understanding of
what's going on.  Nevertheless the others who have commented here
including amirc do have a point.

I think the problem has arisen because the concept of REST mass hasn't
been discussed.

Suppose my log has a rest mass of 1 kg which I find out by weighing it
on some scales.  Then E=mc^2 says that it will have a huge REST
energy.
Now suppose I throw my log (possibly at a fire) then in CLASSICAL
physics (i.e. before einstein) the log has KINETIC energy and it's
mass is the same.
But modern physics (i.e. relativity) says that the MASS (but not the
rest mass) of the log increases (by an incredibly small amount)!!! 
Using E=mc^2 this means that the energy of my log has increased, and
luckily enough the increase in energy is almost the same as the
kinetic energy that we used to have in classical physics.

So what's all this got to do with burning my log?  Well in classical
log burning, my log (and the oxygen that we need to use to burn it)
would have a mass exactly equal to the masses of all the products of
the burning (the smoke the carbon dioxide and the water).  The burning
process however would give out energy (in the form of heat and light),
and this was attributed to some internal chemical energy.

Now we want to do modern log burning.  Since we're only doing
chemistry we'll pretend that atoms are the fundamental building blocks
of the universe and we can't find anything smaller.  Then each atom
will have it's own rest mass.  We can think of our log as groups of
these atoms "bonded" together.  So what's the rest mass of our log? 
Surely it's the sum of the rest masses of the atoms that make it up? 
Unfortunately not, there's a tiny little bit extra which effectively
represents the classical internal chemical energy.  And so in a
chemical reaction (such as log burning) NONE of the atoms change their
rest mass, but the total mass of the chemicals involved has changed a
very tiny bit.

The key thing to understand here however is just how tiny all these
changes in mass are compared to the rest mass.  Have you ever felt
heavier while on a fast train journey?  Or felt suddenly heavier as
your skin absorbed some sunrays?  Hopefully the answer to these
questions is no.  All these forms of energy/mass that we have talked
about are absolutely tiny compared to the huge amount of rest
energy/mass that makes up the objects we see around us.

log burning - a mathematician's revenge