
What's Wrong With E=MC^2? - jawngee
http://www.scientificblogging.com/hammock_physicist/whats_wrong_emc2
======
dakellog
As someone with a Ph.D. in physics, I found the whole article wrongheaded and
partly wrong. Sure, Einstein's original paper (I did read it in its original
German) did not have E=mc^2 in the short form, but don't worry, since it is
still true. If you compress a spring, it weighs more. If you add a photon to a
box, it weighs more. The net momentum of both does not matter here.

~~~
cool-RR
Not to detract from what you're saying, but just a note: The author has a PhD
in physics as well.

------
lutorm
I don't quite know what he's arguing against. The E that's mc^2 has always
been the rest-mass energy. Hence what Doug wrote for the total energy

E^2 = m^2 c^4 + p^2 c^2

I'm not saying the article is wrong, but he sure could have explained more
clearly what wrongheaded thing he's trying to debunk because I didn't get it.
It sounded kind of like railing that E=mgh is "wrong" because it should be
E=mgh+mv^2.

------
chrischen
So basically to be uber geeky you should start espousing e=mc2 + mv2/2?

~~~
Anon84
Or something like this, even
[http://www2.wolframalpha.com/Calculate/MSP/MSP20811972138108...](http://www2.wolframalpha.com/Calculate/MSP/MSP2081197213810800f8h600003aacbaagh259hehc?MSPStoreType=image/gif&s=10)

(From
[http://www.wolframalpha.com/input/?i=Series[%28m0*c^2%29%2FS...](http://www.wolframalpha.com/input/?i=Series\[%28m0*c^2%29%2FSqrt\[1-%28v%2Fc%29^2\]%2C{v%2C0%2C10})]
)

~~~
chrischen
It's so smart! <http://www.wolframalpha.com/input/?i=are+you+stupid%3F>

~~~
sciolistse
though i will say, i find this hilarious..

[http://www.wolframalpha.com/input/?i=population+of+japan+/+(...](http://www.wolframalpha.com/input/?i=population+of+japan+/+\(death+rate+in+japan+-+\(population+of+japan+*+migration+rate+in+japan+%2B+birth+rate+in+japan\)\)))

------
zandorg
I like how it uses Google to test an opinion: I do this for things like spell
checking and phrase verification.

------
xenophanes
It's one character longer than necessary. Try E=MCC

------
TweedHeads
I am no physicist and would appreciate if somebody can explain why the speed
of light is used everywhere in physics, specially in that E=mc2 formula.

What is the meaning of using light when calculating energy or mass?

And what if light is not the fastest thing in the universe, would we need to
rewrite all formulas?

Excuse my ignorance, but this topic really picks my interest.

~~~
ars
It's actually the opposite. The universe has a speed limit. And light moves as
fast as it is possible to go.

As opposed to light itself being the decider of the speed limit.

Light is not the only thing that moves at the speed limit. Gravity does too.
Magnetic and electric forces do as well (which makes sense since light is made
out of a combination of both, but the point is that the individual elements
also move at the speed limit).

Now, why did the universe pick that specific speed as the limit? No one knows.

~~~
TweedHeads
"The universe has a speed limit. And light moves as fast as it is possible to
go."

My question has always been, how sure are we? Any room for error?

~~~
ars
We are actually sure, I'll tell you how.

Start with e=mc2. This has been accurately measured as true.

First of all notice the c (speed of light [speed of the universe]) in there.

People always talk about how things get heavier when they go faster, so why is
that? It's not a magical property of the universe, it's simply e=mc2

As you go faster, you have more energy. Since you have more energy you are
heavier. Now if you want to go even faster you also have to accelerate that
extra mass (energy) as well, so you need even more energy.

Do that over and over and you get the famous relativity equations. You find
that as you get closer to c your mass goes to infinity.

This is probably not enough to convince you, but I'm not done.

This formula was not discovered first, and then relativity from it. It was the
reverse.

It started from noticing that no matter how fast a distant star was moving
(two binary stars orbiting each other), the light always moved at the same
speed.

Start with that assumption, and create rational formulas to explain how that
could work. They are called the Lorenz transform.

Calculate what happens to mass as it undergoes the Lorenz transform and e=mc2
falls out of the equations.

If there was a faster speed possible the Lorenz transforms would work
differently, and e=mc2 would be different - but we know e=mc2 is correct. And
we've also measured parts of the Lorenz transform as correct.

Look for the book: Relativity, the special and the general theory: a popular
exposition by Albert Einstein. Sunheading: A clear explanation that anyone can
understand.

The whole set of formulas is very self consistent, if any one part was wrong
(and we tested many parts) the rest would be wrong too.

The final question is, ok you can't send matter faster than light, but how do
we know you can send a message faster than light? It's because information has
an energy content. Each bit of information is equal to a small amount of
energy. So if you send information, you are sending energy.

As a side note, tricks _might_ be possible, i.e. don't take the long route
through space, but take a short cut. This could work if the universe is curved
(curved in 4d), but current thinking is that the universe is flat. In the book
I recommended Einstein talks about how to measure if the universe is curved or
flat. (For a 3d example it's going through the earth, instead of on the
surface.)

~~~
TweedHeads
"Start with e=mc2. This has been accurately measured as true."

By whom? If tachyons were the new measure for fastest thing in the universe I
guarantee you that the minimum difference between the old equation and the new
one would make no noticeable difference.

"People always talk about how things get heavier when they go faster"

Who says so and who has proved that? You may get heavier by adding gravitron
collisions to your particles, and that doesn't mean it is a law.

"As you go faster, you have more energy. Since you have more energy you are
heavier."

I didn´t know energy had weight, but again, it may be explainable.

"You find that as you get closer to c your mass goes to infinity."

Unproven. Photons travel at the speed of light and they don't have mass.

"This is probably not enough to convince you"

Nop.

"The light always moved at the same speed."

Who say so? What if light has different speeds based on huge gravitational
forces? Nothing to do with the curvature of spacetime (which I call bullshit)
but with the perception of the observer.

"Start with that assumption, and create rational formulas to explain how that
could work."

If your assumptions are wrong your formulas will also be wrong.

"A clear explanation that anyone can understand."

It is not that I don't understand it, it is just that I don't accept it as
truth.

"The final question is, ok you can't send matter faster than light"

I am not talking about matter, it may well be a limit for matter, but how
about other forms of known and unknown energy or radiation?

Relativism is ok regarding the observer and using light as a measurement unit.
But just throwing a huge number c2 in a formula doesn't make it right, just
the same as throwing another t2 (speed of tachyons squared) would make it
right either.

Here is my formula: E=mt2

My question stands: why the speed of light squared?

~~~
ars
"I didn´t know energy had weight, but again, it may be explainable."

If you didn't know that energy had weight, then how could you possibly
understand anything whatsoever about relativity?

You talk about "adding graviton collisions". Go way way simpler. Energy has
weight. Speed things up, they are heavier. Want to speed it even more? You
need to add even more energy than the first time because now you are also
speeding up the energy [weight] from before.

Run the math. Solve. Final result c=speed_limit. The math is easy, don't take
my word for it. Do you know any calculus? That's all you need for the math.

You are talking about advanced topics like gravitons and tachyons, without
even understanding the simple topics like energy having weight [mass].

How do we know that the weight of energy is equal to the energy times
c_squared?

You can measure it, that's how. The earliest particle accelerators can do it.
Actually you don't even need a particle accelerator.

Take a gamma ray (a photon), cause it to split into an electron and an anti-
electron (using a magnet). Measure the energy of the photon that is left over.
The difference is the energy that was consumed in making the electron and
anti-electron.

Measure the mass [weight] of a single electron.

Do math. Result: e=mc2 (i.e. mass of an electron * 2 * c_squared + energy of
leftover photon = energy of starting photon).

