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E =mc{squared}

How Did He Arrive At This ?

What Was The Guy Thinking When He Cooked Up This Mess .

How Did He Arrive At This ?

What Was The Guy Thinking When He Cooked Up This Mess .

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E =mc{squared}

How Did He Arrive At This ?

What Was The Guy Thinking When He Cooked Up This Mess .

How Did He Arrive At This ?

What Was The Guy Thinking When He Cooked Up This Mess .

- #2

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He guessed. :)

Try the search you'll find alot of stuff on this.

Try the search you'll find alot of stuff on this.

- #3

SpaceTiger

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I think it's fair to say that most ground-breaking theories are little more than educated guesses.

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am I missing something here?

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SpaceTiger

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Units are a human invention, so their consistency has no physical meaning. The real key thing here is that the physical concept of energy is related to that of mass, things which had been considered separately prior to Einstein.moose said:

am I missing something here?

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Does this mean units of the "meter" and "kilogram" were invented to have a relationship too?SpaceTiger said:Units are a human invention, so their consistency has no physical meaning. The real key thing here is that the physical concept of energy is related to that of mass, things which had been considered separately prior to Einstein.

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Daniel.

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SpaceTiger

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Not sure what you mean. The units of meters and kilograms are arbitrary scalings to two different kinds of quantities. Nobody writes an equation with one side having units of meters and the other with units of kilograms. That would imply "inconsistent" units.eNathan said:Does this mean units of the "meter" and "kilogram" were invented to have a relationship too?

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SpaceTiger

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We are talking about e=mc^2 here, what this means is that the energy that could come from mass (in joules) is equavilant to the product of the mass (in KG) and the speed of light, c (in meters/second).SpaceTiger said:Not sure what you mean. The units of meters and kilograms are arbitrary scalings to two different kinds of quantities. Nobody writes an equation with one side having units of meters and the other with units of kilograms. That would imply "inconsistent" units.

So what I am saying is this. What if we re-arranged the equation to this.

e=mc^2 where "m" is in pounds, and "c" is in miles per hour, and "e" is still in joules. Would this equation work? no, the units have a relationship. The American Standard Units are terrible :rofl:

- #11

chroot

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Of course it would still work:eNathan said:e=mc^2 where "m" is in pounds, and "c" is in miles per hour, and "e" is still in joules. Would this equation work? no, the units have a relationship. The American Standard Units are terrible :rofl:

http://www.google.com/search?hl=en&lr=&safe=off&q=5+pounds+*+(670616629+miles/hour)^2&btnG=Search

The

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[tex] 1 \ J=1\ Kg\cdot 1ms^{-2}\cdot 1m=\frac{1}{0.453}\mbox{pounds}\cdot \frac{1}{1609}mi\cdot \left(\frac{1}{3600}hr\right)^{-2}\cdot \frac{1}{1609} mi [/tex]

It's not pretty anymore.

Daniel.

- #13

russ_watters

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I wouldn't quite say "arbitrary". Unlike the English system, SI was designed specifically to be easy to use. I don't know the specifics of how it was done, but it is very convenient that (for example) water has a mass of 1g/cc and a heat capacity of 1cal/g*C.SpaceTiger said:Not sure what you mean. The units of meters and kilograms are arbitrary scalings to two different kinds of quantities.

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Daniel.

- #15

Integral

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Just for the record, Einstein did not just "guess" this relationship. It is a derived result of aplying the Lorentz transforms to the kinematics equations of physics.

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DaveC426913

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Consider a slightly different example (because that's the one I know).

[tex]F = \frac{m_1.m_2}{r^2}[/tex]

This is the formula that shows the*relationship* to between two masses and gravity. It tells us that the gravitational attraction is directly **proportional** to the masses of the two bodies and inversely **proportional** to the square of their distances. *Note that there are no units, and that you cannot use this formula to calculate actual values.* you can only show relationships (double the mass to double the force, halve the distance to quadruple the force).

To use it to provide actual figures, we need to provide some units. We will measure the mass in grams and the radius in meters. But now our formula needs a constant: G.

[tex]F = G.\frac{m_1.m_2}{r^2}[/tex]

The constant G is equal to [tex]6.672.10^-11 N m^2 kg^-2[/tex]. Note the units.

If you plug all these together into the formula, including some mass and distance units, you will end up with a number**and** a unit of measurement:**m.a** - as in **F=m.a**. Hey! That's a unit of force!

Note that you could plug inches and stones into the equation, but to do that, your G constant would have to be converted to those units too.

The law itself is universal. The application of that law, is man-made.

[tex]F = \frac{m_1.m_2}{r^2}[/tex]

This is the formula that shows the

To use it to provide actual figures, we need to provide some units. We will measure the mass in grams and the radius in meters. But now our formula needs a constant: G.

[tex]F = G.\frac{m_1.m_2}{r^2}[/tex]

The constant G is equal to [tex]6.672.10^-11 N m^2 kg^-2[/tex]. Note the units.

If you plug all these together into the formula, including some mass and distance units, you will end up with a number

Note that you could plug inches and stones into the equation, but to do that, your G constant would have to be converted to those units too.

The law itself is universal. The application of that law, is man-made.

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Daniel.

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DaveC426913

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I was merely pointing out the difference between proportionality and equality.

E=mc^2 is a proportionality.

Or am I completely wrong?

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Integral said:

Just for the record, Einstein did not just "guess" this relationship. It is a derived result of aplying the Lorentz transforms to the kinematics equations of physics.

I was joking.

- #20

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E = mc^2 is a proportionality and an equality.

For every unit mass m multiplied by the square of the speed of light in any unit, will result in energy released with units composed of those m and c are made of. Its redundant, I dont know why you would want to toy with the units, but the relationship holds anway.

Changing the units will just require a scalar conversion factor, such as G in gravitation or K in electrics to get an answer in joules.

For every unit mass m multiplied by the square of the speed of light in any unit, will result in energy released with units composed of those m and c are made of. Its redundant, I dont know why you would want to toy with the units, but the relationship holds anway.

Changing the units will just require a scalar conversion factor, such as G in gravitation or K in electrics to get an answer in joules.

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- #21

HallsofIvy

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No,you're partly right/wrong.You need both experiments and theory to confirm to you that:DaveC426913 said:

I was merely pointing out the difference between proportionality and equality.

E=mc^2 is a proportionality.

Or am I completely wrong?

[tex] E\sim mc^{2}\Rightarrow E=k\cdot mc^{2} \ \mbox{with} \ k=1 [/tex]

Oh,and logics usually makes a difference.If it hadn't been for logics,science would have been different,to say the least.

Daniel.

- #23

DaveC426913

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The units for energy, mass and speed were in existence before Einstein found this formula.

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It's nothing new...

Daniel.

- #25

SpaceTiger

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I would still say that's pretty arbitrary from the physical standpoint. You don't have to convince me that metric units are easier to use, though. English units drive me nuts.russ_watters said:I wouldn't quite say "arbitrary". Unlike the English system, SI was designed specifically to be easy to use. I don't know the specifics of how it was done, but it is very convenient that (for example) water has a mass of 1g/cc and a heat capacity of 1cal/g*C.

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