Alamar

E=mc^2

E/m = c^2

what is the ratio of Energy to mass in the Universe?

mathman

Total energy in the universe is an open question. There is a zero energy model, where gravity is the negative part. There are also concepts, dark matter and dark energy which add further difficulties to getting an answer.

Alamar

From this, it seems that value of Energy or mass can not be infinite.

topsquark

I've always been a proponent of a finite Universe but specifically how does $\displaystyle E = mc^2$ imply that E or m cannot be infinite? (And if you are going to use that equation for that purpose you should really be using the whole equation: $\displaystyle E^2 = m^2 c^4 + p^2 c^2$.)

-Dan

Alamar

E=mc^2

E/m=c^2

Maximum_Energy / 1 = c^2
We know the mass (1), we know what value c^2 has, we can solve for Maximum_Energy.

1 / Maximum_mass = c^2
We know Energy (1), we know what value c^2 has, we can solve for Maximum_mass.

v8archie

You do know that the E and m in that equation are changes in quantities, right? So in fission, the energy released E is equal to the speed of light multiplied by the difference between the total mass of uranium before the fission event and the total mass of all the elements left after the fission event.

Alamar

I have not looked at nuclear fission much. I did look at nuclear fusion and it can be a cycle.

The CNO cycle (for carbon–nitrogen–oxygen) is one of the two (known) sets of fusion reactions by which stars convert hydrogen to helium, the other being the proton–proton chain reaction.

I'm not sure how fission comes into play with E=mc^2.

My question was: Can you solve for Maximum_Energy and/or Maximum_mass knowing c^2?

topsquark

I'm still fuzzy. What are Maximum_Energy and Maximum_mass? You've got, for example: "Maximum_Energy / 1 = c^2." Why is m = 1? Maximum Energy of what?

-Dan

Alamar

E/m=c^2

Maximum_Energy / 1 = c^2

Maximum_Energy / 1 = 8.98755179*10^16 / 1

8.98755179*10^16 * 1 = Maximum_Energy * 1

Maximum_Energy = 8.98755179*10^16

I hope I cross multiplied correctly. Same can be done if you substitute 1 for Maximum_mass and solve. Here c^2 = 8.98755179*10^16

The reason why I called it Maximum_Energy is because if mass is set to 1, it is at its minimum (and Energy should be at its maximum) Right?

I guess mass could be set to be even smaller, for example instead of 1, it could be set at 0.5?, but then the math gets more complicated.

topsquark

It does increase as m goes to 0. But I suppose that isn't really my question: Maximum Energy of what? If it's the maximum energy a particle could contain then that wouldn't be the maximum. I posted this equation earlier: $\displaystyle E^2 = m^2c^4 + p^2c^2$. The energy increases as p increases as well, even if you don't change the mass.

We really need a better clue as to what you are talking about before we can give you a decent answer.

-Dan