Percentage of known energy in the Universe

[mister i]

TL;DR Summary

It is said that the universe is made up of approximately 4.9% ordinary matter, 26.8% dark matter and 69.3% dark energy. Why isn't ordinary energy included in this "pie"?

It is said that the universe is made up of approximately 4.9% ordinary matter, 26.8% dark matter and 69.3% dark energy. Why isn't ordinary energy included in this "pie"? I suppose it is included within ordinary matter, but could it be calculated what % are particles with mass and what % is pure known energy?

 

[Ibix]

"Pure energy" is a science fiction concept, not a physics one.

The mass of composite particles is not the same as the sum of the masses of their constituent particles, it is true. But you can't divide that into "particles" and "energy" in any meaningful way because mass is not an additive quantity.

 

[PeterDonis]

Why isn't ordinary energy included in this "pie"? I suppose it is included within ordinary matter, but could it be calculated what % are particles with mass and what % is pure known energy?

What do you mean by "ordinary energy"? What do you mean by "pure known energy"?

If you mean radiation, that is a tiny fraction of a percent of the total and is not usually included in such breakdowns for that reason. But neither "ordinary energy" nor "pure known energy" are good descriptions of radiation.

 

[mister i]

My knowledge of physics is very limited, for example I don't know if kinetic energy could have an equivalence with matter through the formula $m=E/c^2$. If it does, then my common sense tells me that it must be very large since there are billions of billions of stars moving at high speeds in the universe.

 

[Ibix]

Kinetic energy can be a contribution to mass when there is kinetic energy in the center of mass rest frame. As a fraction of total energy, it is $1-\sqrt{1-v^2/c^2}$, which is approximately $v^2/2c^2$. For typical speeds of astronomical objects it's utterly negligible (sixth decimal place at least).

 

[Orodruin]

common sense

What people refer to as “common sense” generally provides very poor guidance to the physics of extreme objects (such as the entire universe). It is developed from everyday experience and we have very little everyday experience with extreme objects. There is no a priori reason to believe it should be possible to extrapolate.