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Old February 22nd 17, 09:04 PM posted to sci.astro.research
Phillip Helbig (undress to reply)[_2_]
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Default Cosmic Energy Budget, vs time

In article ,
writes:

Questions (below) relate to total energy (sum of terms) in this paper:

In the paper, "The Cosmic Energy Inventory" Fukugita / Peebles, They


At any rate, this 100% of known stuff (5% if we were to include dark
stuff) must total to the same value no matter what age of the universe I
consider, right?


To the extent that mass is conserved. Of course, they are talking about
mass fractions, not absolute numbers.

In other words, section 7 is post stellar radiation. section 6 is post
stellar nuclear binding energy.


Yes, but how much energy is released by fusion during the lifetime of a
star? 1% of the rest mass or something like that. Negligible at the
precision you have here. Ditto for radiation from starlight. (Almost
all photons are CMB photons, by the way.)


OK, sure, I get the 1% conversion factor. But we can independently
measure the photons (energy) produced. And we know the mass to energy
conversion ratio. So, we can estimate the mass that disappeared, and
appeared as energy (radiation).


Except that most radiation doesn't come from fusion in stars.

We can also guess at volume of universe with age, via creating models.

So, we can estimate the ratio (dE/dt from stellar etc. processes) vs
(dV/dt of universe) to get an energy density of the universe as a
function of age of the universe.

Same as dM/dt vs dV/dt by the way since a reduction in M is what drives
an increase in E radiation (from stellar processes) cosmically speaking.

Similarly, we can guess at dark energy as being proportional to V_universe.


It is exactly proportional, if it is the cosmological constant.

BUT, *if* we find that dE/dt is linarly related to universe volume, and,
dark energy is supposed to be linearly related to universe volume, that
would essentially mean that mass to energy conversion is linear to dark
energy creation.

Right?


Wrong. First, you are almost assuming that that which you wish to prove
is true. Second, just because two things are linearly related doesn't
mean that they are the same thing, nor even that one causes the other.
There is a good anticorrelation between global warming and the number of
pirates, a good correlation between the number of stork pairs and the
birthrate.

In other words, could the cosmological constant just be the conversion
ratio for mass that disappears due to E=mc^2 processes, and space that
appears (currently ascribed to expansion of the universe (more space
today than yesterday due to Hubble expansion)).


No, because the cosmological constant has a different equation of state
than radiation.

These are treated as separate things today, but is there any observation
that requires they actually be unrelated? I mean, if they are both
linear with expansion of the universe, might they be interelated?


See above. You also have it backwards; you need an observation (or
theory) to prove that they are related.

We know of things like water evaporating where a small volume of one
form of a thing is converted into a large volume of a different form of
that same thing (condensed matter water to vapor water). Why can't it
be that what we call empty space is just the "vapor" form of what we
call "matter"?


Because it doesn't work quantitatively.