On 2/17/2017 4:19 PM, John Clark wrote:
On Wed, Feb 15, 2017 Telmo Menezes <[email protected]
<mailto:[email protected]>>wrote:
>
>
Dark Matter and Dark Energy remain complete mysteries.
>
As far as I can tell, what we have is a falsification of current
theories. They appear to be good enough approximations for many
things, but then they fail at predicting the expansion rate of the
universe right? Maybe it's dark matter, maybe it's something else,
They are 2 separate mysteries. Dark Matter is a mysterious something
that makes up 28% of the universe and holds galaxies and clusters of
galaxies together. Dark Energy is a even more mysterious something
that makes up 69% of everything and causes the expansion of the entire
universe to accelerate. And about 4% of the universe is made of the
sort of normal matter and energy that until about 20 years ago was the
only type we thought existed.
There is a straightforward extension of General Relativity and Quantum
Mechanics that explains Dark Energy, however it gives a figure that is
10^120 too large, it's been called the worse mismatch between theory
and observation in the entire history of science. I think it's fair to
say we really don't have a clue about Dark Energy, and Dark Matter is
almost as confusing.
I think there's a lack of appreciation of what kind of knowledge science
obtains. Roughly speaking it provides descriptions which are complete
and precise enough to use to make some accurate predictions in a range
of phenomena. The cosmological constant appears as an integration
constant in solutions to Einstein's equations. And we can measure it's
value and use the equations to make good predictions. So in a sense we
know as much about it as Newton knew about gravity (he didn't know why
the gravitational constant took the value it did either). It would be
good to know more about the CC, but we actually "know" more about it
than we do about dark matter.
Brent
The sciences do not try to explain, they hardly even try to interpret,
they mainly make models. By a model is meant a mathematical construct
which, with the addition of certain verbal interpretations, describes
observed phenomena. The justification of such a mathematical construct
is solely and precisely that it is expected to work.
--—John von Neumann
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