On Sep 15, 11:53 pm, Mason Barge <
masonba...@gmail.com> wrote:
> On Sat, 15 Sep 2012 03:14:35 -0700 (PDT), Martin Phipps
> <
martinphip...@yahoo.com> wrote:
> >On Sep 13, 11:25 pm, Mason Barge <
masonba...@gmail.com> wrote:
> >> On Wed, 12 Sep 2012 21:31:18 -0700 (PDT), Martin Phipps
>
> >> <
martinphip...@yahoo.com> wrote:
>
> >> [...]
>
> >> >God isn't real. It's just your imagination.
>
> >> >And, yes, belief in Dark Energy is belief but it is not religious
> >> >belief. Astrophysicists would be happy if you showed them where they
> >> >made a mistake. One possibility is that time passes more slowly in
> >> >empty space and thus distant galaxies appear farther away than they
> >> >actually are. Alternatively empty space has to be applying some
> >> >outward pressure that causes the universe to expand. It's one or the
> >> >other. You have to follow the evidence.
>
> >> Alternatively?
>
> >> In other words, this is nothing but a lot of guesses to hide the fact that
> >> physics cannot, at least at this point, explain how the universe workd.
>
> >"One or the other" applies to just about everything.
>
> >The defendant is guilty... or he isn't.
> >My wife is pregnant... or she isn't.
> >I'm going to get paid today... or I won't.
>
> >In this case the rate of the universe's expansion is increasing and
> >dark energy is real... or it isn't and it's not.
>
> >It's called being honest.
>
> Nice bit of condescending tone.
Thank you. I try my best to let my distain for ignorance get across.
> These are not "alternatives".
Actually, they are in so far as if time slows down in empty space then
there is no need to presume that the rate of the expansion of the
universe is increasing. It's like this: as the universe expands there
is more empty space between the galaxies. We expect the rate of
expansion to slow down because galaxies are attracted to each other
and, thus, it comnes as a surprise when astromers measure the rate of
universal expansion and find it to be increasing. Dark energy is a
hypothesis: it isn't really a theory because the use of the word
"theory" presumes that scientists know what dark energy is. Basically
the idea is that empty space isn't really empty: quantum fluctuations
allow matter to exist in a vacuum. Physicists are busy trying to come
up with theories to explain why empty space would exert a repulsive
force which would cause galaxies to move away from each other.
To suppose that time passes more slowly in empty space is an
alternative. Imagine if light from a galaxy two million light years
took three million years to get to Earth: we would assume the galaxy
was three million light years away; as the universe expanded it would
appear as though the rate of expansion of the universe were
increasing. The idea that time passes more slowly in empty space
would mean that general relativity as it is now formulated is wrong so
that would be a big deal. In general relativity, gravitation is due
to the presence of matter creating a non-inertial frame of reference:
on result is that time passes at different rates inside a gravity
well; for example, if you were about to fall into a black hole then it
would appear to an observer from far away as though you were moving
very slowly as you passed the event horizon whereas you yourself would
feel as though you were suddenly being ripped apart by the noticably
different extent of gravitational pull being exerted on different
parts of your body.
Another poster claimed that there were a "trillion" different
explanations for dark energy. Well, that's not true: most
explanations assume that the measured expansion of the universe is
accurate; if it isn't then there is no need to hypothesize about dark
energy. Basically, this is how any phenomenon is explained: either it
is a real phenomenon and you have to explain how it occurs or it is
not a real phenomenon and you have to explain why it appears to
occur. Either way you have to explain what is going on and there is
no question of lazily "shrugging" and saying you "can't explain" it
and leaving it at that. Again, if you want to explain what is going
on then you have two alternatives: you either presume the phenomenon
is real and explain how it occurs or presume it is not real and
explain why it appears to occur. Those are two alternatives that you
have available to you every time when you are faced with an
unexplained phenomenon.
> They are two unproven hypotheses to explain
> an unproven and unmeasured phenomenon.
You are misusing the word "proven" here. Theories are not "proven".
Indeed, one explanation for the apparent increased rate of expansion
of the universe requires the presumption that general relativity is
wrong. This is a big deal but, then again, general relativity itself
proved Newton's theory of gravity to be wrong. If general relativity
is wrong then it is a big deal but it is something that physicists
will be able to live with. A lot of physicists would probably be
happier with a new theory of gravity than a theory of dark energy that
presumes the existance of a "negative mass density" in seemingly empty
space. The idea of a "negative mass density" in seemingly empty space
is not satisfying at all: I think physicists would rather dark energy
involved either some sort of electrostatic repulsion or a fifth force,
possibly related to dark matter. On one hand, exotic theories are fun
to speculate about but, on the other hand, it makes physicists feel
unsettled because they know from experience that the simplest
explanation is always more likely to be true.
> They don't even know if the math
> is valid.
Oh they know that the math is valid: the problem is that the math is
very difficult. When Einstein formulated general realtivity he made
at least one simplifying assumption that simplified the math
considerably. If you don't make simplifying assumptions when you
formulate a theory then the math can become too difficult and you
won't be able to make any predictions. The question then becomes if
the theory is robust; that is, if you were to work everything out in
full would you still get the same result. Some physicists believe
that it may be possible to reformulate general relativity and find
that time does proceed at a slower rate in empty space: one physicist
tried and ended up finally having to make a simplifying assumption
that reduced his theory back to general relativity. General
relativity may be robust or physicists may find that small corrections
to the theory can account for the observations that general realtivity
alone cannnot account for.
Martin