Re: Relative motion and energy
- From: shepherdmoon@xxxxxxxxx
- Date: 14 Apr 2005 08:02:55 -0700
Herman Trivilino wrote:
> <shepherdmoon@xxxxxxxxx> wrote ...
>
<snip>
> > Question 3: Doesn't the above example show that mathematical
> > equivalence is not necessarily the same as physical equivalence? In
> > particular, doesn't this show that physically speaking Car A is the
one
> > really moving?
>
> This just establishes that Car A is the one moving relative to the
ground.
> Linear motion truly is relative. There is no experiment that can be
done
> that will distinguish between a state of uniform motion and a state
of rest.
> Circular motion is not unifoirm motion. Circular motion can be
detected
> absolutely. An object in circular motion is accelerating and (at
least in
> principle) a suitably sensitive accelerometer will detect this.
>
> > Question 4: If the answer to Question 3 is "Yes," then what might
be a
> > way to establish the physical difference between geocentrism and
> > heliocentrism?
>
> One could use a suitably sensitive accelerometer, I suppose. The
relevant
> expression for acceleration is v^2/r. Earth moves in a circle of
radius r =
> 1.5 E 11 meters at a speed v = 30 000 m/s. This is 0.006 m/s^2, or
about
> 0.0006 times the free fall acceleration (0.0006 gees). That's a very
small
> acceleration. I don't know if anyone has ever detected this
directly.
>
> I do know, though, that there is a rather long list of observations
> establishing Earth's motion. Parallax of the nearer stars, for
example.
>
> What's next? Is Earth flat and only 6000 years old? Make your case
and
> move on. You can never win arguments with some people.
Thanks for your comments.
First, I agree that you can never win arguments with some people. I
seem to be in a group with those people. However, I do want to learn
more about whether the distinction between the various "centrisms" is
(1) only mathematical, (2) mathematical and physical, or (2) neither
mathematical nor physical.
If it so happens that modern physics says that we can never prove that
earth rotates or goes around the sun instead of that the universe and
the sun go around the earth, then I want to know that. Or there may be
a physical way to tell, but mathematically there may be no absolute
motion or rotation. But if there *is* a way to prove one over the
other, then I want to know that too. If I need to start with learning
what I need to know or study *before* I can know the rest, I'd be happy
for someone to let me know what I need to study.
In terms of acceleration due to circular motion -- is it only the earth
that accelerates toward the sun, or can someone argue that the sun is
accelerating toward the earth?
Also, just as an FYI for anyone who may ever end up arguing with
someone like this in a more direct setting (i.e., not in a group as a
hobby) -- which is an increasing possibility since creationists are
deliberately trying to confront scientists in increasingly public
arenas:
Don't assume that a geocentrist is advocating the Ptolemaic model.
Modern geocentrism is an adaptation of Tycho Brahe's "geo-heliocentric"
model, where the planets orbit the sun, and that subsystem and the moon
-- and indeed the rest of the universe -- rotate around the earth.
Foucault's pendulum, geostationary satellites, the Coriolis effect,
centrifugal forces, even earthquakes are attributed to the rotational
motion of the universe. And all of space (minus the earth, of course)
is supposed to rotate around the earth, so no object in space needs to
exceed the speed of light. The proposed justifications for this model
are (1) the Lense-Thirring effect, where a rotating shell can generate
forces near its center, combined with (2) the equivalence principle (I
think), which allows geocentrists to claim that the force in (1) is
generated not by the rotating earth but by the rotating universe, since
both frames of reference are equivalent (one can be transformed into
the other) in relativity.
In my most recent reply to my opponent, I still claim that the above
scenario doesn't explain geostationary satellites in a way that is
consistent with the assumption of a rotating universe; nor does it
explain why the rotation stops right at the edge of the earth's
atmosphere. I am sure others can poke many more holes in the above,
even if it is a condensed version. Those who want to seriously analyze
these claims can visit http://www.geocentricity.com
There is also another good set of posts and replies here:
http://catholicoutlook.com/centerofmass.php
http://catholicoutlook.com/centerofmass2.php
http://catholicoutlook.com/centerofmass3.php
Where I think Gary Hoge successfully argues that the earth cannot be
the center of mass of the universe, that any center of mass cannot
remain stationary, and that even if the earth were the center of mass,
the gravitational equilibrium points would be elsewhere.
In my opinion, even though the Tychonian model is the only one that can
even come close to matching the heliocentric (or acentric) model in
terms of apparent motions, I think it is a sign of desperation that
modern geocentrists are still trying to use it. As far as I can tell,
the only warrant for that model is the (admittedly sincere) biblical
reason that some people give -- that geocentrism is necessary because
the Bible assumes it to be true and the Bible is inerrant. Aside from
that, though, the Tychonian model seems ad hoc, even clumsy, when you
look at it from afar, even if it is elegant in the way it accounts for
many observations.
Regards,
Shepherdmoon
.
- References:
- Relative motion and energy
- From: shepherdmoon
- Re: Relative motion and energy
- From: Herman Trivilino
- Relative motion and energy
- Prev by Date: Quantum gravity and equivalence principle
- Next by Date: Re: Tackling John Baez Head-On
- Previous by thread: Re: Relative motion and energy
- Next by thread: Ionization potentials of all isotopes Table
- Index(es):
Relevant Pages
|
Loading
