Microgravity parable

Stuf4 wrote:
[snip]

All of this illustrates the futility of science by popularity contest.

If 6 billion people were to hold the same view while one lone person
holds an incompatible view, those numbers do nothing to prove anything
for either side. It is conceivable that the 6 billion are in error
while one person holds an accurate view.


~ CT

"Stuf4, party of 1, your table is ready. Stuf4, party of 1..."
:-)

Mike Hanson wrote...
Out in space and accelerating at
9.81 m/s^2, the man also has weight: he feels exactly the
same force pushing up on the soles of his feet. These two
'forms' of weight are qualitatively identical, and this is
where you have gone wrong: looking out of the window
doesn't count. The key word is 'locally', and the question
is: can you distinguish between the first and second
cases *if you don't know where you are*? And the answer is: no.

You ask whether one can distinguish between gravity and acceleration. But
the question of whether one can distinguish between 'orbital microgravity'
and a 'microgravity field' is a different question.

It's interesting that one can make this distinction by observing a
'floating' particle which is tapped very lightly. In orbit, the particle
will oscilate in space when tapped (when the movement is viewed over an
orbital period), in a freefall or microgravity field the particle will
continue in a straight line. (Using local frames of reference of course.)

Those with a better understanding of orbital mechanics will no doubt tidy
up my post.

- Peter

Stuf4 wrote:
[snip]


"NASA scientists call this microgravity... The term is apt since
Albert Einstein said that acceleration caused by gravity is equivalent
to any other push."

The principle is about _mass_ equivalence, not acceleration
equivalence.

[snip]

That is incorrect. It was the happiest moment in Einstein's life when
he realized that an accelerated reference frame was equivalent to a
frame in a uniform gravitational field. From this basis, Einstein could
later show the equivalence of intertial and gravitational mass. But the
first preceded the second.

In the following, Einstein discusses how he came to believe there should
be *no* preferred reference frame for the description of physical phenomena:

"Then there occurred to me the ... happiest though of my life, in the
following form. The gravitational field has only a relative existence
in a way similar to the electric field generated by magnetoelectric
induction. *Because for an observer falling freely from the roof of a
house there exists--at least in his immediate surroundings--no
gravitational field* [his emphasis in italics]. Indded, if the observer
drops some bodies then these remain relative to him in a state of rest
or of uniform motion, independent of their particular chemical or
physical nature (in this consideration the air resistance is, of course,
ignored). The observer therefore has the right to interpret his state
as 'at rest.'

Because of this idea, the uncommonly peculiar experimental law that in
the gravitational field all bodies fall with the same acceleration
attained at once a deep physical meaning. Namely, if there were to
exist just one single object that falls in the gravitational field in a
way different from all others, then with its help the observer could
realize that he is in a gravitational field and is falling in it. If
such an object does not exist, however--as experience has shown with
great accuracy--then the observer lacks any objective means of
perceiving himself as falling in a gravitational field. Rather he has
the right to consider his state as one of rest and his environment as
field-free relative to gravitation.

The experimentally known matter independence of the acceleration of fall
is therefore a powerful argument for the fact that the relativity
postulate has to be extended to coordinate systems which, relative to
each other, are in non-uniform motion."

(Pais, A. (1982). 'Subtle is the Lord...': The Science and the Life of
Albert Einsteing. Oxford: Oxford University Press. p. 178)

So, Einstein would say that an ISS crewmember has the right to say
he/she is in zero gravity.

Stuf4 wrote:
From Mike Hanson:

(Stuf4) wrote


snip

- Gravity is *distinctly different* from acceleration.

While gravity has a property of acceleration, it is *not*
acceleration. A 'g' is a unit of acceleration standardized upon a
particular case of acceleration due to gravity (the gravitational
acceleration at the surface of the Earth).

snip

I haven't posted here for a while. Decided to take a look, saw an
interesting-looking thread title, and came across the above statement.
You appear to have mangled your terms somewhat:

*Gravitation* is distinctly different from acceleration.

Gravity, however, is locally *indistinguishable* from acceleration.
That this is so led Einstein to apply Occam's razor and postulate that
they are one and the same phenomenon, leading to general relativity.
And since GR has yet to be falsified, one can say that, to the best of
our knowledge, gravity and acceleration are indeed the same thing (and
hence that NASA is correct in its use of the letter g).


This point regarding the equivalence theory has been addressed more
than once on this thread...

One easy way to determine whether you are accelerating due to gravity
or not is to look out the window of your spacecraft to see if there
are any stars or planets nearby.

(I've suggested elsewhere that the root of this confusion in
terminology is a misunderstanding of the equivalence principle.)


~ CT

Note...I recently posted a reply pointing out that the Principle of
Equivalence is *not* rooted in an equivalence between inertial and
gravitational mass. Rather, it comes from the equivalence of inertial
reference frames...those that are accelerating or equivalent to those in
a gravitational field. Also, the nature of inertial mass is not fully
understood and it is only postulated that inertial and gravitational
mass are the same. Experiments carried out show this to be so to within
great precision, but not infinite precision.

Stuf4 wrote:
[snip]

All I was saying was that one particular member has a published
webpage that stands in complete agreement with the position I have
been presenting.

That member does not outline a position of belief that NASA scientists
and astronauts do not understand gravity. So it is not in strict
agreement with your position.

[snip]

Stuf4 wrote:
From Herb Schaltegger:

(Stuf4) wrote:


How ironic that you offer your extrapolation regarding "pretty much
everyone..." while chastising my extrapolation.

This reads as another form of "I'm right/you're wrong", coated with a
heavy tinge of hypocrisy.

And how many posters are publicly supporting your continued games of
semanticism, pedantry, prevarication, equivocation and hand-waving?
None.

But let me guess: the lurkers all support you in email.


Umm, they're not lurking. If you've been following the thread
thoroughly you've seen that Jim Oberg's website has a page that fits
in total agreement with what I've been saying here.

So if, by assumption, Jim agrees with the position I have put forward,
one might ask why he has remained silent. And an obvious follow up is
to ask why others who might agree have remained silent.

My best guess is that there is so much hostility among those who
persist in abusive behavior that a silent majority/minority (?) prefer
to sit out a would be scientific discussion.

(3rd Reich lessons learned have previously been provided as to their
application here at sci.space.)


~ CT

Just to add fuel to this dwindling fire, Oberg, in a recent MSNBC column
on the Chinese launch, says:

" Moreover, Shenzhou’s solar arrays, unlike those on Soyuz, can rotate
to track the sun while the spacecraft itself is aligned for other
purposes, such as Earth observation or long-term microgravity drifting
flight. The Russians did put rotating solar panels on another of their
manned spacecraft, their Salyut-class space stations, and for exactly
this same reason."
See http://www.msnbc.com/news/979759.asp?cp1=1

Did you find the word "microgravity"?
Hmmmm.

Herb Schaltegger wrote:

(Stuf4) wrote:
The statement you are quoting has been accepted physics since it was
spelled out in detail in Isaac's Principia.

You and Newton on a first name basis these days?


Come on, give the guy a break. What he stated is a fact. Gravity is a FORCE.
Acceleration is the result of a force being applied to a mass. Assasinating a
character even when he says something that makes sense devalues the newsgroup.
It is, as far as I know, still in the "sci" hiearchy and not in the "psy".
Analyse the facts, not the personality.


Experiments on the station should really be relabled as "free floating"
instead of "0 g" or microgravity.

"Microgravity" should be for experiments that happen *really* far from the
earth where the gravitational force is truly "micro". As I recall, gravity at
the altitude of the space station is still fairly powerful.

The fact that gravity is still pulling objects down in the space station may
not matter for current experiments where free fall is sufficient. But later
on, when they start to study gravity seriously, it will matter.

In article ,
Harry Kim wrote:

Herb Schaltegger wrote:

(Stuf4) wrote:
The statement you are quoting has been accepted physics since it was
spelled out in detail in Isaac's Principia.

You and Newton on a first name basis these days?


Come on, give the guy a break. What he stated is a fact. Gravity is a FORCE.
Acceleration is the result of a force being applied to a mass. Assasinating a
character even when he says something that makes sense devalues the newsgroup.
It is, as far as I know, still in the "sci" hiearchy and not in the "psy".
Analyse the facts, not the personality.


Experiments on the station should really be relabled as "free floating"
instead of "0 g" or microgravity.

"Microgravity" should be for experiments that happen *really* far from the
earth where the gravitational force is truly "micro". As I recall, gravity at
the altitude of the space station is still fairly powerful.

The fact that gravity is still pulling objects down in the space station may
not matter for current experiments where free fall is sufficient. But later
on, when they start to study gravity seriously, it will matter.

That was so sweeping in it's supidity and ignorance that I don't even
know where to begin. Therefore, I'm not bothering to snip any of it, so
others can revel in it as well, "Ensign Kim." You just hop back aboard
Voyager and warp on off to the Delta Quadrant, 'mmm 'kay?

--
Herb Schaltegger, B.S., J.D.
Reformed Aerospace Engineer
"Heisenberg might have been here."
~ Anonymous

"Herb Schaltegger" wrote in message
...
You just hop back aboard
Voyager and warp on off to the Delta Quadrant, 'mmm 'kay?

Kim's just jealous because it was Paris and not himself that got to make it
with the Captain. Nevermind that they had both turned into salamanders at
the time.
--
If you have had problems with Illinois Student Assistance Commission (ISAC),
please contact shredder at bellsouth dot net. There may be a class-action
lawsuit
in the works.

I had assumed that those who referred to their in-orbit experiments
as being in "microgravity" did so because they were being careful to
acknowledge that despite their free-fall relative to Earth their
experiments might still feel the (micro) gravitational attractions
of other objects such as the surrounding spacecraft and nearby astronauts.