Microgravity parable

************************************************** ****************

Scientist: "I just measured this box with my ruler. It has one
human-foot."

CT: "You mean to say that the box is one foot long, right?"

Scientist: "I mean to say that it has one human-foot."

CT: "How can it have a human foot if it is just a box? I'm certain
that what you mean to say is that your box has the same length as one
human foot, with length being a common quality to both the box and the
foot. But a "human-foot" as a bodily appendage is distinctly
different from a "foot" as a measure of length."

Scientist: "You are just being pedantic. The terminology you are
using may apply to the field of biology, but it does not apply to my
specialty field of measuring boxes."

CT: "Um, no. I see a distinct conceptual difference between a human
foot and the length of the side of a box."

Scientist: "Now you're just playing with semantics!"


~

************************************************** ****************

Scientist: "I just measured this box with my ruler. It has one
human-foot."

CT: "You mean to say that the box is one foot long, right?"

Scientist: "I mean to say that it has one human-foot."

CT: "How can it have a human foot if it is just a box? I'm certain
that what you mean to say is that your box has the same length as one
human foot, with length being a common quality to both the box and the
foot. But a "human-foot" as a bodily appendage is distinctly
different from a "foot" as a measure of length."

Scientist: "You are just being pedantic. The terminology you are
using may apply to the field of biology, but it does not apply to my
specialty field of measuring boxes."

CT: "Um, no. I see a distinct conceptual difference between a human
foot and the length of the side of a box."

Scientist: "Now you're just playing with semantics!"


~

I hope this analogy helps to illuminate the fundamental problem with
the widely used terminology: zero/microgravity.

- 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).

Likewise...

- A human foot is *distinctly different* from length.

A foot may have the property of length, but it is *not* length.

To confuse acceleration measured in 'g' with gravity is the same type
of error as confusing a length measured in 'feet' with those
appendages at the end of your legs.

*

As there are alternative standards for measuring length that have no
basis at all in the human foot (take the meter, for example) a
standard unit of acceleration could be defined on a scale that has
nothing to do with gravity.

Let's say that this time next year, the SI unit for acceleration gets
defined as 10 meters/second^2. This unit standard gets named in honor
of the man who helped popularize acceleration entertainment for
countless families across the planet. The SI standard unit of accel
will be known as the Disney, abbreviated as "D". The unit of 1-D is
based upon a certain ride in Florida that spins you around with 10
m/s^2 of lateral acceleration, nothing at all to do with gravity.

Those wishing to conform with this SI standard can use the following
conversion factor (rounded):

1 D = 1.019 g

Notice that if NASA were to adopt this hypothetical standard, "Zero-g"
research would then be called "Zero-D" research. And when people
thought of Disney's spinning ride in Florida, they would be crystal
clear that measures of acceleration need not be based upon gravity.
No need for confusion.

And when astronauts came back from space, they would be crystal clear
that while they floated around, with their bodies having no relative
acceleration in relation to their spacecraft, gravity never came
anywhere close to zero at any point in their trip. They *never*
experienced zero gravity. They experienced zero acceleration.

..

I hope this helps to clear up the mess that was created by the terms
"zero/microgravity". And if those words ever get stitched to another
NASA mission patch, I hope it includes Mickey Mouse's face to remind
us all of the silliness behind the misusage of those terms.


~ CT

On 8 Oct 2003 10:19:49 -0700, in a place far, far away,
(Stuf4) made the phosphor on my
monitor glow in such a way as to indicate that:


- Gravity is *distinctly different* from acceleration.

While gravity has a property of acceleration, it is *not*
acceleration.

Your continued repetition of this statement does not make it true.

--
simberg.interglobal.org * 310 372-7963 (CA) 307 739-1296 (Jackson Hole)
interglobal space lines * 307 733-1715 (Fax) http://www.interglobal.org

"Extraordinary launch vehicles require extraordinary markets..."
Swap the first . and @ and throw out the ".trash" to email me.
Here's my email address for autospammers:

(Stuf4) made the phosphor on my
monitor glow in such a way as to indicate that:
- Gravity is *distinctly different* from acceleration.

While gravity has a property of acceleration, it is *not*
acceleration.

Verifiable reference, please. Not just the name of a book, please provide
the specific page and a quote.
--
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.

From Scott Hedrick:
(Stuf4) made the phosphor on my
monitor glow in such a way as to indicate that:
- Gravity is *distinctly different* from acceleration.

While gravity has a property of acceleration, it is *not*
acceleration.

Verifiable reference, please. Not just the name of a book, please provide
the specific page and a quote.

I just found this page that gives a good set of q/a's:

http://amos.indiana.edu/library/scri...rogravity.html

Excerpts:

"...there's no such thing as zero gravity."

"...weightlessness and zero gravity are two different things."


I'm sure there are lots more references with accurate physics. Hey,
maybe even *NASA* has an accurate webpage on this. I'll check there
and let you know if I find something good.


~ CT

On 8 Oct 2003 17:41:25 -0700, in a place far, far away,
(Stuf4) made the phosphor on my
monitor glow in such a way as to indicate that:

While gravity has a property of acceleration, it is *not*
acceleration.

Verifiable reference, please. Not just the name of a book, please provide
the specific page and a quote.

I just found this page that gives a good set of q/a's:

http://amos.indiana.edu/library/scri...rogravity.html

Excerpts:

"...there's no such thing as zero gravity."

"...weightlessness and zero gravity are two different things."

Which doesn't mean that gravity is not acceleration. Nice diversion,
though.

--
simberg.interglobal.org * 310 372-7963 (CA) 307 739-1296 (Jackson Hole)
interglobal space lines * 307 733-1715 (Fax) http://www.interglobal.org

"Extraordinary launch vehicles require extraordinary markets..."
Swap the first . and @ and throw out the ".trash" to email me.
Here's my email address for autospammers:

Stuf4 wrote:
From Scott Hedrick:

(Stuf4) made the phosphor on my
monitor glow in such a way as to indicate that:

- Gravity is *distinctly different* from acceleration.

While gravity has a property of acceleration, it is *not*
acceleration.

Verifiable reference, please. Not just the name of a book, please provide
the specific page and a quote.


I just found this page that gives a good set of q/a's:

http://amos.indiana.edu/library/scri...rogravity.html

Excerpts:

"...there's no such thing as zero gravity."

"...weightlessness and zero gravity are two different things."


I'm sure there are lots more references with accurate physics. Hey,
maybe even *NASA* has an accurate webpage on this. I'll check there
and let you know if I find something good.


~ CT

In response to your opening post, I listed many more references. I also
tried to find sources which discredit "microgravity". Mostly I found
sources which defined microgravity. But here are mo

http://dictionary.reference.com/search?q=microgravity
1. An environment in which there is very little net gravitational
force, as of a free-falling object, an orbit, or interstellar space.
2. A minute shift in gravity that can occur through geologic factors
in a region, such as the movement of the earth's crust along fault lines.

http://www.m-w.com/cgi-bin/dictionary
microgravity
a condition in space in which only minuscule forces are experienced :
virtual absence of gravity; broadly : a condition of weightlessness

http://www.bartleby.com/cgi-bin/texi...avity&db=a hd
....1. An environment in which there is very little net gravitational
force, as of a free-falling object, an orbit, or interstellar space. 2.
A minute shift in gravity...

Hmmm...the term is part of the vernacular language.

snip
I'm sure there are lots more references with accurate physics. Hey,
maybe even *NASA* has an accurate webpage on this. I'll check there
and let you know if I find something good.


~ CT

I've found a NASA webpage that comes very close to being accurate:

http://science.nasa.gov/newhome/head...ro-g.plane.htm

Quote:

"What astronauts experience in space isn't really zero-gravity. NASA
scientists call it microgravity or low-g, but it's really free fall or
weightlessness."

I see this quote above to be totally accurate. But later in the page,
there is this fatal error:

"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.

Say that you spin a ball at the end of a tether. It is completely
bogus (vice "apt") to say that you are *increasing gravity* on that
ball. Just the same, it is bogus to say that you are *decreasing
gravity* on a ball that you drop from a tower. There is nothing
"micro" about gravity in a freefall toward the Earth.


~ CT



Full article:
__________________________________________________

Temporary weightlessness

Engineers and scientists experience about 20 to 30 seconds of
weightlessness during each parabola aboard NASA's KC-135 aircraft, an
effective and inexpensive means of testing experiments before they go
to space. Because everything floats, test equipment must be bolted or
taped to the deck, as with the apparatus here for testing liquid
cages.

What astronauts experience in space isn't really zero-gravity. NASA
scientists call it microgravity or low-g, but it's really free fall or
weightlessness.

Gravity goes to the edges of the universe -- it's why planets circle
the sun, stars clump together to form galaxies, and Space Shuttles
stay in orbit.

So what is happening on a spacecraft or when Kornfeld and Antar run
experiments on the KC-135 (as seen at top)?

As a spacecraft orbits a planet, it really falls endlessly in a circle
(or ellipse) that is a delicate balance between the satellite's
forward motion and the planet's gravitational pull. Because everything
is falling together, nothing has weight.

Well, almost no weight. Unless an object is at the precise center of a
satellite's mass, it will try to pull ahead or fall back into a slight
different orbit. And that means that the object will experience a
small amount of acceleration against a wall. And even at the Shuttle's
altitude, a trace of atmosphere is left and gently drags on the
Shuttle which will cause an object to drift inside the Shuttle.

NASA scientists call this microgravity since usually it is equivalent
to about 1/1,000th or less of one Earth gravity (the range depends on
the location in the spacecraft and other factors). The term is apt
since Albert Einstein said that acceleration caused by gravity is
equivalent to any other push.

Free fall can be duplicated, briefly, on Earth, by dropping an object.
Like falling off a cliff, it's not the first step that gets you, or
the long trip down, but the stop at the end.

NASA has drop tubes in which molten droplets of material fall for
about 2 to 3 seconds before hitting a bucket of oil to capture them
safely and cool them off.

For larger experiments, or to train astronauts, NASA uses a KC-135, a
military tanker version of the Boeing 707 jetliner. The pilots guide
these jets on carefully designed parabolic trajectories that resemble
a roller coaster ride.

At the top, the pilot throttles back and noses over, letting the plane
dive to give everyone about 20 to 30 seconds of free fall (actually,
it varies between 0.01 g to 0.001 g; it's not nearly as good or as
long as being in orbit). They do this 40 times on each mission, so
they get about 13 minutes of microgravity time -- at a personal price.

People riding the NASA KC-135 often get extremely sick doing this.
That's why the plane is also called The Vomit Comet.

The things you do for science!

__________________

From Rand:

- Gravity is *distinctly different* from acceleration.

While gravity has a property of acceleration, it is *not*
acceleration.

Your continued repetition of this statement does not make it true.

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

Gravity manifests as a force, not an acceleration.

That is the first conceptual distinction. The second distinction is
that...

Acceleration can be caused by *any* force, not just gravitational
force.


~ CT

In article ,
(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?

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