Gravity

Dear AngleWyrm:
(cross post to sci.astro)
"AngleWyrm" wrote in message
news:A3MNb.66358$nt4.94910@attbi_s51...
Does the effect of gravity actually get from the Sun to the Earth faster
than light?

No. There is no requirement for it to do so in any modern theory.

First, I read that the Sun's photons take something like 8.3 minutes to
traverse the...8.3 light-minute distance to earth (duh), and that this
means
the Sun is presently west of it's apparent position by approximately 20
arc
seconds. [Tom Van Flandern:
http://www.metaresearch.org/cosmolog...of_gravity.asp ].

He goes on to say that it is this point--20 arc seconds west of the
visible
Sun--toward which earth is being pulled. He supports this with the
following:
Such measurements of Earth's acceleration through space are now easy
to make using precise timing data from stable pulsars in various
directions on the sky.
Any movement of the Earth in any direction is immediately reflected
in a decreased delay in the time of arrival of pulses toward
that direction, and an increased delay toward the opposite direction.

The "gravity as geometry" model seems to lack causality, as there is
still
no reason why things should fall together. The model relies on gravity to
portray gravity. However, if we are being pulled towards the current
position of the sun, then something is amiss with the idea that the
impact
of gravity travels. This might open some wonderfully lucid hallucenogenic
visions of gravity as existing outside time, etc.

The space produced by mass/energy has existed for 13 Gy, so it has had
plenty of time to establish itself. "Instantaneous action" is merely the
curvature caused by the planet, orbiting along with the planet.

So does anyone know of where to get pulsar timing data, or how I might
measure Earth's trajectory?

Sorry. Perhaps others can help you.

David A. Smith

"N:dlzc D:aol T:com (dlzc)" N: dlzc1 D:cox wrote in
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"AngleWyrm" wrote in message
news:A3MNb.66358$nt4.94910@attbi_s51...

Does the effect of gravity actually get from the Sun to the Earth faster
than light?
No. There is no requirement for it to do so in any modern theory.

This seems a bit overgeneralized; is there some community repository wherein
all modern theories might be examined?

Has anyone here calculated the position of astronomical bodies, and if so,
did you use instant gravity, or did you use speed-of-light delays? How did
you measure this against observations?

"AngleWyrm" wrote in message
news:RCVNb.80184$8H.115658@attbi_s03...
"N:dlzc D:aol T:com (dlzc)" N: dlzc1 D:cox wrote in
message news:feSNb.4067$bg1.3881@fed1read05...
"AngleWyrm" wrote in message
news:A3MNb.66358$nt4.94910@attbi_s51...

Does the effect of gravity actually get from the Sun to the Earth
faster
than light?
No. There is no requirement for it to do so in any modern theory.

This seems a bit overgeneralized; is there some community repository
wherein
all modern theories might be examined?

Has anyone here calculated the position of astronomical bodies, and if so,
did you use instant gravity, or did you use speed-of-light delays? How did
you measure this against observations?

Good old Newton and Kepler (assumed infinite "c") work just
fine for most of the bodies of the solar system for practical
accuracies. The positions are calculated and adjusted for
"light time" for the time it takes light to travel from the
"actual position" to the observer.

So the speed of light is taken into account for the observing,
and not for the calculating of position.

In General Relativity, it turns out that bodies interact as
though they were being attracted by their partner's "forward"
(future) position when they are orbiting. Van Flandern has
been called on his incorrect assessment of the theory.

"Greg Neill" wrote in message
...
"AngleWyrm" wrote in message
news:RCVNb.80184$8H.115658@attbi_s03...
"N:dlzc D:aol T:com (dlzc)" N: dlzc1 D:cox wrote in
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"AngleWyrm" wrote in message
news:A3MNb.66358$nt4.94910@attbi_s51...
Good old Newton and Kepler (assumed infinite "c") work just
fine for most of the bodies of the solar system for practical
accuracies. The positions are calculated and adjusted for
"light time" for the time it takes light to travel from the
"actual position" to the observer.

Yea, Newton; the Moon is travelling just fast enough to fall around the
Earth. Nice. Problem with his idea was when he said (in part) that gravity
is proportional to the mass of the objects...Looked good on paper until
Galileo dropped a cannon ball and a bullet from the Leaning Tower of Pisa.
"Hey guys: They hit the ground at the same time!" So much for gravity being
proportional to the mass of the objects.

In General Relativity, it turns out that bodies interact as
though they were being attracted by their partner's "forward"
(future) position when they are orbiting. Van Flandern has
been called on his incorrect assessment of the theory.

So here's what little I know of General Relativity: The space-time continuum
is a sort of four-dimensional universe, and matter/energy travel along in
this existence on "straight" lines through this coordinate system, called
geodesics. Rather than any given object's course being curved, GR says it is
distances & time which become distorted by matter/energy, that space-time is
warped by it's contents.

Is it just me, or is it just a matter of point-of-view? Whether we call it a
distortion in space-time, or call it a distortion in the course of objects,
the result is the same, yes? Seems a little cleaner to me to distort an
object's geodesic; doesn't invoke a mysterious fabric of space-time to
distort.

I lose touch when they tell me changes in velocity are communicated by
gravity waves which travel at the speed of light. Then they go hunting for
black holes, dark matter and gravitons, and build Laser Interferometer
Gravitational Wave Observatories.

Could it be that this idea of bodies interacting with the gravitation from a
future location, that arrives at light speed delays, is just a wee stretch
of the chalkboard?

"AngleWyrm" wrote in message
news:TP3Ob.83590the
Yea, Newton; the Moon is travelling just fast enough to fall around the
Earth. Nice. Problem with his idea was when he said (in part) that gravity
is proportional to the mass of the objects...Looked good on paper until
Galileo dropped a cannon ball and a bullet from the Leaning Tower of Pisa.
"Hey guys: They hit the ground at the same time!" So much for gravity
being
proportional to the mass of the objects.

NB Galileo died before Newton was born.
But apart from that, its the force that is proportional, not the
acceleration. The acceleration depends on the force and (inversely) on the
mass, so Galileo's experiment matches Newton's theory.





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"OG" wrote in message
...

NB Galileo died before Newton was born.
But apart from that, its the force that is proportional, not the
acceleration.

Yer right; Newton was born in 1627, the same year Galileo died.

The acceleration depends on the force and (inversely) on the
mass, so Galileo's experiment matches Newton's theory.
Acceleration depends inversely on mass?
Force=Mass x Acceleration ; Newton's Second Law
Force/Mass = Acceleration ; dividing both sides by mass
Thus your assertion holds.

"AngleWyrm" wrote in message
news:TP3Ob.83590$xy6.143355@attbi_s02...

snip

Yea, Newton; the Moon is travelling just fast enough to fall around the
Earth. Nice. Problem with his idea was when he said (in part) that gravity
is proportional to the mass of the objects...Looked good on paper until
Galileo dropped a cannon ball and a bullet from the Leaning Tower of Pisa.
"Hey guys: They hit the ground at the same time!" So much for gravity
being
proportional to the mass of the objects.

This is what happens when you don't read *all* the chapters of the book.

Yes, Newton said F = -G * m * M / r^2

He also said F = m * a

Do the math: (sHead, you may leave the classroom now)

F = m * a = -G * m * M / r^2

dividing by m gives us

a = -G * M / r^2

no dependence on m...

snip

Is it just me, or is it just a matter of point-of-view? Whether we call it
a
distortion in space-time, or call it a distortion in the course of
objects,
the result is the same, yes? Seems a little cleaner to me to distort an
object's geodesic; doesn't invoke a mysterious fabric of space-time to
distort.

Actually, in GR it is called "mass-energy". Whether it 'looks' like matter
or energy or some mixture of the two depends on the relative velocity
between the object and the FOR of the observer. At zero velocity it looks
like stationary matter. At c it looks like energy, at any other velocity it
looks like matter with kinetic energy.

I lose touch when they tell me changes in velocity are communicated by
gravity waves which travel at the speed of light.

Velocity, and its changes, are relative to the measured object and the
measuring FOR. Changes are not "communicated" from one point to another.
The have the interrelationship of two points as a prerequisite. Regardless
of the acceleration applied, the bridge is still stationary WRT the engine
room.

Then they go hunting for
black holes, dark matter and gravitons, and build Laser Interferometer
Gravitational Wave Observatories.

They have already found everything on the list except gravitons - black
holes, dark matter, and gravity waves. IMO, gravitons will never be found,
but we won't know for sure until we look.

Could it be that this idea of bodies interacting with the gravitation from
a
future location, that arrives at light speed delays, is just a wee stretch
of the chalkboard?

Are you talking "time travel?" Or are you still just struggling with
"space-time" as a means of plotting events as points and diagramming
trajectories as "world-lines"?


Tom Davidson
Richmond, VA

In article , tadchem
writes:

"AngleWyrm" wrote in message
news:TP3Ob.83590$xy6.143355@attbi_s02...

snip

Yea, Newton; the Moon is travelling just fast enough to fall around the
Earth. Nice. Problem with his idea was when he said (in part) that gravity
is proportional to the mass of the objects...Looked good on paper until
Galileo dropped a cannon ball and a bullet from the Leaning Tower of Pisa.
"Hey guys: They hit the ground at the same time!" So much for gravity
being
proportional to the mass of the objects.

Galileo did his experments _before_ Newton was even born: The moon's speed
could be considerably faster or slower than it is, and it would still fall
around the Earth: In fact it is alternately slowing down and speeding up all
the time.

Proportional does not mean that gravity varies with mass either: It varies
with the weight of the mass: Heavy bodies like cannon balls have more weight,
and therefore more inertia, and are harder to accelerate: Its a case of
reciprocity? The cannon ball has more weight-force pushing it down, but its
greater inertia makes it harder to accelerate: The bullet is lighter but
accelerates easier: So they both fall at about the same speed: Sumpin like
that anyways(:-)

Cut

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"AngleWyrm" wrote in message
news:RCVNb.80184$8H.115658@attbi_s03...
"N:dlzc D:aol T:com (dlzc)" N: dlzc1 D:cox wrote in
message news:feSNb.4067$bg1.3881@fed1read05...
"AngleWyrm" wrote in message
news:A3MNb.66358$nt4.94910@attbi_s51...

Does the effect of gravity actually get from the Sun to the Earth
faster
than light?
No. There is no requirement for it to do so in any modern theory.

This seems a bit overgeneralized; is there some community repository
wherein
all modern theories might be examined?

They are called libraries.
They are all over the place.
They have been around for years.
However, not all are created equal.
Try yours.

"Chosp" wrote in message
newszYNb.30254$XD5.27370@fed1read06...
"AngleWyrm" wrote in message
news:RCVNb.80184$8H.115658@attbi_s03...
"N:dlzc D:aol T:com (dlzc)" N: dlzc1 D:cox wrote in
message news:feSNb.4067$bg1.3881@fed1read05...
"AngleWyrm" wrote in message
news:A3MNb.66358$nt4.94910@attbi_s51...

Does the effect of gravity actually get from the Sun to the Earth
faster than light?
No. There is no requirement for it to do so in any modern theory.

This seems a bit overgeneralized; is there some community repository
wherein all modern theories might be examined?

They are called libraries.
They are all over the place.
They have been around for years.
However, not all are created equal.
Try yours.

Never could get the hang of paper, but I've been planning to get some for
the kids--I hear books are the next big thing.