From: cflatter@nrao.edu (Chris Flatters)
Subject: Re: The Hole Story
Reply-To: cflatter@nrao.edu
Organization: NRAO
Date: Sun, 20 Dec 1992 22:42:37 GMT

In article 355@well.sf.ca.us, metares@well.sf.ca.us (Tom Van Flandern) writes:
>> Disregard most of what Tom is saying.  Tom is trying is confusing the
>> effects of a field with those of a propagating wave.
>
>     Remember, gravity waves have nothing to do with carrying the
>gravitational force or setting up the static field around a mass.  I was
>discussing pure gravitation, not gravity waves.  The latter, if they exist at
>all, manifest themselves only in cases of rapid acceleration of matter (as in
>supernovas and binary pulsars), and do not carry the gravitational force or
>static field.  Gravity waves are as incidental to the gravitational force as
>is the sonic boom following an asteroid impact caused by the disturbance the
>asteroid makes in the atmosphere.

Quite right. Tom's original posting referred to here tried to draw an analogy
between the force exerted on an orbiting particle by light from the Sun (a wave)
and the force exerted by a gravitational field.

>
>> If you want to calculate the gravitational potential at the Earth (say)
>> using GR you would use retarded potentials to do the necessary integrations
>> in the most general way.  You would find that the gravitational force on
>> the Earth is directed towards the point in space where the Sun was about 8
>> minutes ago (the light travel time between the Sun and the Earth).  In the
>> reference frame of the solar system this is a near as makes no difference
>> to the point in space where the Sun is now so we can ignore the
>> retardation.
>
>     I'm sorry, Chris, but none of the sentences in this paragraph describing
>your impressions of how the universe ought to work is consistent with
>observation or experiment.  Consider:  Aberration for the Earth is 10^-4
>radians, reflecting the fact that the Earth's velocity is 10^-4 that of
>light.  By no stretch of the imagination is 20 arc seconds on the sky a
>negligible amount.  If the Earth's velocity were nearly equal to c, the
>apparent Sun would be well out in front of the Earth, and clearly trying to
>accelerate it.  Since it is 10^-4 of c, the Sun's force vector can be
>decomposed into two components: a central force toward the focus of the
>Earth's elliptical orbit from a mass nearly equal to the Sun's, and a
>tangential force along the Earth's orbit of strength 10^-4 that of the Sun's
>radial force.  The tangential force is always present, and always trying to
>accelerate the Earth in all parts of its orbit.  The absence of such an
>acceleration tells us that aberration for gravity is less than 10^-10 of what
>it is for light.  Either nothing propagates from the Sun, or it propagates
>faster than light by a factor of 10^10.  Try to set up your integration with
>retarded potentials (as thousands have done before you) and see for yourself.

The Sun's retarded position is not the same as its aberr
>
>     The observed direction of the gravitational force acting on the Earth
>can be measured in several ways.  One is to determine the direction of the
>radius of curvature of the Earth's orbital motion using planetary ranging
>observations.  It is toward the true Sun, not the retarded one.  An
>experiment I did myself in the 1970s was to use the Moon's orbit, remove the
>effects of small perturbations such as planets, and determine the direction
>of the body perturbing the Moon's orbit away from a perfect ellipse using
>stellar occultation observations.  Again, that direction was toward the true,
>instantaneous Sun, toward the position among the stars the apparent Sun will
>appear to occupy 8 minutes in the future, but not toward the direction of the
>apparent Sun we now see in the sky.
>
>>> [TVF]: leaving students in a state of disbelief when they learn about it
>>> later in their careers.
>
>     I'm sorry you seem to be in this position yourself.  Please investigate
>the matter until you are satisfied, one way or another.  Let me know what
>arguments concern you, and I can elaborate or supply details of refere
>     Lots of people before you have done this same double-take.vity, by way of
>contrast, does not.
>
>
>and gallim@stsci.edu (Jack Gallimore,P254) replied:
>
>> No, that's crap.  It takes time for all forces to propagate, even gravity.
>> For example, one of the problems in observational cosmology is
>> understanding large sigger than
>10 billion lightyears?  The argument I think you meanike to see the reference
>on the observation you claim to be "true."
>
>     For a history of (unsuccessful) attempts to build theories in which
>gravity propagates, see MTW, chapter 7.  GR was the first theory to get
>around these problems, and its big breakth gravitational radiation, which you
>don't attribute
>> to retarded potential.
>
>     Electrons can only have discrete energy levels.  No spiraling is
>possible.  There aren't any good fundamental explanations of why this is so,
>but it is clear by experiment tintuitive questions, but only a
>beginning.
>
>
>and Benjamin Weinerof gravitational radiation) - a perturbation in the metric.
>Such
>> gravitational radiation (assuming its existence) propagates along null
>> geodesics - lightlike lines.  It cannot escape the black hole.  My message
>> will not reach Tom.
>
>     I don't like mixing gravitational waves with gravitational force.  They
>are separate phenomena -- one doesn't cause the other.  I would have conceded
>that no waves can get out of the black hole, but not at all that one
>shouldn't be able to sense where mass is within thty instantly, or
>after some delay?  If instantly, that seems to orking to get to the next
>level,
>not to glorify past successes.  We can't make progress until we finally see
>where the theories we have start to fail.  -|Tom|-
>
>-- 
>Tom Van Flandern / Washington, DC / metares@well.sf.ca.us
>Meta Research was founded to foster research into ideas not otherwise
>supported because they conflict with mainstream theories in Astronomy.




Xref: sparky sci.astro:13254 sci.physics:21401