Re: anti-gravity? [OT]

On Wed, 24 Apr 2024 16:29:01 +0100, Martin Brown
<'''newspam'''@nonad.co.uk> wrote:

On 24/04/2024 15:30, John Larkin wrote:

On Wed, 24 Apr 2024 08:53:25 -0000 (UTC), Jasen Betts
<usenet@revmaps.no-ip.org> wrote:
 

On 2024-04-22, Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
>

Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:

jim whitby <news@spockmail.net> wrote:
>

Looking for opinion of persons better educatrd than myself.
>
<https://thedebrief.org/nasa-veterans-propellantless-propulsion-drive-
that-physics-says-shouldnt-work-just-produced-enough-thrust-to-defeat-
earths-gravity/>

>
Has anyone come across the alternative theory of gravity which I first
heard of from P.G.A.H. Voigt?
>
It suggests that the current theory of gravity is rather like the idea
we used to have that there was force 'due to vacuum', rather than air
pressure.  It proposes that the real cause of the gravitational effects
we observe is not an attraction but a pressure.
>
The concept is that a force acts on all bodies equally in all dirctions.
When two bodies with mass approach each other, each shields the other
from some of this force and the remaining forces propel the bodies
towards each other.
>
I don't know how it would be possible to test whether this was in fact
how 'gravity' worked and whether it was possible to differentiate it
from the current theory, as the two would appear to have identical
observed effects.

>
Of course little things like the equality of inertial and gravitational
mass (so that objects of different density fall at the same speed) donâ??t
fit easily into such a picture.

>
If you postulate that the forces interact with mass rather than area or
volume, that is easily explained.
>
Why do we assume that gravity is a pull based on mass, when it could
equally well be a push based on mass?

>
Can you get there from Kepplers laws of planetary motion, or even vice-
versa.

>
It might require considerable sleight of hand to have Gauss's theorem
still work even if you could fudge it somehow.
>

If you assume that the Earth is flat and the Moon is painted on the
firmament, then perhaps a push theory of gravity can be entertained, but
it does not seem to work well with the majority understanding of nature.

 
The universe is a giant balloon with stuff painted on it. Or we live
in a planetarium.

>
It is entirely possible that we live in a very sophisticated simulation
and that possibility becomes considerably more likely iff we should ever
succeed in building a non-trivial word length quantum computer.
>

Since gravity moves at the speed of light, none of the classic
equations of planetary motion are true. Lately the 3-body problem is
popular, but the finite speed of gravity complicates that too.

>
Gravitational *changes* move at the speed of light, but the distortion
of spacetime is already there as a property of how objects move in GR.
>
Gravitational waves move at the speed of light but the gravitational
influence of the two massive components in orbit was always there out to
a huge distance determined by their age or the age of the universe
whichever happens to be shorter. It becomes a lot more noticeable when
they get really close together and spin up faster and faster.
>
Errors in the processing of Fortran continuation card beyond 9 were
found by observational discreprancies observed in pulsars that got close
enough to Jupiter occassionally for the gravitational corrections for
delays along light paths near large masses to really matter.
>

An object is not attracted to another object, but to where it used to
be. Objects are attracted to gravity waves.

>
*NO*! That is completely wrong. Classical mechanics requires "the force
of" gravity to have infinite propagation speed or it doesn't work. That
was why Newton found it somewhat troublesome as "action at a distance".
>
https://en.wikipedia.org/wiki/Newton%27s_law_of_universal_gravitation#Newton's_"causes_hitherto_unknown"
>
The solar system would collapse in on itself if the force of gravity was
anything other than *exactly* radial as everything in orbit would then
experience a drag force and spiral into the sun. That clearly doesn't
happen.

But gravity doesn't have infinite speed.

We are attracted to things that don't even exist any more. Some
billions of years from now, the light and the gravity from those
things will cease to arrive, and you can call that event a "gravity
wave." If the light stops, you can call that a "light wave" too.

Earth emits gravity waves as it orbits the sun, so it does experience
a drag force.

Tidal effects slow our orbit around the sun too; our orbital radius is
increasing. The moon's orbit around earth increases too; that has been
measured.

There is also "thermal gravitational wave" emission which I guess
cools things off.