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From: Martin Brown <'''newspam'''@nonad.co.uk>
Newsgroups: sci.electronics.design
Subject: Re: anti-gravity? [OT]
Date: Wed, 24 Apr 2024 16:29:01 +0100
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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.

The only time when it can happen is in accretion disks of compact 
stellar objects or black holes where magnetic forces and thermal 
friction provide the drag and up to about 30% of the rest mass can be 
converted into energy. That mechanism powers quasars and pulsars.

The BOAT event happened fairly recently and blinded the gamma ray 
telescopes with its off scale brilliance. It was an order of magnitude 
bigger than anything that had ever been seen before.

https://www.nasa.gov/universe/nasa-missions-study-what-may-be-a-1-in-10000-year-gamma-ray-burst/

Just as well it was nearly 2bn lightyears away from us!

-- 
Martin Brown