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Subject: Re: anti-gravity? [OT]
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On 4/22/2024 12:11 PM, John Larkin wrote:
> On Mon, 22 Apr 2024 15:00:21 -0000 (UTC), 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) don’t
>> fit easily into such a picture.
>>
>> Also, the rate at which the hypothetical particles collide with matter has
>> to be extremely large in order to work with very dense matter, such as free
>> neutrons.
>>
>> Neutrons have been observed to follow Newtonian gravity to very high
>> accuracy in the lab.
>>
>> And then there’s the complete absence of Brownian motion in free particles.
>> With some huge flux of particles carrying the sort of momentum that would
>> be required to account for the gravitational motion of free neutrons, the
>> resulting fluctuations would be very visible.
>>
>> Besides, if the particles bounce off the gravitating objects, their
>> velocity distribution will change as a consequence. (Some of them will
>> rattle around between them, going faster and faster as the objects get
>> closer.)  Thus there will be a wake effect, like a small plane taking off
>> right after an A380.  No such effects are observed.
>>
>> Not to pile on, or at least not as much as the notion deserves, but if
>> relativity is completely wrong, then there is only one velocity in a given
>> reference frame for which the drag force of such a particle ensemble is
>> zero.
>>
>> And, of course, there’s the question of the origin, distribution, and
>> regulation of the momentum-carrying particles.
>>
>> To have any chance of avoiding even these purely classical effects, the
>> particles would have to have infinite speed, zero mass, perfectly uniform
>> and isotropic distribution in both position and direction, perfectly timed
>> arrival at each object to make the fluctuations cancel out, and on an on.
>>
>> This is the luminiferous ether, on stilts.
>>
>> And then there are matter-wave interferometers, which work not only on
>> electrons, but on neutrons and even buckyballs.  They set far tighter
>> limits on most of these classical effects.
>>
>> So no, these sorts of theories are not good candidates to explain gravity
>> or other relativistic effects.
>>
>> Cheers
>>
>> Phil Hobbs
> 
> Is there any deeper explanation for conservation of energy, and for
> Newton's laws, other than that's just the way things are?
> 
> (That gets philosophical, namely why does mathematics define the
> world?)
> 

I don't think we know for sure that conservation of energy holds on a 
cosmological scale, since we don't know for sure the global topology of 
the Universe.

In a hypothetical Universe that's topologically flat and unbounded 
there's still the boundary condition at infinity to be considered, which 
I think could in principle be a singularity sort of like a "white hole", 
anything could come flying in and conservation of energy can't hold exactly.