Groups > sci.physics.relativity > #461921

Re: Why does gravity have to be transmitted through particles when gravity isn't a force in general relativity?

From	Volney <volney@volney.invalid>
Newsgroups	sci.physics.relativity
Subject	Re: Why does gravity have to be transmitted through particles when gravity isn't a force in general relativity?
Date	2018-06-20 17:42 -0400
Organization	A noiseless patient Spider
Message-ID	<pgeho0$kuj$1@dont-email.me> (permalink)
References	(15 earlier) <8493e532-dd9c-42a9-8a51-bd10cf722462@googlegroups.com> <4a8eb647-a0b3-4430-b16b-77f633985ab7@googlegroups.com> <7da86ff9-35a3-4a37-985c-1fc3107f7829@googlegroups.com> <pgdtr0$fvd$1@dont-email.me> <ad21f357-eb50-4f02-8d79-b66cb1867c36@googlegroups.com>

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On 6/20/2018 4:16 PM, kenseto wrote:
> On Wednesday, June 20, 2018 at 12:02:42 PM UTC-4, Volney wrote:
>> On 6/20/2018 10:53 AM, kenseto wrote:
>>> On Monday, June 18, 2018 at 5:27:14 PM UTC-4, Prokaryotic Caspase Homolog wrote:
>>>> On Monday, June 18, 2018 at 1:19:03 PM UTC-5, kenseto wrote:
>>>>
>>>>> If gravity is strictly attractive, what is stopping the body go all the way to the center of the orbit? The answer: centrifugal force.
>>>>
>>>> [replacement for a deleted post where I made an extremely silly typo]
>>>>
>>>> Centrifugal force does not exist when you describe a system in an inertial
>>>> (non-rotating) frame of reference.
>>>
>>> Assertion is not a valid argument. Centrifugal force exists.
>>
>> No, you assert that centrifugal force exists. Assertion is not a valid
>> argument.
> 
> It is you who made assertions. I  demonstrated to me of the many applications using the CF force.

No, you assert centrifugal force exists. In an inertial frame there is 
no such force, the apparent effect is strictly due to the inertia of the 
masses trying to move in a straight line (Newton's First Law).

Centrifugal force appears real in a _rotating_ frame (centrifuges, 
amusement park rides, merry-go-rounds, etc.) but these are not inertial 
and pseudo-forces are fine. For example, in the rotating frame of a 
merry-go-round, a ball stationary on the floor of the merry-go-round 
will start to roll outward, as observed by an observer stationary on the 
merry-go-round. However, an observer stationary outside the 
merry-go-round (inertial, or close enough) will see a moving ball trying 
to keep moving in the same direction (Newton's First Law).
> 
>>
>>> There are countless applications using CF force...eg: centrifuges to separate material of different densities, gas centrifuges to separate different isotopes to make atomic bombs.
>>
>> Notice that centrifuges are most certainly a rotating (and thus
>> non-inertial) frame, and in a rotating frame you can treat centrifugal
>> force as existing, so centrifuges work. But it's not a real force in
>> inertial frames.
> 
> There are no inertial frame exist on earth.....the earth is rotating. So what is your argument now.

Technically there are, but there are many ways to make effects like 
earth's gravity meaningless, less than the margin of error from other 
effects. For example, demonstrating rotating frames on a merry-go-round 
or something. The floor of the merry-go-round is perpendicular to 
gravity, so gravity doesn't affect the results, like measuring the 
strength of the centrifugal pseudoforce (outwards).

> BTW, why deny the existence of the CF force when it is readily demonstrated?

Demonstrated in non-inertial frames, like centrifuges, merry-go-rounds 
etc. Doesn't exist in inertial frames, or frames close enough to being 
inertial.

> 
>>>
>>>> In an inertial frame, what appears to
>>>> be an outwards-directed force in the rotating frame, is nothing more than
>>>> a consequence of th...

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