Unluckily the earth is not flat even in the curved sense as it is an
ellipsoid with at least a delta north-south/east-west in radius of about
10km.
Even more unluckily gravitation is not a constant it slightly depends on
the density of matter. And last but not least gravity is a force and not
just a curvature of space. From a mathematical point of view there is no
difference between the two views as long as you do not believe that the
gravity force is of purely central nature.
The idea of curvature emerged because physicist had no clue why a photon
could be attracted by a mass. But all EM-mass interact with other EM
mass what leads to the other erroneous picture of virtual particle
background.
I you once understand why/how all mass is EM-mass, then you also will
understand all mistakes of 100 year physics.
J.W.
PS: Who will construct this perfect cannon that is able to do a shot
exactly along the horizon line? Not Boing...
Am 22.01.20 um 22:46 schrieb H LV:
On Mon, Jan 13, 2020 at 12:21 PM H LV <hveeder...@gmail.com
<mailto:hveeder...@gmail.com>> wrote:
On Mon, Jan 13, 2020 at 10:15 AM H LV <hveeder...@gmail.com
<mailto:hveeder...@gmail.com>> wrote:
This is an illustration from Newton's Principia of his famous
cannon thought experiment. It shows how a cannonball fired
horizontally from a mountain top (assuming no air resistance)
will orbit the Earth without falling to the ground if it is
fired with sufficient speed.
https://imgur.com/gallery/dzSLWaa
Now imagine an ice covered planet which is perfectly smooth,
with no mountains or valleys. On the surface rests a curling
stone of a given _weight_. If the curling stone is propelled
horizontally with sufficient speed it will orbit the planet
while sliding over the surface. At this velocity it will be in
free fall so its weight will be effectively zero. The question
is does the weight of the curling stone gradually increase as
the horizontal velocity gradually decreases or does the
curling stone resume its full weight for any velocity less
than the orbital velocity?
Harry
To answer my own question... the classical prediction is the
weight of the stone should increase, because the centrifugal force
is decreasing in the frame of reference of the stone. However, if
gravity in General Relativity is not a force then a corresponding
a centrifugal force does not arise. Therefore, if GR is true, the
weight of the stone should jump to its full weight for any value
less than the orbital speed. (Actually I think there is argument
to be made that even Newtonian gravity is not a force and is just
an acceleration).
Harry
Just a follow up. Since a body sitting at the equator is moving faster
than the same body near the pole it should weigh less due to the
greater centrifugal force caused by the Earth's rotation. Until
recently I don't think anyone had tried to measure this predicted
effect and it was just taken for granted to be true. (There have been
tests on the equivalence of inertial mass and gravitational mass but
this is a different test). However arguments between Flat-Earthers and
Anti-Flat earthers have resulted in amateur empirical investigations
of the matter. Flat Earther's contend the weight should be constant
since they hold the earth is flat and does not rotate. The results so
far seem to be open to interpretation. I am not a Flat- Earther but it
is interersting how this fringe community has turned it into an
empirical question.
Harry
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