Newton's law of gravitational attraction

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Mister X

Posted: Thu Jul 30, 2009 8:34 am

Guest

Hi again

So, Newton postulated:

F = G * (m1 * m2) / (r * r)

Forgetting m1, m2 and G for a moment (they cause me enough grief)...

Why 1/(r*r)

Why not 1/r

Why not 1/r-dot

Why this form.

I am NOT asking for justification based upon current (or even in Newton's
time - then current) experiments.
I am asking for a justification from the mind. Why was it natural to assume
1/(r*r)

I, for example, (in my ignorance) would have assumed 1/r because that is how
a spring acts.
Or I might have used 1/r-dot to bring in damping of some sort.

Anyone?

zzbunker@netscape.net

Posted: Thu Jul 30, 2009 8:34 am

Guest

On Jul 30, 12:34 am, "Mister X" <j...@junk.com> wrote:

Quote:

Hi again

So, Newton postulated:

F = G * (m1 * m2) / (r * r)

Well, Newton built all his force theories on the
aummption that action-at-a-distance is self-evident assurdity.
All the Classical Physics cranks always forget that he
also assumed that both time and space are infinite in extent
in all directions. Both backwards and forward in time.
Which is also the only reason that Classical Fourier Analysis even
works.
So, that's also the reason the people with educable post 1700
Brains
work on DSP, Microcomputers, Optical Computers, Desk Top
Publishing, Holograms,
Laser-Guided Phasors, Multi-Plexed Fiber Optics, Atomic Clock
Wristwatches,
Light Sticks, Compact Flourescent, Laser Disk Libraries, Electronic
Books, HDTV,
Home Broadband, Cyber Batteries, Self-Replicating Machines, Self-
Assembling Robots,
On-Line Banking, On-Line Shopping, On-Line Publishing, Cruise
Missiles, Phalanx,
Drones, UAVs, AAVs, GPS, Weather Satellites, Digital Terrain
Mapping, Data Fusion,
Gas Turbine Engines, Pv Cells, Biodiesel, and Hybrid-Electric
Engines.

Rather than their idiot theories of Ballistics, Thermodynamics,
and Statistical Dynamics.

Quote:

Forgetting m1, m2 and G for a moment (they cause me enough grief)...

Why 1/(r*r)

Why not 1/r

Why not 1/r-dot

Why this form.

I am NOT asking for justification based upon current (or even in Newton's
time - then current) experiments.
I am asking for a justification from the mind. Why was it natural to assume
1/(r*r)

I, for example, (in my ignorance) would have assumed 1/r because that is how
a spring acts.
Or I might have used 1/r-dot to bring in damping of some sort.

Anyone?

Argir Pandev

Posted: Thu Jul 30, 2009 8:34 am

Guest

On Jul 30, 7:11 am, eric gisse <jowr.pi.nos...@gmail.com> wrote:

Quote:

Mister X wrote:

[...]

I am NOT asking for justification based upon current (or even in Newton's
time - then current) experiments.

Then you are being an idiot. Newton's work was based on observation.

[...]

and you are very wise (jackass)... if |m1| <> |m2| then |d1| <> |d2|
in d1/d2 = m2/m1; d being the barycentral distances. but if |d1| <> |
d2| and presumably f21 = (d1/d2) f12 then shouldn't |f12| <> |f21|
which contradicts newton's claim that sun pulls earth with opposite
the force of earth pulling sun?

eric gisse

Posted: Thu Jul 30, 2009 9:11 am

Guest

Mister X wrote:

[...]

Quote:

I am NOT asking for justification based upon current (or even in Newton's
time - then current) experiments.

Then you are being an idiot. Newton's work was based on observation.

[...]

Mister X

Posted: Thu Jul 30, 2009 9:49 am

Guest

OK... I was under the assumption that Newton was not able to verify this
experimentally.
Was he?
I have not read about any experiments like this that he did.

Please explain.

"eric gisse" <jowr.pi.nospam@gmail.com> wrote in message
news:h4rag5$in4$1@news.eternal-september.org...

Quote:

Timo Nieminen

Posted: Thu Jul 30, 2009 10:39 am

Guest

On Wed, 29 Jul 2009, Mister X wrote:

Quote:

At the time, it wasn't particularly natural to assume 1/r^2. Newton went
for 1/r^2 because (a) it fit observational data (acceleration of the Moon,
and gravitational acceleration near the Earth's surface) and (b) because
only for n=2 does 1/r^n gravity gives Kepler's laws for orbits. Newton
wasn't the first to suggest 1/r^2, but he was first to show (b).

From a modern perspective, 1/r^2 is what we expect. Look at Gauss's law.
The usual version for electrostatics will do, but there is an equivalent
version for gravity. The total "amount of gravity" coming out from a body
doesn't change, it just gets spread over a larger area. Since the surface
area of the spherical area over which it is spread increases as r^2, the
strength of gravity falls as 1/r^2.

Quote:

I, for example, (in my ignorance) would have assumed 1/r because that is how
a spring acts.
Or I might have used 1/r-dot to bring in damping of some sort.

Lots of possibilities were suggested at the time, and then when the same
thing was done for electrical forces, various possible force laws were
suggested.

As for bringing in damping, you might like to read about the "Yukawa
potential".

--
Timo

eric gisse

Posted: Thu Jul 30, 2009 11:06 am

Guest

Mister X wrote:

Quote:

OK... I was under the assumption that Newton was not able to verify this
experimentally.
Was he?
I have not read about any experiments like this that he did.

Please explain.

First, stop top posting. It fucks up the flow of conversation - this ain't
email.

Second, review basic history. Newton's works were based on the observations
of Tycho Brahe.

Quote:

"eric gisse" <jowr.pi.nospam@gmail.com> wrote in message
news:h4rag5$in4$1@news.eternal-september.org...
Mister X wrote:

[...]

I am NOT asking for justification based upon current (or even in
Newton's time - then current) experiments.

Then you are being an idiot. Newton's work was based on observation.

[...]

Androcles

Posted: Thu Jul 30, 2009 1:14 pm

Guest

"Mister X" <junk@junk.com> wrote in message
news:Tp9cm.34654$0z7.16696@newsfe07.iad...

Quote:

Hi again

So, Newton postulated:

F = G * (m1 * m2) / (r * r)

Forgetting m1, m2 and G for a moment (they cause me enough grief)...

Why 1/(r*r)

Why not 1/r

Why not 1/r-dot

Why this form.

I am NOT asking for justification based upon current (or even in Newton's
time - then current) experiments.
I am asking for a justification from the mind. Why was it natural to
assume 1/(r*r)

I, for example, (in my ignorance) would have assumed 1/r because that is
how a spring acts.
Or I might have used 1/r-dot to bring in damping of some sort.

Anyone?

Simple:
http://www.androcles01.pwp.blueyonder.co.uk/InverseSquare.jpg
The area is quadrupled when the distance is doubled for any pyramid or
cone.

Androcles

Posted: Thu Jul 30, 2009 2:01 pm

Guest

"Mister X" <junk@junk.com> wrote in message
news:0wacm.70444$YU5.15698@newsfe21.iad...

Quote:

OK... I was under the assumption that Newton was not able to verify this
experimentally.
Was he?
I have not read about any experiments like this that he did.

Please explain.

Newton verified Kepler's laws which were based on observations.
The history is:

1) Ptolemy says the Earth is the centre of the Universe.
He accounts for retrograde motion by assuming planets move in epicycles.
http://en.wikipedia.org/wiki/Epicyclic_gearing
http://www.lasalle.edu/~smithsc/Astronomy/retrograd.html

This idea lasts for 1400 years, during which period we see the
rise and fall of the Holy Roman Empire which discouraged
mathematics. There are no famous Roman mathematicians.
All the famous mathematicians were Greeks before them.

Along comes printing, and with that the spread of books throughout
Europe. This leads to Protestantism, people can now read the bible
for themselves and they challenge Catholic doctrine.

2) Copernicus says "Hold on, things are much simpler if the Sun
is the centre of the Universe and the planets move in perfect circles."
But that meant the Earth was just another planet and it moves, which is
against Catholic doctrine. Such heresy will destroy society. So
Copernicus, a Catholic, keeps his big mouth shut or he's likely to
be burnt for witchcraft. But he tells all on his deathbed.

Along comes Kepler and Galileo, both mathematicians, and say
"Looks like old Nickelarse Copperknickers was about right",
but Kepler goes a step further and says the orbits of planet are
not circular but elliptical. Galileo is told to shut up or he'll
get kicked out of heaven.

3) Newton, another mathematician and strongly religious but not
a Catholic, develops calculus and verifies Kepler's observations.

Then along comes John Goodricke and it all goes pear-shaped again,
but that's another story.

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