Is there any research on whether or not Issac Newton understood why
there was a relationship between mass and gravity?  Or was he the
first to notice the pattern the inverse square of the distance and
mass, and so his calculations was his claim to fame, but never
understanding why the forces occur (like Eisnstein did?).

Newton was not first to notice 'inverse square' law

 [Halley} had  shown that Kepler's third law implied the inverse
square law of attraction and presented the results at a meeting of the
Royal Society on 24 January 1684 . Wren, Hooke and Halley then
discussed whether it could be shown that the inverse square law
implies elliptical orbits for the planets, but failed to come up with
a proof. Halley's work on these problems was disrupted during the
following weeks by the difficulties surrounding his father's
disappearance and death, but by August 1682 Halley was pursuing the
problem further by visiting Newton in Cambridge. There he discovered
that Newton had already achieved a proof of this and of other highly
significant results but did not seem to be going to publish them.
http://www-gap.dcs.st-and.ac.uk/~history/Mathematicians/Halley.html

 Halley also extrapolated the laws to non-planetary orbits, by
calculating
period of the orbit of what is now called Halley comet.

http://seds.lpl.arizona.edu/nineplanets/nineplanets/halley.html

That started a remarkable but gradual expansion of the applicability
of
the Newtonina mechanics.

Newton's contribution in this area was to actually derive shape of the
orbit
(observed by Tycho de Brahe and described by Kepler) by solving the
differential equation (while inventing the calculus in the process).
http://nunic.nu.edu/~frosamon/history/mike2.html

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Clarification of Answer by hedgie-ga on 20 Mar 2003 22:19 PST

1) correction of a typo

Newtonina mechanics   should be  Newtonian mechanics

2) I looked into the date discrepancy :

 "in   84 and 'further'  in 82 "  and found the following,
more detailed and more sholarly description:

http://www.greenlion.com/pr-prsec1.html

It looks like both events, debate and visit happened in 84
and then Newton's manuscript was submitted 86.

I am passing on the 'why' question. It would require clarification
of 'what' that means and a new question. However, on this
brief, $2 level, Einstein was not any closer to the 'why' than Newton.
His contribution did deal with someting else. See comment to
http://answers.google.com/answers/main?cmd=threadview&id=172915

hedgie

Newton never did propose a mechanism for gravity, and in fact was the
first to admit that such a level of understanding was beyond him at
that time. He did, however, reason that, if gravitation is due to an
attraction between masses, then the magnitude of attraction ought to
be in proportion to the mass. He also was the first to explicitly
determine that the change in magnitude due to distance is the
inverse-square law. He confirmed this by his own analysis of Kepler's
laws of planetary motions.

-Mark Martin

"If I have seen further than others, it is because I have stood on the
shoulders of giants" Newton

While possessing stunning  analytical and deductive powers himself,
Newton was a also a synthesist.  He was was able to draw on the work
of others and combine and simplify it.  The passage above refers to
the work of Kepler, Copernicus, and Galileo.  Consideration of the
woks of these people led Netwon to develop his "law of gravitation"
that states thatthe force generated between two masses is proportional
to their masses and inversely proportional to the square of their
separation.

Newton's claim to fame goes well beyond his work on gravitation.  He
made huge contributions to mathematics - inventing calculus, optics -
observing the splitting of white light into colours, and mechanics -
his laws of motion are fundamental.  For three hundred years, his
theories reigned supreme, and only with Einstein was any doubt raised
about the universality of his gravitation law.

Einstein too, stood on the shoulders of giants.  This is the progress
of science.

I must also say that the basis by which mass generates gravity is
still an open question.  You might like to search for information
about the Higg's particle for an update.

Hope this helps.

Xarqi:

I should have stated claim to fame as it related to the subject of
gravity.  Obviously, very few touch Newton in all of the fields you
mentioned.  I'm sure inventing calculus was a decent accomplishment
not to be overlooked  :)

Mr.Sneaky