Re: About Galileo and the Galilean relativity

On Apr 1, 8:49 pm, "oriel36" <kelleher.ger...@xxxxxxxxx> wrote:
On Apr 1, 2:29 pm, "Shaktyai" <Fabrice.All...@xxxxxxxxx> wrote:



I am always amazed by the difference between what popular medias know
of the Galilean relativity, what my students understand of it and
what Galileo is supposed to have written. Here is a good way of
drinking free beer:

Ask ten people to select the proper statement:

1) Is the sun and all the planets revolving around the earth ?
2) Is the earth and all the planets revolving around the sun ?

I have already lost two years in a row a bet with a friend by pooling
my students. I had bet they would have answered: none of the two
statement is true.

So my question comes to this:
Does any one know if Galileo did really say and write that the
heliocentric referential is an absolute preffered referential, or is
it just what the non astronomers have understood of Galileo's
writting ?
And does anyone know if what is todays known as the Galilean
relativity was ever written and thought by Galileo ?

In order to support my scientific thirst I ask you to send me the
equivalent of 25% (in money) of the free beers you will drink because
of me.

Salute forza el canute

Galileo's statements are in line with Copernicus and with Kepler's in
the matter of heliocentric reasoning which uses the Earth's orbital
motion to explain the observed behavior of our planet along with the
others around the central Sun -

"[Here Salviati explains Jupiter's motion, then follows with:]

Now what is said here of Jupiter is to be understood of Saturn and
Mars also. In Saturn these retrogressions are somewhat more frequent
than in Jupiter, because its motion is slower than Jupiter's, so that
the Earth overtakes it in a shorter time. In Mars they are rarer, its
motion being faster than that of Jupiter, so that the Earth spends
more time in catching up with it. Next, as to Venus and Mercury, whose
circles are included within that of the Earth, stoppings and
retrograde motions appear in them also, due not to any motion that
really exists in them, but to the annual motion of the Earth. This is
acutely demonstrated by Copernicus . . .

You see, gentlemen, with what ease and simplicity the annual motion --
if made by the Earth -- lends itself to supplying reasons for the
apparent anomalies which are observed in the movements of the five
planets. . . . It removes them all and reduces these movements to
equable and regular motions; and it was Nicholas Copernicus who first
clarified for us the reasons for this marvelous effect." 1632,
Dialogue Concerning the Two Chief World Systems

It was Newton who jumped the tracks in approaching and trying to
resolve retrogrades.It is like an act of vandalism when it is honestly
compared with what Galileo wrote and affirming the earlier work of
Copernicus and Kepler -

" For to the earth planetary motions appear sometimes direct,
sometimes stationary, nay, and sometimes retrograde. But from the sun
they are always seen direct," Newton

I have only post a dozen times or so in this forum over the last year
and I am winding down altogether.There is always enough time to
address an honest question like yours but in truth,if you come across
the time lapse footage of the Earth overtaking Jupiter and Saturn,all
questions will be answered -

http://antwrp.gsfc.nasa.gov/apod/image/0112/JuSa2000_tezel.gif

Thank you for your time and your intelligent and kind way of answering
my questions. It is pretty rare nowdays with ultra egotic would-like-
to-be physicists.
From what I have understood of Galileo's transcript it appears that in
Galileo's mind the motion of the planets around the sun was an
absolute truth. He did not seem to have realized at this stage that
the difference between his positions and the Church's ones were
merelly du to a change of referential. He was advocating for the sun
to be the center of the universe while the later was for the earth.
That may explain why even todays so many people beleive and say that
the earth and all the planets are orbiting the sun in an elliptic way
without even mentioning the referential.
Before Galileo the human kind used to beleive earth was the center of
the universe, after Galileo they beleive it is the sun.

.

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