Dear Researcher:

"Researcher" <notmy@email.com> wrote in message
news:4535bc59$0$19746$88260bb3@free.teranews.com...

What exactly is meant by the curvature of space from
the practical point of view.

gravitational lensing ...==.. [where the light's path curves IN/THRU space

advance of the perihelion of Mercury... ==..[which is a con]
Shapiro time delay...==.. [which is a dilettante con]

Is it impossible for anything to follow any other line of
travel other than that which fits on this curvature?

Joe Jakarta's answer is correct. Any kind of applied force alters your
path in spacetime... ==.. [see top of post......

If so, what is compelling that traveler forcing him to
take this curvature?

Since the answer above was no...
Curvature is a name for how spacetime is "shaped" by mass / energy.

Does even light have to travel along this path
dictated by this curvature and if so why?

The "dictated curvature" is that same, but the path of light and the path
of even the fastest material particle in the same curvature is different.

David A. Smith

Researcher wrote:

What exactly is meant by the curvature of space from the practical point

view.

Albert lamented that light leaving stars would go to waste and leave
the universe impoverished so he 'bent space' to save this terrible
event from happening.Personally I find the reasoning hilarious but for
some strange reason others do not .

"This conception is in itself not very satisfactory. It is still less
satisfactory because it leads to the result that the light emitted by
the stars and also individual stars of the stellar system are
perpetually passing out into infinite space, never to return, and
without ever again coming into interaction with other objects of
nature. Such a finite material universe would be destined to become
gradually but systematically impoverished."

http://www.bartleby.com/173/30.html

This stuff,and partiularly light leaving stars, is comically priceless
and a person has to be so mesmerised by the fables which created the
early 20th century mathematician's version of astronomy to take it
seriously.

Is it impossible for anything to follow any other line of travel other

that which fits on this curvature?

If so, what is compelling that traveler forcing him to take this

Does even light have to travel along this path dictated by this

and if so why?

Researcher




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Posted via a free Usenet account from http://www.teranews.com

Researcher wrote:

What exactly is meant by the curvature of space from the practical point
of
view.

Does even light have to travel along this path dictated by this curvature
and if so why?

Researcher

To answer your question, The Wheeler and Taylor text or Resnick text
would be helpful but more recent stuff like the following from Steve
Carlip on google groups is even clearer:

Guy Eschemann (guy.eschem...@cipcinsa.insa-lyon.Fr) wrote:
: I have a small question about a thing I didn't understand in
Hawking's
: book. He said that we can explain the movement of the earth around
the
: sun by Einstein's curved space-time theory (the earth is following a
: straight path in a curved space-time). But I don't understand why
light
: for example doesn't follow the same path as the earth ?

This is a good question, which gets at an important feature
of general relativity---the fact that it's spacetime, and not
just space, that's curved.

Think for a minute about an analogy in three-dimensional
Euclidean geometry. If you give a starting point and an
initial direction, that will determine a unique straight
line. But suppose you forget that you're dealing with three
dimensions, and just give the initial direction in the x-y
plane. Then you get an infinite number of possible straight
lines, since the slope in the z direction is undetermined.

In general relativity, to determine a path you have to specify
an initial point and an initial direction *in spacetime*. If
you think about this, you'll see that it means that you specify
an initial direction in space and an initial speed. (In two
dimensions, a line with a slope of 1/2 is specified by saying
"initially move one unit in the y direction for every two units in
the x direction." In spacetime, similarly, you could say "move
one unit in space for every two units in time," which is the same
as saying "start with a speed that is half the speed of light.")

So light doesn't follow the same path as the Earth because the
initial speeds---the initial directions in spacetime---are not
the same. If you forget about time and only think about curved
space, you'll miss this.

Steve Carlip Date: 1997/03/04
Message-ID: <5fft92$82k$1@mark.ucdavis.edu>#1/1
car...@dirac.ucdavis.edu




There are other old google group posts where Carlip refutes Van
Flandern's (retro Laplace) idea that The moon would fall into the
earth if gravity traveled at the speed of light. Carlip's point as I
recall is that since nothing can travel faster than the speed of light
gravity must also travel at the speed of light.

Then we need GR which adds a premise to Newtonian physics. Namely,
that the force of gravity of the earth on the moon is not just a
function of the masses and positions of the earth and moon but in
addition a function of their velocities and rate of change of
acceleration.

Thus the moon can orbit the earth even as the earth moves and the
subsequent required
gravitational signal to pull the moon to the new position of the earth
though arriving late was in the previous signal when the earth was at
its previous position. This new signal applies to the next new position
etc..

The problem with GR is that it involves the addition of a premise to
the Newtonian premises and a better theory with fewer premises is
possible. In this theory gravity is regarded as a force due to
electrostatic dipoles inside all atomic nuclei etc of 10^-18meter
length on the earth(and magnetism similarly) See
http://mysite.verizon.net/r9ns/book03

The bending of light and precession of mercury and other effects of GR
can be explained by this theory with fewer premises.

r9ns@verizon.net

Researcher wrote:

What exactly is meant by the curvature of space from the practical point of
view.

Is it impossible for anything to follow any other line of travel other than
that which fits on this curvature?

If so, what is compelling that traveler forcing him to take this curvature?

Does even light have to travel along this path dictated by this curvature
and if so why?

Researcher

We see more and more galaxies the
further out we look.
If light went in anything but straight lines,
we wouldn't be able to focus on distant
objects.
John

We see more and more galaxies the
further out we look.
If light went in anything but straight lines,
we wouldn't be able to focus on distant
objects.
John

We see more and more galaxies the
further out we look.
If light went in anything but straight lines,
we wouldn't be able to focus on distant
objects.
John