Just interested in the history of the word "spacetime" as becoming one
word.

http://dictionary.reference.com/search?q=spacetime (these guys put a
hyphen)
space-time (spstm)
n. Physics
The four-dimensional continuum of one temporal and three spatial
coordinates in which any event or physical object is located.

For historical research, who changed the dimensions from 3 to 4?

Can I dare ask why?

On Wed, 4 Nov 2003, John Tapper wrote:

Just interested in the history of the word "spacetime" as becoming one
word.

IIRC Einstein used the one-word (German) version. Don't know if it
predates his usage.

http://dictionary.reference.com/search?q=spacetime (these guys put a
hyphen)
space-time (spstm)
n. Physics
The four-dimensional continuum of one temporal and three spatial
coordinates in which any event or physical object is located.

For historical research, who changed the dimensions from 3 to 4?

Can I dare ask why?

4 coordinates = 4 dimensional. Nobody changed dimensions from 3 to 4,
events are described in Galilean/Newtonian mechanics in 4D spacetime. The
change is in whether or not the time coordinate is independent of the
space coordinates (or absolute, if you prefer), or more precisely,
independent of transformation from one inertial coordinate system to
another.

Lorentz transformations give the link between space and time. You might be
interested in reading why Lorentz did that stuff.

The particular 4D spacetime as used in SR can be considered as a
consequence of the LTs, insofar as it gives the LTs. I assume that it's
called Minkowski space for a reason, so you might consider adding that
name to your searches.

--
Timo Nieminen - Home page: http://www.physics.uq.edu.au/people/nieminen/
Shrine to Spirits: http://www.users.bigpond.com/timo_nieminen/spirits.html

John Tapper wrote:

For historical research, who changed the dimensions from 3 to 4?

Can I dare ask why?

You need three spatial co-ordinates and one time co-ordinate to
completely specify an event.

Bob Kolker

Timo Nieminen wrote:

I assume that it's
called Minkowski space for a reason, so you might consider adding that
name to your searches.

Minkowski, a mathematician, taught Einstein and was thoroughly
unimpressesd with Einstein's study habits and attitiude towards
mathematics. Minkowski referred to Einstein as a "lazy dog."

Thus, it is ironic that Minkowski, building on the work of Einstein,
opened his talk at a 1908 conference with: "The views of space and time
which I wish to lay before you have sprung from the soil of experimental
physics, and therein lies their strength. They are radical. Henceforth
space by itself, and time by itself, are doomed to fade away into mere
shadows, and only a kind of union of the two will preserve an
independent reality."

At first, Einstein was upset with what the mathematicians had done to
his theory, so a second irony is that the spacetime viewpoint given
first by the mathematician Minkowski eventually helped Einstein move
from special relativity to general relativity.

Regards,
George

In article ,
John Tapper wrote:
Just interested in the history of the word "spacetime" as becoming one
word.

http://dictionary.reference.com/search?q=spacetime (these guys put a
hyphen)
space-time (spstm)
n. Physics
The four-dimensional continuum of one temporal and three spatial
coordinates in which any event or physical object is located.

For historical research, who changed the dimensions from 3 to 4?

I believe that would be Minkowski.


Can I dare ask why?

Because meaningful vector operations can be performed on four-vectors.
The magnitude of a position four-vector, for instance, makes sense,

A = (ct,x,y,z)

|A|^2 = c^2 t^2 - x^2 - y^2 - z^2

which is a statement of the metric of the space; it is the equivalent of
length and is the quantity that's preserved under a Lorentz
transformation. Galilean transformations preserve lengths which don't
include time.

But I think it's interesting that in some late 19th century studies of
rotating objects, a four-dimensional formalism was developed for
mathematical convenience, with no physical significance ascribed to it.
And even a Newtonian wave equation has the form of

d^2/d(x^u)^2 phi = 0

where c is a wave propagation speed, not necessarily that of light, or
invariant. And the plane wave that shows up in quantum mechanics,

psi ~ exp[i(px - Et)/hbar]

Looks a lot like a four-momentum dotted into a four-position. It's almost
like there's something about nature that wants a four-dimensional
description even if your kinematics don't support it.

--
"Let us learn to dream, gentlemen, then perhaps we shall find the
truth... But let us beware of publishing our dreams before they have been
put to the proof by the waking understanding." -- Friedrich August Kekulé

(John Tapper) wrote:
The four-dimensional continuum of one temporal and three spatial
coordinates in which any event or physical object is located.

For historical research, who changed the dimensions from 3 to 4?

Can I dare ask why?

It was always 4. The premise is built into the structure of
human language, itself. The belief in reality ultimately being
spacetime, rather than space "moving in time" is the essence of
Vedantic philosophy and the essence of its remote offshoot (Zen,
e.g., the famous "flag isn't moving, the mind is" koan); the
essential point underlying Zeno's philosophy, and a foundation
underlying Diodorian and Aristotle's temporal logic formalisms,
a key aspect of St. Aquinas' world view (who also stated that
God's existence is fundamentally at the level of spacetime,
not *in* time), among other places. In a language like Japanese,
the notion of existence as being along a worldline in spacetime
is built right into its verbal morphology, with (for instance)
"being at", "coming" and "going" being represented by the same
word.

Newton's theory was also a theory of spacetime, regardless of
whether it was spelled out as such or not. In particular, the
structure underlying Newton's spacetime is an instance of
what's known today as a Fibre Bundle -- in this case an E(3)
bundle (each fibre being a 3-D Euclidean space), on a E(1)
base space (the time line).

In fact, the same method used to represent gravity geometrically
in Relativity as (primarily) a curvature in time, in spacetime;
applies equally in the Newtonian spacetime. There, the curvature
takes place entirely in the time direction, represented by how
adjacent E(3) fibres are sewn up together. The way fibres
are connected in a fibre bundle is given by its "connection".
In Newtonian space, a connection consists precisely of a
prescription at each point of an acceleration (i.e., gravity).
This tells how a line, that is laid out like an embroidery
across fibres -- which would otherwise be straight (in
accordance with Newton's first and second laws) would curve
over time (i.e. accelerate). The warping is in the warping
of the connections of the adjacent layers to one another.
In place of Einstein's field equations, which relates the
curvature of [space]time with something involving matter
distributions; in Newton's Physics, you'd have Poisson's
equations, which relates the acceleration field corresponding
to the connection to the matter distribution.

So, warped spacetime has nothing to do with Einstein either.
The same geometrical interpretation involving curvature in time
applies to Newton's spacetime too.

Time and space have been recognized as "dimensions",
or ways to quantize experience,
for thousands of years.

Mass and volume followed these two "dimensions"
when man began to barter.

Space was integrated into the time dimension
by the epople who recognized that
spaces were equivalent to time intervals.
Minkowski was the first to expound on this.

Mass was integrated into space and time
when Kepler observed that a constant
was a function of the time periods
and the radius' of the planets.

It was left to Newton to determine that
the constant involved a the dimension called mass.

In other words, Newton and Kepler
integrated mass into space/time.

All properties, including space and mass
can be defined in terms of ONE fundamental dimension,
and that dimension is time period.

Space is basically a time interval.
space = time interval * C

As can be seen, C is a constant that
differentiates between time periods,
which are correlations associated with a single body,
and time intervals, which are correlations
associated with two bodies.

The time equivalent of mass is:

time(mass) = time interval^3 / time period^2 = mass * G / C^3

For details on this,
visit my web site and download the physics tutorial,
which discusses the fundamental,
and derived physical properties in explicit detail.

--
Tom Potter http://tompotter.us

"Gregory L. Hansen" wrote in message
...
In article ,
John Tapper wrote:
Just interested in the history of the word "spacetime" as becoming one
word.

http://dictionary.reference.com/search?q=spacetime (these guys put a
hyphen)
space-time (spstm)
n. Physics
The four-dimensional continuum of one temporal and three spatial
coordinates in which any event or physical object is located.

For historical research, who changed the dimensions from 3 to 4?

I believe that would be Minkowski.


Can I dare ask why?

Because meaningful vector operations can be performed on four-vectors.
The magnitude of a position four-vector, for instance, makes sense,

A = (ct,x,y,z)

How about expressing time, space and mass
in the same units thusly?

A = (MG/c^3,ct,x,y,z)

space(X) = time interval(X) * C
mass(X) * G / C^3 = time intervals(x,y,z)^3 / time period(v,w)^2

Times v and w are periods and precessions respectively.

--
Tom Potter http://tompotter.us

"Alfred Einstead" wrote in message
m...
(John Tapper) wrote:
The four-dimensional continuum of one temporal and three spatial
coordinates in which any event or physical object is located.

For historical research, who changed the dimensions from 3 to 4?

Can I dare ask why?

It was always 4. The premise is built into the structure of
human language, itself. The belief in reality ultimately being
spacetime, rather than space "moving in time" is the essence of
Vedantic philosophy and the essence of its remote offshoot (Zen,
e.g., the famous "flag isn't moving, the mind is" koan); the
essential point underlying Zeno's philosophy, and a foundation
underlying Diodorian and Aristotle's temporal logic formalisms,
a key aspect of St. Aquinas' world view (who also stated that
God's existence is fundamentally at the level of spacetime,
not *in* time), among other places. In a language like Japanese,
the notion of existence as being along a worldline in spacetime
is built right into its verbal morphology, with (for instance)
"being at", "coming" and "going" being represented by the same
word.

Newton's theory was also a theory of spacetime, regardless of
whether it was spelled out as such or not. In particular, the
structure underlying Newton's spacetime is an instance of
what's known today as a Fibre Bundle -- in this case an E(3)
bundle (each fibre being a 3-D Euclidean space), on a E(1)
base space (the time line).

In fact, the same method used to represent gravity geometrically
in Relativity as (primarily) a curvature in time, in spacetime;
applies equally in the Newtonian spacetime. There, the curvature
takes place entirely in the time direction, represented by how
adjacent E(3) fibres are sewn up together. The way fibres
are connected in a fibre bundle is given by its "connection".
In Newtonian space, a connection consists precisely of a
prescription at each point of an acceleration (i.e., gravity).
This tells how a line, that is laid out like an embroidery
across fibres -- which would otherwise be straight (in
accordance with Newton's first and second laws) would curve
over time (i.e. accelerate). The warping is in the warping
of the connections of the adjacent layers to one another.
In place of Einstein's field equations, which relates the
curvature of [space]time with something involving matter
distributions; in Newton's Physics, you'd have Poisson's
equations, which relates the acceleration field corresponding
to the connection to the matter distribution.

So, warped spacetime has nothing to do with Einstein either.
The same geometrical interpretation involving curvature in time
applies to Newton's spacetime too.


What He Said.... and rather well also....

"Robert J. Kolker" wrote in message ...
John Tapper wrote:

For historical research, who changed the dimensions from 3 to 4?

Can I dare ask why?

You need three spatial co-ordinates and one time co-ordinate to
completely specify an event.

Bob Kolker

Actually... that's not what changed.

What changed is the view that time and space are interchangeable, at
least to some extent. If you consider 'dimensionality' the number of
independant directions, or at least semi-independant, then there never
was a change from 3 to 4, it was always just 4.

(...Starblade Riven Darksquall...)