> Chris Burford wrote:
[snip]
> > The proprositions that time can run backwards is not unique to him but is
> > common to the simplistic mathematical modelling of that approach to
> > science, and I suggest is a fundamentally idealist, non-materialist
> > assumption. (i.e. I suggest that along with a basic assumption that
> reality
> > exists, a materialist approach needs to posit that time runs forwards, and
> > cannot run backwards.)
>
> Einstein equated time with space for the simple reason that they can both
> appear on the same graph. If you want to graph velocity, let x equal space
> and y equal time. You can see how easy it is to fall into the trap of
> regarding time as essentially equivalent to space. Past and future are
> reduced to left and right, but for some mysterious reason we're stuck in our
> awareness of what lies to the "left" while always being oriented toward the
> "right."
Most physicists "like" symmetry. With symmetry, things are more internally consistent. The reason physicists often talk about time travel is because they are assuming time is symmetric - that the laws of the universe are consistent regardless of the direction of time. It is a leap to say that because of the symmetry and consistency, it is theoretically possible to make time flow backwards. It is an even greater leap to say that we can build a device or exploit a natural occurance and send people or information backwards in time. But the math, which is the heart of physics, looks the same no matter in which direction time flows.
> Actually, Einstein had nothing to say about time. He was describing an
> ideal abstraction of time. He could never get inside time but could only
> describe the way things in space relate to it. A clock in a rocket
> traveling near the speed of light will tick more slowly. Does that mean
> time itself has slowed down inside the rocket? No. It just means that the
> way the rocket relates to time differs from the way the rest of the universe
> relates to it. Time is not merely its exterior, i.e. its relation to space.
> Time is absolute, as demonstrated by the living occupant of the rocket,
> whose intrinsic sense of time is unaltered, regardless of the velocity.
It is important to reinforce this distinction between the relativity of time as theorized by Einstein, and the notion that time is symmetric according to QM. They are entirely different concepts. Hawking is famous for his _Brief History of Time_, which touches on the idea of symmetric time in a lay forum. However I don't think it's possible to really understand this unless one does the math.
> But have you really traveled backward in time? Not really. It just means
> you've gone back in time *relative to the other end of the wormhole.* You
> cannot go backwards through absolute time. You cannot come out of the far
^^^^^^^^^^^^^ Rather, you would not go backwards through time outside of the wormhole's frame of reference. Remember, there is no absolute frame of reference. ;-)
> > His assertion that the speed of light never changes is arbitrary and
> > strange.
Hardly. It is a conclusion based upon trying to solve Maxwell's Equations and Lorentz Transforms. It may seem arbitrary until you do the math, but when you do the math, it emerges as a clear necessity.
> > It seems to me linked to the idealist thread I am suggesting
> > existed in his thinking.
>
> The mistake here is believing that laws of physics are absolute. Really a
> better word would be "habits" of physics. Every so-called "law" of physics
> had to be established historically. There's no transcendent "ideal" realm
> from which laws could be given prior to the big bang.
There is no such thing as "prior" to the big bang. Time itself began with the big bang. A statement implying time outside of the big bang ("before the big bang", "cause of the big bang", etc.), is like saying "what is the sound of one hand clapping?" Your statement was correct, of course, it is just a peeve of mine to see people casually mention the big bang yet not fully apply the concept with their choice of words.
Anyway, laws of physics, by definition ARE absolute. That is what makes them laws. F=ma is a law, gravitation is a law, etc. If they are shown to be not absolute, then they are not laws. Without accepting certain concepts as laws, it would be hard to apply the scientific method.
BTW, most physical scientists ARE idealists. They hold the ideal that at some level, the universe is explainable.
Matt
-- Matt Cramer <cramer at voicenet.com> http://www.voicenet.com/~cramer/ Thou art God and I am God and all that groks is God, and I am all that I have ever been or seen or felt or experienced.
-Mike