Re: The simplicity of relativity (for TomGee and others)

From: PD (pdraper_at_yahoo.com)
Date: 03/07/05 

Date: 7 Mar 2005 07:18:05 -0800

Don1 wrote:
> PD wrote:
> > TomGee wrote:
> > > PD wrote:
> >
> > [snip]
> >
> > > >
> > > > I don't know why you think it's simpler. Conceptually, general
> > > > relativity is *very* simple. What's complicated about general
> > > > relativity's explanation?
> > > >
> > > >
> > > I just feel that if you cannot understand it, it cannot be as
> simple
> > as
> > > you claim it to be.
> > > >
> > > >
> >
> > What could be simpler than abandoning independent space and time
with
> > independent units, and replacing them with one substrate,
spacetime,
> > with common units? Why insist that one is measured in meters and
the
> > other in seconds, when there is really only one unit required (take
> > your pick!). Why insist on keeping track of that painful conversion
> > factor 2.99E8 m/s, and why fret about why the speed of light has to
> > have THAT particular value? Why not use a consistent system of
units
> > where the maximal speed turns out to be 1, a much more intuitive
and
> > sensible number? Indeed, name a single positive number that is more
> > intuitive than 1.
>
> One "what". Everything you measure has to have units. What is the
unit
> of spacetime?
> >
> > What could be simpler than saying that a ball rolls on the space on
> > which it is constrained in a straight line if there is no force
> acting
> > on it to change its motion in that space? If that space happens to
be
> > the interior of a bowl, it still rolls in a straight line on the
> > surface of that bowl,
>
> A straight line is a line in one direction; looking from any angle,
> even from one end.

Define "straight" and how you could tell whether a line is straight.

Secondly, suppose I asked you to start walking on a straight line from
here northward. What would you do?

>
> veering neither left nor right on the bowl's
> > surface!
>
> The ball rolls round and round inside the bowl.
>
> Which is more complicated, insisting that the bowl must be
> > applying a force that constrains its motion in some complicated
way,
> or
> > abandoning the force entirely and showing that the inherent
curvature
> > of the bowl makes a straight line drawn on its surface result in a
> > closed path?
> >
> To draw a straight line requires a plane surface, so that the line is
> straight in all three directions.

How can you tell if the surface a line is in is a plane? How can a line
(a one-dimensional object) be straight in three directions at once?
Again, define "straight" and tell me how you'd know if a line was
straight.

>
> > Here is a little parable to illustrate the general attitude, if not
> the
> > point, with light borrowing from JAW and RT.
> >
> > THE BOY AND THE PIGEON
> > ======================
> > A boy sat next to a pigeon on a park bench in the city. A rat
walked
> up
> > and asked, "How far is it to the library from here?"
> > The pigeon said "Five blocks."
> > The boy said, "Don't be ridiculous. It's seven blocks from the
> library
> > to here, but nine blocks from here to the library."
> > Pigeon: "How do you figure that?"
> > Boy: "The library is three blocks east and four blocks north. But
the
> > streets east of here are one-way south for three blocks, so you
have
> to
> > go east for four blocks, then north four blocks, then west a block 

--
> > if you're going from here to there. If you're going from there to
> here,
> > of course, it's only seven blocks. Anyway, the bare minimum is
seven
> > blocks. How do you get five?"
> > Pigeon: "I just fly from here to there. Five blocks."
> > Boy: "Fly DIRECTLY? But you can't do that! You have to go east or
> west,
> > and then north or south, or vice versa. You can't do both at once!"
> > Pigeon: "Why not? I just do it, all the time."
> > Boy: "That seems complicated. How do you keep track of what you're
> > doing at any given instant? How do you know if you're going
east-west
> > or north-south?"
> > Pigeon: "I don't. I just GO there."
> > Boy: "How do you know it's five blocks?"
> > Pigeon: "Look at the map in your back pocket. Good. Now take your
> > fingers and hold them five blocks apart on the map. Sure, follow
the
> > east-west street if you like to mark the distance."
> > Boy: "OK, one finger on the map where we are here and the other
> finger
> > five blocks east of here."
> > Pigeon: "Now swing one of your fingers in an arc, keeping the
> distance
> > between your fingers the same, up toward the library."
> > Boy: "Son of a gun. It's five blocks, if I fly right over the
> buildings
> > and leave the streets."
> > Pigeon: "And you'll note that 3 squared plus 4 squared yields 5
> > squared. This is another way that you can find the distance, even
> just
> > knowing the east-west distance and the north-south distance."
> > Boy: "But that seems so complicated! Why would I want to take
> east-west
> > squared and north-south squared and add them and then take the
square
> > root?? That is just nuts! I don't understand it! It can't be
right."
> > Pigeon: "But that's only because you insist on using east-west and
> > north-south for your directions. YOU are the one making it
> complicated
> > by insisting on using the streets. Me, I just go there. Five
blocks."
> > Boy: "I'm just used to the east-west and north-south. I'm not sure
I
> > can fly."
> > Pigeon: "It doesn't matter whether you can fly or not. The fact
that
> > you can't fly has made you think that distances are east-west and
> > north-south. But the distance is five blocks, whether you think of
it
> > that way or not."
> > The rat concluded that there was no hope for the boy and strolled
off
> > to find a discarded bit of hot dog. The pigeon spread his wings and
> > flew to the library.
> > The boy sat on the bench, scratching his head, bemoaning the fact
> that
> > he was sure he'd never get the hang of east-west squared plus
> > north-south squared, square-root, and thinking in his head that
there
> > MUST be a simpler way, without leaving the streets.
> >
> > PD
>
> Who is the dip that wrote that parable(:-?
That would be me. What's your problem with it?
> 
> Don

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