[ExI] QT and SR

Lee Corbin lcorbin at rawbw.com
Thu Jul 17 23:04:45 UTC 2008


Damien writes

> Perhaps a more interested question about the string is whether it's 
> actually meant to connect stern to bow, or to extend perpendicularly 
> from the hulls of craft which all launch from the same starting line? 

I don't know whether or not the question would be more
interested, but I am.  That sounds like it could scythe down
a lot of buildings and trees especially if those strings don't
break right away, and I'm certain that the spaceport authorities
would forbid that kind of maneuver.

> My impression is that Lorentz contraction is only in the direction of 
> flight,

That's right, it is only in the direction of relative movement

> but perhaps not, since (last I heard, decades ago) an accelerating
> globe does not get flattened into a pancake but  *rotated*.

I haven't heard that one, unless you mean the effect whereby
you can see the trailing face of a perfect cube as it flies past
at nearly the speed of light. Suppose that the back end of 
the cube has four corners A, B, C, and D, and that A and
B are nearest you. (We may also, for clarity, say that for
the side of the cube facing you, the A and B are at the
left of your field of vision, and two other corners not
mentioned, say X and Y are at the right side, on the
leading face of the cube as it moves past you from left
to right.)

Light from the far corners C and D of the cube that would
not normally be visible can be seen, since a photon that leaves
C finds its way to your eye unimpeded since the cube has
hastened out of the way. This results in it looking to you as
though the cube is traveling by at a rotated angle with its
back face almost as visible as the side facing you.

> When you fall into a black hole you're squeezed as well as 
> stretched, and since gravity is (they assure us) indistinguishable 
> from acceleration...

You've switched to General Relativity effects now, I think.

Moreover, the only reason you are squeezed is that the source
of the gravitation is supposed to be a point source.  For example,
we suppose the mass of a black hole to be concentrated at its
center.

But let's consider instead an extremely massive planet
built like a large cube, and the density of its matter arranged
so that when you're near the middle of one side and feeling 
yourself being pulled in, the molecules on your left side are
being pulled in a direction perfectly perpendicular to the surface
of the planet just as are the molecules from your right side. Then
there is no squeezing effect. The squeezing effect when near a
spherical gravitating body arises from your molecules on your left
and on your right being pulled not in a parallel direction, but
rather towards a common central point.

But the stretching effect would persist near this cubic planet
because if, say, you're falling feet first, the molecules in your
feet are closer to it and so are being pulled with a stronger
force than are the molecules in your head. (I'm sure you 
already understand this "tidal effect" but I'm writing right
here for other readers who don't.)

Lee




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