Stephan,
Your reply actually answers my reply to Stevens answer. You are
saying that I will never be able to test this hypothesis because the axis of
contraction is never going to present itself to the stationary observer - I
liked your "silhouette" analogy. You mentioned this concept of being "real" or
just a trick of light is controversial. So I guess I am just piling speculation
on top of controversy when I raise the question of stationary objects on the
spatial axis where time is occurring at different rates due to equivalence. We
know time is slower a the bottom of a gravity well due to mass while to achieve
an equivalent slowing of time without a gravity well takes high velocity on the
luminal scale like my basketball question. This high velocity reflects the
Pythagorean relationship between time and space from which they derived Gamma
(where the Y axis is a constant 300m/s ?). My question is therefore how does
space contract for "equivalent" acceleration vs spatial acceleration? Does the
gravitational vector define the axis that contract? Would these "pancaked"
basketballs sitting in a deep gravity well be stackable such that millions of
basketballs would now fit where only a few "un-contracted" balls should fit?
Regards
Fran
<http://www.mail-archive.com/>
Re: [Vo]:checking my understanding of Lorentz contraction
Stephen A. Lawrence
Thu, 01 Apr 2010 06:40:36 -0700
On 03/31/2010 11:52 PM, Francis X Roarty wrote:
> Am I correct in believing a near luminal basketball could pass through
> the eye of a stationary needle?
>
No. The basketball is contracted fore-and-aft, but not side-to-side, as
viewed by an observer sitting next to the needle. So, it's going to be
too wide to fit through the needle's eye, even though it may be
*thinner* than the needle's diameter.
As Steven Johnson already said, the basketball "pancakes", but the
pancake is flying along with one flat side to the front, so it's "splat
time" when it hits the needle. You could also say the basketball has
been replaced with its silhouette.
It's the fact that there's no side to side contraction which leads to
all the arguments over whether the contraction is "real". The
fore-and-aft contraction is arguably just a "trick of the light".
The fore-and-aft contraction seems to be mostly an artifact of the fact
that time is skewed between the reference frames, and in order to
determine how "long" something is, you need to find the locations of the
front and back of the object "simultaneously". The definition of
"simultaneous" turns out to be frame dependent, which is how an observer
on the basketball and one sitting by the needle end up disagreeing about
whether the basketball is contracted or not.
Spinning disks, on the other hand, cast a rather different "light" on
the matter, as a spinning disk which can't stretch will, in principle,
crack as it spins up, due to the contraction of the rim. That makes the
contraction seem rather "real". A really long train also cannot
accelerate at more than a certain rate without breaking apart, as it
turns out the cars at the back of the train must move faster than the
ones in the front due to the train's contraction as it speeds up. At
some point they'd have to break the lightspeed barrier to avoid being
left behind by the shrinking train. That, also, makes the contraction
seem rather "real".
