Reality and Relativity
Introductory
note: I’m not really discussing reality in a metaphysical sense, arguing that
all people experience the same world.
For now, absolute reality means a physical property that all ideal observers
can agree on, despite their “individual realities” or experiences. I’m not arguing that we all live in some sort
of absolute reality and experience it differently- my metaphysical beliefs are
still relatively tentative and I don’t want to make such a strong claim. I’m looking for a reality built on things
everyone agrees on, not arguing that this reality exists metaphysically or that
we all reside metaphysically in it.
We’ve been studying special relativity in physics, so in class today, instead
of focusing on Lorentz transformations and Minskowski matrices, my mind
wandered off in a different tangent. How can one reconcile special
relativity with the concept of an absolute reality? Basically, I’m
accepting the claims of special relativity, that one’s measurements of space
and time, relative to another’s, is dependent on the relative velocity between
the observers, and simplifying the universe to two observers, A and B, between
which there is a relative velocity V which is near c, the speed of light, and
an infinite number of events for them to measure. Let both measure the
length of a rod which is at rest relative to A. (This is actually two
events, one for measuring each end.) A will measure the “proper” length
of the bar, but B will get a different value. A will claim that this is
because B didn’t measure the ends of the bar simultaneously (to A, B’s clock
runs slow), but B will claim the same of A. When both complete the proper
Lorentzian calculations they each determine the length
of the bar is their own value (that is, the length is relative to their
motion). Allowing for the idea of ‘reality’ to include the length of the
bar, it seems as though A and B have their own ‘realities’ because they don’t
measure the same length of the bar and experimentally, there is no way to
determine which frame, if either, is at rest- a rest frame is arbitrarily
defined (again, from special relativity). However, I really don’t like
the idea that each person has his/her own reality- I’d rather we all share one
absolute reality, or at the very least, some things must be shared between all
realities. (In a physical sense- I believe absolutely that such
intangible things such as morality holds for all
people regardless of their observed reality.) Also, if everyone has their
own observed ‘realities’, can we say that anything is absolutely true, in a
physical sense? Does the rod have a true length? A’s and B’s
observed realities aren’t completely separate- there are some things linking them.
For example, A exerts a gravitational pull on B and vice-versa. However,
this doesn’t show much promise for defining some sort of absolute reality
between them, much less for defining a true length for the bar.
One
could redefine absolute reality so that, instead of being based on separate
entities of space and time, it is based on invariants such as distance squared
minus c squared times time squared and causality (which isn’t affected by
special relativity). All observers,
regardless of motion, can agree on these values. Also, you could define the “true” parameters
of the bar to be its proper length, etc, that is the length measured in a frame
of reference in which the velocity of the bar is zero.