This Quantum World

Turtles all the way down?

Page 1 of 2

In this article (look here for an explanation of the title) I will argue that the spatial differentiation of the physical world is incomplete. It doesn't go all the way down. If in our minds we partition the world into smaller and smaller regions, there comes a point when there isn't any material object left for which these regions, or the corresponding distinctions, exist. Much the same is true of the temporal differentiation of the world.

To summarize (and refresh our memory) let us take another look at these stationary states of atomic hydrogen:

Relative position probability distributions associated with various stationary states of atomic hydrogen

And let us again imagine a measurement designed to determine the electron's presence in or absence from a region like the little box in the first image. Without the measurement, the electron is neither inside nor outside this region, for if it were inside, the probability of finding it outside would be zero (the outside would be black), and if it were outside, the probability of finding it inside would be zero (the inside would be black).

Yet being inside and being outside are the only relations that can hold between a given electron and a given region. If neither relation holds, that region simply does not exist as far as this electron is concerned.

But conceiving of a region R is the same as making the distinction between "inside R" and "outside R." Hence we may say that the distinction we make between "inside R" and "outside R" is a distinction that the electron does not make, or we may say that the distinction we make between "the electron is in R" and "the electron is outside R" is a distinction that Nature does not make. It corresponds to nothing in the physical world. It exists solely in our heads.

Spatial distinctions are therefore relative and contingent:

relative because the difference between "inside R" and "outside R" can be real for a given object at a given time and not have any reality for a different object at the same time or for the same object at a different time,
and contingent because the reality of that difference (for a given object O at a given time t) depends on whether a relation (inside or outside) exists between O and R at the time t, which in turn depends on whether the proposition "O is in R at t'' has a truth value ("true" or "false"), which in turn depends on whether a truth value is indicated ("measured").

An example: If we put a dim light source behind the slit plate in our two-slit experiment, an electron may or may not scatter a photon as it emerges from the slits. A scattered photon "carries" information about where it was scattered, and thus about the slit taken by the electron by which it was scattered. If two electrons pass the slit plate simultaneously but only one of them scatters a photon, then one went through a single while the other went through both slits as an undivided whole. In this case the distinction between L and R is simultaneously real for one electron and not real for another. (Reminder: the reason why an electron can pass through both slits as an undivided whole is that, as far as this particular electron is concerned, "both slits" exists as an undivided whole.)

<< Start < Prev 1 2 Next > End >>

< Prev		Next >

[ Back ]

Who's Online