**The Keychain Interpretation of Higher Dimensions**

Ever since I first read about string theory, I was fascinated by the
idea that space might have extra dimensions balled up so small that
travel in them could not be measured. I wondered how these extra
dimensions might influence the 4 dimensions we live in. As I understand
it, string theory and the newer M-theory use these dimensions and
vibrations in these dimensions to explain the masses and charges of
particles in the Standard Model, with varying degrees of success.
Beyond defining the basic properties of matter , though, I havenŐt read
anything explaining how motion in higher dimensions might manifest
itself to be perceived in the visible universe. This is potentially
interesting because the small size of these dimensions implies that the
*entire universe* may be locally connected.

Simply stated, the Keychain Interpretation says that multiple, parallel universes, defined as discrete space-time continua, coexist as separate realities tied together on loops in higher dimensions. Think of an entire universe as a single key, with a specific set of grooves corresponding to its measurable physical properties. This includes the positions and momenta of all the particles at any particular moment. Needless to say, the number of grooves and the number of possible groove depths is staggering, but still, it fits the model of being a key. One key equals one measurable present for one universe.

For the purpose of illustration, let us consider just one higher
dimension, which we arbitrarily dub the 5^{th} dimension. Each
universe is separated by a distance that is small relative to the Planck
scale, yet it spans the entire space-time of each universe. The
universes lie next to each other like keys on a chain, similar but
discrete because they are only measurable as a collection of quantum
states. Unmeasured states may be regarded as superimposed keys, and the
fewer states one measures, the fewer keys one distinguishes on the
chain.

What, exactly, is the loop? Other than binding the keys together, what does it do? How can one move along the loop? To further explore the idea of coexisting possible universes, read the following thought experiment.

For additional dimensions beyond the 5^{th}, we can imagine
chains of keychains, and chains of chains of keychains, where each
multiverse on each chain contains a discretely measurable set of similar
keys. Alternatively, we can imagine a 6^{th} dimension that is
roughly equivalent to our 4^{th} dimension of time, providing a
continuous evolution from one set of possible spacetime continua to
another. Perhaps something changes about the keys, like a base pattern
that corresponds to a different set of physical constants. This could
have a large effect on the properties of each universe or could be
minor, depending on the change.

At any given time, we perceive only a single universe, a single key on a chain. However, the other keys are here too, so long as we don’t attempt to measure them. When we measure a particle, we fix one groove on our key, thus separating our universe from universes with a different groove. Perception is the key.