Intuitive Significance
In the ADM formalism we introduce a family of spatial hyperslices. This allows us to think of the geometry of "space" as evolving over "time". This is an attractive viewpoint, but in general no such family of hyperslices will be physically preferred. The Weyl hypothesis can be understood as the assumption that we should consider only cosmological models in which there is such a preferred slicing, namely the one given by taking the unique hyperslices orthogonal to the world lines of the fluid particles.
One consequence of this hypothesis is that if it holds true, we can introduce a comoving chart such that the metric tensor contains no terms of form dt dx, dt dy, or dt dz.
The additional hypothesis that the world lines of the fluid particles be geodesics is equivalent to assuming that no body forces act within the fluid. In other words, the fluid has zero pressure, so that we are considering a dust solution.
Read more about this topic: Weyl's Postulate
Famous quotes containing the words intuitive and/or significance:
“If mothers are told to do this or that or the other,... they lose touch with their own ability to act.... Only too easily they feel incompetent. If they must look up everything in a book, they are always too late even when they do the right things, because the right things have to be done immediately. It is only possible to act at exactly the right point when the action is intuitive or by instinct, as we say. The mind can be brought to bear on the problem afterwards.”
—D.W. Winnicott (20th century)
“Of what significance the light of day, if it is not the reflection of an inward dawn?—to what purpose is the veil of night withdrawn, if the morning reveals nothing to the soul? It is merely garish and glaring.”
—Henry David Thoreau (1817–1862)