Originally posted by CLPrimeThat's a pretty good explanation.
This has a good explanation of what happens during metric expansion: Universal Misconceptions #1: The expansion of time.
If anybody is brave and wants some related imagery, check out these Space-Time Diagrams related to the expansion of the universe. Physicists and their students use these to help them understand the relationships between time and space. The "light cone" is a key concept these portray and the red line here shows our past light cone:
Even these diagrams give a distorted view (because of the curvature caused by gravity) the same way looking at a flat map of the Earth on a Mercator projection distorts the view of the curved (somewhat spherical) Earth, but the light cones help us understand this distortion. Eventually he shows how to replace the space distortion by creating time distortion, reinforcing their interchangeability as explained in CLPrime's link, which is pretty interesting. When he does that the light cone actually looks like a cone.
A more simple explanation of space time diagrams is given here so maybe read this first before the link above: www.astro.ucla.edu...