Ask Ethan: How Small Can A Piece Of The Universe Be And Still Expand?
Galaxy-sized? Human-sized? Atom-sized? Even smaller? How tiny can a bit of space be and still expand?
“We now have the best picture of how galaxies like our own formed their stars.” -Casey Papovich
The expansion of the Universe has a long and amazing history. When Hubble first noticed the relationship between a galaxy’s distance from us and how redshifted its light was, he knew immediately it was a consequence of Einstein’s General Relativity. When Hubble announced his discovery, Einstein immediately recanted his cosmological constant — a “fudge factor” to keep the Universe static — and called it his greatest blunder. But while the space between galaxies expands, atoms, human beings and planets remain the same size over time. What determines this? Jeroen van Rijn wants to know:
What scale limit if any are we talking about when we say the universe expands? Does it mean Planck length isn’t a constant so much? Do atom’s orbits grow corresponding with this stretching of space or does the strong force counteract this?
