Portal:Cosmology

The metric expansion of space is a scientific theory first proposed by Fr. Georges Lemaître according to which the increase of the distance between two distant parts of the universe with time. It is an intrinsic expansion whereby the scale of space itself changes. This is different from other examples of expansions and explosions in that, as far as observations can ascertain, it is a property of the entirety of the universe rather than a phenomenon that can be contained and observed from the outside.

Metric expansion is a key feature of Big Bang cosmology, is modeled mathematically with the FLRW metric, and is a generic property of the universe we inhabit. However, the model is valid only on large scales (roughly the scale of galaxy clusters and above). At smaller scales matter has become bound together under the influence of gravitational attraction and such things do not expand at the metric expansion rate as the universe ages.

Did you know...

• ... that space is flexible, and has been expanding at a measurable rate since the beginning of time?

• ... that most of the atoms in our bodies were created in stars through fusion?

• ... that the Earth isn't flat, but the universe is? Based on Einstein’s Theory of General Relativity, there are three possible shapes that the Universe may take: open, closed, and flat. Once again, measurements by WMAP on the CMBR have revealed a monumental confirmation – the Universe is flat.

• ... that the average density of visible matter in the universe is about 10–30 g/cm³?

• ... that the temperature of the cosmic microwave background is 2.7 K?

• ... that the Earth is neither the center of the Universe nor the galaxy, because the universe has no center?

• ... that considering only the largest structures, the Universe is made up of filaments, voids, superclusters, galaxy groups and clusters? By combining galaxy groups and clusters, we come up with superclusters. Some superclusters in turn form part of walls, which are also parts of filaments.