Expansion of the universe

(Last edited: Saturday, 30 September 2023, 7:04 PM)
Image/Video/Audio Source: https://en.wikipedia.org/wiki/Expansion_of_the_universe#/media/File:CMB_Timeline300_no_WMAP.jpg

Image/Video/Audio Source: https://en.wikipedia.org/wiki/Expansion_of_the_universe#/media/File:CMB_Timeline300_no_WMAP.jpg

Short Definition:

The expansion of the universe is a phenomenon, which describes the inherent property of the universe, where two galaxies that are gravitationally unbound tend to increase the distance to each other and the rate of expansion is even accelerating. Far away parts of the observable universe will not be observable in the near future, because the velocity of expansion is higher than light speed from an outside perspective.

Detailed Definition:

The expansion of the universe is a phenomenon, which explains an inherent property of the universe to expand. The fact that the universe seems to expand, was first doubted because of the gravitational force and the fact that releases of energy like the big bang should normally lose power and should slow over time, but the opposite was observed. The elusive culprit was found quite fast. Dark matter is to be responsible for this phenomenon, but since we know even less about dark matter than about the expansion of the universe, details of how and why it expands are still unknown. 

This expansion occurs at every location of the universe and only gravitationally bound galaxies will be able to observe each other, because unbound galaxies will escape our observable universe at some point. The expansion can in some way be compared to an elastic rubber band, where the distances also increase when you stretch it, but not literally and not on a human scale. It is more that at a scale so far zoomed out, that the universe looks like a cosmic fluid and at this scale it is apparent that the density is decreasing over time. There are three viable methods to measure this expansion. One is based on redshifts, while another on the cosmic distance ladder. Those measurements gave non-matching results, and so 2018 information from gravitational waves made it possible to determine the rate of expansion even more precisely.


Expansion à from Latin expandere à spread out

Universeà from Old French univers à from Latin universum

Sample Sentence(s):

In a thought experiment of an ascending civilization in a faraway galaxy in the far future, they would only be able to observe their neighbouring galaxies and will think  that this is all there is to the universe and all this due to an expansion of the universe.


The rate of expansion of the universe is thought to be accelerating.


Expansion de l'univers


Ausdehnung des Universums


Ekspansja Wszechświata


Utvidgning av universum

Links to Videos/Articles:

Expansion of the universe - Wikipedia

» Dictionary of Space Concepts