Is there a name for a point at the edge of the observable universe at which there is no visible matter, that appears completely dark?

I'm thinking something like "empty space", but that could equally apply to an empty void between galaxies, which isn't quite what I'm looking for.

So it would refer to a theoretical line in space from the observer to the edge of the universe which contains no visible matter. Is there a term for this?

  • $\begingroup$ Maybe I don't quite understand your question, but why would we need a special name for voids near the edge of the observable universe? $\endgroup$ – PM 2Ring Mar 6 at 19:55
  • $\begingroup$ I think the reason is indirectly implied from your comment, because "voids near the edge of the observable universe" isn't precisely what I'm looking for either. Cosmic voids can be obscured behind galaxies, so that wouldn't work as a description either. I just want to be able to describe the "blank" areas without having to write a full sentence each time. Maybe something like "empty cosmic sky", or "transparent cosmic background"? $\endgroup$ – Paul Mar 7 at 13:42

There is no name for this.

As we look further in space, we also look further back in time. The "edge of the observable universe" is in the early universe. At an early time in the evolution of the universe, the whole of space was so hot and dense that it was opaque. In whichever direction we look, we can't look back further than this. The is called the cosmic microwave background. There is no direction in which we can look in which we don't see the cosmic microwave background. There is no direction that contains no visible matter.

There are directions that contain no galaxies or other more nearby objects, but there is no name for these directions.

  • $\begingroup$ @Paul Sure, the CMB has been redshifted to microwaves, but it was originally visible light, and like most of the light in the universe, it was emitted by hot hydrogen & helium. FWIW, it was originally an orange colour, as shown at the end of this answer. $\endgroup$ – PM 2Ring Mar 7 at 15:29

The observable universe is merely how far we can see with current telescope technology.

Space itself is endless. Oh, there's no end of people here who will aggressively argue this. But empty space, by definition, cannot have an end. It can only be infinite. Literally infinite.

There could very well be an edge in the sense that there's no more matter, where stars, planets and galaxies etc simply tapers off. After that, it would be endless black space.


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