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The Ladder of Scale

Everything between the edge of the solar wind and the edge of what light has had time to reach, ordered on the only axis that can hold it: the logarithm of light-years. The unit shifts as you climb — astronomical units, light-years, thousands, millions, billions — because no single one survives the whole climb. Parsecs are given alongside, since that is what the literature quotes.

Where this is soft

The numbers below are the ones this page is least able to defend. They are listed because a page that only shows what it is confident about is not showing you very much — and because these are the questions worth putting to someone who works on this.

  1. Nothing here carries a citation. Not one row here names where its number came from. The redshifts and distances are literature values entered by hand; the arithmetic connecting them is checked, the sources are not.
  2. Redshift is stored as text, because real structures span a range — the CfA2 wall runs from about 0.015 to 0.03. The check uses the midpoint, which for a wall 500 million light-years deep is a fiction of convenience. A proper treatment would carry the range through and quote a distance range too.
  3. There is no uncertainty column, because for most of these there is no agreed measurement to attach one to. A cluster's distance has an error bar. A supercluster's size mostly has a convention.
  4. Sizes above the galactic scale are definitions, not measurements. Laniakea's 520 million light-years is the span of a velocity-flow basin; the voids are quoted as effective-sphere diameters; the walls are longest extents. These are not the same kind of number, and the page currently prints them in the same column.
  5. Three structures here may not be structures — the Hercules–Corona Borealis Great Wall, the Giant GRB Ring and, on the strongest reading, Quipu. They are included with the argument in their notes. Whether that is the right call, or whether they belong in a separate register, is a judgement this page has made without authority.

From the Cosmic Structures database in Notion. Distances are comoving — the separation today, not the light-travel time; at z = 1.6 the two differ by more than half. Sizes above the galactic scale are soft: a supercluster has no edge, and the figures quoted are the longest extent usually cited, not a measured boundary. Structures whose reality is still argued over say so in their notes rather than being left out.