Please register ( or log-in ) to create and edit pages

User Tools

    Please register ( or log-in ) to create and edit pages
  • Register

Site Tools


Main Menu

Main menu
[ Click categories to expand ]

Other categories

For tests only


Also see:

Content Guidelinesplugin-autotooltip__plain plugin-autotooltip_bigContent guidelines

Ideas for new topics are always welcomed, from experts and non-experts alike - if you're not sure if they'll be accepted by other editors, put them in the 'Proposed content' section for approval. The easiest way to create a new page is to use the

Registrationplugin-autotooltip__plain plugin-autotooltip_bigRegistration

At present, only registered users can create and edit articles. The registration process is very straightforward. Just click the 'Register' link at the top right of any page.

After you've registered, you'll be able to login with your password at any time…

How to edit pagesplugin-autotooltip__plain plugin-autotooltip_bigEditing pages

Once you're logged in, a grey floating 'Tool' menu at the right hand side of the screen enables access to all the main 'Content Pages' for editing. (Note: Some pages, such as the site info etc. are locked)

Like most Wikis, the site doesn't use

Importance Ratingsplugin-autotooltip__plain plugin-autotooltip_bigImportance ratings

In a departure from the usual Wiki format, Wikenigma assigns 'Importance Ratings' to some pages.

The idea is to separate articles which are considered (by the editors) to cover exceptionally important unknown issues from those which (although also u…

Faqplugin-autotooltip__plain plugin-autotooltip_bigFrequently Asked Questions

Q. Why the weird syntax? A. Like most Wikis, the site doesn't use HTML for formatting (security reasons etc). A guide to the special syntax can be found here. Unfortunately it can be quite confusing at first - but there's now a new 'Visual …

Newsplugin-autotooltip__plain plugin-autotooltip_bigNews

[ newest at the top ]

• Oct 2020 : A milestone of 500 unknown articles has been reached.

• Aug 2020 : Currently (beta) testing the new 'WYSIWYG' (What You See Is What You Get) page editor. It greatly simplifies the editing process, avoiding the need to learn th…

Contactsplugin-autotooltip__plain plugin-autotooltip_bigContacts

Use this form to send a message to Wikenigma . . . [ * note: all fields must be completed ]

Legalplugin-autotooltip__plain plugin-autotooltip_bigLegal

Content in general

Please note that in common with other publicly editable wikis, this website is not responsible for content posted by the public. Nevertheless, the ongoing editing process should be able to remove unsuitable content in a reasonable time. If you…


541 unknowns listed

Wikenigma supports:

plugin-autotooltip__plain plugin-autotooltip_bigDonate to Wikenigma . . .

The best way to donate is by adding new original content !

That can either be by contributing to an existing article, or by creating a new page with an as-yet-unlisted 'Known Unknown'.

Any registered user can create content.

A-Z listing
rss / xml feed
sitemap file

Wikenigma - an Encyclopaedia of Unknowns Wikenigma - an Encyclopaedia of the Unknown Science

Dark Matter

“The nature of the dominant component of galaxies and clusters remains unknown.”

Source: Measuring the dark matter equation of state (Mon. Not. R. Astron. Soc. 415, L74–L77)

In the 1930s, astronomical observations of galaxy rotations showed that the outer regions were rotating (about the galaxy's 'centre') at the same speed, or faster, than the central regions. Subsequent calculations referring to the galaxy's mass, and thus its internal gravitational attractions, showed that if the outer regions were rotating at the observed speed, they would fly away from the centre and the galaxy would disintegrate.

As a means of explaining the anomaly, the idea of Dark Matter was proposed. For the explanation to work, the galaxies would have to be surrounded by a 'halo' of Dark Matter - a previously unknown form of matter that has mass, and yet does not interact with 'ordinary' matter in any other way than by gravity. Further calculations showed that for the galaxies to hold together, there would need to be approximately five times more Dark Matter (in terms of mass) than standard matter.

The current estimates are that Dark Matter makes up 26.8% of the universe. The rest being Dark Energyplugin-autotooltip__plain plugin-autotooltip_bigDark Energy

"“The observational results of the latest 15 to 20 years have established a standard model for the cosmology which has some amazing consequences. A mysterious entity, the dark energy, has been confirmed as the dominant component of the Universe, and is als…
(68.3%) and visible matter (4.9%).

Since its proposal, various experimental projects have attempted to 'observe' dark matter [refs needed]- or more accurately its effects, as it would need to be 'invisible' to have escaped detection up until now. To date no experiment has been able to directly and unequivocally detect Dark Matter.

Alternative theories to explain the galaxy rotation enigma include the so-called MOND theory, which proposes that (the force of) gravity is not constant throughout the universe.

Further reading : Wikipedia

Note that of the 4.9% of 'ordinary matter' (a.k.a. 'Baryonic matter') only around 10% of that is currently accounted for. The so-called 'missing baryons' have now begun to be observed according to a 2017 paper published in arXiv Missing baryons in the cosmic web revealed by the Sunyaev-Zel'dovich effect

Importance Rating


    Share this page :


DOKUWIKI IMPLEMENTATION DESIGN BY UNIV.ORG.UK