A small number of scientists defines space dust as the observable portion of dark matter. Space dust is comprised of small particles (about 0.1 mm) which reflect light on a very large scale. This is what can be seen of dark matter, not observable directly, but its hypothetical effects have been noticed.

Space dust, also referred to as cosmic dust, is categorized by the name of its location, such as intergalactic dust (between galaxies), interstellar dust (possibly concentrated in a nebula), interplanetary dust (like in a circumstellar disk), and circumplanetary dust (like the one found in a planetary ring). In the solar system that we're part of, this cosmic dust determines the occurrence of the zodiacal light phenomenon (a triangular, pale, whitish light extending from the proximity of the Sun along the ecliptic or zodiac horizon). In this tiny fraction of the Milky Way galaxy, the cosmic dust sources are the dust from the Kuiper belt, asteroidal dust, comet dust, and interstellar dust crossing our solar system.

The theory came into being by associating the scarceness of both particles' sightings. While space dust needs to reflect the light at a precise angle (logically, towards the viewer) in order to be spotted, dark matter has only revealed its hypothetical appearance during the event that nowadays everyone seems to know a lot about - the Big Bang. The energy released during the first few seconds of that process is calculated to have been exerting amounts of 10 to 100 gigatons of pressure per square inch, and, where it reached its peaks - even per square centimeter. It's not something you're likely to relate to anything you know, which makes it so difficult to comprehend. Back then, 13.7 billion years ago, that energy was generated by atoms smashing against each other at incredibly fast velocities, something that the Large Hadron Collider tries to mimic these days (or, most likely, next year).

Today, a handful of researchers claims that dark matter can actually be seen, just like during the Big Bang but way less obvious and strong, only in nebulae. Basically, the generated pressure was of such incredible strength on so tiny areas that the atoms of dark matter couldn't deal with it, and a reaction process occurred, generating light.