The hypothesis of dark matter has an elaborate history. In the appendices of the book Baltimore lectures on molecular … See more

In standard cosmological calculations, "matter" means any constituent of the universe whose energy density scales with the inverse cube of the scale factor, i.e., ρ ∝ a . This is in contrast to "radiation", which scale… See more

The arms of spiral galaxies rotate around the galactic center. The luminous mass density of a spiral galaxy decreases as one goes from the center to the outskirts. If luminous mass were all the matter, then we can model the … See more

The exact identity of dark matter is unknown, but there are many hypotheses about what dark matter could consist of, as set out in the table below.
Dark matter can refer to any substance which inter… See more

If dark matter is made up of subatomic particles, then millions, possibly billions, of such particles must pass through every square centimeter of the Earth each second. Many experiments aim to test this hypothesis… See more

Because dark matter has not yet been identified, many other hypotheses have emerged aiming to explain the same observational phenomena without introducing a new unknown type of matter. The theory … See more