It's hard to explain stuff you can't see! But, this animated stick-figure drawing describes dark matter and how we know it exists. It likens the galaxy to a merry-go-round, holding the stars on their circular path. The one-minute...

When we take things apart, we can learn how they work. Physicist Clifford Johnson explains how we break down all objects into elementary particles of matter and forces. Patterns have been identified with the particles, the existence dark...

This video lesson has the goal of introducing students to galaxies as large collections of gravitationally bound stars. It explores the amount of matter needed for a star to remain bound and then brings in the idea of Dark Matter, a new...

Crash Course is a fast, funny, irreverent look at history beginning with the Big Bang Theory. In this episode, brothers John and Hank Green gives us their take on what makes Big History so darn important. [13:55]

A mysterious X-ray signal from the Perseus cluster of galaxies, which researchers say cannot be explained by known physics, could be a key clue to the nature of Dark Matter. (July 21, 2014) [3:42]

The Fermi Gamma-ray Space Telescope recently produced a map of the night sky. Out of 1873 new sources, nearly 600 were complete mysteries. In this week's ScienceCast, researchers speculate on the nature of the mystery objects - including...

Today on Crash Course Astronomy, Phil dives into some very dark matters. The stuff we can actually observe in the universe isn't all there is. Galaxies and other large structures in the universe are created and shifted by a force we...

Find out that the matter we can actually observe in the universe isn't all there is. Galaxies and other large structures in the universe are created and shifted by a force we detect mostly indirectly, by observing its impact, dark...

Much of what exists in the universe is believed to be invisible, and that there may be other dimensions. A scientist discusses research into dark matter and what we know so far. Aired June 22, 2009 [12:07 min]

The history of the Universe decorates the night sky. Learn how to watch this history by studying cosmic light emissions. [6:22]

This week scientists announced that they have confirmation on the presence of dark energy in the universe. We'll talk about their study and what it means.

A smashup between two galaxy clusters left an unexpected amount of dark matter in its wake.

Nobel Prize-winning astrophysicist Adam Riess discusses the mysterious force known as dark energy in this audio recording. Learn how he believes this dark energy is accelerating the expansion of the universe. [22:36]

The spy telescopes are wide-angle and short in length--earning them the nickname "stubby Hubbles." [18 mins. 8 secs.]