"Very well." He cleared his throat. "Matter, as we know it: Atoms, stars and galaxies. Planets and trees. Rocks and us. This matter accounts for less that five percent of the known Universe. About twenty five percent is Dark Matter and seventy percent Dark Energy. Both of which, are invisible. This is kind of strange, because it suggests everything we experience is really only a tiny fraction of reality. But it gets worse, we really have no clue what Dark Matter and Energy are, or how they work. We are pretty sure they exist, though. So, what do we know? Dark Matter is the stuff that makes it possible for galaxies to exist. When we calculated why the Universe is structured the way it is, it quickly became clear there's just not enough normal matter. The gravity of the visible matter is not strong enough to form galaxies and complex structures. The stars would more likely be scattered all over the place and not form galaxies. So we know there is something inside and around them. Something that doesn't emit or reflect light. Something, dark. Besides being able to calculate the existence of Dark Matter, we can see it. Kind of. Places with a high concentration of Dark Matter bend light passing nearby, so we know there's something there that interacts with gravity. Right now, we have more ideas about what Dark Energy is not, that what it is. We know Dark Matter is not just clouds of normal matter without stars, because it would emit particles we could detect. Dark Matter is not Antimatter, because Antimatter produces unique Gamma Rays when it reacts with normal matter. Dark Matter is also not made up of Black Holes. Very compact objects that violently effect their surroundings, while Dark Matter seems to be scattered all over the place. Basically, we only know three things for sure. One, something is out there. Two, it interacts with gravity. Three, there is a lot of it. Dark Matter is probably made up of a complicated exotic particle that doesn't interact with light and matter in a way we expect. But right now, we just don't know." He pauses. "So, that was Dark Matter. Shall I move on to Dark Energy?"