A brief description of the Local Group of galaxies which contains the Milky Way, the Andromeda galaxy, and dozens of dwarf galaxies all gravitationally bound to each other.

A brief description of what scientists mean when they say we "know" something.

A brief description of the structure of atoms - how they are mostly empty space - and why the everyday objects you use don't collapse and fall in on themselves.

A brief description of what we mean when we talk about interacting galaxies.

A brief description of nuclear fusion, which is the process by which stars produce light so that they can shine.

A brief description of giant molecular clouds and why they are important for stars.

A brief description of the observational evidence we have supporting our assertion that the Milky Way galaxy is spiral in shape. 

A brief description of the 21 centimeter radiation (light) that the Hydrogen atom emits and the mechanism behind this emission.

A brief description of what astronomers mean when they say that "all pulsars are neutron stars but not all neutron stars are pulsars."

A brief description of neutron stars, which are essentially the end state of massive stars some of which become pulsars.