From the Extrasolar Planet web page. The Pioneer 10 Spacecraft. This is the fastest human-made object. The closest stars are 100 million times further away from us than the largest distance humans have traveled. The electromagnetic spectrum.
Light is a wave that can travel through space.
Different kinds of light are characterized by different wavelengths. Radio waves have longer wavelengths than other kinds of electromagnetic radiation, so they are less likely to be absorbed or scattered by interstellar dust. A map of the sky, showing the cosmic microwave background, as seen by the COBE spacecraft. The Arecibo 300 meter radio telescope. This is used for Project Phoenix.