Q. What is the Cosmic Microwave Background Radiation?

A. CMBR is long-wavelength electromagnetic radiation which we receive from all points of the sky.

Q. Where does CMBR lie on the electromagnetic spectrum?

A. It's in the microwave and far-infrared spectrum, of lower energy than visible light and most infrared, but above radio.

Q. Is it important in the big picture?

A. Yes, CMBR makes up more than 70% of the energy in the radiation reaching us from space -- and a lot more than 90% of the photons.

Q. Where does it originate?

A. From the "Oort Soup" -- all sorts of planetesimals and planets in interstellar space, distant from stars.