Vacuum

From Conservapedia

A vacuum is any region in space devoid of atoms and molecules. Such a region does not conduct heat (although heat can travel through it by radiation) or transmit sound waves and has important uses for both science and technology.

While a perfect vacuum is theoretically possible, it has never been replicated in the lab. Pascal was the first person to prove the existence of a vacuum.

Source

The New American Desk Encyclopedia, Penguin Group, 1989