If someone were to ask what you thought vacuum cleaners were, probably the first response would be to wonder if you had heard the question correctly. It seems like a strange thing to be asked, particularly before you know who's been doing the asking. For convenience we'll suppose the question was from David T Kenney and was asked in 1910. It's your business what you were doing in 1910.
While most people these days -- more than 97 years after the question was hypothetically posed to them -- would say that a vacuum cleaner was a kind of machine, it's only recently the vacuum cleaner has become a machine. Before the middle of the 20th century people had the job of vacuum cleaner and therefore for people would think you were talking about people, possibly even then. It is a testament to the gentle and easygoing nature of the past that this didn't produce more hurt feelings.
The first vacuum cleaner was a now-anonymous (his name was removed in 1964 for betting on baseball games) attendant to Evangelista Torricelli in 1643. The great physicist had poured mercury into a tube sealed at one end, turned it upside-down, and in so producing created a perfect vacuum at the top of the tube and a perfect mess all over the table. Naturally Torricelli ordered the cleaning of the table, the tube, and while he was at it, the vacuum, whose state Torricelli said was abhorrent. With a few quick motions of a damp cloth a new profession was born.
Curiously the new profession was almost stillborn: the attendant started out holding the vacuum to clean it, and it slipped out of his hands. The attendant swiftly replaced it with the vacuum from the top of a barometer, and all was well even though Torricelli believed every day for the rest of his life that the atmospheric pressure was very high and the projected weather was ``fair to aneroidal''.
Vacuum cleaning was regarded for a wide while as an affectation among the scholarly classes. For much of the 17th century it was nearly as popular as making up grammatical rules for Latin or wearing caps and gowns everywhere. It was not until the reign of French King Louis XV -- who did not exist, but was hastily added when it was realized that they had jumped right from Louis XIV to Louis XVI and it looked funny having the number laying around un-Louised -- that it made the social leap from the laboratory to the royal court. In so doing it slipped on the windowsill and suffered a sore ankle for months.
The post of Royal Vacuum Cleaner was soon established, along with a fleet of assistants, keepers, letters-go, attendants, absentias, the fellow who owned the mop, the keeper of the mop, the fetcher of the mop, and the keeper of the fetcher. Within a generation vacuum cleaning cost the court at Versailles over 34,002 livres per year, so you can understand the scandal when it turned out they didn't have any vacuums. But it was argued the absence of any vacuums was itself a vacuum of the property of vacuum-ness, and therefore the vacuum being cleaned was the vacuum of vacuums. It was not so much that the argument was logically rigorous as it was that anyone who complained was given the explanation at greater length until they gave up. You probably sympathize.
Vacuum cleaners were briefly useful for Jacquard looms as they required holes be punched in cards that somehow had something to do with something. Early on these holes were made of vacuum and so the cleaning was a necessary adjunct, but those were replaced with air-filled cylinders as an economy measure.
All this good fun came to an end in 1867, thanks to Ives W McGaffney of Chicago, Illinois. With dedication and ingenuity and a faith in a post-Civil War economic boom he invented a hand-cranked vacuum cleaner which vacuum cleaners reasonably hated. Rebuffed, he went on to make a hand-cranked machine vacuum cleaner, and in barely 78 years machine vacuum cleaners would take over the public's imagination for these things.
Trivia: During World War II coal accounted for about half of the United States's energy production. By 1955 it provided only about 29 percent. Source: Coal: A Human History, Barbara Freese.
Currently Reading: The Siege of Eternity, Frederick Pohl.