All we know is that their planet is located in a barred spiral galaxy on the Cepheus-Draco border - which should make it easy to find.
The address of Mrs Dubcek's apartment, where The Solomon's live, is given as 417 Pensdale Road, Rutherford, Ohio. We know this from an episode where Harry suffers amnesia after being swept up in a tornado. He manages to find his way home because his address is written on a piece of paper that he finds in his wallet. However a search for the location on Google Maps suggests that it is entirely fictional. Only the state of Ohio exists - there is no evidence either of a city called Rutherford or even a university called Pendleton.
It's not clear but a quick search reveals that Third Rock from the Sun is also the name of a song (from the album of the same name) recorded by American country music artist Joe Diffie.
Certainly the chorus lends itself well to the underlying theme of the sitcom:
And elsewhere we're told of a waitress who "calls the cops, says she saw it all / Swears a giant alien has landed at the mall."
The song was released in June 1994, just a year and a half prior to the shows first airing on TV. To the best of our knowledge he hasn't sued, but then again his record has been nowhere near as successful as the TV sitcom the bears the same name.
However it has also been pointed out to us by a 3rd Rock Fan that Third Stone from the Sun is the title of a song by the late, great Jimi Hendrix and included on the 1967 Are You Experienced album. A mostly instrumental track, voices however can be heard in the background of what appears to be a dialogue between two extra-terrestrial observers of Earth:
Starfleet to scoutship, please give your position, Over.
I'm in orbit around the third planet from the star called
The sun. Over.
You mean it's the earth? Over.
Positive. It is known to have some form of intelligent
Species. Over.
I think we should take a look.
- Lyrics Freak | Jimi Hendrix lyrics - Third Stone From The Sun lyrics
According to highly trusted sources (and not just the man in the pub), back in the 1980s when producers of the hit TV sitcom Cheers were looking to cast for a new character they approached John Lithgow, having had him in mind for the role from the beginning. When he turned down the part they naturally had to look elsewhere. As a result Kelsey Grammer got the role of Frasier Crane.
Cause and effect, chain of events
All of the chaos makes perfect sense
When you're spinnin' round, things come undone
Welcome to Earth, third rock from the sun