<P> The opening title sequence, which was produced by the London graphic design firm SVC Television, opens with computerized shots of planets and celestial bodies, some either with the planets dancing or moving in warp speed . It opens and closes with a shot of Earth (which at the open is where the show's title logo appears, after a sunburst appears on the side of Earth). For the sixth and final season only, the typeface of the cast and creators' names was altered . </P> <P> The six seasons had 139 episodes in the series . </P> <Table> <Tr> <Th_colspan="2"> Season </Th> <Th_colspan="2"> Episodes </Th> <Th_colspan="2"> Originally aired </Th> <Th_colspan="3"> Nielsen ratings </Th> </Tr> <Tr> <Th> First aired </Th> <Th> Last aired </Th> <Th> Rank </Th> <Th> Rating </Th> <Th> Tied with </Th> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 20 </Td> <Td_colspan="1"> January 9, 1996 (1996 - 01 - 09) </Td> <Td> May 21, 1996 (1996 - 05 - 21) </Td> <Td> 22 </Td> <Td> 12.1 </Td> <Td> N / A </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 26 </Td> <Td_colspan="1"> September 22, 1996 (1996 - 09 - 22) </Td> <Td> May 18, 1997 (1997 - 05 - 18) </Td> <Td> 27 </Td> <Td> 10.8 </Td> <Td> Law & Order </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 27 </Td> <Td_colspan="1"> September 24, 1997 (1997 - 09 - 24) </Td> <Td> May 20, 1998 (1998 - 05 - 20) </Td> <Td> N / A </Td> <Td> N / A </Td> <Td> N / A </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 24 </Td> <Td_colspan="1"> September 23, 1998 (1998 - 09 - 23) </Td> <Td> May 25, 1999 (1999 - 05 - 25) </Td> <Td> N / A </Td> <Td> N / A </Td> <Td> N / A </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 5 </Td> <Td_colspan="2"> 22 </Td> <Td_colspan="1"> September 21, 1999 (1999 - 09 - 21) </Td> <Td> May 23, 2000 (2000 - 05 - 23) </Td> <Td> N / A </Td> <Td> N / A </Td> <Td> N / A </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 6 </Td> <Td_colspan="2"> 20 </Td> <Td_colspan="1"> October 24, 2000 (2000 - 10 - 24) </Td> <Td> May 22, 2001 (2001 - 05 - 22) </Td> <Td> N / A </Td> <Td> N / A </Td> <Td> N / A </Td> </Tr> </Table> <Tr> <Th_colspan="2"> Season </Th> <Th_colspan="2"> Episodes </Th> <Th_colspan="2"> Originally aired </Th> <Th_colspan="3"> Nielsen ratings </Th> </Tr>

When did third rock from the sun start