<P> As the theme of the show revolves around science, many distinguished and high - profile scientists have appeared as guest stars on the show . Famous astrophysicist and Nobel laureate George Smoot had a cameo appearance in the second season . Theoretical physicist Brian Greene appeared in the fourth season, as well as astrophysicist, science populizer, and physics outreach specialist Neil deGrasse Tyson . </P> <P> Cosmologist Stephen Hawking made a short guest appearance in the fifth - season episode; in the eighth season, Hawking video conferences with Sheldon and Leonard, and makes another appearance in the 200th episode . In the fifth and sixth seasons, NASA astronaut Michael J. Massimino played himself multiple times in the role of Howard's fellow astronaut . Bill Nye appeared in the seventh season, and Elon Musk made an appearance in the ninth season . </P> <Table> <Tr> <Th_colspan="2"> Season </Th> <Th_colspan="2"> Episodes </Th> <Th_colspan="2"> Originally aired </Th> <Th_colspan="4"> Nielsen ratings </Th> </Tr> <Tr> <Th> First aired </Th> <Th> Last aired </Th> <Th> Viewers (millions) </Th> <Th> Viewers rank </Th> <Th> 18--49 rating / share </Th> <Th> 18--49 rank </Th> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 17 </Td> <Td_colspan="1"> September 24, 2007 (2007 - 09 - 24) </Td> <Td> May 19, 2008 (2008 - 05 - 19) </Td> <Td> 8.31 </Td> <Td> 68 </Td> <Td> 3.3 / 8 </Td> <Td> 46 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 23 </Td> <Td_colspan="1"> September 22, 2008 (2008 - 09 - 22) </Td> <Td> May 11, 2009 (2009 - 05 - 11) </Td> <Td> 10.03 </Td> <Td> 40 </Td> <Td> N / A </Td> <Td> N / A </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 23 </Td> <Td_colspan="1"> September 21, 2009 (2009 - 09 - 21) </Td> <Td> May 24, 2010 (2010 - 05 - 24) </Td> <Td> 14.22 </Td> <Td> 12 </Td> <Td> 5.3 / 13 </Td> <Td> 5 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 24 </Td> <Td_colspan="1"> September 23, 2010 (2010 - 09 - 23) </Td> <Td> May 19, 2011 (2011 - 05 - 19) </Td> <Td> 13.21 </Td> <Td> 13 </Td> <Td> 4.4 / 13 </Td> <Td> 7 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 5 </Td> <Td_colspan="2"> 24 </Td> <Td_colspan="1"> September 22, 2011 (2011 - 09 - 22) </Td> <Td> May 10, 2012 (2012 - 05 - 10) </Td> <Td> 15.82 </Td> <Td> 8 </Td> <Td> 5.5 / 17 </Td> <Td> 6 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 6 </Td> <Td_colspan="2"> 24 </Td> <Td_colspan="1"> September 27, 2012 (2012 - 09 - 27) </Td> <Td> May 16, 2013 (2013 - 05 - 16) </Td> <Td> 18.68 </Td> <Td> </Td> <Td> 6.2 / 19 </Td> <Td> </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 7 </Td> <Td_colspan="2"> 24 </Td> <Td_colspan="1"> September 26, 2013 (2013 - 09 - 26) </Td> <Td> May 15, 2014 (2014 - 05 - 15) </Td> <Td> 19.96 </Td> <Td> </Td> <Td> 6.2 / 20 </Td> <Td> </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 8 </Td> <Td_colspan="2"> 24 </Td> <Td_colspan="1"> September 22, 2014 (2014 - 09 - 22) </Td> <Td> May 7, 2015 (2015 - 05 - 07) </Td> <Td> 19.05 </Td> <Td> </Td> <Td> 5.6 / 17 </Td> <Td> </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 9 </Td> <Td_colspan="2"> 24 </Td> <Td_colspan="1"> September 21, 2015 (2015 - 09 - 21) </Td> <Td> May 12, 2016 (2016 - 05 - 12) </Td> <Td> 20.36 </Td> <Td> </Td> <Td> 5.8 / 19 </Td> <Td> </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 10 </Td> <Td_colspan="2"> 24 </Td> <Td_colspan="1"> September 19, 2016 (2016 - 09 - 19) </Td> <Td> May 11, 2017 (2017 - 05 - 11) </Td> <Td> 18.99 </Td> <Td> </Td> <Td> 4.9 / 19 </Td> <Td> </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> 11 </Td> <Td_colspan="2"> 24 </Td> <Td_colspan="1"> September 25, 2017 (2017 - 09 - 25) </Td> <Td> May 10, 2018 (2018 - 05 - 10) </Td> <Td> TBA </Td> <Td> TBA </Td> <Td> TBA </Td> <Td> TBA </Td> </Tr> </Table> <Tr> <Th_colspan="2"> Season </Th> <Th_colspan="2"> Episodes </Th> <Th_colspan="2"> Originally aired </Th> <Th_colspan="4"> Nielsen ratings </Th> </Tr>

When does the big bang theory season end