By Max Tegmark
By John D. Barrow, Frank J. Tipler
By J.G. Taylor
By Stephen Richards
By John Archibald Wheeler
By Keith J. Devlin
By Roger Penrose
By Christophe Galfard
By Lawrence M. Krauss
By Leon M. Lederman, Christopher T. Hill
By Joseph Silk (, Savilian Professor of Astronomy, University of Oxford)
By Carl Sagan
By Tony Hey (University of Southampton), Patrick Walters (University of Wales, Swansea)
By Carlo Rovelli
By Stephen Hawking (University of Cambridge)
By Clegg, Brian, Pugh, Oliver
By Giles Sparrow
By Frank Close (Professor of Theoretical Physics and Fellow of Exeter College, University of Oxford)
By B. Greene
By George Musser
By Professor Brian Cox, Andrew Cohen
By Tom Kerss, Royal Observatory Greenwich, Collins Astronomy
By Frank Wilczek (Author)
By Lisa Randall
By Dr Sten Odenwald
By Michael Wall
By Michael Brooks, Rick Edwards