From Alec Williams, Whitehead, County Antrim, UK
To find evidence to back string theory, Joseph Conlon suggests looking for certain primordial gravitational waves from very early in the universe. Presumably, these would be stretched as the universe expands, just as light waves are. Radiation we see as the cosmic microwave background was stretched many, many times from its original form. Gravitational waves from before the CMB would be stretched (and weakened) even more (17 February, p 40). Would they still be detectable?
