They come across two physicists (Barnes and Henderson) who are investigating a strange liquid that exhibits negentropy, which Davis describes as being akin to "Time's Arrow" as "Any clock you care to mention – a pendulum for instance – might just as easily run forward as backward.
Fowler is invited to visit Henderson's lab, during which time the two geologists come to believe that the physicist is trying to effectively build a way to view the past firsthand.
[2] In the preface for Reach for Tomorrow, Clarke notes that "Time's Arrow is an example of how hard it is for the science-fiction writer to keep ahead of fact.
"[3] Eric S. Rabkin likewise commented that "this paleontological possibility.... [slowly uncovering the petrified mud tracks of a huge dinosaur being stalked by some other animal] had not been found in life before Clarke's story, but has been since".
[11][12] Rabkin discussed the story in his 1980 text about Clarke, noting that the author "adds his own twists to the classic tale of time travel".