Science fiction writers have speculated about time travel for more than a hundred years. H. G. Wells’s novel, The Time Machine has been an enduring classic in publishing, with too many editions to keep track of. Some of them have very fun covers, however.

It is a subject that continues to fascinate writers, including in my own work in a story that I’m working on now. But what does science say about time travel? Is it possible? Is it just a fantasy?

Recently, physicists have made discoveries about dark energy that may indicate that no time travel into the past would be possible because of the direction of the physical properties of particles.

But one thing is for sure – the imagination works in both directions, to the past as well as the future. We cast our minds into the past to learn about what we can do in the future, to see what went right, and what went wrong. Or maybe it is just for entertainment?

• – David W. Wooddell